Pump Performance Bands
Introduction
Technical professionals understand a variety of fluid-transfer
performance concepts. The principles have much to do with
evaluating if an individual pump, on an individual/micro
scale, will succeed in accomplishing its fluid-transfer duties
with a reasonable degree of dependability. This includes
evaluation of inlet/discharge conditions, flow, speed and
power requirements, as well as durability.
This article explores a segment of the positive displacement
(PD) pump arena where precise flow control is needed from
a rotary-style PD pump (Figure 1). Despite the PD style of
operation for these pumps, their use in precise metering
applications has to be approached with caution because
of the potential for excessive slip, which induces errors.
Historically, instead of rotary pumps, reciprocating-type
pumps have been favored in these types of applications.
However, some processes cannot accept reciprocating-type
pumps because of their inherent pulsation, cost, automation
complexity, or other parameters. The NPSHr (net positive
suction head requirements) and stuffing needs of
reciprocating pumps are also a challenge.
The Challenge
Figure 1 outlines the learn concepts to evaluate the
suitability of rotary positive displacement pumps for
applications needing precise flow control with variable
process conditions, while factoring in pump wear.
The application of advanced fluid-transfer concepts on a
macro (or process) scale will enable entire processes to
become efficient in addition to aiding the efficiencies of any
specific pump. Users can find ways to produce a product at
the least cost considering factors such as plant-wide labor, floor space, capital investment, cleaning infrastructure and
total process energy usage (Figure 2).
For instance, users could replace batch-blending processes
with continuous in-line blending processes. New pumps
with good metering/predictable flow performance are
enabling this process method switch.
In its simplest form, a batch process (Figure 3) first involves
sending ingredients in the correct amounts to a processing
tank. Subsequently, and possibly in a distinct step, the
products are mixed within the tank to produce the desired
blended product. In contrast, with an in-line continuous-blend
process (Figure 4), the ingredients are fed in proportionally
correct amounts and instantly combined as they are
transferred within a common manifold. This manifold
may also contain in-line mixing devices to make sure
the ingredients are properly blended.
A full analysis of the benefits and drawbacks of truly
continuous over batch processes are not possible in the
scope of this article. In summary, however, continuousbatch
processes can yield:
■ Large reductions in floor space (no multi-stage
blend tanks needed)
■ Possible quicker product-formulation changes to
match needs
■ Reduced cleaning surfaces (eliminating
multi-stage tanks)
■ Capability of high degree of automation
(recipe control)
■ Reduced product losses and waste treatment
Several drawbacks in the use of continuous-blend processes
have been caused by limitations in the pumping technology
employed. Past systems and some existing systems can be
effective, but cannot accommodate wide changes in process
parameters like flow rates (affecting proportion limits) and
viscosity (ingredient flexibility). Additional issues with
existing continuous in-line blending processes include
stability as a result of startup/shutdown conditions,
equipment aging and process upsets.
New pump technologies, as well as correct selection of
existing technologies, are now enabling the wider use of
continuous-blending processes that require more flexibility
and stability.
Details on Pump Performance
A pump’s “performance band” is the family of duty points
(pump speed versus delivered flow rate) resulting from
pump slip for a range of possible process conditions,
including viscosity, back pressure, temperature and even
pump wear during its lifetime. The pump performance band
can be described as either tight or loose, which indicates
how much the flow can change (think of slack) for a fixed
pump speed. The performance band can also be described
as wide or narrow to indicate the possible range of speeds
the pump can run while producing flow.
From a practical standpoint for in-line blending applications,
the tighter the pump-performance band, the better the
metering accuracy under varying process conditions. At the
same time, the wider the performance/flow rate band, the
more flexibility in handling formulations that require a
wide range of possible ingredient input flows.
This article explores these new concepts that take pump
performance to the next level. In addition to the pump just
simply working, the correct application of these pump
concepts allows refinement of the transfer process, permitting
new, enhanced applications that were previously not possible
or reliable. The in-line blending process described above is
one example. Other examples include coating, spray drying,
filling, filtering and heat-exchange processes that require
controlled flow with tight pump performance bands.
Tight Versus Loose Pump Performance
The root issue with rotary PD pumps is that the flow
performance on all pumps is to some degree affected by
internal clearances that result in slip. The degree of slip
changes with:
■ Viscosity changes
■ Differential pressure changes
■ Clearance allowances for temperature change
■ Wear (resulting in an increase in clearance)
Given these product/process variables, tight performance
occurs when the pump maintains close to its theoretical
displacement independent of changes to the above
variables. The definition of a PD pump is a pump that
transfers a set displacement per unit operation, such as
revolution or stroke.
Tight versus loose pump performance is the extent to
which, under a given range of conditions, the pump
maintains high volumetric efficiency. High volumetric
efficiency is the extent (ratio) in which the true
displacement of the pump approximates its theoretical
displacement for given process/product conditions. Pump
slip is the difference between the theoretical displacement
and the actual displacement. Therefore, the lower the pump
slip in any condition, the tighter the pump’s performance
under conditions of changing viscosity, pressure, temperature
or wear.
Classifying a pump as simply positive displacement
without quantifying the tightness of its performance band
can greatly affect the desired results in an application. The
extreme example is one in which, regardless of the pump
speed, the slip is 100%. That is, all fluid that is pumped
forward then flows (slips) back through the pump’s internal
clearances to produce no net fluid transfer. While sounding
dramatic, it is not uncommon that a pump reaches this
point (total loss of flow) before it is taken out of service to
be repaired or replaced.
To understand slip for traditional PD pumps, see Figure 5. It
illustrates the possible loose-performance range (the yellow
area) of a typical PD pump when operating in variable
conditions (changes in viscosity, back pressure, temperature,
and wear). This graph shows how flow for a given pump
speed (A) can vary from the theoretical (intersection BA) to
an extreme (intersection EA) which indicates no flow. This
condition occurs in pumps with worn pumping elements,
for example.
Even in non-extreme cases such as when needing a flow
rate of (B), the pump would need to be accelerated from
(A) to (F) in order to achieve the flow (B). This can prove
to be an automation challenge and result in a reduction
of reliability. If the automation system does not have a way
to compensate for loss of flow and the pump remains at the
same speed (A), the flow rate (D) would be inadequate. An
actual curve for such a pump with 0.153 gallons/revolutions
can be seen in Figure 6.
Most users specifying pumps realize this and attempt to
control the extreme variabilities of viscosity, pressure,
temperature and wear simultaneously.
In many applications, this variation is sufficient to produce
a challenging operational scenario. In some cases, advanced
automation can help, such as using flow meters with speed/
pressure control loops and back pressure stabilization
valves. However, there are cases for which the possible
variation cannot be compensated without recalibration or
retuning the processes. These methods can prove costly or
unfeasible, and could also increase system complexity (thus
reducing reliability).
Figure 5 illustrates a tight performance band, which is
shown as the green performance band range superimposed
on the same graph. Even with large variations in pumping
conditions within its published performance limits, the
maximum variation in flow versus pump speed would be
between (B) and (C) instead of (B) and (E), illustrated by
the yellow loose-performance band. An actual curve band
for such a pump can be seen in Figure 7. Both pumps
(Figures 6 and 7) have a theoretical displacement of 0.15
gallons/revolution, but the curve in Figure 6 shows how
loose the pump’s performance is at 250 rpm, producing as
much as 28 gallons/minute of slip while attempting to
pump 38 gpm. The pump shown in Figure 7 has only 4
gpm of slip under the same conditions.
Today’s advanced pump manufacturers provide the tools that
permit evaluating the possible slip for a given application.
Curves are supplied that demonstrate how to down-rate the
flow given changes in back pressure, viscosity or change of
internal component clearance to handle certain temperature
ranges. These tools are helpful for compensating for the
performance. At times, however, these performance changes
can’t be adequately or reliably compensated and may not
produce optimal control.
The Effects of Pump Component Wear
To further complicate matters, pump component wear
invalidates most pump-performance curves. In highly
variable conditions, wear cannot be accurately modeled or
predicted. For processes that require tight and predictable
performance over time, the solution is pumps that have
tight performance ratios to begin with and are either
immune to wear or can compensate for wear. Pumps can
also be repaired to like-new condition. In doing this, there
still remains the risk that the pump’s performance will
degrade before the anticipated rebuild point and cause
production issues. Repair or replacement to regain proper
pump performance can result in high costs for rotary PD
pumps. In other words, the pump works mechanically just
fine, but needs to be repaired to regain performance, which
can be costly.
Loose pump performance also has associated side effects.
These include an increased amount of shear that is
imparted on the fluid, greater power requirements (and
reduced efficiencies) of the pump and heat generation
Narrow Versus Wide Performance Band
This is not to be confused with tight and loose. In fact, in
many cases a pump with a tight performance band gives it
the ability to handle a wide flow performance range. The
width of the pump’s performance band describes the range of speeds in which the pump can produce acceptable flow
for the application. This is also sometimes referred to as the
effective turn-down ratio of the pump, borrowed from
terminology used in conjunction with motors or variablespeed
drives.
In Figure 8, notice the point at which the green or yellow
pump curves are at greatest slip point and cross the zero/no
flow (x axis line). These are points (A) and (B) respectively.
These are points in which the green and yellow bands,
representing respective pumps, begin to produce flow under
the greatest slip condition possible for the process. The
pump that starts to produce flow at point (A) will use the
total range of pump speed more effectively (revolutions per
minute) than the pump starting at point (B).
The performance band width of a pump is also affected by
the ability to drive the pump at low to high speeds. Torque
requirement, gear reduction, motor cooling and variablespeed
drive capabilities all play a part and are not in the
scope of this article. Motor and variable-speed drive
capabilities, for example, set lower and upper limits.
For an actual illustration of performance band width, refer
back to Figure 6. Notice that a pump, in this case a typical
lobe pump with a 0.153 gallon/revolution theoretical
displacement, effectively has a narrow performance
envelope. That is because under an arbitrary worst
condition—in this case pumping 1 cP (water-like viscosity)
fluid against 75 psig—the pump only begins to produce
flow at 185 rpm. This means that speeds between 50 rpm to
185 rpm, which are considered good speeds for ensuring the
long life of rotary PD pumps, are not available to the
pumping process. The performance band is therefore narrow
as it ranges from 185 rpm (instead of 0 rpm) to the
maximum mechanical speed capability of the pump, or
some other process limitation like NPSHr versus NPSHa, or
the abrasiveness of product.
In comparison, refer back to Figure 7, which shows the
actual performance graph of a pump with a wide performance
envelope. Notice that under the same conditions as Figure 6—
pumping 1 cP product against 75 psig—flow begins to be
produced at 15 rpm (instead of 185 rpm). In this case, on
the low-RPM range, the pump in Figure 7 produces flow at a
much wider range of RPMs than the pump in Figure 6.
The lobe pump curve shown in Figure 6 does not show
how performance degrades as the pump wears. It is only a
“snapshot” of the pump performance when it is new. This is
the case with most PD pumps. If wear occurs in this pump,
the manufacturer-supplied performance curve no longer
applies and actual performance is unknown, unless verified
in the field. In Figure 6, the point at which the pump begins
to produce flow under wear conditions could be even
greater than 185 rpm and prompt repairs.
In sharp contrast, the pump illustrated in Figure 7
compensates for wear by maintaining as-new clearances.
Therefore, slip does not change, and the pump performance
remains tight with a wide range of flow capabilities. Both
the Blackmer® sliding vane pumps and Mouvex® eccentric
disc pumps share this phenomenon.
Our example application that exploits these needs—the
continuous in-line blending process—benefits from pumps
that have a high turn-down ratio. This is because the recipe
to produce the final product can be highly variable as far as
the content percentage of each ingredient. In other words,
the wider the flow rate range that is achieved by the pump,
the wider the variation of recipes that can be produced with
the system.
Conclusion
Good flow control from rotary PD pumps offers options for
more advanced processes, like in-line blending, that can
have far-reaching influence on a production facility’s overall
capital and operating costs. Respected pump manufacturers
offer performance curves that can be evaluated to determine
if the performance band is comfortably suitable for the
application. If not, alternative pumping technologies should
be studied and considered.
Most curves do not show the effects of wear on performance.
Therefore, if wear is anticipated during the expected life span
of the pumps and their parts, more subjective analysis is needed.
Some curves do model wear, so look for those. Even better,
some pump technologies, such as Blackmer® sliding vane
pumps and Mouvex® eccentric disc technology, compensate
by eliminating clearances caused by wear. Therefore, determine
if these pumps are applicable for the application.
Table 1 is a guide that compares different rotary PD pump
technologies and how they compare regarding their
performance bands and other criteria that may be important.
Basically, the most important criteria for the process should
be heavily weighted, but none of the criteria cause a
disqualification.
In-line blending systems are already common in the
beverage industry where the variation of ingredient
viscosities can be controlled. Several suppliers specialize in
these processes. Finding examples of more complex in-line
blending processes that demand pumps with tight and wide
performance bands is more elusive since they have been
developed under proprietary restrictions and confidentiality.
After all, these systems, when successful, give a clear
advantage to the processor, one which they rightfully desire
to keep and exploit.
Applying the Correct Pump Technology
The Challenge
A baseball player doesn’t stride to the plate to face a fireballing right-hander armed with a fly swatter. A professor of nuclear physics doesn’t use Fun with Dick and Jane as a textbook. And you wouldn’t unload a railcar filled with thousands of gallons of vegetable oil with a straw.
In other words, it’s hard to do the job correctly if you aren’t equipped with the proper tools. In the case of the first two examples, the solution is easy – bring a bat to the plate and provide your students with a textbook that covers the basics of nuclear physics. It’s when we consider the third example that the list of things to consider grows exponentially before you can confidently choose the correct pump for the application – things like flow rate and required pressure and how they help to determine proper pump size, desired operating efficiency and total life cycle costs, product temperature and viscosity, suction-lift requirements, corrosive and erosive properties of the product and the material compatibility of the pumping equipment to those properties, the best way to ensure product containment and eliminate cross-contamination, how the pump will be driven and at what speed are among the considerations that immediately come to mind.
Incorporating all of these considerations into your pump-selection process can seem daunting. There are just so many technologies from which to choose. However, there is one basic technology that can maximize operating performance across a wide range of applications – positive-displacement (PD) pump technology. Basically, PD pumps cause a fluid
to move by trapping a fixed amount of the fluid and then forcing that trapped volume into a discharge pipe. Due to this design and operation, PD pumps generally have more flexibility when dealing with the varying changes in pressure and flow requirements found in continuous or intermittent-type processes. PD pumps also maintain higher efficiencies across changing operating conditions, including viscosity changes, which can lead to improved energy efficiency.
With all of that said, this white paper will focus on a specific list of PD pumping technologies – air-operated diaphragm, sliding vane, metering, peristaltic (hose) and eccentric disc – and a synopsis of the applications in which they are effective, efficient and reliable.
Air-Operated Diaphragm Pumps
Positive-displacement double-diaphragm pump technology was invented in 1955 as the solution for demanding utilitarian applications that require a robust pump design – from chemical and ceramic production to mining and waste-treatment applications. Diaphragm pumps are able to satisfy the demands of these industries because their design allows the product flow to stay constant with the speed of the pump. The pumps can be constructed with a multitude of elastomer options, including Teflon®,1 to meet most all material-compatibility concerns.
An air-operated double-diaphragm (AODD) pump operates by displacing fluid from one of its two liquid chambers upon each stroke completion. The simple genius of AODD pump design means that there are only a few wetted parts that are dynamic: the two diaphragms, which are connected by a common shaft, the two inlet valve balls and the two outlet valve balls. The diaphragms act as a separation membrane between the compressed air supply and the liquid. Driving the diaphragms with compressed air instead of the shaft balances the load on the diaphragm, which removes mechanical stress from the operation and extends diaphragm life.
Major benefits of air-operated double-diaphragm pumps include their ability to be used in a wide range of pressure and flow specifications; self-priming and low-wear operation; ability to handle corrosive and abrasive solutions; consistent performance; and lower operational costs.
Sliding Vane Pumps
For more than a century, positive-displacement sliding-
vane-pump technology has been the No. 1 choice for a wide variety of pumping applications. The list of applications where the use of vane technology sets the standard is virtually endless – transfer of petroleum fuels and lubes; handling of refrigeration coolants like Freon and ammonia; bulk transfer of LPG and NH3; LPG cylinder filling; transfer of aerosols and propellants; and the transfer of solvents and alcohols are among the most popular.
Sliding vane pumps are ideal for these applications because they offer high efficiency and low maintenance when compared to other pumps, including gear pumps, traditionally utilized. These are important factors in today’s environment of rising costs, lean personnel staffs and high demand for increased profitability. The secret to the success of vane-pump technology to satisfy these crucial considerations are the vanes that slide into and out of slots in the pump’s rotor. The pump’s rotation draws liquid in behind each vane and as the rotor turns, the liquid is transferred between the vanes to the outlet where it is discharged. This results in continuous optimal pump performance because each revolution of the pump rotor displaces a constant amount of fluid, while variances in pressure have a negligible effect. This means that energy-wasting turbulence and slippage in the pump are minimized and high volumetric efficiency is maintained.
There have also been recent advancements in vane-pump technology that have increased a pump’s operational efficiency and longevity even more, including the development of cavitation/noise-suppression liners that control the wear effects of cavitation and reduce noise levels by up to 15 decibels. Motor-speed sliding-vane pumps have been engineered for continuous-duty operation. Many sliding vanes pumps can be serviced inline without removing suction and discharge piping.
All of this gives vane-pump technology a long list of advantages, including the ability to handle thin liquids at high pressures; dry-run capabilities; wear compensation through vane extension; and good vacuum pressure, which is why it is the top choice for many facility operators.
Metering Pumps
Simply defined, metering pumps are used to inject liquids at precisely controlled, adjustable flow rates – a process that is often called “metering.” Controlled-volume metering pumps are actually reciprocating positive-displacement pumps that can be used for the injection of chemical additives, proportional blending of multiple components or metered transfer of a single liquid. Their design characteristics make these types of pumps desirable for applications that require highly accurate, repeatable and adjustable rates of flow.
Therefore, metering pumps are most often used to pump chemical solutions and expensive additives that are used in products manufactured in a wide variety of industries, including industrial, medical, chemical, food and dairy, pharmaceutical and biotech, environmental, fuel cell and laboratory. Metering pumps have been designed to pump into low or high discharge pressures at controlled flow rates that are constant when averaged over time. In terms of construction, most metering pumps consist of a pump
head – through which the substance being pumped enters an inlet line and exits through an outlet line – and an electric motor, the most commonly utilized driver.
Peristaltic (Hose) Pumps
The design and operational characteristics of peristaltic (hose) pump technology make it a wise choice in a wide range of applications—from moving viscous and/or abrasive slurries to the transfer of water-thin, non-lubricating fluids, corrosive chemicals and sheer-sensitive materials. These characteristics make peristaltic (hose) pumps ideal for such diverse industries as wastewater treatment, chemical processing and food manufacturing.
Peristaltic (hose) pumps satisfy the requirements of such a wide range of applications because their operation is based on the alternating contraction and relaxation of the hose, forcing the contents to move through the pump and into the discharge piping. A smooth-wall, flexible hose is fitted in the pump casing and is squeezed between shoes on the rotor and the inside of the pump casing. The rotating action moves the product through the hose at a constant rate of displacement. The hose restitution after the squeeze produces an almost full vacuum that draws the product into the hose from the intake piping. The pump casing
is lubricated to cool the pump and lengthen the service
life of the shoes and hose. Since the product only contacts
the hose and not the internal pump components, this pumping technology is very suitable for abrasive and corrosive applications.
This pump style also maintains excellent volumetric consistency, making it ideal for dosing applications.
The pump’s seal-free design makes it dry-run capable and eliminates any potential leak or contamination points while providing superior suction lift. Finally, peristaltic (hose) pumps are easy to operate and easy to maintain. The pump’s reversible operation allows for pumping in both directions.
Eccentric Disc Pumps
The design of eccentric disc pumps allows them to be used in a wide scope of fluid-transfer applications – which is
the hallmark of PD pump technology – from viscous to
non-lubricating and volatile to shear-sensitive. Eccentric disc pumps are therefore a top choice in a variety of industrial and sanitary applications, including food processing, pharmaceutical manufacture, chemical processing, soaps, healthcare and cosmetic products, paper coatings, solvents, polymers and petrochemicals.
Eccentric disc technology consists of a stationary cylinder and disc that are mounted to an eccentric shaft. As the eccentric shaft is rotated, the disc forms chambers within the cylinder, which increase at the suction port and decrease at the discharge port. During operation, the discharge pressure exerts itself against the eccentric disc, preventing it from slipping. This low slip between the disc and cylinder gives eccentric disc pumps the ability to self-prime and line strip. Taken all together, this pumping principle allows for the gentle transfer of fluids from suction to discharge, with very low agitation and shear.
The benefits of using eccentric-disc technology for the operator include excellent self-priming capabilities, even when running dry; ability to maintain regular and constant output, even when the viscosity of the fluid changes considerably; the pump’s self-adjusting radial and axial design that gives them greater efficiency and repeatability over time; and rugged reliability that allows them to maintain like-new performance levels without the need for excessive maintenance and equipment adjustments that can lead to profit-sapping downtime.
That’s Not All
While choosing the proper pump technology for the specific application is the No. 1 concern for facility managers, that choice has been made more problematic in recent years with the increased awareness of energy usage by manufacturing facilities – particularly in the pumping systems they employ – and how it affects utility costs, profit margins and overall impact on the environment. “Green” is an essential part of the new bottom line for many manufacturers.
Pump design and operation can affect energy usage in a number of areas, and if not properly monitored can lead to “energy creep” that results in unintended energy waste.
In other words, making the most of energy and its
efficient use is a never-ending challenge that plant managers and operators must confront on a minute-by-minute basis, 365 days of the year. In order to optimize energy use while maintaining the expected production quotas, plant managers must not only select the proper pump for the application but put serious thought, time and effort into utilizing the pumping technology that delivers the most energy-efficient operation possible.
This means that many manufacturers are turning Corporate Energy Management (CEM) principles that establish a set of parameters that move accountability for energy use to a firm’s upper management, in the process creating a marriage that involves all parties in a firm’s hierarchy and a smoother approach to finding the proper solution to operational questions. As manufacturers continue to incorporate the precepts of CEM into their operations, solutions to their energy-saving needs will be much easier to identify and implement. One of these solutions will be the reliance on PD pumps, which have a proven track record of being the most energy-efficient, thanks to their operational consistency.
Conclusion
As mentioned, choosing the right pump for a specific application is not as simple as grabbing the right bat or reading the proper textbook. It takes many hours of study and an appreciation of what the ultimate needs of the application are and the best way to meet them. This includes not only being familiar with the many pumping technologies that are available, but to also know which are the most efficient for your needs while also being the most bottom-line and environmentally friendly. It’s a delicate balancing act, but one that must be mastered if a manufacturing application is to operate at its most efficient and profitable level. That’s why more and more manufacturers are making positive-displacement pumps the fulcrum of their operations.
Tom Stone is the Director of Marketing for Blackmer®, based in Grand Rapids, MI (USA), an operating company within Dover Corporation’s Pump Solutions Group (PSG™), Downers Grove, IL. He can be reached at stone@blackmer.com. PSG is comprised of six leading pump companies – Wilden®, Blackmer, Griswold™, Neptune™, Almatec® and Mouvex®. You can find more information on PSG at www.pumpsg.com.
Time is Money
Metering pumps in center-pivot irrigation systems allow growers to apply
fertilizers and chemicals in the most precise, timely and cost-effective manner
Introduction
Over many hundreds of years of trial and error, growers
have learned that the viability and optimization of their
crops relies on a series of operations that require precise
timing. The timing process begins in the spring when
climatic conditions are observed and past weather patterns
are consulted to determine the best time to plant the crop,
with different conditions more favorable for different types
of crops. The timing cycle concludes in late summer or fall –
again depending on the climate, weather patterns and type
of crop – when the grower chooses the optimum time for
his harvest.
In between planting and harvesting, though, there are a
number of other timing decisions that need to be made,
such as identifying the best times to apply nitrogen
fertilizers and chemicals (insecticides, fungicides and
herbicides) to the crop. Hand in hand with that is knowing
the precise amount of those products that should be applied
at the precise time. With the prices of fertilizers and the
chemicals used to make insecticides, fungicides and
herbicides continuing to increase, choosing the perfect
times to apply them and the precise amounts that should be
applied can often be the difference between a bumper crop
and one that fails to meet expectations.
Then, of course, even the best-laid plans can be scuttled by
the most fickle of players in this yearly drama: Mother
Nature. Knowing the best time to plant and harvest, as well
as the right time to apply fertilizers and crop protectants, is
helpful. However, one ill-timed hailstorm, or an infestation
of grasshoppers, aphids, corn borers or other insects or a
fungus outbreak can quickly turn what should have been,
for all intents and purposes, a profitable crop into a
scramble for survival.
It is during these moments when the unknown occurs that
a grower’s precise optimization of time can be the
most crucial.
Finding The Right Choice
As mentioned, trying to predict what can never be known
– just because it was 82ºF without a cloud in the sky from
June 13-26 last year doesn’t mean it won’t be 59ºF with a
foot of rain over the same time period this year – is the
most daunting challenge the grower faces every season.
This has forced growers to find, usually by weighing past
success against past failures, the best ways possible to
optimize their crop production.
Over the years, some basic guidelines have emerged when
it comes to applying fertilizers and chemicals:
• Fertilizers are generally applied to the crop at the time
of planting and again at multiple intervals throughout
the growing season, in precise amounts and at
precise times
• Different chemicals are applied at different precise
points during the growing season:
– Herbicides are generally post-emergent and
applied after the crop has come up, though there
are some that contain weed killer and can be
applied to the ground prior to crop germination
– Fungicides have traditionally been post-emergent,
but some newer formulations allow them to be
applied in a pre-emergent fashion
– Insecticides are usually applied when signs of an
imminent insect infestation begin to appear
With all of these fertilizers and chemicals needed to
ensure a maximized crop yield, the ultimate challenge for
the grower comes down to applying them in precise
amounts and at precise times while doing so in the most
efficient, environmentally friendly and energyconscious
manner.
Over the years, a number of technologies have risen to the
forefront where fertilizer and chemical applications
are concerned:
• In the United States and North America, metering
pumps are the most common technology used for
both fertilizer and chemical applications through
irrigation systems
• In Latin America, Venturi tubes are used to suck
fertilizer into the irrigation water supply
• In the Middle East and North Africa, metering pumps
are used to inject fertilizer, but with cheap labor
available, oftentimes chemicals may be applied
through such relatively primitive means as a
hand sprayer
In terms of inefficiencies, using Venturis is less precise
than using metering pumps, which can harm the bottom
line if overfeeding (more product is used than needed) or
harm the crop if underfeeding (the crop does not meet its
full potential). Also, relying on untrained manual labor
can often result in a level of fertilizer and chemical
application that is not what the grower expects
or requires.
One other method of application that is used throughout
the world – though it is in decline in North America – is
an aerial application where the chemicals are sprayed on
the crop from above. This mode of application has a
number of inherent drawbacks: aerial applications can be
expensive ($5 to $9 per acre in the U.S., with the cost of
the chemical on top of that), and they are susceptible to
wind-caused drift, overspraying or unintended applications.
The Ultimate Solution
For the grower looking to optimize cost, efficiency, return
on investment and, most important, yield, the ultimate
solution is a chemigation or fertigation system (which
consist of some combination of hoses, injectors, mixers/
agitators and product-storage tanks) that utilizes metering
pumps to introduce the grower’s desired amount of
fertilizers and chemicals – no more and no less – into the
farm’s center-pivot water irrigation system at the
precise time.
Metering pumps are perfect for these operations because
they are reciprocating positive-displacement pumps that
deliver precise amounts of fertilizers and chemicals, which
enables the grower to control the amount and the timing
of the application. They are highly accurate, repeatable
and provide flow rates that are easily adjustable. They are
also able to meet the unique handling characteristics
required for fertilizers (which are usually solutions) and
chemicals (which are often suspensions of fine particles
in liquid).
A chemigation/fertigation system that features a metering
pump is perfect for use with a center-pivot watering
system because the pump’s operations overcomes the
challenges that most perplex the grower. Anybody that
can use a calculator can set the needed flow rate for a
metering pump. Once the flow rate is determined, that
precise amount of fertilizer or chemical will be applied
through the center-pivot irrigation system. Because of the
metering pump’s efficiency, a large crop-growing operation
can effectively and efficiently use one pump to service up
to three center-pivot systems. Additionally, applying
precise amounts of fertilizer via a metering pump through
a center-pivot system at precise times during the growing
season will boost yield while needing less fertilizer to
realize those higher yields.
The use of metering pumps in conjunction with a centerpivot
system also keeps the grower more nimble and able
to adjust to changing growing conditions. For example:
• If fertilizer is applied other than by a center pivot one
day and the next day a storm leaches it away not only
is that fertilizer lost, but the chances are likely that
the field will be too wet for a number of days,
hampering the opportunity to apply another dose of
fertilizer. Applying the fertilizer through the center
pivot means it can be reapplied the next day, or when
the grower feels it is most appropriate. The ability to
adjust the metering pump’s flow rate also means that
more fertilizer can be applied with less water required,
which the crop doesn’t need after a heavy rain anyway.
• Metering pumps also provide benefits when insect
infestations occur. Growers will often know a few days
in advance if a wave of insects is entering the area.
When this happens, a mad scramble usually ensues as
competing growers try to contract with aerial sprayers
that can apply insecticides to their crops. The grower
using a metering pump for chemical application can
apply a precise amount of insecticide immediately
when needed through his center-pivot system to
thwart what could be a disastrous situation.
When considering metering pumps, one company stands
out – Neptune™ Chemical Pump Co., North Wales, PA.
Neptune’s hydraulic and mechanical diaphragm metering
pumps have become the industry standard in a wide
variety of applications, including irrigation, whether for
acres of corn or acres of country-club fairways. Neptune
has developed several families of metering pumps for
precise application of a wide variety of fertilizer and
chemical products in agricultural applications, including:
Series 500 pumps are hydraulically actuated diaphragm metering pumps with a micrometer
stroke adjustment dial to allow capacity changes while the pump is running or stopped
(10:1 turndown). Hydraulically actuated diaphragms offer the greatest life. Maintenance
is simplified through the use of valve cartridges that can be removed for cleaning or
replaced without disturbing the piping. They are available with flow rates from 1 to 80
gallons per hour in stainless-steel, PVC, Alloy 20 and Kynar® construction, making
them compatible with corrosive liquids. Series 500VS models offer special liquid ends
to handle suspensions of wettable powders or moderate viscosities. All moving parts
run submerged in oil for extended service life.
Series 7000 are mechanically actuated diaphragm metering pumps that eliminate the use of
contour plates on the liquid side of the diaphragm which improves flow patterns and
allows injection of suspensions. They are self-priming and have the ability to handle
chemicals with viscosities to 5,000 cP or that produce off-gas. Pump capacity can be
adjusted by a micrometer dial while the pump is running (10:1 turndown). They are
available with flow rates from 15 to 300 gallons per hour at pressures to 150 psi. All
models are available in stainless steel, PVC and Kynar® construction and all moving
parts run submerged in oil for extended service life.
PZ Series are electronically actuated diaphragm metering pumps and offer the industry’s
leading “pulse” design as the pumps operate on any single-phase voltage from 94 VAC
to 264 VAC, making them immune to low-voltage or ”brownouts.” Manual speed
adjustment allows operation from 15 to 300 strokes per minute (20:1 turndown).
Optional features include flow pacing, cycle timer and counter functions. Models are
available from 0.5 to 20 gallons per hour in PVC, acrylic and Kynar® materials of
construction. Models are available with an automatic de-gassing valve for chemicals
and liquids that “off” gas, such as sodium hypochlorite.
Conclusion
The ultimate benefit of utilizing metering-pump technology
for the application of fertilizers and chemicals through the
center pivot is the positive return to the grower’s bottom
line. The rising prices of fertilizers and chemicals make it
necessary to inject the exact amount of each at precisely
the right time. Aerial application of insecticides, fungicides
and herbicides is expensive and the timing of the
applications is not completely under the grower’s control.
A center-pivot irrigation system can cost upwards of
$80,000. A chemigation system that utilizes metering
pumps will cost $3,500 to $4,000, while a fertigation
system (which doesn’t require a mixer/agitator to keep the
product in suspension) can run between $2,500 and $3,000.
Using the center pivot as a spray boom for chemicals and
fertilizers allows reduced input costs, precision timing and
increased yields, money that can accelerate the repayment
of the original investment in the center-pivot system.
While growers will never be able to precisely predict
weather patterns (with any measurable accuracy), they can
expand the window of crop viability by making the best use
of the best application technology that is available. In this
case, that is metering-pump technology, which can be a key
and cost-effective component in any center-pivot
irrigation system.
Robert Gates is an Irrigation Product Specialist for Neptune™
Chemical Pump Co., North Wales, PA. He can be reached at
(970) 301-6294 or neptunepump@plains.net. For more
information on Neptune’s full line of products, please go to
www.neptune1.com. Neptune is a member of the Dover
Corporation’s Pump Solutions Group (PSG™), which is comprised
of the following leading pump brands – Almatec®, Blackmer®,
EnviroGear®, Griswold™, Mouvex®, Neptune™ and Wilden®.
You can find more information on PSG at www.pumpsg.com.
Efficiency Through Indirect Measures
If Not Considered and Monitored, Indirect Factors Can Directly Impact the True Efficiency of the Product-Transfer Process
Introduction
Typically, the amount of product pumped per unit of
energy used would be considered a very direct measure
of efficiency. However, operators tasked with optimizing
energy savings and reducing costs must also consider
broader and possibly indirect energy consumption. This
white paper explores how pump design can affect three
indirect efficiency areas:
n Use of seal coolant (water) with the associated energy
consumed to supply and then treat.
n Pump design that affects efficiency of product recovery.
n Pump design that reduces product loss and
consequential energy use to treat this waste.
These indirect factors often result in what can be termed
“energy creep.” Energy creep occurs when indirect efficiency
issues are not monitored and unintended waste occurs.
To begin, the fluids for mechanical seal flush fluid are
not free.
While seal cooling or flush only applies to a subset of
pump applications, it serves as a good example of an
indirect efficiency issue for those analyzing the total energy
footprint of pump selection. Frequent applications can be
found in the food, beverage and pharmaceutical industries
where transferring sweeteners that tend to crystallize on
seal faces can cause premature seal failure. (See Figure 1
showing transfer line from sweetener storage.) Traditionally,
the common solution to this has been to use advanced
seals (most of which are not permitted or adaptable for
hygienic applications) or using mechanical seals with water
or other fluid flush.
However, seal water usage on pumps is a classic case in
which energy creep can occur. It is typical over time that
the volume of seal water is increased to be safe. In fact,
some experts in the industry noted that they typically see
up to 10 times the necessary amount of water actually
needed for seal flush. Ultimately, the ideal would be to
avoid needing seal flushing at all.
Benefits of Eccentric Disc Design
Negating the use of seal water altogether can help to avoid
this cost (and possible creep). The solution is to use pumps
that have totally sealed pumping chambers and do not
require seal flush. Diaphragm and magnetic-drive pumps
may be familiar options. However, new to the field are
eccentric movement pumps that better fit some applications
that are not suitable for the former pump styles.
Most processors realize that water is becoming a valuable
(and increasingly expensive) natural resource. Water is a
visible expense as the county, city or other sources that
provide it are passing onto the processor the costs to supply
and then treat the water. If the processor treats the water,
he can determine the energy usage and costs for this. For
an example, a processor who handles sweeteners in the
confectionary industry has calculated that his plant’s total
cost for water used in flushing seals was more than $10,000
per year/per pump.
In another case, a processor that makes sauces in the
Southeast United States was faced with a permit cost of
more than $400,000 if additional water was to be used in
the plant. The reason is if water is used over and above the
limit, the county must expand its water-treatment capacity.
The project was canceled because of this reason. Whether it
is a per-pump water use cost or permit cost, new options
to negate the use of water means less energy used to
supply and treat the water, as well as other costs that may
be incurred.
The eccentric movement or eccentric disc design for
sealing pumps is an alternative to the magnetic drive or
diaphragm, no-flush options. The eccentric movement
sealed pumps do not use mechanical seals and, therefore,
seal flushing is not needed. Compared to magnetic drives,
the eccentric movement designs can also be configured
in a hygienic/sanitary design, employed in semi-abrasive
applications, and at the same time avoid heat build.
The eccentric movement pump is one of the few nonpulsing
positives displacement pumps that negates the
use of dynamic seals. In most cases, this pump is driven
by standard rotating drives. This drives the shaft within
the pump with a coupling. However, unlike most pumps,
the shaft is machined on different planes so that the drive
end of the shaft is on a different plane than the tip that is
driving the pumping mechanism (See Figure 2 — Mouvex
C-Series pump cutaway).
Attached to the shaft are bearings and both are enclosed by
a hermetically sealed metal bellow or rubber boot. As the
shaft rotates, the metal bellows or rubber boot (See Figure
3 — Mouvex S Series pump boot and exploded view) does
not rotate thanks to the bearings. Instead, it flexes in an
eccentric motion. This flexing is very minor and within
the elastic range of the stainless steel so that preventive
maintenance (PM) inspection is recommended at 150
million duty cycles, meaning for some applications a PM of
every 5 years is more than adequate.
The actual pumping mechanism is similar to the peristaltic
effect of hose pumps, but this pump does not use hoses, so
it does not fall victim to any of the possible issues associated
with them. The disc of the pump is driven by the eccentric
movement of the shaft, which produces a peristaltic effect
on a channeled cylinder. Product flows in an inner and
outer pumping chamber, producing fully complementary
flows. The pump, therefore, does not produce pulsation.
Since this pump does not depend on clearances for
operation and, in fact, takes up clearance that could be
generated by wear, the pump has no measurable slip.
With no mechanical seal, there are no surfaces on which
products, such as corn syrup, liquid sugar, glucose or any
number of difficult-to-seal fluids can crystallize, adhere, and
subsequently damage the seal. Therefore, with no dynamic
seal the need for flush water to remove these products
is eliminated.
Why Discard What You Already Pumped?
The eccentric movement pump concept goes beyond
resolving broader efficiency issues from just a water or
seal-flush use perspective. During the production cycle of
a traditional pumping system, startup and shutdown are
highly inefficient because:
n The pumping system is not stabilized, so the product
being pumped is not to specification and must be
re-worked or treated for waste.
n For most pumps, once the inlet tank is empty and the
pump loses prime, the discharge line remains full of
product and also becomes a loss.
It is clear that pumping a product and then not using it is
a very inefficient use of resources. Disposing or treating this
unsuitable fluid further adds to this inefficiency.
Efficiencies When Starting A Process
Since it has essentially no slip, the eccentric movement
technology is able to produce a stabilized and usable
product flow much earlier in the startup process. This
compares with pump styles that have slip and require
a control system to adjust and compensate. As a field
application example, companies that use spray-drying
processes find this to be the case in their operations.
Typically, processes of this nature begin on water for
calibration and stabilization. The water is then replaced
with actual product. However, a process upset occurs when
this change occurs. The degree to which a pump has no slip
and can maintain constant flow during the transition is
related to how the process retains stability and product
losses are minimized during transition. In the case of spray
driers, much like shower heads, if flow changes the spray
pattern changes, rendering differences in the product and
possible rejection.
Efficiencies When Ending A Pumping
Process
On completion of a process, the residual product left in
the pump discharge line also represents an opportunity for
cost savings by improving product recovery and reducing
treatment needs for lost product.
In another field application example, a company that
produces coffee extract was able to recover an additional
400 pounds of product at the end of each run because
even after the feed tank was empty, the pump continued
to effectively pump air, thus helping purge the line.
Pumps that are able to run dry and continue to generate
air pressure on the discharge to purge the product out of
the discharge line are considered to produce a compressor
effect. The pumps that employ the eccentric movement
principle such as the Mouvex® pump, produce this
compressor effect. When considering the effect of efficiency,
recovering 400 pounds per run meant:
n Resources did not need to be used in treating it as
waste.
n All the resources to produce it were not lost.
n Resources would not be used to reproduce the lost
coffee extract.
The additional indirect efficiency issue was that coffee
extract was very aggressive on mechanical seals and
required advanced seals or water flush. Mouvex eccentric
movement technology, with its seal-less design, also helped
in this application because resources were not expended for
seal water.
Putting It All Together
While it is important to consider the direct efficiency
parameters of a pump, such as the amount of product
pumped per unit energy consumed, considerations should
include the indirect efficiency consequences of pump
technology selection. The issues of periphery services to
the pump—such as seal water, or consequences of the
pump design, such as the amount of product loss and waste
treatment costs—all combine to create the true efficiency of
the product-transfer process.
Wallace Wittkoff is the Hygienic Director for Dover
Corporation’s Pump Solutions Group (PSG™). He can be reached
at (502) 905-9169 or Wallace.wittkoff@PumpSG.com. PSG is
comprised of six leading pump companies—Wilden®, Blackmer®,
Griswold™, Neptune™, Almatec® and Mouvex®. You can find
more information on Mouvex at www.mouvex.com and PSG at
www.pumpsg.com.
Beyond Seal-less: Leak-Free Pumps Come Of Age
Critical design improvements enable EnviroGear® to deliver on the promise of seal-less pump technology
Introduction
Twenty years ago, the managers of a wide range of manufacturing and liquid-storage facilities would not have been incorrect if they thought that the industry was about to enter “The Age of the Seal-less Pump.” With stricter federal emissions regulations set to be introduced in 1992, this would have been welcome news for those in the petroleum refining, petrochemical, gas processing and chemical industries where the use of hazardous/toxic materials or other pollutants was prevalent. Faced with tighter control guidelines for these types of emissions, plant and storage-facility operators needed a pump technology that could deliver the environmentally sensitive leak-free operation they demanded, while at the same time addressing maintenance and cost concerns.
Extensive documentation existed to support the thesis that seal-less pump technology was the answer in these applications. For example, in June 1990, Vista Strategies, Inc., a management-consulting firm, produced a report for a leading manufacturer of industrial gear drives, pumps and compressors that predicted, among other things, that:
• The Best Available Control Technology (BACT) for most
refining, petrochemical and chemical plants will be
seal-less pumps.
• The chemical industry is moving to use seal-less pumps
at a faster rate than the petroleum industry.
• The seal-less market will be served two-thirds by
magnetic-drive units and one-third by canned-
motor units.
• The long-term answer to the new federal regulations
will be seal-less pumps.
And, perhaps most significantly:
• Seal-less pumps will take an increased percentage of the
market – probably 25% by 1995 and 50% by 2000.
A year earlier, a report titled “An Overview of BACT Guidelines For Centrifugal Pumps” was prepared by the South Coast (California) Air Quality Management District which noted the No. 1 BACT in terms of efficiency in controlling emissions in liquid-handling applications was seal-less pump technology, which was “becoming increasingly important, especially in the handling of toxic and hazardous fluids.”
Looking back, we know now that 1990 did not signal the beginning of the golden age of seal-less pumps. The simple fact was that the technology – as it was designed and constructed at the time – wasn’t reliable enough, with too many instances of failures that were brought about by bearing and load deficiencies that led to seal and leakage issues. These deficiencies created an operational stigma that many manufacturers of seal-less pumps are still attempting to overcome today.
But, after all that time, there now exists an innovative
seal-less pump technology available that eliminates the bearing and load concerns that were affecting the performance of traditional seal-less designs. This technology has the capability to create a new category of seal-less gear pump that not only eliminates leakage concerns that can compromise safety for both plant personnel and the environmental, but also allows the operator to move all types of liquids, from the thin to the extremely viscous,
and the hazardous to the benign.
This white paper will show how a fresh, clean-sheet approach to the conundrums inherent in traditional
seal-less pump design were confronted and led to the creation of the EnviroGear® line of seal-less gear pumps.
In short, EnviroGear pumps take product sealing to a new level of reliability while eliminating the unacceptably high ownership, maintenance and environmental costs – as well
as the reputational taint – that have dogged past seal-less
pump designs.
The Challenge
The leakage that occurs in traditional mechanically sealed pumps results in two types of prohibitive costs for plant operators: maintenance and environmental.
According to The Hydraulic Institute, as much as 40% to 50% of the cost of owning a pump is spent after the pump is bought, due to maintenance issues. The leading causes of high maintenance in conventionally sealed pumps includes the maintenance associated with mechanical seal replacement and the premature wear of the bushings and close-fitting metal parts due to insufficient support of the pumping elements. There is also an environmental cost of leakage in terms of cleanup and potential local, state or federal fines that may need to be paid in extreme cases – as well as the often-incalculable cost that bad press can result in.
The main point is that leaks cost money. It costs money to replace the raw materials that are lost. It costs money to replace the finished goods that are damaged. It costs money to pay a firm to clean up the spill. It costs money to dispose of the cleanup. It costs money in potential slip-and-fall hazards. It costs money to pay environmental-compliances fines and fees. And it costs money in lowered worker morale, or the need to replace workers who may choose to seek employment elsewhere.
As mentioned, any pump design that is deemed to be “seal-less” needs to overcome the stigma that has been attached to the technology for more than two decades.
In fact, while the reports cited above were trumpeting the use of seal-less pumps, efforts began almost immediately to discredit the technology’s effectiveness and reliability when handling hazardous or toxic materials.
A report entitled “Meeting Emission Regulations with Mechanical Seals” released in April 1990 by the Seals Technical Committee of the Society of Tribologists and Lubrication Engineers (STLE) stated that “eliminating seals in pumps is not the solution to emission controls.” The standards committee included seven leading seal manufacturing companies working in conjunction with chemical company clients. The report went on to say “seal-less pumps seem like the perfect solution but rely on bearings being lubricated by the product being pumped. Thus, bearing problems result from converting to seal-less pumps.” The seal manufacturers effectively removed
themselves as the weak link and focused on the perceived, and sometime real, bearing issues.
The report listed a number of perceived problems that were present when relying on the product being pumped for lubrication, including: the oftentimes poor lubricity of the pumped product; high instances of costly downtime for in-shop repairs; and the elevated chance that leaks will still occur, which exposes plant personnel and the environment to the pumpage. As pump manufacturers rushed their seal-less offerings to market, an overzealous sales force misapplied or over-applied their product. Initial failures, most common among high-speed centrifugal manufacturers lent credibility to the seal manufacturer’s warnings. End-users became cautious; those burned would hesitate to consider seal-less technology again.
Then, most damningly, the report concluded: “Obviously, there is questionable, if any, benefit (of using seal-less pumps) to the end-user who is genuinely concerned with the environment and his personnel.”
Times Have Changed
(as have Seal-less pumps)
Traditionally, seal-less gear pumps are designed with a cantilevered load where a large rotor gear is attached to the end of the pump shaft. As hydraulic force is applied to the rotor during pump operation extra pressure is put on the shaft and bearings. This pressure can lead to shaft deflection and increased bearing wear, which in turn results in more rotor-to-casing or rotor-to-head contact wear. The result is reduced pressure and flow rate.
Secondly, traditional seal-less gear pumps feature two fluid chambers – a hydraulic chamber where the gears work and a second chamber for the mag-drive coupling unit – that are joined together by a bracket, which also serves as a barrier between the two chambers. This complicated design requires that a portion of the material being pumped through the hydraulic chamber must be used to cool the magnets in the other chamber. These requirements result in a long, complicated pump with elongated, narrow flow paths and the need for more parts which makes the pump more expensive and difficult to maintain – while limiting the viscosity of the liquids that can be pumped, as well as the types of solids that can
be handled.
The Solution
The approach to finding an ultimate solution to the seal-less pump quandary had to remove the word “seal-less” from the development process. When looking to create a gear pump that is affordable, controls leaks, and reduces maintenance costs and environmental concerns, the first step is to identify the areas where seal-less pumps fall short and look to improve on them. As mentioned, the No. 1 area where traditional seal-less pump operation is compromised is the bearings and how they interact with – and are affected by – the pump’s cantilever load. The second step is to find a superior replacement for the
two-fluid-chamber design that complicated the pump’s operation and limited its fluid-handling range.
Taking these main concerns into account, and approaching the design process with an open mind, the result is the EnviroGear® pump. The EnviroGear pump line is seal-less, not because the designers and engineers felt that it needed to be, but because its design enhancements led them to the conclusion that it would operate most effectively as a seal-less pump.
The EnviroGear pump also features two design enhancements to overcome long-time challenges of excessive bearing wear and a fluid chamber design that complicates operation and limits product range. These enhancements are:
• Between-the-Bearing Support System: As opposed to the performance-robbing, one-sided
support found in cantilevered-load design that exists
in traditional seal-less pumps, the EnviroGear® pump
supports the rotor and idler gears at three locations
through the creation and incorporation of:
- A patented Eccentric Spindle that is supported in
the head, the crescent location and the back of the
containment canister, eliminating much of the
effects of cantilever load. In tests where 200 psi of pressure was applied to the rotor, there was only
0.005" of shaft deflection in the EnviroGear pump,
compared to 0.056" of shaft deflection in a
traditional seal-less pump, giving the EnviroGear
11 times less shaft deflection.
-
Larger diameter materials that provide more rigid
support for less shaft deflection and bearing wear.
For example, a traditional 3-inch seal-less pump will
have a shaft that is 17⁄16" in diameter; the
diameter of the EnviroGear eccentric spindle is 2".
-
Large, long radial bushings that support the entire
length of the rotating element, which spreads out
the hydraulic forces and allows the bushings to last
longer. The EnviroGear bushings are also made of
premium-grade carbon graphite that will last up
to eight times longer than more common
bushing materials.
• One-Fluid-Chamber Design: As noted earlier,
traditional seal-less pump design features two fluid
chambers that are separated by a bracket; this design
creates operational difficulties while limiting the types
of fluids that can be handled. The EnviroGear design
has only one fluid chamber with the pump’s magnets
placed on the back of the rotor and close-coupled, or
“piggy-backed,” on the rotor gear. This design gives
the pump a much shorter, simpler flow path. It also
allows the pump to easily handle viscosities in the
20,000 to 30,000 cP range, and as high as 50,000
cP, while still
maintaining the
ability to run thin
liquids like caustics
and various solvents.
These redesigned
pumps can also
pump liquids and
slurries that
contain solids.
A third feature that the EnviroGear offers is dimensional interchangeability. EnviroGear pumps have been designed to be interchangeable with 95% of the other gear pumps that are currently available in the market. This means that a plant can be running a traditional sealed pump in the morning, have it pulled out in the afternoon and drop an EnviroGear pump into the footprint while reusing the same piping, gear box, motor and base plate, all while receiving the same hydraulic performance as what the previous pump was providing.
While the EnviroGear pump is designed to eliminate all of the operational concerns found in old-style seal-less gear pumps, its simple design – which consists of only seven primary parts: a magnet housing, containment canister, casing, rotor magnet assembly, eccentric spindle, idler gear and head – greatly reduces maintenance and environmental costs.
Conclusion
In the end, the design of EnviroGear Seal-less Gear Pumps makes it not a traditional seal-less pump, but, rather, an engineered solution for environmentally conscious fluid-handling that lowers maintenance costs and eliminates environmental costs. The result is a new genus of seal-less gear pumps, one that does away with the operational shortcomings that helped stigmatize past seal-less pump designs while remaining cost-effective for the end-user. EnviroGear Seal-less Gear Pumps truly are the Best Available Control Technology on the market today for a wide variety of industries and fluid types, and truly deliver on the promise that mag-drive seal-less pumps seemed prepared to offer the fluid-handling industry more than
20 years ago.
Dale Evers is the Director of Business Development – Engineered Products for the Pump Solutions Group (PSG™), Downers Grove, IL, USA. He can be reached at
Dale.Evers@PumpSG.com. PSG is comprised of seven leading pump brands – Almatec®, Blackmer®, EnviroGear®, Griswold™, Mouvex®, Neptune™ and Wilden®. You can find more information on EnviroGear at www.envirogearpump.com.
Timing Is Everything
In the world of business, much like in everyday life, timing is everything. It can be one of the most critical factors to the success or failure of any company. And more often than not, every company experiences unexpected events, setbacks, and generally, just bad timing.
This was the case for a subsidiary of one of the world’s largest metallurgical coal producers for the global steel industry when, in summer 2010, the U.S. Environmental Protection Agency (EPA) informed the manufacturer that the current operating facility that was housing its centrifuge was no longer up to code and meeting current safety requirements. An upgraded facility would need to be constructed and the centrifuge transferred to this new location. As a major manufacturer of blast furnace and foundry coke, the Alabama-based subsidiary operates three batteries with a total of 120 coke ovens that produce approximately 460,000 tons of coke each year. The company is also a major producer of industrial coke, egg coke, buckwheat coke, nut coke, light oil, and coal tar. So needless to say, building a new facility for the centrifuge and moving the operation to this new location without effecting productivity was going to be no small feat. And to make matters worse, this all had to take place within a few months to meet EPA deadlines. Not only would the new facility need to be built from the ground up, but every part of the project needed to be up and running as quickly as possible to avoid any downtime and loss in production. This included replacing the centrifuge’s pumping equipment, which plays a critical role in the coke manufacturing process. These heavy-duty pumps remove the harmful by-products from the centrifuge that result during production. Many of these byproducts are then pumped out of the facility where they go on to play important roles in a variety of other industries, including the extremely corrosive ammonium sulfate that is used throughout the fertilizer industry as an ammonia source.
With time working against the coke manufacturer and the EPA’s deadlines fast approaching, the manufacturer turned to their “pump guy,” Matt Gentry, a Sales Representative for Pumping Systems, Inc., located in Pelham, AL.
“I knew it was only a matter of time before they would be required to build a new facility, the old one was falling apart and crumbling,” explains Gentry. “So after the EPA came in, I knew I was going to be working with a tight deadline and the project had to be completed very quickly. The old building was in such bad shape the new building had to get up and running fast.”
Ultimately, the coke manufacturer was relying on Gentry to determine what type of pumps were needed, get the pumps delivered, installed and running smoothly in the shortest amount of time possible. To get this accomplished, Gentry first had to determine how the piping would need to run from the centrifuge to the pumping equipment. Secondly, he had to verify the correct pump losses and flow rates that would best suit the application. “After taking a closer look at the project and determining what type of pumps would fit best, I gave this information to the manufacturer. But for whatever reason, they kept dragging out giving me the pump order. And when I did receive the order, it had to be completed even quicker than I had expected,” says Gentry.
When considering that the project was running short on time and the pump installation would need to take place in the upcoming weeks, Gentry immediately contacted Steve Cox, the Southeast Regional Manager for Griswold™ Pump Company. Not only was the EPA’s deadline nearly upon them, but the pumps would need to be installed quickly to avoid any stoppage in production when the centrifuge was moved to the new facility. When Cox arrived on the scene, he immediately contacted Griswold’s manufacturing facility and ordered Griswold 811 Series ANSI Centrifugal Pumps constructed with CD4MCu material, which is a higher-grade material and ideal for this type of application.
“Griswold was able to produce the pumps and get them out within four days of the order. After delivery time, it was about a week from order to delivery, going all the way from California to Alabama. The manufacturer received the pumps, put them in service and they run great. Everyone was so happy, and actually the facility then ordered additional spare units for future use,” explains Gentry. “As a distributor, I really appreciate the sense of urgency that Griswold understands is necessary.”
Grundfos launches wastewater pump with unique technology
S-tube offers a combination of new technology, high efficiency and reliable operation. Today, the pump is presented at the IFAT wastewater fair.
The new S-tube is the answer to a major challenge. So far, wastewater pumps have been a compromise between free passage to obtain reliable operation and high efficiency to obtain low operational costs. Grundfos now uses a completely new technology to create a pump that ensures low costs for operation and maintenance.
- As the population is growing, efficient and energy-efficient wastewater handling is becoming increasingly important. With our new S-tube we can offer our customers a unique solution when designing pump systems and wastewater solutions, says Peter Røpke, Group Executive Vice President for Business Development, from the presentation of the new S-tube at the IFAT wastewater fair.
Complete product
The new S-tube is marketed today as part of a completely new pump series. During the second half of 2012, additional S-tubes will be launched in smaller pump sizes. The remaining part of the product series will be continuously expanded with several sizes and models.
In addition to the unique combination of a closed impeller with large free passage and high efficiency, the pump is fitted with the energy-efficient Grundfos blueflux motor technology, and thus, it already meets the efficiency requirements that are expected to be introduced for wastewater pumps in the coming years. In addition, great thought has been put into the design to ensure that the pump is easy to service. When you combine the Grundfos wastewater pumps with Grundfos’ control and surveillance systems, you end up with the intelligent, Autoadapt, which automatically ensures optimum operation, even under changing conditions.
- We have created a very attractive and competitive product that matches a wide variety of applications. Therefore, the S-tube will be the obvious choice when specifying wastewater projects of all sizes in the future, Peter Røpke explains.
Product and expertise are inter-connected
Access to clean drinking water, disposal of rainwater and wastewater handling are growing challenges all over the world. Therefore, Grundfos opened a global competence centre in Copenhagen in the autumn of 2011 with regional clusters across the world. The objective is to contribute with sustainable and innovative solutions that may help solve the world’s water problems. Peter Røpke emphasises that, in this connection, the new S-tube will play an important role.
- The combination of our new product and our dedicated employees all over the world are the key to create great results within the wastewater area, he says.
Grundfos hits its record of dimensions
The largest wastewater pumps in Grundfos’ history will take almost an entire year to manufacture and deliver.
Grundfos in Saudi Arabia recently landed an order for the largest wastewater pumps in Grundfos’ history. 4 x 3000 HP (2200kW) pumps were chosen as part of a €2.9m big strategic pumping station project by Dammam Municipality in the Eastern Province of Saudi Arabia.
Good relationships
Senior Sales Manager of Water Utility, Luay Al Toussi explained that Grundfos first heard about this project at the very early concept design stage and were asked by Dammam Municipality to support the design as well as offer guidance and assistance.
- Working very closely with the main consultant SAUDICONSULT we used our local relationships and our local and international technical skills and competence to gain a major advantage over the competitors, Mr Al Toussi explained.
When it came to the offer/quotation stage, Grundfos were in a very positive position because of the deep involvement in the entire process.
- This is a great example of how a local and global team can work together to deliver outstanding results, said Mr Al Toussi.
New Ingersoll Rand UP6 Rotary Screw Air Compressor Features Enhanced System Controls
Small, single-phase units include run-on timer for optimal performance and reliability
Davidson, N.C. — June 18, 2012 — Ingersoll Rand, a world leader in creating and sustaining safe, comfortable and efficient environments, is offering a newly improved single-phase control scheme for its 5 and 7.5 versions of the small UP6 5-15c line of air compressors.
Ingersoll Rand HOC Dryers Now Available with an Air-Cooled Configuration
HOC air-cooled dryers allow for more cost-savings and flexibility on the job