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.

Grundfos CRH Pump

Changing A Mechanical Seal

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.   

 

The UP6 single-phase compressors are versatile compressors, ideal for small manufacturing shops, vehicle services environments, paint booths and general industrial applications up to 28 cfm. With food grade coolant and cleanup equipment, these compressors are also ideal in small food and beverage applications. Ingersoll Rand has added a run-on timer and load/unload and blowdown solenoids to improve the reliability and performance of single-phase units in these applications.  

 

A compressor that does not include an enhanced control scheme can easily be misapplied and fail in an environment where the compressor starts and stops too many times per hour. The Ingersoll Rand enhanced control scheme allows the compressor to operate unloaded with the motor continuing to run for the appropriate length of time, ensuring that the reliability and performance of the system is protected. 

 

“Having a compressor start and stop too many times an hour is not good for the machine, and increases the chance for motor capacitor failures,” said Matthew Smith, Americas region commercial rotary product manager for Ingersoll Rand. “The enhanced control scheme on the Ingersoll Rand UP6 5 and 7.5 single-phase machines is designed to keep the motor continuously running for at least six minutes. This enables the system to protect itself from damage caused by inadvertent misapplication. It also increases the product’s longevity, reliability and performance.” 

 

The enhanced controls will also be available as an aftermarket kit for existing units. For more information on the Ingersoll Rand UP6 5-15c line of rotary screw air compressors or to find a local dealer, visit ingersollrandproducts.com. 

 

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About Ingersoll Rand

Ingersoll Rand (NYSE:IR) advances the quality of life by creating and sustaining safe, comfortable and efficient environments. Our people and our family of brands — including 

Club Car®, Ingersoll Rand®, Schlage®, Thermo King® and Trane® — work together to enhance the quality and comfort of air in homes and buildings, transport and protect food and perishables, secure homes and commercial properties, and increase industrial productivity and efficiency. Ingersoll Rand products range from complete compressed air systems, tools and pumps to material and fluid handling systems. The diverse and innovative products, services and solutions enhance our customers' energy efficiency, productivity and operations. Ingersoll Rand is a $14 billion global business committed to a world of sustainable progress and enduring results within our company and for our customers. For more information, visit ingersollrand.com or ingersollrandproducts.com.

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

 

Davidson, N.C. — June 26, 2012 — Ingersoll Rand, a world leader in creating and sustaining safe, comfortable and efficient environments, has added an air-cooled model to the heat-of-compression dryer product line to allow for greater flexibility, energy efficiency and reliability in a low profile package.

HOC dryers turn wasted heat into useful energy, resulting in clean, dry air at a fraction of the cost of traditional desiccant dryers. By using heat produced during the compression process, HOC dryers can deliver instrument-quality air using virtually no energy.

The air-cooled model is an extension to the water-cooled HOC dryer released last year. These new models deliver Class 2 (-40 °F) air for customers that do not have a water source available yet desire the energy efficiency benefits afforded by the new HOC dryers. The unit is also flexible and can be connected to as many as three oil-free compressors, reducing footprint requirements and installation costs.

“With the formal introduction of the air-cooled models, the HOC product line is complete,” said Scott Hardeman, marketing manager for the customer center and AIRD channels at Ingersoll Rand. “The new addition offers flexibility for either air- or water-cooled operation to meet customers’ specific application requirements to maximize energy conservation and savings.”

HOC dryers feature smart control technology to maximize savings under all operating conditions. By monitoring inlet process air conditions, smart control technology adjusts dryer operation to deliver consistent, dry air and helps maximize dew point and temperature spikes. The advanced air-cooled HOC model offers superior dew point performance by providing constant -40 degrees °F pressure dew point under all load conditions.

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About Ingersoll Rand

Ingersoll Rand (NYSE:IR) advances the quality of life by creating and sustaining safe, comfortable and efficient environments. Our people and our family of brands — including Club Car®, Ingersoll Rand®, Schlage®, Thermo King® and Trane® — work together to enhance the quality and comfort of air in homes and buildings, transport and protect food and perishables, secure homes and commercial properties, and increase industrial productivity and efficiency. Ingersoll Rand products range from complete compressed air systems, tools and pumps to material and fluid handling systems. The diverse and innovative products, services and solutions enhance our customers' energy efficiency, productivity and operations. Ingersoll Rand is a $14 billion global business committed to a world of sustainable progress and enduring results within our company and for our customers. For more information, visit ingersollrand.com or ingersollrandproducts.com.

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Food Applications In The Vacuum Pump Industry

It seems there are as many applications for vacuum pumps in the food industry as there are different foods to eat. From meat packaging that evacuates the air out of a plastic package (4 torr) to improve shelf life to protein dryers that process meat byproducts to isolate their proteins for use as food or dietary supplements. The product which has been broken down using various chemicals, is heated and vacuum is applied to dehydrate it for storage and packaging. Because the product is degraded by excess heat, vacuum is key in efficient processing (28”HgG).

In the poultry industry the product is first eviscerated using vacuum (25-28”HgG), can then be marinated under vacuum 28”HgG, the partial vacuum applied opens the pores of the meat allowing the marinate to completely penetrate in as little as 15 minutes, and then finally packaged under vacuum.

Evaporation is a very common process in the food industry. It describes a process where water is evaporated or “flashed off” of various liquids in order to condense them or ultimately convert them from liquids into solids, usually in the form of a powder. By controlling the temperature and pressure (or absence of) in the evaporator, the vapor pressure of the water in a product can be reached, causing some of the water to change phase from a liquid to a vapor. This water vapor is then pulled out of the evaporator, through a condenser, and into the vacuum pump. When this occurs, the solids are suspended in the remaining water, but now in a more concentrated solution.  In some types of evaporators, called multi-effect, this concentrate is evaporated several times resulting in a very concentrated end product.

There are several types of evaporators including the falling film, rising film, plate and circulation.  A falling film evaporator (Pictured below) is used in the production of dairy & juice products, milk concentrates and powders, whey products, sweetened and unsweetened condensed milk and evaporated milk.

Some basic concepts that can be learned with this example are that evaporation &  drying are most energy intensive, i.e. the addition of heat.  Vacuum accelerates the evaporation process, i.e. the boiling point of the solution is reduced by the lower pressure & resulting vapor. In the case of processing cheese whey a multi-effect evaporator is used in converting the watery liquid into a thick slurry which can then be spray dried into a powder and packaged in snacks. The whey solids are very high in protein and certain nutrients, and are resold for use in candy, cattle feed and nutritional supplements.

Pump selection is based on a common operating pressure of 27-28”HgG, and capacity is usually selected by two factors; what a desirable time frame is for hogging down the evaporator, and what the gas load will be once the evaporator is at normal operating conditions. Many times, these considerations result in a dual system, with two identical vacuum pumps which can be run together for hogging, or individually for holding. Common pump sizes are 10-25Hp two-stage liquid rings.

Pump down formula does not consider any type of friction loss from the vacuum pump to the chamber:

S=V/T In (P1/P2) Where S is pump speed in acfm, V is volume of chamber in cu/ft, T is time in minutes, In is the natural log, P1 is the starting pressure and P2 is the final operating pressure measured at the vacuum pump inlet.  What size pump would be required to evacuate a 20cu/ft chamber from 760torr to 50 torr in 3 minutes;

20/3 In (760/50) = 18.14acfm

Liquid Ring Designs

Today two main types of liquid ring vacuum pumps can be found, the radial flow or conical pump and the axial flow or flat port plate pump. Inside the two main designs three main types of liquid ring vacuum pump sub-designs can be found, the true single stage, the single stage variable port plate and the two-stage pump design.

The true single stage axial flow design is pictured above with its large inlet port on the right and smaller discharge port pictured on the left side.  It features a suction port, impeller and discharge port. The final vacuum the pump can achieve is designed through the distance between the inlet and discharge port. True single stage pumps can achieve roughly 26"Hgv or 4"HgA and if the discharge is roughly atmospheric, say 30"HgA then the compression ratio is 30:4. As the gas enters the pumps inlet its conveyed and compressed until it reaches the beginning of the discharge port where almost all of the gas is then exhausted. Of course not all of the gas escapes and some finds its way back to the pumps inlet where it re-expands to the operating pressure.These rough vacuum pumps are one of the most durable pumps ever made and are used on a multitude of rough and wet vacuum applications.

The single stage variable port plate design is only available with the axial flow pump. It's construction includes the suction port, impeller and a valved discharge port shown above. If the final vacuum is determined by the total distance between the inlet and discharge port, then increasing the distance between them is the solution to increasing the compression ratio. The variable port plate only allows as much air to discharge as required while maintaining good efficiency through out the low pressure curve. In general a single stage flat port plate liquid ring vacuum pump can achieve 28.9"HgV or roughly 1"HgA and with an atmospheric discharge our compression ratio is roughly 30:1. As the gas is conveyed and compressed it enters the discharge area but it's not allowed to escape all at one time (as with the true single stage) as the port plate has multiple small slots (as shown below) that are covered by individual teflon valves. As the gas enters the compression cycle, only the valves that need to react will operate creating a more efficient Hp/cfm ratio, and lower service liquid usage than traditional designs. The final horizontal port is not valved as this is the final fail safe for all the gas to be exhausted before intake is reached in the compression cycle.

The third and final liquid ring is the two-stage design pump wich uses two impellers in series to achieve a final pressure of 28.9"Hgv. The first stage is 3 times as large as the second stage and if we assume the first stage has a displacement of 100 and the second stage has a displacement of 33 then our staging ratio is 100/33 or 3:1. For example, if our pump is "blanked off" generating the best vacuum it possibly can produce, then our compression ratio can be said to be roughly 30:1. The theoretical interstage pressure is then found by examining the 1st stage inlet pressure and the final stage discharge pressure, or in our example 5.5:1.  Some two-stage liquid ring pumps can be favored over single stage valve and conical pumps for increased capacity per Hp at approximatly 27"Hgv to 28.9"Hgv.

Two-stage liquid ring machines should not be operated below 27"Hgv due to the designed staging ratio of the pump. For example,assume the pump is now operating at 20"HgA at the inlet and maintain our 30"HgA discharge condition as before, then our compression ratio becomes 30/20 or 1.5r. The first stage displacement of 100cfm/1.5r = 67cfm discharge into the inlet of the second stage, which carries a displacement of 33cfm, so our capacity can be choked by the 33cfm second stage limitation and over compression results. The interstage pressure may be found by examining the inlet pressure and staging ratio, or 60"HgA at the interstage. Interstage bypass valves are available to compensate for operating pressures above 27"Hgv to relieve over compression and reduce the operating horsepower.

Laboratory Vacuum Pumps

Most Laboratory vacuum applications operate at partial vacuum levels between 1 Torr and 277 torr(29.88"HgV & 19"HgV). This pressure range is where most common lab applications operate and also represents the rough range of vacuum.

Common lab applications can be defined as vacuum filtration, liquid aspiration and similiar applications that use vacuum to move liquids and are best served in the 60- to 277 Torr range. Partial vacuum below 60 torr can be detrimental to filtration and aspiration applications as vapor pressure concerns come into play. If the partial vacuum is allowed to move as low as the vapor pressure rating of the material this will result in the evaporation of the filtrate and can prove unfavorable for both the application and the vacuum pump. These common laboratory applications are typically served by a "House Vacuum System" or HVS, and can be designed to operate anywhere in the 60- to 277 Torr range.

Laboratory applications including evaporation, distillation, gel drying, and vacuum ovens require a partial vacuum range of 1- to 60 Torr. HVS can also be designed to accommodate these requirements. This pressure range crosses into the use of smaller individual laboratory vacuum pumps and is a perfect fit for dry diaphragm pumps.

Drying/freeze drying, molecular distillation, and glove box applications all require a partial vacuum from 1- to 10-3 Torr. These low pressure applications cannot be served by the typical HVS but require the use of 2-stage oil flooded rotary vane vacuum pumps.

Gas chromatography/mass spectrometry (GC-MS) type lab applications require a partial vacuum as low as 10-8 Torr and are served by turbo-molecular vacuum pumps.

Definition:
SCFM is measured at standard conditions (Air at 68F, 29.92"Hg or 14.pais)
ACFM is measured at actual inlet conditions

When sizing for typical medium sized labs, as a rule of thumb, use 1.0 scfm per outlet and a 50% usage factor. Because the majority of vacuum pump manufacturers rate their vacuum pumps capacity in ACFM a simple method of converting these flow rates has been developed in the lab vacuum industry. The method is based on Boyle's gas law which describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system.

Example: A small laboratory vacuum system requires 20scfm of air at a partial vacuum level of 25"HgV at sea level, convert the mass flow rate to a volumetric flow rate and select a vacuum pump. If the pressure in the system decreases then the volume of the gas occupied will increase proportionally according to the following formula:                                                      P1V1=P2V2

                                                V2= 29.92x20/4.92 = 121.6acfm @ 25"HgV
                                                V1= 4.92x121.6/29.92 = 20scfm @ 25"HgV

Pump Selection: After determination of the pressure and flow required for the house vacuum system, specific application requirements need to be considered before final pump and system selection including;

1. A close look at the process constituents may include simple water, saline or biological media thats non-corrosive but very wet. Another application may include more corrosive material such as bleach and require a thorough examination of the pump system construction, its operating fluids if applicable, pre-filters or condensers/traps may may have to be evaluated. Pre and discharge manifold arrangements including discharge drains may require consideration.
2. Where is the vacuum pump system to be installed? Is there an area classification? It's hot in Houston and it's well known that heat is a major enemy of mechanical and electrical equipment. That mechanical room that used to be 75 degrees back when there were only 3 or 4 pieces of equipment in it keeps growing, and the ambient temperature right along with it. Consider the type of vacuum pump technology, can the technology be water cooled? does the facility offer chilled water? It's estimated that for every 15 to 18 degrees F above the maximum rated operating temperature (180F) of oil in a rotary vane vacuum pump, the oil degradation rate doubles. As a rule of thumb regarding electric motors, for every 18 degrees F rise above the highest allowable stator winding temperature reduces the motor insulation useful life in half.
3. Other factors such as space requirements, operating sound levels and operating budgets must also be considered.

Common HVS Vacuum Pump Types:

1. Oil sealed liquid ring vacuum pumps use light weight oil in the pumping chamber to create compression. They are one of the most reliable vacuum systems available and be configured for air or water cooling. Liquid ring pumps operate with the lowest sound pressure compared to any other vacuum pump available in the market today. Pump operating temperatures can be selected form 165F to 190F in order to match the expected gas load to be handled. Since the oil in the compression chamber is not used as a lubricant, it can easily last for one year or more before an oil change is necessary. Oil can be selected to include anti-wear, anti-oxidants, and corrosion inhibitors to tolerate many mild corrosive gas and vapors. Liquid ring pumps are capable of producing pressures as low as 28.9"HgV (25.9 Torr) and can discharge up to 30psig with an atmospheric inlet depending on the pumps configuration. Pumps are available as either single or 2-stage designs depending on the pressure/capacity requirements and use single acting mechanical shaft seals.
2. Water sealed liquid ring vacuum pumps use water in the pumping chamber to create compression. They are one of the most robust vacuum systems available and can tolerate up to 1/4" soft solids and large condensable loads. These systems can be configured as once through or total recirculated seal fluid to meet the application and customers requirements. Liquid ring vacuum pump systems also offer very low operating sound pressures. Water sealed liquid ring systems offer the coolest operating temperatures compared to any other vacuum pump in its class featuring near isothermal compression. Pumps are available as single or 2-stage designs to meet application requirements and use single acting mechanical shaft seals. Water sealed liquid ring vacuum pumps are capable of producing pressures as low as 28.9"HgV (25.9 Torr). Pump construction is available in cast iron, CI/stainless or all 316 stainless steel to handle very corrosive gas and vapors.
3. Oil flooded rotary vane single stage vacuum pump systems can produce a partial vacuum as low as 1 Torr. Due to their internal design these pumps should only be selected for applications that require lower pressures from 75 Torr to 1 Torr. When operating oil flooded vacuum pumps above 75 Torr you can expect the pumps operating temperature to be hotter than normal. The elevated operating temperature leads to a shorter oil and oil mist eliminator life, shorter bearing, seal and vane life expectancy along with oil blowing out the pumps discharge port. In special cases the pump can be water cooled and secondary mist eliminators can be applied to manage the situation. In other situations an auto-purge system may be utilized to help control condensable pump loads from condensing inside the pump and creating vane and cylinder   damage. Rotary vane vacuum pumps are best applied to clean dry applications but over the years have been   adapted to operate beyond their intended capabilities. We want to pay close attention to the pumps rated water vapor handling characteristics before applying this machine to wet applications. Pump construction is cast iron with ductile iron rotor using 3 phenolic vanes, needle bearings and viton lip seals.
4. All of the above vacuum pump technologies can be used in conjunction with a backing blower to achieve a lower working pressure. Rotary claw and liquid ring vacuum pumps can utilize a VFD.
5. Dry rotary vane single stage vacuum pumps can produce pressures as low as 27"HgV. They are constructed of cast iron with ductile iron rotor using up to 6 carbon vanes, sleeve bearings and lip seals. These pumps offer low initial cost but higher life cycle cost than their oil flooded counterparts as vanes must be replaced every 1-2 years of operation. These pumps should not be used in wet applications due to the carbon dust accumulation in the pumping chamber. When the carbon dust comes into contact with water and vapor mist it has a strong tendency to transform into what looks like tiny BB shaped balls that can interfere with the pumps normal operation creating internal leak paths or catastrophic vane failure. Great care should be considered when specifying this technology to protect the pump from wet or dirty pump loads. Dry rotary vane vacuum pumps will produce one of the highest sound levels of any mechanical vacuum pump.     
6. Rotary claw vacuum pump systems offer no fluids in the pumping chamber and up front seems  to allow a more environmentally friendly atmosphere compared to pumps that use oil or other fluids in the pumping chamber. The issue here is that the labyrinth seals are not 100% leak proof and over time oil from the gear box makes it’s way into the pumping chamber. Because there is no “clean up equipment” on the discharge side of the pump hot oil vapor is allowed to discharge directly into the atmosphere. The claw vacuum pump offers an ultimate vacuum level of 27"HgV and can discharge up to 32psig with an atmospheric inlet. The claw pumps operating temperature is hotter (350F> range) compared to pumps with fluids (190F<) in the pumping chamber and generally exhibits a higher sound level as it operates at 3500 rpm. The claw pumps internals are coated with molybdenum disulfide (MoS2) and can tolerate wet and mild corrosive gas and vapors. Because of the claws unique design it performs with the greatest Hp to cfm efficiency (depending on the operating vacuum level) than any other vacuum pump in its class.. Maintenance cost is about the same compared with pumps that use oil in the pumping chamber and still require regular oil changes in the gear box. The claw pump is only available in an air cooled configuration and uses labyrinth shaft seals.

Other HVS pump technologies are available to fit special lab requirements including the scroll vacuum pump
(0.1 Torr) and the twin screw dry vacuum pump (.075 Torr). The screw is available with several types of
protective coatings to handle corrosive gas and vapor. Fixed pitch screw pumps offer high discharge
temperatures that lend itself to handling many acids with low vapor pressures. Variable pitch dry screw
vacuum pumps offer lower discharge temperatures and can successfully pump potentially heat sensitive
reactive gases. Sound levels are high and require discharge silencers.

Vacuum Pressure Flow Through Orifices

Many applications with respect to compressed gas and vacuum require the use of understanding and experience of applying orifices. Applications include pressure and vacuum measuring devices, control valves, anticavitation valves, various material handling processes, agitation of liquids and slurry's to mix, prevent settlement of solids, or accelerate oxidation or fermentation.

The flow of gas through pipes and orifices is usually measured in cubic feet per minute as this is the unit of measure used when designating compressors and vacuum pump capacities. The flow of air may also be measured in linear feet per minute (LFM), usually called velocity. Velocity is the rate of flow past a certain point. Just before a flowing fluid at a certain pressure and temperature reaches the orifice it's forced to converge, creating a higher pressure upstream of the orifice. As the fluid passes through the orifice it expands (velocity reduces) creating a lower pressure on the downstream side. When the flow rate through an orifice is subsonic (velocity less than Mach 1) a reduction of backpressure will increase the mass flow through the orifice until the pressure is lowered to a critical level. At this point of critical pressure differential the flow rate stops increasing all together. The flow is said to be choked, the velocity at the orifice has just reached sonic (Mach 1) and will no longer increase no matter how much further the downstream pressure is reduced.

The relation between cubic feet per minute and velocity is given by the formula: V= FxA
Where  V - Cubic feet per minute

F - linear feet per minute
A - Area of hole or pipe in square feet

Consider a hole 1/10 of a square foot in area and the air is flowing through the hole at a velocity of 500 ft. per minute, then we have a flow of (1/10 x500) 50 cubic feet per minute.

An orifice is a round hole with a sharp edge in a thin plate. There are two types of gas flow through an orifice depending on the pressure ratio as previously mentioned. When the ratio of downstream absolute pressure to upstream absolute pressure is above approximatly .5 (based on air from 0-250F), the flow is subcritical (subsonic) and will vary depending on the pressure. Flow (Velocity) through an orifice will gradually increase until the ratio equals .5, at this point the throat velocity of the orifice reaches the speed of sound (Sonic Velocity) and the flow becomes critical and will remain constant for any ratio below .5. The critical ratio can be calculated for any gas if the ratio of specific heats is known;

rc = P2/P1 = (2/K-1) k/k-1

Because many different final shapes of orifices are possible, and these different shapes have a large effect upon the flow of gas through them, coefficients have been assigned to approximate the flow. For example an orifice with a well rounded entrance has a .98 coefficient assigned and will pass nearly twice as much air per minute compared to an orifice with a sharp entrance which has a coefficient of .53. When dealing with a number of small orifices, the volume of air that will pass through them per minute is the same as will pass through one large orifice having an area equal to the sum of the areas of the small orifices.

The flow of gas through orifices depends upon the air pressure, the orifice diameter and the coefficient of the orifice shape. Many complicated formula have been devised for calculating the flow and one when simplified is approximately as follows:

Where W = Weight of gas in lbs./cu.ft.

Therefore it can be seen that the volume varies directly as the coefficient of the orifice, the square of the diameter, the square root of the pressure, and the square root of the reciprocal of the weight. Since air has a weight of .0766 and hydrogen .0053 lbs. per cu. ft. it can be seen from the above formula that the light hydrogen will flow about four times as fast as air.

Selection of Process Vacuum Pumps

A Liquid ring vacuum pump? Dry Screw or dry claw? A Steam jet ejector? Rotary piston or rotary vane pump? Comparison of available pumping systems as they relate to specific applications can be difficult and time consuming.

The first step in evaluating alternatives is to eliminate from consideration pumps or pumping systems that can't meet process requirements. This involves a consideration of (1) required suction pressure and capacity, and (2) reliability and maintenance. Following elimination of those pumping systems that can't meet process requirements, the most economical system can be determined by considering (3) purchase and installation costs and (4) operating costs. Final selection is subject to constraints imposed by (5) environmental considerations.

The most important parameters affecting final selection of the vacuum pump comes down to the suction pressure (P2) and the throughput the pump must handle (V2). The suction pressure is calculated by subtracting the losses in the suction line from the system operating point back to the vacuum pump. Line Losses include losses across sections of manifold, bends, and losses across filters, KOP's, scrubbers and precondensers.

When calculating the load to the vacuum pump, it's important to first examine the process. What are the primary sources of vapor or gas load to the pump. Is evacuation time a major concern. The checklist below will provide a basis for calculating capacity requirements for a vacuum pump.

Sources of Vapor-Gas Load
1) Air Leakage
2) Vapors of Saturation
3) Evaporated Vapors         
4) Evacuation of Process Equipment
5) Decomposition
6) Reaction Products
7) Sparge Gas
8) Stripped Gas out of Process Material
9) Dissolved Gas
10) Purge gas from instrument lines

After the process design has been completed pump selection can be prepared through the following questions:

1) P1 - Starting pressure
2) P2 - Operating Pressure
3) Pd - Discharge Pressure
4) Tg - Gas Temperature
5) Tw - Temperature and type of available cooling water
6) Ts - Temp and type of sealing liquid in the case of a liquid ring
7) Non-Condensable Pump Load
8) Condensable Pump Load

A reality check is necessary at this point to determine if the presented process conditions are indeed realistic. For example if the condensable pump load is 50lb/hr of water vapor at an inlet gas temperature of 110F and the operating pressure (P2) is requested to be 45mmHgA, is this possbile? A quick look at a steam table chart indicates that at 110F. water has a vapor pressure 65.9mmHgV. This means that as the pressure is reduced on the water at 110F it will continue to flash off until all the water is removed. Not until all the water is removed will the pressure move lower than the stated vapor pressure of 65.9mm@110F.

I've created a general list of available capacities and operating pressure ranges for the most often used process vacuum pumps and systems.

Steam Ejectors, single stage: 10-1,000,000 cfm (50mm)
Steam Ejectors, two-stage: 0-1,000,000 cfm (4mm)
Steam Ejectors, three-stage: 10-1,000,000 cfm (800 microns)

Liquid Ring Vacuum Pumps, single stage: 3-18,000 cfm (25mm)
Liquid Ring Vacuum Pumps, two stage: 3-6,000 cfm (25mm)

Rotary Piston Pumps - single stage: 3-800 cfm (5 microns)
Rotary Piston Pumps - two stage: 3-800 cfm (.001 microns)

Rotary Vane Pumps - oil sealed once-thru two stage: 100-600 cfm (.5mm)
Rotary Vane Pumps - oil sealed recirculation two stage: 3-150 cfm (.001 microns)

Rotary lobe blowers - single stage: 30-30,000 cfm (400mm)
Rotary lobe blowers - two stage: 30-30,000cfm (60mm)

Dry Screw - single stage: 60-600 cfm (.0075mm)

Dry Claw - single stage: 30-350 cfm (75mm)

This list should help in your preliminary process of eliminating pumps that can't meet your process requirements. Further assessment of the pumps reliability to the process including tolerance for solids, liquid slugs, reactive gasses, response to surge in gas or air leaks, performance in pumping condensable loads or excess discharge pressures etc... must be evaluated before making the final selection.

Liquid Ring Vacuum Pumps

In a liquid ring pump, an impeller with at least 12 or more fixed blades is mounted eccentrically in a drum shaped casing between 2 end plates. As the impeller rotates the sealing liquid moves out by centrifugal force to the wall of the casing forming the liquid ring. The process gas is drawn into the pump by the expanding pockets trapped between the liquid ring and the impeller hub. The air is then discharged slightly above atmospheric pressure after being compressed as the pockets between the liquid ring and the impeller hub decrease.

As a vacuum pump the liquid ring can generate pressures down to 28.9"HgV and as a low pressure compressor with an atmospheric inlet will produce up to 30 psig at the discharge. Liquid ring compressors are also available as double acting machines and can produce pressures over 200psig at the discharge with an atmospheric inlet.

Rotary Vane Vacuum Pumps

Rotary vane vacuum pumps consist of two moving parts - a rotating hub mounted eccentrically in a casing and two or more sliding vanes housed within this hub. As the hub rotates within the casing, the vanes are thrown out against the casing wall, thus dividing the space between the rotating hub and the casing wall into segments. The suction fluid is pulled into the pump be the expanding segments and then compressed before discharge. Rotary vane pumps can be used as vacuum pumps or as low and medium pressure compressors, can be oil-less, drip oil, oil metered, or oil flooded in design.

Single stage dry rotary vane vacuum pumps will produce pressures down to 25"HgV, where drip oil machines will produce pressures down to 27"HgV and oil flooded single stage pumps will produce 29.9"HgV. 2-Stage rotary vane vacuum pumps can produce pressures as low as .0004mm. Single stage rotary vane compressors can produce anywhere from 10psig to 150psig and 2-stage compressors will produce up to 300psig.