Archive | Compressed Air Systems

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3:44 pm

June 30, 2014

New Line of Large, Energy-Efficient Motors for High-Torque Industrial Applications

By Jane Alexander on June 30, 2014 in Compressed Air Systems, Energy Management, Maintenance, Motors & Drives, MT, News, Products, Pumps 0

Baldor Electric Co. has introduced a new line of energy-efficient, large AC - GPM Induction Motors. Used in high-torque industrial applications, including pumps, fans, conveyors and compressors, the product line is available in stock ratings 250 – 1000 HP, 2300/4000 Volt, totally enclosed (TEFC), fan-cooled, foot mounted designs.

Features and benefits of the stock-motor lineup include:

Cast iron frame, end shields and inner caps
Insulated opposite drive end bearing
Drive end slinger
100 ohm platinum winding RTDs
Provisions for bearing RTDs
Space heaters
Suitability for use on VFD 2:1 CT, 10:1 VT

The GPM line of large AC motors can also be ordered as custom items, ranging from 250 – 1500 HP, 460, 575, 2300/400 Volt, TEFC, in foot-mounted designs.

According to Baldor, stock, as well as custom units in this product family, can be used on variable frequency drives.

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1:16 pm

June 19, 2014

Compressed Air Challenge: Why Is Your Pressure So High?

By Maintenance Technology on June 19, 2014 in 2014, Compressed Air Systems, Featured, Homepage-Right-Side, Maintenance 0

By Ron Marshall, CET, CEM for the Compressed Air Challenge (CAC)

There was a day when most air compressors were rated at 100 psi: Rarely did general plant compressed air systems exceed this threshold. Over the years, however, plant pressures have climbed—and this has cost industrial customers a bundle.

A good exercise for anyone involved with compressed air systems in a plant is to question the pressures in those systems. Running your system at levels higher than what’s required costs about 1% for every 2 psi of extra pressure at levels around 100 psi. Moreover, unregulated air demands consume about 1% more flow for each 1 psi in added pressure. Excessive air pressure can cost about 10 to 15% more in wasted energy for every 10 psi increase. On a 100 HP air compressor running full time, this waste costs about $12,000 per year at 10 cents per kWh.

Why is your air pressure so high and what can be done about it? Here are some possible causes and solutions:

Pressure-critical end uses. There may be some air-using equipment that will malfunction if the pressure falls below a certain point. This forces compressor pressures higher. Many times these applications are attached to the system with poor connection practices, which can cause a 20 to 30 psi pressure differential. If these can be upgraded and improved, the pressure can lowered.

Perceived high-pressure applications. Equipment operators often think they need high compressed air pressure because of misinformation—or because “that’s the way it has always been done.” If a handful of questionable applications are forcing pressures up, it is time to question assumptions and verify actual requirements.

Piping loss. Compressor pressure may be jacked up because undersized main-plant piping is causing a restriction. Upgrading this piping size or reconfiguring it can remove restrictions and allow lower compressor pressure.

Dryer and filter differential. Many times, air dryers and filters in the compressor room are the culprits in causing restrictions. If the dryers are undersized or filters are clogged due to poor maintenance, the compressor pressure must rise to overcome this loss.

Transient demands. There may be occasional transient high-flow demands in the plant caused by a special compressed air process or machine. If this demand exceeds the capacity of the running compressors, the pressure may be pulled down to unacceptably low levels. As a way to compensate and prevent it from falling below what is minimally acceptable, the pressure is often jacked up to high levels. Applying local storage receivers as buffers can reduce transient demands

Factory default settings

Often, if a compressor is purchased with a high-pressure rating of say 125 psi, the factory default will be a set value near this capacity, sometimes for no particular reason other than “just because.” To save costs, plant pressures should only operate at levels required by legitimate end-users.

More information about the benefits of lowering compressed air pressure can be found at the CAC Website (compressedairchallenge.org) and in CAC’s Best Practices for Compressed Air Systems Manual. While you’re there, check out the online calendar for a schedule of upcoming training events. MT

rcmarshall@hydro.mb.ca

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3:58 am

June 9, 2014

Compact-Footprint, Refrigerated Dryers for Rotary Compressors Offer Simplified Maintenance

By Jane Alexander on June 9, 2014 in Compressed Air Systems, Energy Management, Maintenance, Mechanical Systems, MRO, Preventive Maintenance 0

Kaeser Compressors has released a new line of refrigerated dryers for use with rotary compressors up to 40 hp. The Kryosec TAH-TCH series can handle flows from 12 – 159 cfm. Incorporating copper-brazed stainless steel plate heat exchangers, they provide drying at ambient temperatures up to 122 F.

The units’ air-to-air and air-to-refrigerant heat exchangers are combined with the condensate separator in a single assembly to save on space and weight. According to the manufacturer these new units have an exceptionally compact footprint and, with their low profile, easily fit under machine platforms and in tight corners. They can also be wall-mounted.

Other features include an Eco-Drain electronic demand drain for dependable condensate drainage without pressure loss and a hot gas bypass valve that adjusts cooling capacity to match varying conditions. With all components, including heat exchangers, refrigerant circuit, condensate separator and drain, easily accessible when the side panels are removed, maintenance is simplified.

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9:22 pm

December 19, 2013

Overcoming Your Challenges: Efficient Compressed Air Piping

By Maintenance Technology on December 19, 2013 in Compressed Air Systems, December, Maintenance 0

By Ron Marshall, for the Compressed Air Challenge (CAC)

Getting your compressed air to flow where it needs to go requires a transmission system—a network of piping that connects your compressors to the end-uses. This piping system can have a big effect on the overall efficiency of your equipment. Around the 100 psi range, for every increase of two psi in compressor-discharge pressure caused by piping pressure differential, compressor power increases by 1%.

Piping is required in the compressor room to connect the compressors, dryers and filters together in a logical arrangement using wet and dry headers. In addition, a distribution header transmits the output of the compressed air room to general areas of the plant. Down-drop piping at the end-use connects the distribution header to the compressed air uses.

Generally, the desired maximum pressure differential measured between the discharge of the compressors and the furthest point in the distribution system should not exceed 10%. Since this calculation includes the air dryers and filters, where most of the system pressure differential normally occurs, that leaves only 2 to 5% for the piping distribution system. Based on years of experience, the Compressed Air Challenge has developed some recommended guidelines to achieve these levels:

Compressor-room headers…

Header sizing should be large enough so the air velocity in the pipes does not exceed 20 fps (feet per second) in velocity at expected peak flows. Entry points into the header should be at a 45-degree angle to prevent back-pressure. Use of T-connections and two flows in opposite directions should be avoided.

Distribution headers…

Piping from the outlet of the compressor room to end-use down-drops should be sized so the air velocity does not exceed 30 fps or, in cases of very long runs, sized large enough so the total pressure differential does not exceed the 2 to 5 % percent pressure differential mentioned above.

Distribution-header pressure differential can be greatly reduced by installing a loop system rather than radial feeds. Use of smooth-bore pipe—such as aluminum or copper—can reduce losses. Take care not to downsize because of this effect or benefits could be lost.

Down-drops…

The connections between the distribution header and various end-uses should be sized based on end-use flow characteristics and length of the drop. Installing standard-sized piping drops is not a good practice, as some end-uses requiring high flows for short durations may be starved for air pressure during such events.

At first glance these recommended pipe sizes may seem excessive compared to typical sizes. For example at 100 psi, using 2” pipe, the flow should not exceed 220 scfm to keep piping velocity under 20 fps, and no higher than 330 scfm to stay under 30 fps. The energy savings gained, however, can quickly pay for the larger piping size.

More information about compressed air piping issues can be found at the CAC Website (www.compressedairchallenge.org) or in our Best Practices for Compressed Air Systems Manual. While visiting the Website, check out CAC’s upcoming training schedule in our online calendar. MT

The Compressed Air Challenge® is a partner of the U.S. Department of Energy’s Industrial Technology programs. To learn more about its many offerings, log on to www.compressedairchallenge.org, or email: info@compressedairchallenge.org.

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7:18 pm

October 9, 2013

Compressed Air Challenge: Dry Compressed Air Efficiently

By Maintenance Technology on October 9, 2013 in Compressed Air Systems, Maintenance, October 0

By Ron Marshall, for the Compressed Air Challenge (CAC)

Air is like a sponge: It soaks up as much moisture as it can hold. When moisture-laden air is sucked into the intake of an air compressor and squeezed, like a sponge, it releases the moisture it has absorbed. If left untreated, this moisture will flow downstream with the compressed air. As it flows, it will gather the dust, rust and lubricant that exist on the compressed air piping walls and form a soupy mix that contaminates downstream equipment.

In an effort to prevent this contamination from occurring, compressed air is normally dried and filtered at various strategic points before it’s sent to plant end-uses. The type of air dryer and level of filtration varies, depending on the quality of compressed air required. (In general, the better the quality of air required, the more expensive it is to produce.)

Refrigerated air dryers and desiccant air dryers are two of the most common types.

Refrigerated air dryers…
These types of dryers cool air to near the freezing point of water using a refrigeration circuit and a heat exchanger. As the air cools, water condenses out of it and is removed via a water separator. This produces a dew point (the temperature at which the moisture within air starts to condense) of between 35 and 40 F. It is the refrigeration circuit in these dryers that consumes most of the energy; a smaller amount of energy is lost due to pressure differential. Rated specific power on these units is about 0.8 kW/100 cfm.

Desiccant dryers…
These types of dryers use a moisture-adsorbing material, such as activated alumina, to remove water molecules from the air stream. Most models incorporate two separate vessels containing desiccant: When one vessel is drying, the other is regenerating to remove adsorbed moisture. Once regeneration is finished, the dryer automatically switches sides. The regeneration process consumes most of the energy in desiccant dryers; a small amount of energy is lost due to pressure differential. These types of units typically produce compressed air with dew points of -40 F. Rated power consumed ranges from 2.0 to 3.0 kW per 100 cfm.

The key to energy efficiency of compressed air dryers is realizing that standard units consume near full power—even at light (or zero) loads. Because such dryers are usually sized for the worst-case scenario (i.e., the hottest, most humid day, when the compressor is at full load), the average loading at normal conditions is typically much less than the dryer rating. Thus, it’s desirable to select a dryer that can turn its energy down with reduced loading. A second benefit can be gained if the dryer has a low-pressure differential.

Cycling or thermal-mass refrigerated dryers reduce energy with reduced loading. For desiccant dryers, the use of dew-point controls or capacitive sensing of the desiccant moisture content will reduce wasted energy from unnecessary regeneration cycles. Often, the choice of these strategies will pay for themselves very quickly.

More information on this topic and others can be found in the Library section of the CAC Website, or in our Best Practices for Compressed Air Systems Manual. MT

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731

2:27 pm

August 20, 2013

Overcoming Your Challenges: Remember Your ‘Three 100s’

By Maintenance Technology on August 20, 2013 in August, Compressed Air Systems, Maintenance 0

By Ron Marshall, for the Compressed Air Challenge (CAC)

During the heat of summer, a common complaint in many plants involves the issue of wet compressed air. An ugly slurry of rusty, oily, moisture-laden air—smelling much like an old unwashed gym sock—can collect inside piping and spray out on the precious product of your efforts. When it does, it soils clean surfaces, ruining machinery and contaminating all it encounters. Try as you might, after tuning and maintaining your air-drying units to perfection, the bubbling mass somehow still manages to get past filters, dryers and drains.

In response to the problem, extra filters may be installed, with timer drains blasting hundreds of cubic feet of compressed air in an attempt to cleanse and flush the contamination away. That course of action only makes things worse—and pressure problems start to appear due to the extra load.

If the above scenario sounds familiar, you may need to pay attention to the following “three 100s” characteristics of your air dryers: Most air dryers sold in North America are rated for compressed air at 100 psi, an inlet-air temperature of 100 F and ambient conditions of 100 F. Read on. . .

Pressure. . .
If your compressed-air pressure is lower than 100 psi, it means higher-than-rated air velocities are flowing inside the piping of the air dryer. Such velocities make it harder to cool the compressed air to the temperatures required to make rated dewpoint—and harder to separate the moisture that’s left when the water vapor condenses.

Inlet temperature. . .
The compressed air produced by your equipment is always completely saturated with water vapor as it enters the air dryer. The hotter the air, the more water vapor it contains. A rule of thumb is that every increase of 20 degrees F in air temperature doubles the amount of water in the air. Dryers can only remove the amount of water they’re designed to handle. The refrigeration circuits of refrigerated dryers (and desiccant beds of desiccant dryers) have been sized only for the amount of water contained in air at the rated 100 F temperature.

Ambient temperatures. . .
The refrigeration circuits in refrigerated dryers need to expel the heat created when the water vapor condenses. The heat-exchanger circuits are designed for 100 F ambient conditions. Hotter temperatures reduce the effectiveness of the dryers.

So, if your facility is experiencing wet-air problems, you would be wise to check on your equipment’s “three 100s.” If they’re out of line, the cause of the wet air should be investigated. For example, ventilation problems can lead to overheated compressor rooms, causing ambient temperatures to exceed dryer ratings. High ambient conditions also affect the air compressors, allowing discharge temperatures to greatly exceed design conditions. This means what might have been diagnosed as a dryer problem is really a ventilation problem.

Note: Even when ventilation is improved, dryers sometimes will still need to be oversized to account for conditions that exceed ratings. CAC’s Best Practices Manual shows correction factors to use in doing this the right way. Information on purchasing the manual can be found at the CAC Website. While you’re there, check out and register for our November Webinar. MT

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8:07 pm

June 19, 2013

Overcoming Your Challenges: Stop Draining Away Your Profits

By Maintenance Technology on June 19, 2013 in Compressed Air Systems, June, Maintenance 0

By Ron Marshall, for the Compressed Air Challenge (CAC)

Most compressed air systems incorporate one or more deliberately installed “engineered air leaks” to drain water and lubricant from the system. Unfortunately, these devices often waste significant volumes of expensive air and, ultimately, energy.

When air is compressed and cooled to atmospheric conditions (or dried, in the case of refrigerated air dryers), water vapor contained in it is squeezed and condensed. Similarly, air compressed by lubricated screw compressors contains a small amount of lubricant. The problem: If moisture and lubricants aren’t eliminated from compressed air, they will contaminate downstream air-powered devices—or worse, cause product-quality or other issues.

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9:24 pm

April 24, 2013

Compressed Air Challenge: VSD Compressors — Turn On Cruise Control

By Maintenance Technology on April 24, 2013 in April, Compressed Air Systems, Maintenance 0

Accurate control of pressure in compressed air systems is always of primary concern, but there are many ways to achieve it. Some are more efficient than others. One of the biggest innovations in the field of compressed air efficiency is the invention of VSD-controlled compressors. VSD compressor control can put your air system pressure on “cruise control.” Let’s turn to an automobile analogy in comparing compressor control strategies.

One could use modulation control mode, which is similar to driving a car with the pedal to the metal and using the brakes to provide constant speed. Modulation control chokes off the inlet flow to the compressor to control the output pressure. This mode of operation is the least efficient way to provide constant pressure, with the compressor consuming 85% power even at only 50% output flow.

Another control mode involves loading and unloading a compressor between two set pressure points, with the average of the two readings providing the desired pressure. This approach is similar to driving down the highway and controlling the speed by throwing the vehicle’s transmission alternately into drive and neutral. Air compressors in this mode of operation use less power than modulation—but can still consume between 70 and 85% power at a 50% loading level, depending on the frequency
of cycles.

A third mode is akin to a driver on a busy highway who repeatedly starts and stops his engine (slowing down or going faster) to reach a desired average speed. This method would be equivalent to a start/stop compressor operating mode: an efficient way to run small compressors, but hard on the motor.

In the three modes described above, average pressure could be adequately achieved, but it would come with either higher-than-desired energy consumption or wider pressure fluctuation. In a compressed air system, the desired result is a constant steady pressure—one set high enough to provide sufficient power to compressed air consumers, yet low enough to limit the energy consumption of the compressed air system.

Leveraging VSD control
VSD-controlled air compressors have accurate controllers on board that sense the actual pressure and speed up or slow down the compressor so as to keep a constant discharge pressure. The benefit is that the pressure can be set at a lower, more efficient level. Moreover, as the motor slows, the power consumption is almost linear to the speed reduction, saving even more. These units are more expensive and more complex than standard fixed-speed compressors but often, especially when an air compressor needs to be replaced anyway, the new VSD compressor will pay back the extra cost very quickly.

While these types of units are most appropriate for smaller single- and two- compressor systems, they can save significant energy in larger multi-compressor systems—if applied and controlled appropriately. To determine if VSD compressor control is appropriate for your plant, have an energy analysis of your system performed by a qualified compressed air energy-service company.

More information on this topic and many others can be found on the CAC Website (www.compressedairchallenge.org), in our online Library and our Best Practices for Compressed Air Systems Manual. MT

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