April 2018

bag and pocket filter

The Difference Between Pocket Filters and Bag Filters

EFS /

The terms bag filter and pocket filter are often used interchangeably – but there is a difference between these two industrial air filters.

Typically, a bag filter has a metal frame (galvanized steel or aluminum) with anywhere from 3-6 pockets of micro glass or synthetic filtration media. The ‘pockets’ of a bag filter are not ‘rigid’ and sometimes have a tendency to collapse in the air stream, especially under high airflow.

Engineered Filtration Systems (EFS) has a soft pocket bag filters which is uniquely designed with an extruded aluminum frame for added durability. In addition, the seams of the pockets are ultrasonically sealed, as opposed to sewn like most bag filters, to prevent leakage and reduce tearing. Bag filters come in a range of efficiencies from MERV 8 to MERV 14.

Rigid Pocket Filters

A pocket filter, also known as a rigid pocket filter, on the other hand is made with a high-loft synthetic media so the ‘pockets’ stay rigid in the airstream and will not collapse. In addition, the frame (also known as the header) of most pocket filters is plastic which eliminates the possibility of corrosion.

Pocket filters can be used to remove both dust and fine particles and have a very high-dust holding capacity.

EFS’s rigid pocket filters come in two efficiencies; the F5 Rigid Pocket Filter is a MERV 8 and the F6 Rigid Pocket Filter is a MERV 11. Depth-loading, synthetic media provides exceptional dust holding capacity. The synthetic media consists of non-shedding fibers that are specially developed to resist moisture and chemicals making it resistant to bacterial growth.

The polyurethane header ensures leak-proof bonding of the pockets to header and eliminates the possibility of corrosion.

All EFS Rigid Pocket Filters are progressively structured and provide exceptionally low pressure drop at high efficiency levels. The air filter pockets are self-supported, stay rigid in any air stream and can withstand extreme humidity and high velocities as well as turbulence. This air filter is free of metal parts and that reduces the risk of corrosion and punctures.

Call Engineered Filtration Systems today for the best commercial rigid pocket air filters.

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graphic image of turbine

Increase Gas Turbine Output at Your GT Power Plant with Evaporative Cooling

EFS /

Evaporative cooling pads are a cost-effective solution to increasing the power output of gas turbines in warmer areas or during hot summer months. Other methods of cooling inlet air can prove prohibitively expensive or inefficient. In areas where the air is hot and especially humid, a combination of evaporative cooling and other cooling methods may be necessary.

Hot Weather and Power Output

Gas turbines can produce as much as 20 percent less energy on a hot day than on cold days. On hot days, air is less dense. Power output decreases, because the flow of mass through the turbine decreases with hotter air. Although the turbine may be moving the same volume of air at a certain shaft speed, the power output will depend on mass flow of air. Hotter, less dense air provides lower flow of mass through the turbine, thus decreasing power output.

Evaporative Cooling

Evaporation converts liquid water to vapor in what is called a phase change. During this change in phase from liquid to vapor, water will either absorb or release heat. A pound of water changing from liquid to vapor will consume 1160 BTUs of heat. A hot breeze on a scorching summer day will feel cooler due to the evaporation of perspiration off the skin, thus absorbing heat and cooling the body. This is evaporative cooling.

Evaporative Cooling Pads

Evaporative cooling pads utilize the principle of evaporative cooling and are the most commonly used method of cooling gas turbine inlet air. The media is made of a wetted, cellulose fiber pad in a honeycombed design. When hot inlet air enters the gas turbine system, the wetted, honeycombed surfaces of the media cools the inlet air.

In areas without relatively low humidity, evaporative cooling pads can increase power output of gas turbines by as much as 15 percent. In especially hot and very dry environments, power output can be increased by as much as 60 percent.

High humidity can decrease the cooling effect of evaporative cooling pads. Even with high humidity, though, evaporative cooling pads can increase power output by as much as 10 percent. In areas with very high humidity, operators may wish to employ a combination of evaporative cooling and another cooling method, such as high-pressure fogging.

Costs of Evaporative Cooling

Evaporative cooling is a cost-efficient solution to cooling inlet air compared to other methods like a chiller installation. Evaporative cooling pads are relatively inexpensive, but they do require lower air velocities than other cooling methods.

Some facilities may need to retrofit air ducts to lower air velocity so that water is not stripped from the cooling media, causing wetting of ducts and possible compressor blade fouling. Retrofitting for evaporative cooling is generally inexpensive though, and operating costs of using evaporative cooling are low compared to other cooling methods.

Conclusion

Evaporative cooling pads utilize natural processes to cool inlet air, thus increasing power output of gas turbines in high heat environments relatively inexpensively. Engineered Filtration Systems’ evaporative cooling pads are specially coated to resist deterioration and prevent algae and minerals from adhering to the pad.

For more information about increasing power output with evaporative cooling, contact Engineered Filtration Systems online. Or, call us, at 1-800-796-4337.

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