Control.com - Nerds in Control

We have recently upgraded our old Air Inlet Filter House - turbine and generator side - with a new self cleaning filter house which has a lot of SOVs to pulse clean the system. We asked the local GE packager to show "something" that would be a performance benchmark. The packager says there isn't anything to benchmark the performance except that you can check the CDP, which if it's found to be normal is a decent benchmark of performance.

I wish to know what are the practices adopted worldwide to gauge the performance of such jobs. Is the CDP, as our packager claims, is a true measure of air flow, or should there be some means to measure the air flow directly in the Inlet flow path? How can we ensure the effectivenes of the pulse cleaning system in a given time (time duration for which the performance test lasts - usually a week)? What exactly are the performance guarantee procedures in such cases?

Thanks in advance,

Zayed

Air filters remove contaminants (down to a certain size) from the air that flows through them. As filters do their job the contaminants collect on the outside of the filter media, and they are less effective at allowing air to pass through, meaning the axial compressor can't flow as much air as when the filters were new and clean, which means CPD will decrease over time as the filters get dirty, which means power output will decrease proportionally.

A self-cleaning air filter system just knocks the larger particles off the filter. It's like removing the air filter from a car or truck or some other vehicle with an internal combustion engine and using compressed air to blow backwards through the filter to knock the larger particles off, then re-installing the air filter in the vehicle. By doing so, one has "extended" the service life of the filter and saved some money by not simply replacing the filter with a new one. But at some point the filter will still need to be replaced; as the smaller particles, which can't be removed so easily from the media, build up and restrict the air flow through the filter.

Usually, the justification for purchasing a self-cleaning air filter system is to increase the time between filter changes, by using high-pressure air through solenoid-operated valves to periodically dislodge larger contaminant particles from the outside of the filter media. Without some method of method of knocking the larger particles off the filter media as they collect over time the filters will have to be changed to improve air flow through the filter. By employing some method of removing the larger particles periodically, the filters shouldn't have to be changed as often. But, they will still have to be changed.

It's pretty clear that someone didn't understand the purpose of self-cleaning air filters, which is primarily to extend the service life of the filters.

What was the criteria for the purchase? To remove smaller particles than the previous filters? To reduce the frequency of changing filters? Did the supplier promise a turbine efficiency increase (power ouput or heat rate improvement)? 'Cause, air filters alone (self-cleaning or not) ain't generally gonna give you that much of an efficiency increase (power output increase or heat rate improvement) unless the old filters were very restrictive or they were very ineffective at removing contaminants which cause compressor fouling. Now that may have been another criteria: reduce compressor fouling by improving filtration. But, you're not telling us what the justification was for purchasing the new filters; we don't know why new filters were purchased so we can't tell you how to gauge the performance.

This is SOOOO typical of a certain region of the world. Buy something without understanding the justification for purchase; don't put any kind of performance guarantee based on the purchase justification into the contract; and then accuse the supplier of not meeting a performance guarantee that you can't even describe (you're asking the supplier to provide performance benchmarks *AFTER* the purchase).

Further, I'll bet that no pre-filter replacement "performance data" was captured, to use to compare against any post-filter replacement "performance data", so trying to conduct any "performance test" now would be virtually impossible by definition.

It's too late to hold the supplier accountable if performance criteria weren't specified, no pre-replacement data was compiled, and no performance test methodology was agreed to in advance.

Now I'm sure a filter manufacturer could conjure up some spreadsheet data to the contrary, but on a real-time, day-to-day basis, any "performance improvement" from an air filter change is going to be pretty negligible unless the old filters were very restrictive and/or allowed a lot of contaminants into the compressor which caused "accelerated" performance decreases and required "excessive" compressor cleaning to overcome. The benefits of any filter change will probably only be apparent over some period of time, such as weeks or months or years. And that will also depend on the environment (humidity, dust, type of other contaminants in the air (cement dust; road dust; refinery air contaminants; etc.).

Time to get back to basics: what do filters do and what are they capable of doing. Then, and only then, can "performance" criteria be determined, and demonstrated. And, do that *before* a contract is signed, *not* after. It makes for a lot of hard feelings on everyone's part if everyone isn't in agreement in advance on why and how.