Air Compressor Package FAT, SAT & Precom/Com 3

[sheiko]

Hi,
I am confused between FAT (Factory Acceptance Test) and SAT (Site Acceptance Test) of control systems relative to precom/com. I know what each term means but i would like to know their respective objectives, scope and sequence with one another? Also, is it possible to perform FAT during precom/com on site instead of factory? Is SAT part of precom/com? In a nutshell what are the limits between each above mentionned activities?
The context is an air compressor package.
Thanks



"We don't believe things because they are true, things are true because we believe them."

 

[zeusfaber]

All these tests are ways of reducing risk. If there was no risk of getting any of the stages wrong, or the consequences were utterly trivial, it wouldn't be worth investing in the various tests.

The FAT gives you confidence in the quality of the equipment build. You might choose to combine FAT with commissioning, but not if you're relying on FAT to assure you that the equipment is safe to instal - nor if shipping costs back to the factory are extortionate - nor if the kit is going to sit on the shelf for a while, but then be needed to be installed and put into service so quickly that you can't afford the time to return to works if it turns out to be defective - nor if there's a lot of work in way/wake if you only find the kit needs taking out for repairs after you've built it in.

To me, a SAT is a System Acceptance Test. You're testing not just the equipment, but also the quality of the installation and set-to work and the interaction with the rest of the system. If you combine SAT with commissioning, you run the risk of invalidating the early parts of the SAT when you adjust things later on in the process. With some kit, this risk might be acceptable - but if not, then the SAT will give a more authoritative result if saved until after all the tinkering is over.

This is a classic engineering compromise: The earlier you start testing, the more testing you end up paying to do. The later you leave it, the more it will cost you to fix anyting you find. If you understand the risks and costs, you can tailor a package that is most likely to be best value for money.

A.

 

[JLSeagull]

I love to say that "It Depends". For example, what kind of plant, what utilities, what feedstock, located near Chicago or the middle of Nigeria, etc.

I think of pre-commissioning and commissioning in relation to starting a processing plant. Pre-commissioning begins after mechanical completion for a portion of a facility.

So, what is an air compressor package? I once bought a compressor package at Sears. However perhaps you are dealing with four trains of 6000 hp gas turbine driven air compressors operating with from one to four online and sequenced based upon load and run time.

A control systems factory acceptance testing for an air compressor package would simulate what ever sequence is required before you let the package ship. If nothing else this indicates that the controls are programmed. The FAT is done before you let them load the package for transportation. Once loaded the client is likely invoiced.

Site acceptance testing is usually a misnomer. You already accepted the system. The invoice has been paid. Now you are paying daily field service rates to assure that the system will work now that it is hooked up.

For commissioning let's say that you have that gas-turbine driven air compressor package. Mechanically complete means that the welders are done. However don't just start that lube oil package until it is chemically cleaned to the manuracturers specification. Don't light off the driver until the fuel gas is tested and all logic simulated, calibrated and lockouts ready for removal.

So, the definition for these terms should be written in the specification before the inquiry is issued for bids.

 

[sheiko]

Thanks guys,

I better understand now.

So, does the "S" of SAT mean SITE or SYSTEM?

And, can we say that FAT/SAT terminology is relative to control systems and that, in fact, the Commissioning includes the SAT as acceptance of the control system (once connected to the process)?

PS: My package is made of 4 screw compressors, motor-driven, working in sequence depending on the air demand...



"We don't believe things because they are true, things are true because we believe them."

 

[Ashereng]

SAT is Site Acceptance Test.

FAT is testing at the factory what the supplier provides.

SAT is testing at the site, where what you bought is now integrated into everything else, and testing that it works in context of the "everything" else.

For example, at a FAT, make sure the control system's data historian is collecting data. At the SAT, make sure that the data can be exported to the site host at the required schedule.

One way I look at it is the FAT is for the vendor to prove he did his job. The SAT is for the engineering house to prove that we did ours.

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Albert Einstein
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