Acceptance Criteria for Air Blow in API standard 4

[wangduyu]

Hello, is there any acceptance criteria for air blow to clean the pipe line, clearly specified in API standard?

Thanks a lot.

 

[EmmanuelTop]

I'm not aware of such criteria defined in API standards but I might be wrong. I have never come across any universal guidelines or acceptance criteria for general cleaning and flushing of the pipework. Based on my commissioning experience, determining the requirements for internal cleanliness of piping is solely the responsibility of the end user (= client, asset owner). These requirements are mutually agreed between the asset owner and the contractor and subsequently formalized in the test package(s) and procedures.

There are some interesting guidelines and reference materials prepared by GEA and EPRI (Electric Power Research Institute). See attached.




Dejan IVANOVIC
Process Engineer, MSChE

 

[wangduyu]

Thanks EmmanuelTop for the good document, I will keep on search in API standard, look like there is no such criteria.

Once I found, I will come back here to post it.

 

[LittleInch]

IMO, air blowing is a poor way to clean any pipe or pipeline. You might get rid of some dust, but any particles of a decent size, as small as sand, will simply not move unless you reach sonic velocity, at which point the damage done by the particle exceeds the benefit of having a clean pipe....

Anything bigger than a grain of sand would not move or if it does, becomes a highly dangerous projectile.

If you start very clean then I have seen cleanliness targets based on the number of hits on a very thin aluminium screen on the end of a tee where flow diverts to one side.

Emmanual top - that's a great document.

one thing to remember in the pack and blow techniques is that the velocity at the far end from the vent point is very low and hence even repeated blows will not shift this debris unless you can stagger the blow.

Whatever you do you will find more dust and debris when you start using a system so prepare for lots of filter changes...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EmmanuelTop]

That is absolutely correct. If anyway possible (and applicable - I could not imagine using water in flushing long distance pipelines), water should be used for cleaning/flushing.

During the (pre-)commissioning job in Qatar, we found several helmets, wrenches, and one fire extinguisher in the compressor suction line (36" dia). The line was flushed with water and all that stuff was found in the temporary strainer. I don't think the air would be able to move a fire extinguisher that far

Dejan IVANOVIC
Process Engineer, MSChE

 

[zdas04]

War stories, great. I found a skid (6X6X36 inch timber) in a 16 inch line once. We retrieved it by pushing a pig with water. I don't think it would have come home with air. Hard hats, coveralls, and welding masks/gloves are too common to be remarkable. The ends of welding rods show up a lot too. A fire extinguisher would have been notable.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[wangduyu]

Yes, water will be the first option for pipe clean, effective and safe. But we have to use air because the pipeline is cryogenic, to avoid difficulty to low the daw point before commissioning.

Thanks everyone for input

 

[zdas04]

For cryo pipe I would pump dense phase CO2, but using air is a really bad idea.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[wangduyu]

Good idea to use CO2, but take a lot of effort to recover CO2, we cannot exhaust CO2.

 

[zdas04]

Can't exhaust CO2????????????? Have you stopped breathing? Is this a robot? It's cryo pipe, use liquid nitrogen.

In any case, with that statement I'm done. I have zero time for anyone who would rather leave a cryo line full of hard hats, fire extinguishers, and construction skids because of the myth of AGW.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[georgeverghese]

The formula given in chapter 7 of this attachment is the same as what was used by Siemens for air blowing the DN500 fuel gas piping to 2 units of 275MW GTs' in power gen application here in Victoria, Australia recently.

If you want to lower the dew point in the cryogenic piping, you could first use pipeline pigs with methanol.

Else you could dry with hot air from a TSA mole sieves unit - this is what we do for defrosting air separations plants (-195degC operating temp) before startup - finally check air quality at all exit point with a portable dewpoint meter that reads down to -100degC water dewpoint. TSA mole sieves unit should also remove CO2.

 

[georgeverghese]

If the cryogen flowing through this line is incompatible with defrosting air ( flammability ; corrosion; some other reaction etc), then a final purge with N2 or some other dry gas (with suitable dewpoint characteristics) should be used.

 

[wangduyu]

Ha, Zdas04, yes, you are right, it is ok to release C02 freely. We are working in Shipyard on barg, not a site where plant will stand with permit to exhaust, small amout is OK, large amount exhaust of CO2, local authority will think we start to use pressure vessel or compressor, any other set of safety regulation will come up to us.

 

[wangduyu]

Hi,georgeverghese, thanks for the case presented. part of those pipe will serve for methanol.

our dew point is -70 degress.

 

[LittleInch]

My point was that regardless of what you do, your pipe will not be "clean" until you really work it during commissioning so make sure your important equipment is protected by some decent strainers.

Last compressor station in the desert blew a lot of dust out of the pipe by air bangs, but commissioning brought the welding rods, some rocks, a cut out from a weldolet, the odd water bottle and even a plank of wood rattling around the scrubber. I have never been more grateful for the extra cost of installing a really really strong top hat filter on the inlet to the compressor as it ended up with 20 bar [sic] across it and still didn't break, but collected a lot of sand, water and the odd large item which could easily have wrecked the compressor. It was bent a bit, but some of the weedy looking filters you can see for commissioning wouldn't stand any damage or significant DP.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

The comm crew had trouble with getting the purpose built conical strainer vendor to commit to a notional rupture pressure on this fuel gas air blow operation