11 replies to this topic

[GASCO]

hi all

Can someone write the exact procedure to commission a new line servicing gas "mainly C1,C2" pressure 30 bar.

This gas is going to a compressor and we always have high delta P across the strainer of the suction of compressor

When we cleaned and removed the strainer we found it’s full of fine black powder, we continuously have this problem so we changed the

Strainer mesh size to larger holes

can someone write better approach to solve this problem other than changing the strainer mesh size?
what the possible source of this black powder ? could it be because the line is new?

[Art Montemayor]

Gasco:

You obviously obtained the service of a bad piping contractor. You also failed to tie the contractor to a contractual agreement whereby the line would not be accepted until it produced a commissioned and clean operational run of at least several days on stream.

There is no telling what was left in the line after completion. Your company obviously inspected and accepted delivery of the line and paid for its full construction. It would be expected that you also pigged the line and ran it with a smart pig before accepting it.

All the issues being raised are issues that the owner assumes as his/her responsibility and, consequently, must take out insurance or invoke contractual terms to protect himself/herself. I have to assume this was done prior to letting the construction contract.

[GASCO]

Art Montemayor

Unfortunately this bad piping company supposed to be one of the largest construction company in the world
What we think the contractor did for commissioning the line is after the hydro test of the pipes that did not dry the line properly and after two years “because the project got delayed”. Dirt started forming in the line.

So what I am asking is there any way to solve this problem.

[Art Montemayor]

Depending on what else is "wrong" or deficient with this pipeline, one way to attack the problem is to pig it. I would hire a pigging contractor and have the line analyzed after which the results of the findings could be evaluated and a decision made as to whether to clean out the line or to administer any suspected repairs.

After sitting idle without any drying or inert atmosphere, this line should be suspect and a thorough analysis would be in order, in my opinion.

[TechExpert]

One method is to recommission the line after a Shut down. Various steps such as

1) for preliminary cleaning :line flushing (if the line size is less than 10") or card-board blasting (if the line size more than 10" or cryogenic line)
2)Drying of line through plant air.
3) Since the line is going to Compressor suction, target test shall be conducted. Then depending on the number of spots found on the target plate, clearance to line can be given.
4)Leak test (testing each and every flange with soap solution, after pressuring the line at 5-6 kg/cm2g)
5)Then inertizing the line (since a hydrocarbon line) through nitrogen.
6)Ready for commissioning

But this can be done during a shut down.

PKS

[aanita]

Black powder and line not dry out after the Hydro test - It looks corrosion products of HC componentents. Did you check the composition of blak powder.

[djack77494]

Good advice given here. Have the material analyzed so you know what you are dealing with. A good cleaning followed by inspection also seem in order. The worst possible solution is to change out the strainer for a coarser one. That merely sends the problem downstream (i.e. to your compressor). The strainer is there for a reason, and it's doing its job. I hate to say this, but someone in the owner's organization did not do their job. Assuming the design was done in reasonably good fashion, and that the construction followed the design, and that the precommissioning activities were correctly done, then the problem was likely wtih the owner. Unless the hydrotest contractor was instructed to drain and then dry out the line after hydrotesting, the only one left is the owner. Others do as instructed; the owner must exercise due diligence to ensure that the instructions are completed and are followed.

[Himanshu Sharma]

Sir,

Your "Black powder" formation may be because of corrosion of iron with hydrogen sulfide (H2S) corrosion.

Corrosion products include black or blue-black iron sulfides, pyrite, greigite, mackinwaite, kansite, iron oxide (Fe3O4), magnetite, sulfur (S), and sulfur dioxide (SO2).

You may please check the feed for H2S concentration.

I don't agree with the idea of providing a larger mesh size strainer as it shifts the problem to a major area of concern, the compressor itself !

As far as other pre-commissioning steps are concerned,in addition to them i would like to do chemical cleaning of suction line and KOD rather more important in case of positive displacement compressor.

[Padmakar Katre]

Sir,
I don't agree with the idea of providing a larger mesh size strainer as it shifts the problem to a major area of concern, the compressor itself !

Dear Himanshu,
Great Point to add at least for me.

[GASCO]

Dear friends

After period of time we stopped getting the black powder.
However, the suction strainer mesh have been removed completely along with the trip signal
"Previous trip signal of high delta P across the strainer was initially 0.8 bar then increased to 1.5 bar then after removing the mesh there is no trip value"

The decision of the removal was approved by the operation people and the compressor vender GE
just sharing you guys what happened later on

[djack77494]

Strainers and their use are amazing. We specify strainers to protect a system or piece of equipment downstream. They do this by removing any solids that might be present, since those solids can potentially damage things downstream. Of course, when a strainer removes solids, the solids are retained by the screen and result in additional pressure drop. When we see that pressure drop, which is like a signal saying "Your strainer is doing its job", we don't like it. Often the suggestion is made to remove the strainer or the screen in the strainer. I have never understood this reasoning, and I would ask if there is a problem with allowing the solids to continue moving downstream. If the answer is "yes", then what alternative is proposed to remove the solids? If the answer is "no", then why was the strainer specified in the first place? If you assume that the solids might be present during initial operations but then will disappear, then try to retain the strainer in the hopes that it will soon be "invisible".

[GAURANG PATEL]

hi all

Can someone write the exact procedure to commission a new line servicing gas "mainly C1,C2" pressure 30 bar.

This gas is going to a compressor and we always have high delta P across the strainer of the suction of compressor

When we cleaned and removed the strainer we found it's full of fine black powder, we continuously have this problem so we changed the

Strainer mesh size to larger holes

can someone write better approach to solve this problem other than changing the strainer mesh size?
what the possible source of this black powder ? could it be because the line is new?

The root cause of your problem is like this:
After hydrotest, line was not properly drained, dried & purged.
Because of that, over period of time corrosion takes place & rust formation occured.
This rust was not even cleaned by pigging/card board blasting/blowing.

Solution:
To change the mesh size is not solution.
I would suggest first of all go for card bord blasting several times say 15 times depending upon volume of pipe & dust.
Then go for pigging say 5 ties.
Then go for chemical cleaning followed by mild passivation.
I can ensure you your proble will be solved forever.