Use of CS Flanges/Blinds for SS Piping Hydrotests 1

[Cuemaster64]

Gentlemen/Ladies, Most definately Professionals,

A question has arisen on my new site assignment. I have been tasked with testing a large amount of Stainless Piping and was considering ordering SS Blinds and Paddles to accomplish this but 2 superiors have said that for testing I should only need to have CS Blinds and Paddles to accomplish the testing.

I am of the opinion that it should be similar metals to similar testing gear.
Water to be used at this time is going to be Plant Potable Water and in the winter time Polypropolyne Glycol/Water mix.

Further to testing with fluids I am also of the belief that Carbon tested water should not be used for testing of SS lines. We plan on holding our testing water in a holding tank for transfer back and forth between tests. Thoughts??

I look forward to your responses.

Regards,

 

[bimr]

What is the application that the stainless piping will be used?

 

[austsa]

Using SS blinds is the perfect scenario. No disadvantages, other than cost. If you have lots of piping with same flanges, then investing in a few sets of SS blinds is the way to go.
IMO using CS blinds is "acceptable" if water can be fully drained/dried after the hydrotest. Intricate instruments should be removed from the system prior to the test. Naturally, try to use blinds that still have reasonable coating on them.
austsa

 

[bimr]

The water quality of the water used for hydrotesting may be a significant issue. There are many examples of poor water quality that initiated corrosion problems.

http://www.nickelinstitute.org/~/Me...sedforCoolingandHydrostaticTesting_10085_.pdf

http://www.australwright.com.au/datasheets/advice/Stainless Steels/Hydrostatic Testing SS.pdf

http://www.assda.asn.au/component/rsblog/view/33-hydrostatic-testing-of-stainless-steels

It is also generally considered to be good practice to keep stainless steel and carbon steel material separate in the fabrication yard.

For mixed metal piping, MIC corrosion will tend to attack the carbon steel components. In the case of mild steel pipework, hydrotest/storage waters are commonly treated with acorrosion-preventative hydrotest package that contains an oxygen scavenger, a biocide, and, frequently, a corrosion inhibitor. Such treatments are not generally used in the case of stainless steel pipelines and vessels.

http://products.asminternational.org/fach/data/fullDisplay.do?database=faco&record=981&trim=false

 

[stanier]

You could simply use CS blind fanges with a 1.6mm stainless plate between flange face and gasket. If the blind flange is retained then it will not corrode due to the water contents and will not contaminate the water.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[bimr]

Isn't that more or less the same thing as a paddle or spectacle blind flange mentioned in the original post.

 

[jtseng123]

Also pay attention to chloride content. We limit to 30 ppm for SS. We have one fabricator reuses test water. Water is filtered prior to each use.

 

[DLite30]

A drain and fill for a hydrotest would not be a sufficient flush anyway, so that's a moot point. I would use steel blinds.

 

[stanweld]

Carbon steel blinds are commonly used for the hydrostatic test of stainless steel pipe systems. There is gasketing between the carbon steel blinds and the s.s. flanges. If one is highly concerned with iron contamination from corrosion of the carbon steel blind over the highly limited exposure time during fill, test, drain and dry, coat the exposed surface.

 

[donf]

Another option is to use a "blind" gasket with the CS blind flange. Two things to look out for:

1. Make sure that the gasket is cut without the typical centering pin hole.
2. Some gasket materials are permeable until they're compressed. Obviously, the gasket area at the bore of the mating pipe will not be compressed. (ePTFE is one such material)

donf

 

[jtseng123]

I just have several SS vessels and one big CS duct with SS branch. I ask both US vendors to consider if any iron contamination through water. Below are their responses:

Vendor 1: We’re estimating that the stainless nozzle will be exposed to iron contaminated water for no more than 3 hours (two hours to fill, one hour for hydrotest), then wiped down post hydrotest.  This happens frequently with stainless nozzles, and is considered industry standard.  If you would like, we can inquire with a coating supplier, and explore the possibility of doping the stainless items with a rust inhibitor, which may or may not assist in preventing contamination.

Vendor 2: We have experience over multiple projects using carbon steel blinds and carbon steel bolting / nuts without carbon contamination to stainless steel vessels / components.  We have never used oxygen, scavenger, corrosion inhibitor during the hydrotesting of SS vessels and we did not intent to use any such compound during the hydrotest.  There will be gaskets in place between the carbon steel test blinds and stainless steel flanges during hydrotest.  If you have any additional questions, please let me know.
 

 

[SNORGY]

Unless the SS lines are in some critical service or other and need to be absolutely clean and / or pickled, I see no issue whatsoever with CS test blinds at all here.

With respect to what I interpret to be meant as the re-use of water recovered from previous hydrostatic tests in carbon steel piping systems, maybe that is an issue in that you probably don't want to be flushing an inappropriate amount of entrained mill scale out of your SS piping system after the test.

 

[BigInch]

I'm with Snorgy. Provided there are no extenuating circumstances that you have not mentioned. You'd have to be pretty fanatical to not use CS! If it was critical, you should not be using plant water as well.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[BigInch]

Besides, you already have your answer from two (2) supervisors. Do you think we can really tell you anythibng of better value than that given the extremely limited information indicating NO extenuating circumstances what so ever.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[jtseng123]

I raise the issue and let vendors respond. I will not force them to do thing that has no solid proof or is not common practice. They take the responsibility and consequence.

 

[BigInch]

jtseng, the OP is not dealing with vendors. HE must make a responsible decision.
The best advice anybody can give him at this point is to do what his supervisors tell him to. Fortunately, they are not wrong.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek