How can I stop rust during Hydro??

[andrewsjo]

We are about to hydrotest, then ship some large equipment. We typically make this equipment in Stainless steel, however this latest batch is made of 516G70 carbon steel. (2) questions:

1) Can anyone recommend an additive to put in the hydro fluid that might slow oxidation of the inner surface?

2) These units will likely be sitting in storage for 4-12 months after delivery. Is there a temporary coating suitable for the pertrochemical industry that we can apply to the equipment's ID?

Thanks!


John
Mechanical Engineer
Artisan Industries Inc.

http://www.artisanind.com

 

[btrueblood]

John,

Not only should the additive for the hydro fluid not cause rust, but it should not promote rusting as the fluid dries out over time...

1.) you could use pure ethylene glycol, but it never really dries out at ambient conditions, and is toxic to wildlife if spilled.
2.) you could add corrosion inhibitors to water, with the caveat above. I found a product called DePhos 8028, from DeForest Enterprises (

http://www.deforest.net),

which is a phosphate-based inhibitor. It worked well for both brass and iron/steel, including when both materials were present at once, and during "dry-out". This was after testing a bunch of different products that didn't work.

Good luck,

Ben

 

[jte]

andrewsjo-

I did a short stint years ago for a company in Waltham and Fall River. Nice area.

Unless you have some particular concerns about rust due to process reasons (and then you should consider stainless), I wouldn't worry about using an inhibitor. The hydro just won't be long enough to cause substantial oxidation. Wipe it dry at the conclusion of the hydro (blow out the crevices with compressed air), toss in a few boxes of dessicant, and button up the vessel using 1/4" thick steel blinds (for the nozzles that you aren't providing proper blinds for) and gaskets.

Ultimately, though, your client may have something to say about it, so check with the client. I've been involved with procuring vessels for a while with both an E&C and now working directly for a refinery and we just don't see any problems that we'd tie back to corrosion during a hydro.

jt

 

[tickle]

In the past, we have dried out vessels by blowing through with warm air and then filling with nitrogen (add a cheap pressure gauge ton one of the flanges to allow people to check the vessel still contains N2)

Remember that N2 is the biggest killer on chemical plants so have big labels informing every one

Similarly, add big labels showing that the vessel has dessicant bags inside. Also I am assuming that jte was being flippant when he said "toss in a few boxes of dessicant" and proper care is taken to ensure that the dessicant is in properly sealed permeable bags that are attached to the vessel in a suitable location to allow easy extraction at the job site. Your packers would be able to assist.

If the equipment is small enough then it may be packaged in a sealed crate with dessicant dessicant bags.

 

[jte]

tickle-

Oh, come on! It's soooo much fun to watch them process engineers crawling into the itty bitty spaces in vessels to clean up the bits of dessicant prior to commissioning the vessel!

Yes, yes, all items, large and small, which are shipped loose with the vessel should be properly stowed and secured for transportation. Might be a good idea to mention the dessicant to the client so that it can be removed prior to erecting the vessel (assuming it's vertical). It might be a lot easier to get the crud out while you don't need ladders inside the vessel to get around.

I have also seen vessels inerted, but usually only for special reasons (metallurgy, process requires extremely clean, ocean transport, etc). As tickle pointed out, label it well and discuss it with the client. INERT GASSES KILL through oxygen depravation. They don't injure. You just take a breath, perhaps two until you lose conciousness. From what I understand, the body's exhalation reflex is triggered by the amount of CO2 in the lungs. Displace the CO2 with N2 and the body thinks it doesn't need to breathe.

The pressure gage is nice to ensure that the inert gas is still contained in the vessel. However it provides NO ASSURANCE that the vessel has a safe atmosphere for entry. You can pop a manway and equalize the pressure, send a man in and drag a corpse out minutes later. The only way to ensure a safe atmosphere in a vessel which has been inerted is to open it up at both ends and blow air through it. Then perform a gas test to make sure the oxygen content is high enough. Then be careful with any voids/nooks/crannies in the vessel which may not have been vented. Those of you who know my style know that I don't use all caps often. This is one rare topic on this board which warrants all caps.

jt

 

[pennpoint]

jte
Your message rang clear with me, and I hope with others.

pennpoint

 

[arto]

John-
For Hydrotest Fluid, check out Rustlick:

http://www.itwfpg.com/tech/rustlick/B.pdf

[look in the Size V test files ]

For long term preservation see if these are compatible with the processes, catalysts, etc.: [MIL-Spec approved, from Turbine land]

Tectyll 511M from Daubert:

http://www.tectyl.com/

{They have a whole bunch of other VCI products :

http://www.daubertvci.com

}

ZeRust Blocks: [wire in place on shipping flanges]

http://www.ntic.com/documents/InfoSheets/Info Sheet Vapor Capsules.pdf

 

[deanc]

Add Sodium Nitrite to the water. Acts as a oxygen scavenger.

Try Accelerator 131 from Henkel Surface Tech.

Works good,fairly cheap and safe. You can sewer it. Use about 5/1000.

 

[unclesyd]

Check out this site as they make inhibitors for before, during and after a hydrotest.

http://www.cortecvci.com/Products/products.php?showonly=WaterFuelAdd

 

[jte]

Folks-

Ran across a good source of info regarding the hazards of Nitrogen atmospheres. From the Chemical Safety Board site:

"...the Board initiated a review of similar incidents nationwide. The CSB study identified a total of 85 incidents that occurred in the U.S. between 1992 and 2002 and involved exposure to a nitrogen-enriched atmosphere. Together these incidents caused 80 deaths and 50 injuries."

That's roughly an average of one fatality in the USA every 90 days due to Nitrogen asphyxiation. "It's just an inert gas! What are you worried about?"

http://www.csb.gov/index.cfm?folder=completed_investigations&page=info&INV_ID=41

jt