Corroded Relief Valves

[Bader]

Gent.

We have Water Oil Separator equipment in the plant, and there are some relief valves in the gas & liquid sides.

We have a problem with a repetitive corrosion in the relief valves annually, every time we dismantle the relief valve the inspection revealed a highly corrosive rate. (196 MPY). The body material is carbon steel & we cannot utilize stainless steel due to carbonate.
Our usual treatment methods are as following:

• Preheat.
• Grinding.
• Remove the defected materials.
• Welding overlay.
• Coating (APCS-2A & APCS-114).

I am wondering if there is any solution to reduce the corrosion rate, can we utilize rapture disc / line relief or other methods?

Please help if you face this situation before and you know away to resolve it.


Your quick & active response will be highly appreciated.

I am always ready for help as much as i can .. so just let me know your Problem .

 

[pleckner]

I would highly recommend the use of a rupture disk for this application. It is a classic!!!

You can get more insight from my articles on Rupture Disks at

http://www.cheresources.com.

On the menu at the left hand side of the site, click on "Free Aricles", then "Pressure Relief Design"

 

[Ashereng]

Yes. A rupture disc protecting the PSV due to corrosion is a very common use of rupture discs. Add a pressure gauge/transmitter between the disc and PSV to detect the rupture disc rupturing also.

How about other materials? You mentioned not stainless steel (I am assuming the 300's familie, eg 316SS). How about other materials? Monel? Hastelloy?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[pleckner]

You can count on changing the PSV material of construction to anything will be more expensive than using a rupture disk.

 

[Bader]

Thanks gentlemen for your response.

But do you think that line relief valve will help, i mean the relief lined with plastic or other not corroded materials will be effective for this case or not and if any one use the line relief valve is it efficient !!.



I am always ready for help as much as i can .. so just let me know your Problem .

 

[gerhardl]

As given by earlier replies: best would be rupture disc with pressure gauge between disc and PSV.

You have to go into details to find a suitable rupture disc, both to adjust to correct rupture pressure suitable to pressure relief for valve, disc and vessel.

Note tolerance requirements for bursting disc: distance from burst pressure down to normal working pressure, could be larger than for the PSV, and likewise tolerance from burst pressure up to granted burst pressure for the disc higher than required relief pressure for the vessel.

Hence: disc with suitable tolerance and suitable materials: Plastic, monel, silver(?)

Suitable bursting discs would probably be the cheapest solutions in the long run, if you do not have frequent overpressures activating the PSV, eating up bursting discs.

If the latter is the case you should have a look at the total relief and process control concept.

You do not mention sizes and pressures, or describe how the overpressure problems occurs. If you find a suitable in-line relief valve, with lining and materials compatibel to the fluid (oil, oil derivates, petrol,water,waste-water, fat,sea-water others???) it would probably work if the sizing and and overpressure surge are within the necessary limits. Liquid will have to be free of sand or particles. I would not go for this solution myself.

There is a but anyway: it would probably not be allowed or sensibel to have this as the only relief for a pressurized vessel.... and then you are back to the start.

 

[pleckner]

For the parameters needed in sizing a rupture disk and what to look for (as pointed out by gerdhardl) see my articles I referenced in my first post.

There is a lined PSV that you can investigate. Go to

http://www.richter-ct.com.