valve modifications

[eli73]

Our chemical plant has a plunger type valve on the drain of a pressure vessel. After repeated failures due to corrosion, they took a commercial valve and under the direction of an experience ME modified it by creating a new, sturdier valve body made from a different alloy and thicker pipe on the discharge side. It has worked well. My question is: How does that affect the legality of using that valve and are there any methods to have the valve tested and stamped to approve it for service, or is that even possible?

Thank you.

 

[within]

The legality of the changes that you have made to this valve basically depend on what the changes are, and what part of the world you are in. Here in Europe all valves supplied must meet the requirements of the Pressure Equipment Directive. If you have changed the pressure boundary in any way then you must document what you have done and show that it meets recognised standards.

Using ANSI standards I would say that you should produce a fully documented technical appraisal of the valve. For this you will have to check the pressure/temperature ratings, the body wall thickness, and flange dimensions. You should also produce some bonnet thickness calculations and carry out a body hydraulic test.

Overall it could be cheaper to purchase a new valve.

Best of luck.

 

[bcd]

eli73,

In North America, the requirements are essentially the same as those in Europe as decribed by "within". However, they are not directly listed in a "directive".

While so far, the valve performance is everything expected, here are some things to think about in your situation.

1. If this valve fails and injures somebody or results in expetnsive plant damage, who is responsible? Right now, it is the owner of the plant.

2. What steps have been taken to verify that the valve is suitable for this application. Hazard analysis, laboratory testing, and other items need to be conducted and documented to be able to demonstrate that potential risks were evaluated and addressed. If this is not done, then the lawyers will have a field-day, and the potential punitive damages awarded at the end of the very short trial will be impressive. Of course, OSHA will also increase the financial penalty.

3. The same issues as 2 above apply if someone is injured using the valve. Is there written documentation warining any user or maintenance person of the hazards associated with the valve. If not, this is "failure to warn", which is also a very short trial.

4. If the experienced ME is liscensed, it helps to alleviate the issue, but make sure that they take responsibility for the product they created. They must have documentation that proves the product is suited for the service, and that all potential safety hazardos that can be created in the design, manufacturing, installation, and maintenance areas is identified and steps in place to mitigate the potential for injury.

bcd