Use of 300# rated valve for 600# rating 2

[NS13]

Could some one please advice on the below limitation / proposal
My customer requires a 600# valves (flanged) but the weight of this is approx 30T. Importantly the max design pressure / temperature is less than 300# valve which weigh 9T.

My proposal
1. Offer 600# as a 300# valve This will involve customer to change the mating flange of the pipe
2. Offer 600# with higher wall thickness of a 600# design but the flange to remain as 300#. - This will involve customer to change the mating flange of the pipe

In either case, if the mating pipe flanges cannot be changed to 300#, Can customer explore converting adaptors (to mate the valve flange of 300# to pipe flange of 600#)

Advantage
1. The proposal meets your design requirements
2. The weight savings is approx 00T, which is also a cost saving.

Limitation
1. The valve can only be certified as 300#

 

[RVAmeche]

I don't understand how a Class 600 valve could have a lower design pressure/temperature than a Class 300 valve, unless it's something to do with the valve weight itself limiting it. Have you confirmed those numbers are correct and the it's not a typo or something odd?

If a Class 300 valve meets the requirements, inquire as to why it's a Class 600 system? Could be they're just over-conservative...but I'd definitely want their process people to buy off on it before installing it.

 

[NS13]

Thanks - RVAmeche

Yes - that was equally surprising us, we had requested the customer clarifying this, which they have confirmed the data is correct, and the choice of 600# for these lower condition than 300# is due to piping design (which is complete).

Under this limitation, the above was my proposal - As I have limitation in handling this heavy valve for testing and assembly, but if either of my proposal is acceptable - this woulb be a win-win situation.

My question is - Is my proposal technically acceptable.

 

[RVAmeche]

If you've confirmed that the actual design temperature/pressure of the system is below Class 300 limits, and there's no transient or rare events that exceed those limits, then it seems like the Class 300 valve would meet the technical requirements. Definitely get that in a formal RFI or whatever mechanism you use for documentation.

From the clients POV, assuming the above is correct, the only thing I'd be concerned about is having an odd valve that I now need different spare parts for. But if it meets the technical requirements and is significantly less weight that's just gravy on top.

Also, I assume the valve manufacturer is reputable? The only other thing I could think of is this is some random valve company and they "say" the Class 300 meets the requirements, you fire up the system during commissioning, and something bad happens. Lawsuits from stuff like that aren't unheard of.

 

[NS13]

Thanks - RVAmeche

YOu are right and that is what is my concern. Now from the data sheet - I have reckoned that the 600# valve design parameters are less than that of 300#. However I will not be able to certify my proposed valve as 600# due to this "you fire up the system during commissioning, and something bad happens. Lawsuits from stuff like that aren't unheard of".

From manufacturer standpoint, I have considered the wall thickness of 600# valve, but with a 300# flange, wherein the body section will be designed to 600#, and the flanges to 300# (this reduces the weight of the valve to less than half from 20T to 9T. SO the buyer will have to mete my valve flanges with an adapter to suit their 600# piping.

Would this be a technically acceptable solution

 

[pennpiper]

NS13,
I'm sorry I do not have the answer to your situation.
My purpose here is to help you get your answer faster.
1, You need to give more information for us (example: What is the size of the piping involved in this post?

2, Use the proper terminology when asking your questions. Using the term "300# valve" or "600# design" is way out of date when discussing piping flanges and valves. The correct terminology is as used by "RVAmeche" e.g. Class 300 or 600, etc.

Sometimes its possible to do all the right things and still get bad results

 

[LittleInch]

Is your proposal technically acceptable.

Almost certainly No, but you are proposing what could be an acceptable alternative.

Making the body equivalent thickness to a class 600 valve but with class 300 flanges makes no sense. Your valve is then limited by the rating of the flange.

What design code is this to?
Is there a customer specification?

It is common that specs require a valve to be fully rated to the nominal class limit, in your case class 600.

All you can do is offer a wholly class 300 valve with class 300 flanges and se what happens

Only the customer can decide whether this reduction in weight and presumably cost is worth changing their piping design to class 300.

It does seem strange that they haven't modified their design to meet the stated process conditions, but that's their problem.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.