R 717 Relief Header Piping 1

[maxoverdrive]

If any of the code gurus could help translate a code regarding ammonia relief header piping it would be much appreciated. Is I read and understand this the header must be 15 ft above the highest traversed elevation. however, it does not stipulate the sizing. Assuming a standard engine room with 10 compressors and associated vessels there may be as many as 20 reliefs. Code states worst case scenario yet if a manifold valve is installed only 10 may relieve at once. Even so 10 3/4 inch valves leads to an enormously disproportionate relief header. Any serious suggestions or precedent articles that would clarify for APPROPRIATE piping size?

 

[Montemayor]

maxoverdrive:

What you seem to be looking for is a code-specified size of Ammonia Relief Header. No "code" is, in my opinion, ever going to specify or recommend a size for a relief header. Design (engineered sizing) is not the objective of a code. You have to do that. In order to come up with an adequate, safe, and successful size for a relief header you have to have (or generate) a lot of basic data and calculate the size using conventional Fluid Mechanics logic and theory. I normally employ the Darcy-Weisbach relationships for such an application.

You make reference to a "Code", but fail to identify it. We can't address something that isn't identified or detailed out. You have to furnish specific basic data appropriate to resolve the problem. If you don't know the quantity and quality of basic data required, then you don't know how to size the header and the concern for code stipulations should be a secondary - or tertiary concern. You have a more basic problem confronting you than just a code.

In NH3 relief, you should, in the back of your mind, be very concerned in having to deal with 2-phase flow. This can originate at the source of the relief or can be generated by relieving liquid NH3.

The configuration of the feed laterals into the relief header is just another important point that can cause a lot of grief.

I hope this helps you out.


Art Montemayor
Spring, TX