Set pressure of safety valve 1

[ekschwab]

On a non-fired boiler steam line... has anyone ever seen the design pressure of B31.1 piping being LOWER than its relief valve setting?

There are multiple relief valves in the line, each at an incremental pressure than the previous. The first valve will lift at the design pressure of the pipe. Subsequent valves that lift to accommodate the capacity will be at higher pressures (above the design pressure of the piping).

I did not design the system. I am observing and questioning what is already being considered. It does not sound right to me and I do not see B31.1 clearly permitting this.

 

[rneill]

Biginch,

That is probably the case in pipeline systems but it is extremely common for gas plants, oil batteries and other plant process systems to have piping that operates well below design pressure for the life of the facility. More commonly, the system pressure drops over time as the production decreases and the field matures.

If I had to guess, I'd say that less than 10% of the plant piping systems I ever deal with (and I deal with a lot of old established systems as well) have operating pressures in excess of 80% of the design or MAWP.

 

[BigInch]

I worked gas gathering systems at Trans Texas Gas, compression & transmission and liquid plants at Northern Natural, Enron and Transco Gas and designed a lot of gas systems for other folks and can't recall seeing it anywhere there, nor on any liquid lines either. Like I say, what's the point in having MAOPs if somebody's going to set reliefs lower than that.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[rneill]

While, one argument is that it is very easy to do an MOC and to evaluate and reset a PSV at a future date if necessary whereas it is very difficult to change the MAOP after the fact.

 

[BigInch]

If the PSVs were set at reasonable levels, there would probably be no need to reset them.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv