ASME B31.3 Monitoring pressure upset conditions

[Tarkjell]

Our Process deparment has asked a question regarding allowance for increased pressure.

In ASME B31.3 para. 302.2.4 it is described allowance for increased pressure rating (33% or 20%).
Increased pressure is allowed if the duration is within limits described by the Code.

Process is asking whether it is necessary to monitor these occasional events?
Does the code describe any logging/monitoring of pressure and duration?

I have looked in the Code for it but cannot find description of such demand.

Do you have any comment on this?

 

[aurrous]

You'r question is a little vauge, and i dont have a b31.3 book in front of me. However, I can say that normally when looking at working pressures in a line, you have to take into consideration what the material data sheets say the pipe can hold, what your maximum allowable working conditions are, what the design pressures are, working temps, design temps, Max temps, material types. Normally in a working boiler as long as you dont start violating any of your maxes or come close to the 80% marks you dont have to document anything because all those factors should be pre calculated into boiler. Provided this is a once in a while deal. If your cosntanly hitting your 30% marks, you might look at redisigning your line, and moving the code boundery. If your violating your maxes, you should not only document it, but notify the AI imediatly.
Worse case senerio go to the b31.1 book in the 102.x.x + look at what they say there, then figure out the diffrences between the b31.1 and b31.3 you probably wont find much detail in the 31.3 section due to it being less critical piping, normaly open air vents and drains, which shouldnt see a whole lot of exstreams.

 

[davefitz]

not in my field of expertise, but there were some pipeline failures recently related to short term overpressure events ( "water hammer&quot aggravated by apparent pipe damage by excavating equipment ( Olympic pipeline failure 2000). I believe there were new federal rules issued that go beyond ASME code rules for pipelines.

Normally overpressure is limited by the use of relief valves, but some pipeline systems allow alternate overpressure protection by use of pressure switches and fast acting stop valves ( must close within 1 sec) plus multiple independent press red valves in series, etc , etc. In an extraordinary event ( fire) some overpressure is allowed, but generally below the proof testing pressure used during hydrotest.

I think the pressure monitoring and recording may be required for systems that are routed in the public domain( fuel pipelines), and these rules are separate from ASME.

 

[krossview]

Tarkjell, one of our clients is doing exactly what you describe and have done this on a number of projects, but only on piping, not on vessels as far as I know. Reference is made to the same section of ASME B31.3 code

They do monitor and record an overpressure event to proof to the local AI or boilers branch that they are in compliance with the code. A PLC records the time duration and pressure when the design pressure of the pipe is exceeded. The system is shutdown when the pressure reaches the 33% overpressure mark.

High pressures only experienced in the first phase of the project and cost savings are the main reasons behind this option. From a personal standpoint of view I do not recommend designing a system so close to the upper limits, but code allows it.

I strongly recommend you check your local AI on this subject and see what they have to say. I second the viewpoints from Aurrous

 

[reichertc]

I truly hate it when process engineers read that section of the code. I have had this request made a number of times, and I have only allowed the use of it once. In this case, recording devices were installed to monitor pressure and temperature. In any event, the refinery had to have a lot bigger problems than this section of pipe overpressuring for this upset condition to be reached.

That said, it may be an economical approach to follow when doing revamps to an existing system.

Please note that usually the process guys and the owners only seem to read Para 302.2.4(f) and do not read the rest of the conditions (a-i) that must be met before these excursions can be permitted. Once they see the amount of work involved in applying this paragraph, most of the time a relief valve is installed.

Anyways, the requirement to record conditions will fall with your local inspector. And if the local inspector did not require it, I would. If a system has a relief valve set at 33% higher than the flange rating of the system, what would prevent the owner from operating continuously at 30% over the flange rating????