Temperature range
Temperature range
(OP)
What are rules for deciding the lower limit of piping design temperature range?
Is it the lowest possible temperature the pipe could see in it's life. ie shut down in the coldest winter or can more a resonable temperature for the annual shut down be used.
The systems we design are base load and only shut once a year. (a lot less than 7000 cycles)
Thanks
Is it the lowest possible temperature the pipe could see in it's life. ie shut down in the coldest winter or can more a resonable temperature for the annual shut down be used.
The systems we design are base load and only shut once a year. (a lot less than 7000 cycles)
Thanks





RE: Temperature range
-2 ºC 80%
-5 85%
-10 90%
-12 95%
-15 98%
-16 99%
-19 100%
If that is the case, you should design for -15ºC and if the temp drops to -16, you can continue to operate if you can, but if you can't, you can still claim you did perform to the minimum contract delivery requirements.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Temperature range
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Temperature range
If the line is always in service, then the fluid will keep it warm in most situations too. When its out of service, the stress' are lowered and that is acceptable. Just have a proceedure to bring the line back up to temperature as you put it back in service.
RE: Temperature range
In our case we may only see maximum temperature (brust disk pressure) a few times in the life of the plant and the low tempetures will only happen once a year at shut down.
If we take the lowest possible temperature during the shuts we are being very conservate.
I have seen a calculation in another code (AS4041) where the you can calculate the equivant number of cycles based on the frequency of the different temperatures. And also Increase the allowabe stress range for when the cycles are less than 7000.
RE: Temperature range
Temperature cycles are based on process start-ups going from ambient temp to normal operating temp and back, i.e. not based on excursions of ambient temperatures superimposed on a constant normal operating temperature. On a well insulated line, an ambient temperature excursion to a 500 yr Lo temperature may not affect the temperature of the piping material at all.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com