Refinery Fluid Thermal Expansion Due to Steam Tracing
Refinery Fluid Thermal Expansion Due to Steam Tracing
(OP)
Hello, i am currently a process engineer at a refinery and im looking into the effects of steam tracing on lines and the resulting thermal expansion if the line is blocked in. The lines are full of hydrocarbons and I was wondering if line length matters as we typically only see leaks on our longer lines. Me question is; if a one foot line is blocked in and steam traced at 350 oF and a 100 ft line is traced at the same temperature with the same fluid inside and fill volume percentage, will the resulting pressure on the pipe and flange be the same, or does total heat into the system matter at all? Hopefully this makes sense, im essentially trying to figure out why we are having more leaks on our longer lines than our shorter ones.





RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
In theory, there is no difference between long and short lines if the same heat flux were applied. In practice, as you have observed yourself, the differences do appear - mostly due to localized overheating, condensate pocketing, etc.
For longer lines, installation of TSV is recommended. Various companies have different guidelines with regards to the liquid volume threshold (volume of trapped liquid above which thermal expansion relief needs to be provided), and this is in line with field observations that shorter lines usually do not experience overheating. You can read more on thermal expansion in API 520 and http://www.chemwork.org/PDF/papers/what%20you%20sh...
Dejan IVANOVIC
Process Engineer, MSChE
RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
http://abiquim.org.br/congresso/cong_cd/fullpapers...
RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
RE: Refinery Fluid Thermal Expansion Due to Steam Tracing
The TSV leak rate can be calculated if you know how the liquid density changes with temperature rise; usually mass rates are low and may be accomodated with a 1D2 orifice or even smaller, but if you face the risk of a engineering safety audit, better to have these rates calculated.