Hello all,
I have some questions regarding the relief scenario and sizing basis of a PSV protecting a heat exchanger.
The exchanger is a heater with the tube side being liquid product entering the heater at 140 degrees F and 180 psig. The shell side is steam at 400 degrees F and 240 psig. The PSV is located on the tube side outlet line and has a set pressure of 400 psig.
Per the typical 2/3rds or 10/13ths standard, a tube rupture scenario would not be considered. The product vapor pressure at shell side temperature (244 psig) is less than set pressure (400 psig), and pump deadhead is less than set pressure, so blocked outlet scenario is not considered.
All other scenarios simply result in a higher temperature product, which downstream equipment can accommodate. Per API 521, fire scenario is considered due to the heater being at grade level.
This is the first sizing I have done being a tube side fire scenario with shell side being steam. Is it realistic to consider the sizing basis to be a fire scenario resulting in product vapor being discharged through the PSV, or have I overlooked something that I should also look into? If so, would it be safe to assume the wetted surface area is equal to the total surface area of the vessel in this scenario?
Please see generic diagram below.
Attached Files
Edited by tamueng, 08 November 2023 - 11:05 AM.