Thermal Relief For Exchanger In Long Loop
Thermal Relief For Exchanger In Long Loop
(OP)
I have a heat exchanger in a water loop fed from a storage tank to a pump where it is circulated through the tube side of an exchanger and back to the pump suction (drops from the loop to users as-required). The exchanger shell side has steam to heat the water. Although the water valves at the exchanger are locked open, there are valves at the pump suction and pump discharge that are not locked open, and if closed, could block the cold side of the exchanger. Since this is a long loop, is a thermal relief valve in the loop required?





RE: Thermal Relief For Exchanger In Long Loop
RE: Thermal Relief For Exchanger In Long Loop
RE: Thermal Relief For Exchanger In Long Loop
But I would suggest there is no need for a TRV here on the tubeside if the following conditions are met or are applicable:
a)A small hole is drilled on the pump discharge check valve.
AND
b)If you've got regular packed glands on the centrifugal pump inboard and outboard shaft seals, then these would act as a relief path since no packed gland is completely leak tight.
AND
c)All block valves between the HX tubeside and the pump shaft seals are locked open.
RE: Thermal Relief For Exchanger In Long Loop
RE: Thermal Relief For Exchanger In Long Loop
This will then exclude tube rupture overpressure.
If there was no tube rupture ( and tubeside DP = > shellside DP) , the max boiling pressure of the tubeside contents cannot exceed the max normal supply pressure of the steam on the shellside, which would only be less than tubeside DP.
If the pump is stopped at the time of the blocked in scenario, could the tubeside operating pressure drop to atmospheric or some low pressure. At some low pressure, would the tubeside contents then boil up to