Polymerization reactor with jacket
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For a polymerization reactor with a jacket, during the hydrostatic test, which should be done first: the jacket test or the vessel body test?
Logically, the main body should be fabricated first; once it is qualified, the jacket is welded to it. The jacket of the main body is then tested for water tightness. After that, the water inside the inner cylinder is drained, and the pressure in the jacket and outside the cylinder is checked, finally the water in the jacket is removed.
Theoretically, the vessel body should be made first, but if the pressure during jacket testing is higher than that the vessel body can withstand, a compromise can be made
The body and the jacket are manufactured separately, one after the other. Because there are various operating states, internal and external pressures sometimes cancel each other out and sometimes add up. For example, a steam-heated jacket can have a positive pressure of several kilograms while heating; if the inlet and outlet valves are closed and low-temperature material is introduced into the tank, the jacket may become under vacuum with negative pressure, and so on.
When the inner cylinder is at atmospheric pressure, the jacket can be installed first; during jacket testing, a person can enter the inner cylinder to conduct inspections
Please see the requirements specified in GB/T150.4-2011. Clause 11.4.8, page 337: For vessels with jackets, a pressure test of the inner cylinder should be conducted first; once it passes, the jacket should be welded on, followed by a pressure test of the space inside the jacket.