I need information on how to test most/all types of heat exchangers. I do not need to research the test pressures, just the methodology. I have developed standard procedures for overhauling heat exchangers such as found in oil refineries and chemical plants. Sometimes you test the bundle, the the shell side, sometimes the tube side together with the shell side, etc. Sometimes you have to employ test rings, etc. The standard procedures are used mainly for shutdown/turnaround work.
TEMA's Standard Test for heat exchangers reads as follows:
"The exchanger shall be hydrostatically tested with water. The test pressure shall be held for at least 30 minutes. The shell side and the tube side are to be tested separately in such a manner that leaks at the tube joints can be detected from at least one side. When the tube side design pressure is the higher pressure, the tube bundles shall be tested outside of the shell only if specified by the purchaser and the construction permits. Welded joints are to be sufficiently cleaned prior to testing the exchanger to permit proper inspection during the test. The minimum hydrostatic test pressure at room temperature shall be 1.5 times the design pressure, corrected for temperature, except where other Code requirements govern."
That is essentially all TEMA specifies, except that it allows for a pneumatic test (which I won't do) in the event that liquid(s) cannot be tolerated as a test fluid medium.
Of all the turnarounds I remember, heat exchangers have always been tested with water. I remember air tests being conducted for some vessels (they taped all flanges to detect leaks), but rather as an exception to the rule.
We have done already two turnarounds and we fairly know which heatexchangers give trouble. Typically it are the vacuum jet overhead condensors (gases) and cooling water in the tubes.
The crude-vacuumbottoms and other oil to oil exchanges normally don't give problems, we never found a leak.
We do the test on all the tubes, but thouroughly testing is done with the vacuum condensors, because you need to know in an early stage if it is retubing or pluging, and plan for replacing the whole bundle. There are special air tools for tube bundle testing. Basically one man at channel head side with an airgun and another at floating head side to plug the other end with a pressure gauge.
It is easier to test then pressure testing in the shell with water to find leaking tubes.
As far as I know that the hydrotest by air is safety concern and water is usually used. I have seen incidents with air hydrotesting that caused fracture of some vessels.
Therefore, recently we have done both air and water hydrotesting for some equipement in the plant where the fluid service either vapour or liquid.
That was done by subcontractor with special devices with given instructions (i.e. time of pressurizing, holding, and repeating)
I dont have this procedure now but this what I have experienced.
The air test is not a hydrotest, with the hydrotest you evaluate the structural integrity, with the air test you localize problems.
The engineer who executes a hydrotest on a boiler with steam, will lose his license and face juridical penalties.
