Until recently, the visual method has provided the most reliable steam trap testing. On lines thatreturn the condensate to the boiler, all that is required is a three-way valve or a pair of valves. The piping must be configured so the operator can shut off the condensate return line and allowthe trap to discharge to the atmosphere. The visual method requires training and experience. When the condensate reaches the atmosphere, part of it converts to flash steam, and the observermust be able to differentiate between this and live steam.
Flash steam appears as a lazy whitecloud.
For best results with the visual method, a valve should be installed upstream of the trap. The valve is closed for a minute or two before the test to accumulate some condensate. When thevalve is opened, the tester should be able to hear or see the trap handling more condensate as thesludge passes. It should be evident if live steam follows the all-condensate sludge. Another effective technique, if the system includes a bleed-off valve upstream, is to reduce theloadby draining the condensate.