Finding out failed steam traps and fixing them up can avoid the wastage of steam and improve the productivity and performance of the steam system. It would be worthwhile to understand the implications of steam trap failures on the performance of the steam system.
Simply put, steam traps fail in two ways: open and closed. When a steam trap fails open, it acts like an open valve, completely leaking the steam and condensate. When a steam trap fails closed, it acts like a closed valve not allowing the steam and condensate to pass through it. Whether a steam trap fails open or closed, it does equal damage to the steam system and hence, should be repaired or replaced.
Failure detection is easy if a steam trap fails open and it discharges into the open. If a stem trap fails closed or if a steam trap from which condensate is being recovered fails open, the detection becomes difficult. Hence, it is always advisable to use correct equipment to monitor the steam trap performance on a regular basis.
A Steam Trap Fails Closed :
If a steam trap fails closed, following are the different problems associated with the failure.
Water hammer and pressure surges
Presence of water i.e. condensate in the steam system results in a phenomenon called as water hammer. Condensate, if not removed by a steam trap accumulates at the bottom of the steam lines. In such situations, a bi-phase flow exists in the piping. During such bi-phase flows, condensate is dragged by the steam to travel along with the steam at speeds much higher than the maximum allowable speed for condensate. This results in slogs of condensate travelling at very high velocity in the steam lines. When this slug hits some bend or some equipment, a pressure wave is generated which is called as water hammer.
Fail closed steam traps are the major reason for water hammer.
Water logging in the process
When a steam trap installed on a process equipment fails closed, it stops removing condensate from the process. As a result, condensate accumulation takes place inside the process vessel. Water logging has multiple disadvantages with respect to the performance of the process. First of all, the product which is surrounded by water won’t get heated. This results in non-uniform heating of the product. Water logging will also increase the time required to heat the product to the desired temperature.
Damage to piping and process equipment
Condensate is pressurized fluid. If condensate remains in the steam system and there is a sudden drop of pressure, it will flash and will expand in its volume. Such sudden expansion can damage the piping. Water hammer as well as moisture entrained in the piping can damage various equipment fitted on the line.
As it can be seen from the points mentioned above, presence of water in the system is a possible safety hazard. A failed steam trap compromises the safety of the steam system.
A Steam Trap Fails Open
When a steam trap fails open, following are the problems which might be faced :
Increased steam consumption
When a steam trap fails open, it simply acts like an open valve and hence, a lot of steam would leak through it. As a result, the overall steam consumption of the plant will go up, reducing the efficiency of the operation.
Increased load on the boiler
If a leaking trap is discharging to the drain, the entire steam and hence the heat energy that is being leaked, will be wasted. This also increases the boiler load. Many times, it has been observed that a same size of boiler can be used to heat more processes if all the pipe leaks and leaking steam traps are repaired or replaced.