Page 204 - Root Cause Failure Analysis

192 Root Cause Failure Analysis
Thermal elements can be designed to operate at any steam temperature. In steam-trac-
ing applications, it may be desirable to allow controlled amounts of condensate to
back up in the lines in order to extract more heat from the condensate. In other appli-
cations, any hint of condensate in the system is undesirable. The thermostatic trap can
handle either condition, but the thermal element must be properly selected to accom-
modate the specific temperature range of the application.

Thermostatic traps are compact, and a given trap operates over a wide range of pres-
sures and capacities. However, they are not recommended for condensate loads over
15,000 lb per hour.

PERFORMANCE

When properly selected, installed, and maintained, steam traps are relatively trouble
free and highly efficient. The critical factors that affect efficiency include capacity and
pressure ratings, steam quality, mechanical damage, and calibration.

Capacity Rating

Each type and size of steam trap has a specified capacity for the amount of condensate
and noncompressible gas that it can handle. Care must be taken to ensure that the
proper steam trap is selected to meet the application’s capacity needs.

Pressure Rating

As discussed previously, each type of steam trap has a range of steam pressures that it
can handle effectively. Therefore, each application must be carefully evaluated to
determine the normal and maximum pressures that will be generated by the steam
system. Traps must be selected for a worst-case scenario.

Steam Quality
Steam quality determines the amount of condensate to be handled by the steam trap.
In addition to an increased volume of condensate, poor steam quality may increase the
amount of particulate matter present in the condensate. High concentrations of solids
directly affect the performance of steam traps. If particulate matter is trapped between
the purge valve and its seat, the steam trap may not properly shut off the discharge
port. This will result in live steam being continuously exhausted through the trap.

Mechanical Damage
Inverted-bucket and float-type steam traps are highly susceptible to mechanical dam-
age. If the level arms or mechanical links are damaged or distorted, the trap cannot
operate properly. Regular inspection and maintenance of these types of traps are
essential.