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Thermostatic traps
THERMOSTATIC TRAPS (bellows & bimetallic) operate on a difference in temperature between
condensate and steam. They build up condensate so that the temperature of condensate drops down
to a certain level below saturation temperature
in order for the trap to open. By backing up
condensate, the trap will tend to modulate open or closed depending on load.
In a bellows trap, should the bellows become compressed by water hammer, it will not function
properly. The occurrence of a leak will prevent the balanced pressure action of these traps. When
either condition occurs, the trap will fail in its natural position either opened or closed. If the trap fails
closed, condensate will back up and no sound will be heard. If the trap fails open, a continous rushing
of live steam will be heard
w
ith bimetallic traps, as the bimetallic plates set due to the heat they sense
and the cooling effect on the plates, they may not set properly which will prevent the plates from
closing completely and allow steam to pass through. This will be heard as a constant rushing sound.
NOTE:
A complimentary Steam Trap Trouble Shooting Guide is available. Visit our website
WWW.UESYSTEMS.EU
Locating faulty valves
Utilizing the contact (stethoscope) module in the Ultraprobe, valves can easily be monitored to
determine if a valve is operating properly. As a liquid or gas flows through a pipe, there is little or no
turbulence generated except at bends or obstacles. In the case of a leaking valve, the escaping
liquid or gas will move from a high
to a low pressure area, creating turbulence on the low pressure
or "downstream" side. This produces a white noise. The ultrasonic component of this "white noise" is
much stronger than the audible component. If a valve is leaking internally, the ultrasonic emissions
generated at the orifice site will be heard and noted on the meter. The sounds of a leaking valve
seat will vary depending upon the density of the liquid or gas. In some instances it will be heard as a
subtle crackling sound, at other times as a loud rushing sound. Sound quality depends on fluid
viscosity and internal pipe pressure differentials. As an example, water flowing under low to
mid
pressures may be easily recognized as water. However, water under high pressure rushing through
a partially open valve may sound very much like steam. To discriminate: reduce the sensitivity,
touch a steam line and listen to the sound quality, then touch a water line. Once you have become
familiar with the sound differences, continue your inspection.
A properly seated valve will generate no sound. In some high pressure situations, the ultrasound
generated within the system will be so intense that surface waves will travel from other valves or parts
of the system and make it difficult to diagnose valve leakage. In this case it is still possible to diagnose
valve blow-through by comparing sonic intensity differences by reducing the sensitivity and touching
just upstream of the valve, at
the valve seat and just downstream of the valve.
