Protecting the Pressure Transmitter
Measuring steam pressure is a common application in the HVAC industry, but finding a transmitter that can handle PressureFig1the higher temperatures of steam can be a challenge. Steam, under typical HVAC and process pressures, may reach temperatures ranging from 212°F to 400°F, but most pressure transmitters maximum temperature limits are around 200°F. An inexpensive and effective solution is to install a steam syphon between the steam source and the pressure transmitter. The Model PT steam syphon from Kele is an excellent choice.
The steam syphon protects the transmitters from the extreme temperature of steam. The key to an effective steam syphon is the condensate that forms in the syphon loop (see Figure 1). This water barrier not only acts as a heat buffer, but also protects the transmitter from harsh chemicals and impurities as well. In new installations, it is recommended that water be added to the syphon to protect the transmitter in the initial startup when condensate has not yet formed.
The Model PT steam syphon is good for systems up to 400°F. Higher temperatures will require additional measures to dissipate the greater amounts of heat. These additional measures are effectively nothing more than putting more distance between the steam and the transmitter. For more information on temperature ranges higher than 400°F visit Providing Steam Isolation & Temperature Protection. For best results mount the Model PT in an upright vertical position.
Additional transmitter protection may be needed from sudden pressure shock waves. In these instances the 47S stainless steel snubber from Kele mounted between the transmitter and the Model PT dampens the effects of shock waves and prevents transmitter damage.