Correct installation of steam pressure gauges 2

You need some arrangement to keep steam from actually contacting the gauge internals. A diaphragm will work, but the more common method is a pigtail.

The choice between a conventional 'straight' mount for a pressure gauge or a pressure transmitter versus a pigtail, eals or some other design is dependent on the steam pressure and temperature. On a recent design, we utilitized seals for transmitters on the 650 psig steam line and pigtails for the pressure gauges. For the 200 psig and lower steam systems, instrumentation was 'direct mounted'.

The question is whether the instruments you choice are capable of withstanding the temperature/pressure for the system for continuous operation. If the answer is no, you look at an alternate installation detail. For example, the pig tail keeps a seal of condensate up against the gauge and thus, the gauge internals does not see the saturation steam temperature.

Or so, this is how it's been explained to me when I asked <g>.