Direct Mounted Flow/Temperature Switch-Trip amplifier

hi 2 all ,

according to our consultants specifications,direct actuated field mounted flow/temperature switch should not be used instead receiver switch /trip amplifier should be used to generate contacts .

where as for level /pressure direct diect field mounted is acceptable .

wats the logic behind this?

Logic? Many consultant's need to justify their existance (and billing).

One possible thought? If they are using pulse type flow sensors, and actual temperature sensors (RTD's, Thermocouples), then you generally do need a signal conditioner in order to yield an actual value. Simple level and pressure switches though don't need any conditioning.

Then again, do you need actual flow or temperature? In many cases, a simple thermostat can work for out of range indication, and a simple paddle switch can be used for flow determination.

Flow switches and temperature switches have been used successfully for decades. It isn't possible to give a definitive answer without knowing the details of the process and the devices, but in general the answer doesn't make sense.

If this guy is a consultant, you are paying him. I suggest you ask him this specific question. If he can't give a clear, definitive answer related to your specific application then show him the door. A general statement like "It is bad practice" without an explanation of why means he doesn't understand it himself.