Hi, im working in heat recovery

[Gunstein30]

Hi,

im working in heat recovery boiler project.

And need to install pressure transmitter in a ducting.

Media inside ducting : Hot Clean Air (200-400 deg C)
Pressure to be measured : 0 - 1000 mbar (From Blower Specification)

This hot air is comes out from exothermic process and using blower to dissipate the heat to atmosphere.

Since the media is hot air with temperature max.400 degree Celcius, and pressure to be measured only up to 1000mbar or 1 barg. It was difficult to find the correct method for this.

How to install such kind pressure transmitter in such kind of condition?

Thanks,

Jason Fernandez

 

[danw2]

There are some pressure transmitters with fins between the process connection and the sensor element for heat dissipation, but they're not common. The more common technique of temperature reduction is to use some length of uninsulated impulse tubing between the source and the pressure transmitter.

There is no flow through the impulse tubing; the transmitter is dead headed at the end of the impulse tubing. Heat transfer is primarily conduction and steel tubing is not very conductive, a little goes a long way.

The rule of the thumb is to use 1 foot (30cm) of tubing to drop 100°F. In reality, tubing that long is far longer than needed to drop conductive heat, but the rule of thumb length allows for removing the transmitter from radiant heat which is just as destructive to the electronics. A shorter length of tubing with a heat shield also works.

The vendor Sick goes with the rule of thumb:
blog: Link
white paper: Link

The vendor Kulite provides the calc if you want to minimize the length of the impulse tubing
Link

 

[IRstuff]

So, hypothetically, one could further reduce the length of piping if it were finned to increase the heat transfer into the ambient?

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[danw2]

Yes, in fact without finned transmitters Kulite's revised rule of thumb is, "As a rule of thumb, one foot of steel tubing, any diameter, will isolate a transducer from any temperature."

And I've seen it work. See this thread for EdStainless's similar experience:
Link