Pressure transducers are sensitive instruments. It’s how they can accurately measure pressure. If they weren’t sensitive, they wouldn’t be very good sensors.
That means they have important limitations of which you need to be aware. One of those is temperature. Many electronic pressure transducers perform well in low temperatures, down to -40 °F. However, finding electronics that can handle high temperatures, around 200 °F or higher, is difficult.
Those that exist carry a premium, or are mechanical. They may be worth it, but you might also be able to work with a standard model.
So how can pressure transducers measure in high temperatures? How can they punch above their weight on heated lines and vessels? There are really two options: dissipate the heat, or insulate the sensor from it.
One of the simplest and least expensive ways to install a pressure transducer in a high temperature tank or vessel is simply to put a heat sink between the sensor and the pressure port. The heat sink can take a variety of forms, but works by dissipating the heat from the media and the vessel itself.
This could be as simple as a metal valve on the bottom of a tank. It may dissipate enough heat to bring the temperature down within spec for the transducer.
Or it might not.
Perhaps you need a capillary tube, or an actual heat sink (something with metal fins that increases surface area), or just a length of pipe. The more surface area you put between the pressure transducer and the heat source, the greater the cooling effect.
Heat dissipation is a good technique if the characteristics of your liquid won’t experience an undesirable change with the drop in temperature. Anything that will gum up the sensor face or the heat sink with the temperature drop will prove problematic for this approach.
Placing a non-conductive material between the sensor and the heated vessel is another good option to protect a pressure transducer from high heat. This insulates the sensor from the heat source.
A popular example of an insulator is Teflon. It comes in a variety of pipefittings and is famous for a number of desirable characteristics, including its performance in high temperatures. Were it not for this, the no-stick pans of the 80s and 90s would have been substantially less successful.
Making The Choice
There is a critical, albeit obvious, difference between the two methods that we need to crystalize in order to choose the right one: insulation does not dissipate heat, and dissipation does not insulate. An insulator will not cause a significant temperature drop in the media itself. However, it also won’t conduct heat to the body of the sensor.
One method might work where the other doesn’t. It might not matter much which method you choose. Luckily, they’re both fairly cheap to try out.
If you’d like to discuss your need for a pressure transducer with a sensor expert, give us a call. We’re happy to help any way we can – even if it means we recommend a different solution.
Need a reliable pressure transducer? You can gamble, or you can try one from APG. Learn more about our best-in-class pressure transducers below: