by Rebekah Fuller, IQS Editor
To all extreme feminists out there, I apologize, but I readily admit that there are some things I would rather just have a man do for me. I’m all about being an independent woman making a living and supporting myself; however, when it comes to things mechanical or electrical…that’s just what they are to me – thingies. Say I encounter a pressure gauge in real life: I wouldn’t give much thought to the thingy. I’m good just as long as my tires have the right pressure and my doctor says I have healthy blood pressure. I did, however, discover some tips for selecting pressure gauges.
First of all, if you are replacing an old pressure gauge – DO NOT THROW IT AWAY! Seems like common sense, right? If you have a part number and the actual part, it makes life a lot easier. Also, if you know the necessary connection size and mounting (back or lower/stem mount), you’re in good shape. Next, you will need to know the pressure range (pounds per square inch, or “psi” is standard) of your application and the space available for the fit of the new gauge. The most accurate readings for analog meters with needles are found within the middle third of the gauge. This means that you should buy one that’s about twice your normal operating pressure. For an air compressor with a normal working pressure of 50 psi, select a gauge with a 100 psi range, so the needle will land within the most accurate region of the gauge.
Keep this rule of thumb in mind: if the needle is pointing straight up, the operating pressure is normal. This way, if you have an easy visual of the gauge, you can quickly tell if things are OK. Remember, don’t select a range that is too low. If your pressure does go above normal, you want some space to spare so your gauge won’t break. Always choose a bigger psi if you can’t find one exactly twice your working pressure. If a 160 psi gauge is not in stock, a 200-psi gauge can be substituted. Gauge dial sizes range from 1 inch to 10 inches, accommodating spatial limitations and easy readability. The 2 ½ inch gauge is the most common size, offering hundreds of options.
Of course, there are systems that require more complex features, such as digital pressure gauges and differential pressure gauges, switches and transmitters. Pressure gauges can be equipped with electric contacts to turn on signal lights, sound alarms or operate a pump or valve. Display types include graphical and video displays, besides digital readouts or analog dials.
Throttling devices are used to decrease the effects of pressure pulsation and/or vibration on pointer movement, including throttling screws, pulsation dampeners, elastomeric bladders, pressure snubbers and needle valves. Some pressure gauges are not used to display a measure of pressure; instead, they monitor pressure and send an electronic output signal for any required changes in the system.
Besides general air, fuel, gas, oil and water pressure applications, there are many specific uses: specialty tanks, such as fire extinguishers and medical gas cylinders, liquid filled gauges in nitrous systems, stainless steel gauges in sanitary applications or where high pressure cleaning is involved – to name a few. Compatibility of wetted parts with the process materials is essential in corrosive environments. To achieve the best performance, consider the effects of ambient temperature, air-borne particulate, condensation, humidity, water and chemicals. Pressure gauge manufacturers and suppliers offer product ranges that include high and low pressure gauges, temperature gauges, vacuum gauges, thermometers, thermowells, transmitters and transducers.