A Practical Guide To Pressure Gauges //
Nearly every industry, from aerospace to food and beverage, has systems and processes for which the level of pressure must be constantly monitored. A lack of vigilance can have disastrous results.
Pressure gauges are used for this purpose. They come in a variety of configurations designed to meet the specific needs of a range of applications. The devices use different methods of measurement (discussed in detail below) and offer varying ranges and levels of accuracy.
We'll provide an overview of pressure gauges below. We'll cover the different measurement approaches as well as the different types of devices available. You'll also learn how to select a suitable pressure gauge for your application.
Different Methods Of Measuring Pressure
Pressure is measured using one of three approaches. Gauge pressure is evaluated against air pressure. Differential pressure is measured as the difference between the applied pressure at two distinct points. Absolute pressure is a combination of gauge and atmospheric pressure.
The measurement approach used depends largely on the application and sometimes on convention. For example, measuring pressure in automotive tires is done with a gauge. Measuring pressure in aircraft is done with an altimeter.
Overview Of Types Of Pressure Gauges
Several devices have been designed to measure pressure in industrial applications. They include transmitters, switches and transducers. Each one poses advantages in certain circumstances, but also introduces potential drawbacks.
Pressure transmitters convert pressure into an electrical signal. The signal can take one of a few different forms, including millivolts and analog 4–20 mA current loops.
Pressure switches work in a similar manner to transmitters. Available in numerous designs, they're typically used in applications for which fluid pressure needs to be monitored.
Pressure transducers are composed of two main components. One is elastic (typically, a thin diaphragm) and undergoes physical changes when exposed to process pressure. The other component reacts to the changes and generates an electrical signal.
Factors To Consider When Buying A Pressure Gauge
It's important to take several things into account when deciding which pressure measurement device to purchase for your process. Accuracy is crucial, of course, but there are varying levels. The cost of the instrument rises with the level of accuracy.
Range is also important. As a general rule, plan to purchase a gauge that covers twice the range of your process's typical operating range.
Also, consider the ease with which the instrument can be read. Various gauges come with indicators that range in size. If your plant personnel are unable to get close to the gauge, make sure the indicators are large enough to be read at a distance.
Consider environmental factors. What environmental circumstances might impair the instrument's ability to accurately measure process pressure over time? Will the device be exposed to severe temperatures? Will it be housed in an area filled with contaminants? Will the gauge be exposed to water that is likely to freeze? Some pressure measurement instruments are better suited to cope with severe conditions.
Common Reasons Pressure Gauges Fail
Pressure gauges fail for a variety of reasons, a few of which we hinted at above. For example, extreme temperature can cause the casing to crack and the joints to loosen. Corrosion can weaken the frame and allow fluids and gases to escape. Continuous mechanical vibration, common in manufacturing applications, can adversely affect the instrument's accuracy. Repeated pressure spikes can damage the instrument.
It's important to take those potential issues into account. But the real problem is that pressure gauges are oftentimes installed to monitor processes for which they're unsuitable.
An example would be a device that has a low tolerance scale being installed to monitor an application that sees frequent pressure spikes. Or an instrument that is unable to withstand corrosion being installed to measure pressure in an environment filled with corrosive media.
The best solution for your process is the one that can deliver the required level of accuracy and tolerate the conditions to which it will be exposed. Contact our factory-trained personnel to discuss the instruments you need to monitor pressure in your application.
View our recommended Pressure Gauges