8 Things You Need to Know When Selecting a Pressure Gauge


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Mechanical pressure gauges are a reliable source of accurate pressure measurement. While its use and requirements may vary from one industry to another, following are the 8 factors that you need to keep in mind while selecting a pressure gauge:

1.Gauge accuracy

The accuracy of a pressure gauge is defined either as a percentage of the full-scale range or a percent of the span. The higher the accuracy, the costlier the gauge, which is why the application of the gauge needs to be carefully considered while deciding the level of accuracy required. While the use may vary from industry to industry, the general guidelines are as follows:
Test Gauges and Standards: 0.25% through 0.10% full scale accuracies.
Critical Processes: 0.5% full scale accuracy.
General Industrial Processes: 1.0% accuracy. Less Critical Commercial Uses: 2.0% accuracy.

2.Mounting

When selecting a pressure gauge, you must bear in mind the connection location. There are multiple mounting options available, those being:
Direct stem mount lower connect
Remote wall/surface mount lower connect
Panel surface mount back connect
Panel hole U-clamp flush mount back connect (for panel mounting)
Panel hole front flange flush mount back connect (for panel mounting)

3.Connection Size

Pressure gauges are available in both bottom and back (center and lower) connections. They are available with a variety of connections including NPT, DIN, JUS, BSP & SAE. The most common connection sizes are 1/4″ NPT and 1/2″ NPT. In order to select a gauge connection best suited to your needs, always consider the following factors:
Process pressures
Gauge size and weight
Space limitations
Leak integrity
Past experiences with gauges, if any

4.Gauge size

The dials of pressure gauges range from 1.5” to 16 “in diameter. Generally, the size of the dial is determined by the ease with which the gauge could be read, space limitations and accuracy requirements. For instance, in areas that aren’t easily accessible, a larger dial will be required, whereas a smaller size dial can be used in easily accessible areas.

5.Type of Display

Pressure gauges are designed with the options of both analog and digital displays. Traditionally, the analog display has been widely sued, but the digital display is also catching up. Usually, the application of the gauge usually determines which kind of display is required.

6.Pressure Range

It is important to select a pressure range that is approximately twice the normal operating pressure of the media. You must always ensure that the maximum operating pressure should not exceed 75% of the full scale range as it may ultimately result in fatigue failure of the pressure sensor inside the gauge. In case of presence of pulsation during the process, maximum operating gauge pressure should not be allowed to exceed 50% of the full-scale range.

7.Environment

The environmental factors to be considered when selecting a pressure gauge as the ambient temperature in the area of use can affect the accuracy and integrity of the gauge, and therefore must be chosen keeping in the following factors:
Ambient temperature
Air-borne particulate
Condensation
Humidity
Water
Chemicals present (chemical composition)

8.Process Media (Wetted Parts)

The selection of the pressure sensor material is dependent on the process fluid to which the gauge might be subjected to avoid corrosion. The pressure sensor elements are available in a wide variety of metals:
Brass
Phosphor
Bronze
Alloy steel
Stainless steal
Monel
Inconel

Note: It is highly recommended to have a sensor element that is compatible with the fluid, otherwise the use of diaphragm seals are inevitable.
In order to avoid errors due to misapplication, damages to personal property due to injuries and accidents and additional costs; it is highly recommended that you must keep the factors discussed in this article in mind when selecting a pressure gauge.

Author Bio: Edward Simpson is a seasoned Calibration and Technical Engineer working for RS Calibration Inc. Edward has a knack for finding faults in machines and does not rest until they are rectified to perfection. He lives in Pleasanton, CA and can be contacted anytime for matters related to machines. He also invites people to visit his company www.rscal.com to learn more about the type of calibration work he does.