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Selection Of Pressure gauge :- Mechanical pressure gauges find their use in any kind of industrial set up. They provide a reliable source of accurate pressure measurement. Although user requirements may vary from one industry to another, we have some common factors that you need to consider when selecting a pressure gauge.
Pressure Gauge Accuracy
The accuracy of any given pressure gauge is defined as a percentage of the full-scale range or a percent of the span. The higher the accuracy, the more it cost to buy the gauge. This is the reason why the application requirements of the gauge need to be carefully considered while deciding the level of accuracy. Even though their use varies from one industry to another, the general guidelines are as follows:
- Test Gauges and Standards: 0.25% through 0.10% full scale accuracy.
- Critical Processes: 0.5 % full scale accuracy.
- General industrial processes: 1.0% accuracy. Less critical commercial users: 2.0 % accuracy.
MOUNTING
There are multiple mounting options available:
- 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)
GAUGE SIZE
The dials of pressure gauges range from 1.5″ to 16″ 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.
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 connections sizes are 1/4″ NPT and 1/2″ NPT. In order to select a gauge connection that is best suited to your needs, you need to consider the following factors:
- Process pressures
- Gauge sizes and weight
- Space limitations
- Leak integrity
- Any past experiences with gauge, if any
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.
- Phosphor
- Brass
- Alloy steel
- Bronze
- Stainless steel
- Inconel
- Monel
It is highly recommended to have a sensor element that is compatible with the fluid otherwise the use of diaphragm seals are inevitable.
ENVIRONMENT
The environmental factors to be considered when selecting a pressure gauge are:
- Ambient temperature
- Condensation
- Humidity
- Air-borne particulate
- Water
- Chemicals present (chemical composition)
TYPE OF DISPLAY
Pressure gauges are designed with the options of both analog and digital displays. Traditionally, the analog display has been widely used, but the digital display are replacing them very fast. In most cases, the application of the gauge will determine which kind of display is required.
PRESSURE RANGE
It is important to select the 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.