A Test Pressure Gauge is highly efficient indicator equipment for sensing pressure fluctuations. It is made of components like a Bourdon tube, diaphragm, and springs to help improve its function and operation. It has diverse applications in the petrochemical, pharmaceutical, chemical, sanitary, and process industries.
These components act as sensing elements and vary with the type of Test Pressure Gauge required. Each type also has its specific display type. Digital and analogue displays are the most common.
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In this FAQ guide, you will read about the features, specifications, tests, types, installation, and operation of a Test Pressure Gauge. Let’s dig about it!
What is a Test Pressure Gauge?
A Test Pressure Gauge is a pressure-measuring device used to find and maintain the pressure of liquid or gas relative to the vacuum, atmosphere, or the differential pressure between two points.
It is available in different types, specifically manufactured to meet the required application demands. It has two main working mechanisms; analogue and digital working. In the analogue working, there is a curved Bourdon tube featuring an oval cross-section that straightens on the application of pressure.
Motion is produced internally by the liquid and measured in the non-clamped tube terminal. The tube is attached to a dial that displays the pressure and turns clockwise upon sensing pressure.
In digital working, advanced sensors and microprocessors are involved in giving highly accurate readings on a digital indicator or a screen. It also involves the usage of strain gauge sensors that monitor electrical resistivity changes on the application of pressure.
What are the Features of a Test Pressure Gauge?
The various excellent features of a Test Pressure Gauge are:
- Brass connection
- 3 inches dial size
- Internal zero adjust
- EN 837-1
- Special bronce Bourdon tube
- Grade 2A ASME B 40.1 accuracy (±0.5% of span)
- Stainless steel bayonet lock case
- Teflon-Coated pinion gear and bearings
- Only 0.25 NPT lower connection
- Adjustable pointer in black with red tip
- Mirror band dial
- to 1000 psi available ranges
What are the Specifications of a Test Pressure Gauge?
The major specifications of a Test Pressure Gauge are:
- 160 mm nominal size
- 6 to 400 bar indicating the range
- Up to full-scale value is the maximum pressure static load
- 9 times the full-scale value is the alternating load
- 3 times the full-scale value is the short-term load
- ½ inch thread
- -20°C is the minimum, medium temperature
- +80°C is the maximum, medium temperature
- -20°C is the minimum ambient temperature
- +60°C is the maximum ambient temperature
- 3% / 10K temperature behavior from normal temperature +20°C
- ø0.3, ø0.4, and ø0.8 are the throttle options
- Approximately 3.0 kg weight
What are the Types of a Test Pressure Gauge?
The major types of a Test Pressure Gauge are:
Analogue Test Pressure Gauge
It is traditional equipment that is reliable and accurate and uses mechanical internals and a needle for functioning. When using it, you must ensure that the pressure applied is full scale’s half.
Digital Test Pressure Gauge
It is modern equipment having a strain gauge and a diaphragm. It features easy identification and recording of the readings because of the digital display.
Differential Test Pressure Gauge
It involves relatively measuring two pressure values. It has two ports with a significant pressure difference, either negative or positive values.
Absolute Test Pressure Gauge
In this, the relative comparison is between the vacuum (absolute or complete) and pressure. This is why you will always get positive absolute pressure values. It is used in applications requiring the use of altimeters, deep vacuum or atmospheric equipment, and barometers.
Hydraulic Test Pressure Gauge
It has a very high-pressure range up to hundreds of bars. It should always be used with oil.
Atmospheric Test Pressure Gauge
It helps measure air pressure and is widely used by meteorologists. It tells about weather patterns and weather forecasting information.
What are the Different Categories of a Test Pressure Gauge?
The different categories of a Test Pressure Gauge are:
Oil Test Pressure Gauge
It helps calculate and monitor oil pressure in different applications, like in vehicle engines. Some of its significant applications are:
- Industrial lubrication system
- Cutting fluid system
Water Test Pressure Gauge
It is useful in measuring water pressure in water and plumbing systems. Its major applications are:
- Utility industry
- Plumbing purpose
- Domestic use
Air Test Pressure Gauge
It helps test and monitors the air and pneumatic system.
It aids in testing filter conditions, air supply, fan efficiency, and speed.
Its main applications are:
- Air cylinder
- Air compressor
- Tyre pressure
Boiler Test Pressure Gauge
It shows water pressure within a heating or boiler system against the atmospheric pressure of the surrounding. It has relatively low water pressure, i.e. less than 4 bar.
What is the Test Pressure Gauge Accuracy?
The Test Pressure Gauge Accuracy is the error or difference between the indicated reading and true value as a full-scale span’s percentage. Some general guidelines are:
- The standard is 0.25% through 0.10% full-scale accuracy.
- 5% full-scale accuracy is for the critical processes.
- 0% accuracy is the industrial process standard.
- 1, 6% or 2.0% accuracy is for the less critical commercial use.
What are the Temperature Conditions for a Test Pressure Gauge?
Different temperature conditions required for the normal operation of a Test Pressure Gauge include:
The most suitable ambient temperature ranges between -20 and +150°F for accurate working and long life of the Test Pressure Gauge. The pointer response will be slow if the temperature is less than this range.
If the temperature is very high, then a 1.5% change in accuracy per 100°F increase will be observed in this range. However, a dura-gauge with normal glass windows can tolerate up to 250°F operating temperature.
A Test Pressure Gauge containing liquid can tolerate a maximum of 200°F. If containing glycerin filling, it is at the risk of getting yellow at this temperature compared to the one with silicone filling.
Hot or Extremely Cold Media
To bring very hot or cold process media into the required ambient temperature range, a capillary line assembly with a 5-foot length can be installed.
What are the Dampening Devices and Diaphragm Seal Recommendations for your Test Pressure Gauge?
A diaphragm seal or an isolator is installed in various applications where viscous fluids or corrosion is involved. It offers protection to the device in a few cases, where:
- Clogging or blocking of the pressure element by the process fluid is expected.
- A change in ambient temperature that may result in the freezing of the process fluid is predicted.
- The material of the pressure element is not potent enough to bear the corrosive nature of the process fluids.
A dampening device can be installed to combat the situation if there are extremely high or low-pressure fluctuations in the Test Pressure Gauge. The function of the dampener is to decrease the magnitude of the pressure pulse, increasing the quality and life of the Bourdon tube.
Proper cleaning of the dampener is essential to prevent plugging of the orifice caused due to the presence of impurities in commonly used media such as water and hydraulic oil.
To get dampening in your equipment at minimal cost, throttle screws and plugs can be installed. The best thing about this dampener is its perfect fitting in the socket.
You must know the following information:
- Filling fluids
- Diaphragm temperature and pressure limits
- Seal assembly’s pressure rating
- Seal configurations
- Filling fluid’s temperature range
- Temperature and pressure limits of the bottom housing material
- Diaphragm seal displacement
- Temperature errors or accuracy of the seal assembly
The measuring element’s volumetric displacement must equal the diaphragm’s volumetric displacement in the Test Pressure Gauge where the seal will be connected. The proper seal filing must also be ensured, and a continuous duty seal must be installed.
The seating of the diaphragm against a matching surface is good for preventing process fluid leakage or diaphragm damage in case of emergency failure. The clamping arrangements allow cleaning of the seal from the inside and field disassembly.
The most common causes of diaphragm failure include filling leakage, high temperature, or corrosion.