"Ji" Pressure Gauges
Definition & Type of Pressure Gauges:-
Pressure gauges are the instruments is process control industry for Testing & Measuring the condition of fluid like liquid & gas that is specified by the force which would exert, when at rest on a unit, such as Kg/Cm2, Bar, PSI, mmWc, Ton, mBar, mmH20, mmHg, kPa, mPa.
The main process in Process Control Industries in the modern world involve the Testing & Measurement of pressurised liquid and gas systems.
Pressure is probably one of the most commonly measured variables in the power plant.
It includes the measurement of steam pressure, feed water pressure, condenser pressure, lubricating oil pressure and many more.
Pressure is actually the measurement of force acting on area of surface.
We could represent this as P = F / A.
Type of Pressure Gauges:-
Type of Pressure Gauges includes:-
- Stainless Steel Pressure Gauge (Industrial Heavy Duty SS316L)
- Stainless Steel Pressure Gauge (Economical SS304)
- MS Powder Coated Pressure Gauge (MS Case & Brass Internals)
- Inner-built Capsule Pressure Gauge
- Capsule Diaphragm Pressure Gauge
- Sealed Unit Diaphragm Pressure Gauge
- Compact Sealed Unit Diaphragm Pressure Gauge
- Differential Pressure Gauge
- Master Pressure Gauge (0.5% & 0.25%)
- Draught Pressure Gauge (Draft Gauge)
- Electrical Contact Pressure Gauge
- Compound Gauge
- Vacuum Gauge
Major Causes of Pressure Gauge Failure:-
1) Vibration:- It isn’t uncommon for different pieces of equipment to vibrate,
however, excessive vibration leads to gauge failure.
negatively impact gauge accuracy in two ways:
• It makes it difficult to read a pointer accurately when the gauge is
• It causes an incremental damage to the pointer mechanism since
vibration can move a pointer off zero, thus producing inaccurate
Install gauges that resist vibration, such as a liquid-filled or direct drive gauge with only a single moving part.
2) Temperature:- Extreme temperatures impact not just the equipment but the gauges as well. They can cause loosening and sweating in metal joints, causing them to crack.
If the gauges are not designed to operate in extreme temperatures, they will start malfunctioning in a short period of time.
Use gauges that are designed for extreme temperature conditions to be assured of reliable information for the lifetime of the instrument.
3) Corrosion:- If the process media are corrosive, then the gauges used in these process streams must be made from internal parts that are resistant to corrosion as highly corrosive media damage the sensing material in the gauges.
Install a diaphragm seal constructed from a material that can withstand the corrosive materials used in the process.
4) Clogging:- If you use any viscous media or medium containing suspended particles or with crystallizing or congealing properties, it can potentially clog the pressure system and give unreliable gauge readings.
The clogged gauges often ‘freeze’, which can be really dangerous as it may indicate no pressure when the system in fact might be under tremendous pressure.
It would be ideal to use a diaphragm seal equipped with flushing ports to constantly flush the diaphragm surface.
5) Steam :- If the media you use produces steam or high pressure vapors, it can damage the internal components of the gauge.
You can install a mini-siphon with an internal chamber or a full siphon to reduce the surges. Include a coil for horizontal applications and a pigtail for vertical ones.
6) Pulsation:- Pulsation causes regularly occurring overpressure spikes. A rapidly cycling medium within a pressure system can cause the gauge pointer to move erratically, causing the pressure gauge to spike intermittently and leading to the breakdown of the internal parts.
You can address this issue by installing a restrictor or a pressure snubber which help in slowing down the media by reducing the size of the intake orifice and minimizing the pressure fluctuations.
7) Overpressure:- In most cases, the process media is transported through piping systems at relatively high pressure and gauges that are appropriate for that pressure are installed for process monitoring.
However, if the workers switch pumps on and off, or open or close valves, then a surge of media flows through the pipe, impacting the pressure gauge and causing a spike that damages the gauge.
You must use reliable gauges whose tolerances are several times higher than the standard flow pressure or install overpressure protectors on gauges where overpressure spikes tend to occur.
8) Mishandling:- If the pressure gauge isn’t handled properly or if they are mistreated, they will start to malfunction earlier than expected. It is important to understand the main reason why your gauge is failing in order to take the right preventive steps.