A short presentation on Pressure and Pressure Measuring Instruments: Part 2 of 2 - What is Piping

A short presentation on Pressure and Pressure Measuring Instruments: Part 2 of 2

DIAPHRAGM (Continued from part-1, click here to go to part-1):

  • It uses the deflection of a flexible membrane that separates regions of different pressure.
  • The amount of deflection is repeatable for known pressures so the pressure can be determined by using calibration.
  • The deformation of a thin diaphragm is dependent on the difference in pressure between its two
  • The reference face can be open to atmosphere to measure gauge pressure, open to a second port to measure differential pressure, or can be sealed against a vacuum or other fixed reference pressure to measure absolute pressure. The deformation can be measured using mechanical,optical or capacitive techniques. Ceramic and metallic diaphragms are used.
  • Range: (-) 10000 to (+) 10000 mmWC

ADVANTAGES:

  • Small size & moderate cost
  • Linearity
  • Adaptability to slurry services & absolute & diff. press.
  • High over range characteristics

DISADVANTAGES:

  • Limited to low pressure
  • Difficult to repair
  • Less vibration & shock resistance
Diaphragm
Fig. 7: Diaphragm

Capsule:

  • A capsule is formed by joining the peripheries of two diaphragms through soldering or welding.
  • Used in some absolute pressure gages.
Capsules
Fig. 8: Capsules

Range of Elastic-Element Pressure Gages:

Range of Elastic-Element Pressure Gages
Fig. 9: Range of Elastic-Element Pressure Gages

Accessories:

Accessories
Fig. 10: Accessories

Diaphragm seals: These are designed to isolate the sensing element of pressure gauges from process fluids.

Gauge Saver: Gauge Savers also known as over pressure protectors are applicable where pressures exceed the maximum pressure rating of the pressure gauge.

Pulsation dampener: Dampeners considerably reduce the pulsations and  makes the gauge reading easier and also improves the life of the gauge.

Syphon : This connected between the pressure gauge & process in applications, where high temperature like steam, vapours or fluids are present. It acts as a cooling coil and protects the gauge from high temperature and also helps in dissipating heat.

PRECAUTIONS: WHEN  FIRST  INSTALLED  THE SYPHON SHOULD   BE FILLED WITH WATER  OR ANY OTHER  SUITABLE  SEPERATING  LIQUID.

  • U TYPE – FOR HORIZONTAL  PRESSURE  TAPPING
  • Q TYPE – FOR  VERTICAL  PRESSURE  TAPPING

Needle valve: The large round handle offers maximum ease and precise control to throttle the pressure to the gauge.

Block & Bleed Valve: Equipment Isolation with automatic pressure bleed for safety

Manifolds:

  • These are fluid distribution devices.
  • These are used in conjunction with pressure gauges, differential pressure gauges & differential pressure transmitter.
  • They combine instrument isolation & equalizing in one block.
  • The manifolds are available in 2way, 3 way & 5 way types with remote & direct mounting styles

Gauge cock: It is used in conjunction with siphon as an isolation valve. It is not recommended for pressure over 100 psi.

Various Instruments
Fig. 11: Various Instruments

 

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