Pressure Measurement instrumentation Questions and answers UAE

Pressure Measurement instrumentation Questions and answers UAE

PRESSURE

19. What is absolute pressure?

Absolute pressure is the total pressure present in the system

Abs. pressure = Gauge pressure + Atm. pressure.

20. What is absolute zero pressure?

Absolute zero = 760 mm Hg Vacuum.

21. What is the maximum Vacuum?

The maximum Vacuum = 760 mm Hg.

22. What is Vacuum?

Any pressure below atmospheric pressure is Vacuum.

23. What are the primary elements for measuring pressure?

The primary elements used for measuring pressure are:

·        Bourdon tube.

·        Diaphragm.

·        Capsule.

·        Bellows.

·        Pressure Springs.

The above are known as elastic deformation pressure elements.

Type of  Bourdon tubes.

·        ‘C ' type.

·        Spiral.

·        Helix.

Diaphragm: The diaphragm is best suited for low-pressure measurement.

Capsules     : Two circular diaphragms are welded together to form a pressure capsule.

                      Material Used: phosphor bronze, Ni-spank stainless steel.

Bellows       : Bellows is a one - piece, collapsible, seamless metallic unit with deep folds    

                       Formed  from very thin walled tubing.

                      Material used: Brass, phosphor bronze, and stainless steel.

 Used for high  Pressure .

Pre.spring: Pressure springs of helical or spiral shape used for measuring high pressures.

24. How will you calibrate an absolute pressure transmitter-using vacuum manometer Range 0-400mm abs?

The procedure for calibration is as follows:

·        Connect air supply to the transmitter.

·        Connect a test gauge of 0-1.4 Kg/cm2 to the output.

·        Connect Vacuum pump with tee off to the manometer.

·        Apply 760 mm Vacuum (or nearest) and adjust zero.

·        Apply 360 mm Vacuum adjust span. (760 - 360 = 400 mm abs.)

25. You are given a mercury manometer range 0 -760 mm. A vacuum gauge reads 60 mm vacuum & the TX. reads 710. The test manometer reads 50 vacuums?

 Which of the two in correct?

The transmitter is correct because 760 - 50 = 710 mm abs.

26. Why is an inclined manometer used?

It is used to extend the scale of the instrument. Because the manometer is at an angle to the vertical.

27. What is the principle of a pressure gauge?

Pressure works on Hooks law.

Principle: "Measuring the stress in an elastic medium"

28. Draw and explain a pressure gauge? What is the used of a Hairspring?

The parts of a pressure gauge are:

1.      'C' type Bourdon tube.

2.      Connecting link.

3.      Sector gear.

4.      Pinion gear.

5.      Hair Spring.

6.      Pointer.

7.      Dial.

Uses of Hair Spring: Hairspring serves two purposes namely

·        To eliminate any play into linkages.

·        It serves as a controlling torque.