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Instrumentation and Control Engineering Materials-Free Download

• Question 21. Name Different Types Of Bourdon Tubes?

Answer :

Types of bourdon tubes:

1. C type

2. Spiral

3. Helix

• Question 22. What Are Primary Elements Of Measuring Pressure? Which Type Of Pressure Can Be Measured By These Elements? 

Primary elements of measuring pressure are:

a. Bourdon Tube

b. Diaphragm

c. Capsule

d. Bellows

e. Pressure springs

These elements are known as elastic deformation pressure elements.

• Question 23. What Is The Use Of Valve Positioner?

Answer :

Valve positioner can be used for following reasons:

a. Quick action

b. Valve hysterisis

c. Viscous liquids

d. Split range.

e. Line pressure changes on valve

f. Bench set not standard

g. Reverse valve operations

• Question 24. What Is The Use Of Double Seated Valve?

Answer :

In double seated valves the upward and downward forces on the plug due to reduction of fluid pressure are nearly equalized. It is generally used on bigger size valves and high pressure systems. Actuator forces required are less. 

• Question 25. What Is The Use Of Single Seated Valve?

Answer :

The single seated valve is used on smaller sizes where an absolute shut off is required. The use of single seated valve is limited by pressure drop across the valve in the closed or almost closed position. 

• Question 26. Name Different Parts Of A Pressure Gauge? Explain The Use Of Hair Spring In The Pressure Gauge?

Answer :

Pressure gauge includes following components:

a. ‘C' type bourdon tube.

b. Connecting link

c. Sector gear

d. Pinion Gear

e. Hair spring

f. Pointer

g. Dial

Use of hair spring: Hair spring is responsible for controlling torque. It is also used to eliminate any play into linkages.

• Question 27. Tell Me How Is Flow Measured In Square Root?

Answer :

Flow varies directly as the square root of pressure. Thus, F=K of square root of applied pressure. Since this flow varies as the square root of differential pressure. 

The pressure pen does not directly indicate flow. Thus flow can be determined by taking the square root of the pen. Assume the pen reads 50% of the chart. So, flow can be calculated using the pen measure in the chart. 

• Question 28. Explain How Can A D.p. Transmitter Be Calibrated?

Answer :

D.P. transmitter can be calibrated using following steps:

1. Adjust zero of Xmtrs.

2. Perform static pressure test: Give equal pressure on both sides of transmitter. Zero should not shift either side. If the zero shifts then carry out static alignment. 

3. Perform vacuum test: Apply equal vacuum to both the sides. Zero should not shift.

4. Calibration procedure: Give 20 psi air supply to the transmitter and vent L.P. side to atmosphere. Connect output of the instrument to the standard test gauge. Adjust zero. Apply required pressure to the high pressure side and adjust the span. Adjust zero gain if necessary. 

• Question 29. What Is Bernoulli's Theorem. State Its Application?

Answer :

Bernoulli's theorem states that the ‘total energy of a liquid flowing from one point to another remains constant'. It is applicable for non-compressible liquids. For different types of liquid flow Bernoulli's equation changes. There is direct proportion between speed of fluid and its dynamic pressure and its kinetic energy. It can be used in various real life situations like measuring pressure on aircraft wing and calibrating the airspeed indicator. It can also be used to low pressure in the venturi tubes present in carburetor. 

• Question 30. Explain Why Is The Orifice Tab Provided?

Answer :

Following reasons justify for providing orifice tab:

1. Indication of orifice plate in a line

2. The orifice diameter is marked on it.

3. The material of the orifice plate.

4. The tag number of the orifice plate.

5. To mark the inlet of an orifice

Source: Contents are provided by Technicalsymposium Google Group Members. 
Disclaimer: All the above contents are provided by Google Group members. 
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