Recent questions tagged control-valves

Description : How will you select the control valve characteristics ?

Last Answer : The graphic display of flow various lift shows then the Desired or inherent characteristic is changed by variations pressure drop. This occurs as the process changes from condition where most of pressure drop takes ... the valve. b) The pressure drop across a valve should be as low as possible. 

Description : How will you change the action of a control valve ? 

Last Answer : 1. If the control valve is without bottom cap. The actual needs to be changed. 2. If bottom cap is provided. a) Disconnect the stem from the actuator stem. b) Separate the body from the bonnet. ... back the stem to the actuator stem. h) Fix back the bottom cap. i) Calibrate the valve. 

Description : How will you change the valve characteristics with positioner ?

Last Answer : The positioner contains different types of came in it. selection of the proper cams in it.By selection of the proper cam the valve opening characteristics can be changed. 

Description : What is a solenoid valve ? Where it is used ?

Last Answer :  A solenoid is electrically operated valve. It consist of a solenoid ( coil ) in which a magnetic plunger moves which is connected to the plug and tends to open or close the value. There are two types ... :  1. Normally open 2. Normally closed  USE : It is used for safety purpose. 

Description : What are the different valve characteristic ?

Last Answer : The different types of valve characteristic are : 1. Linear 2. Equal Percentage 3. Quick Opening. 1.Linear: The valve opening to flow rate is a linear curve 2.Equal percentage: For ... At small opening the increments in flow rate is more. At higher opening the flow rate becomes steady.  

Description : What is the use of Angle valves ?

Last Answer : Angle valves are used where very high pressure drops are required and under very severe conditions. Where the conventional type of valve would be damaged by erosion. 

Description : What is the use of booster relays ?  

Last Answer : Booster relays are essentially air load, self contained pressure regulators. They are classified into three broad groups :  1. Volume Boosters : These are used to multiply the available volume of ... 3. Reversing Relays : This produces a decreasing output signal for an increasing input  signal.

Description : What is the use of link connected to the valve positioner ?

Last Answer : The link serves as the feed back to the value. Ant valve movement is sensed by this link. Sometimes due to line pressure changes on H.P. service the valve position may be changed, the ... this change and the positioner will produce an output which will operate the valve to the original position.

Description : What are the advantages of Camflex valves ?

Last Answer : Camflex valves are intermediates between globe valve and butterfly valve. The plug rotates 60' for full opening. Advantages: 1. Actuator forces required are very less. 2.Extended bonnet and hence can be used ... on high temp. and very low  Temperature. 3. Variations in flow. 4. Light weight.

Description : What is a cage valve ? 

Last Answer : A cage valve uses a piston with piston ring seal attached to the single seated valve "plug". Here the hydrostatic forces acting on the top or the piston or below the valve plug tend to cancel out. The seat ring is clamped in by a cage. Cage valves are generally used for noise reduction. 

Description : What are the different types of plugs ?

Last Answer : The different types of plugs are generally used are : ( 1 ) V. port plug ( 2 ) Contoured plug V-port plug: Ported plug are generally used on double seated valves. This is because ... balance area. Contoured plug: Contoured plugs are generally used on single seated valve with small trim sizes. 

Description : What is the use of three way valves ?

Last Answer : Three way control valves are only used on special systems, where a dividing or mixture of flows according to a controlled ratio is required.

Description : What is the use of butterfly valves ?

Last Answer : Butterfly valves are used only in systems where a small pressure drop across the valve is allowed. The butterfly is fully open when the disc rotates by 90. A drawback of this valve is that even a very small angular displacement produces a big change in flow.

Description : When can a by pass be not used on a positioner ? 

Last Answer : A by pass on a positioner cannot be used when : 1. Split Range operation. 2. Reverse Acting Positioner. 3. Valve bench set not standard. 

Description : What is the use of a valve positioner ?

Last Answer : The valve positioner is used for following reasons : 1. Quick Action control valve. 2. Valve hysteresis. 3. Valves used on viscous liquids. 4. Split Range. 5. Line pressure changes on valve. 6. Valve Bench set not standard. 7. Reversing valve operation. 

Description : How will you work on a control valve while it is line ?

Last Answer : While the control valve is in line or in service, it has to be by passed and secondly the line to be depressurized and drained. 

Description : What types of bonnets would you use of high temp. and very low temp. ?

Last Answer : High temperature: Bonnets are provided with radiation fins to prevent glad packing from getting damaged.  On very low temperature: Extended bonnets are used to prevent gland packing from getting freezed

Description : What is the use of double seated valve ?

Last 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 i.e. A small size actuator. 

Description : What is the use of single seated valve ?

Last Answer : The single seated valve is used on smaller sizes, and in valve of larger 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.  

Description : What are the different types of control valves ?  

Last Answer : The commonly used control valves can be divided as follows. 1. Depending on Action. 2. Depending on the Body. 1. Depending on action: Depending on action there are two types of control valves, (1) ... valves single or double seated. 2. Angle valves. 3. Butterfly valves. 4. Three way valves. 

Description : What is a control valves ? 

Last Answer : A control valve is the final control element, which directly changes the valve of the manipulated variable by changing the rate of flow of control agent. A control valve consists of an operator and valve body. ... 3 psi on the diaphragm the value is closed and 15 psi air signal it in fully open.