Valve Terminology

Solenoid Valve Terminology

Now is a good time to explain some of the terminology used in order to help you with your selection.

  • 2 way is a two port valve that turns the flow on or off
  • 3 way is a three port valve that allows flow through the valve into a chamber, and then out through the valve exhaust. The universal function can also be used as a diverter valve.
  • 5/2 way is a five port, two position valve that will put a fluid or air into one end of a double acting device as well as allowing the other end vent to exhaust.
  • Zero Differential are solenoid valves that can operate under zero head pressure (do not need a differential pressure drop across the valve to work). This is made up of two categories, direct acting and coupled diaphragm.
  • Direct acting are solenoid valves that are activated purely by the electromagnetic forces in the valve and do not rely on the fluid pressure to assist. Hence they are used where little or no fluid pressure is available such as vacuum service or low pressure applications.
  • Differential operated are solenoid valves that do rely on the fluid pressure to assist in activating the valve. This helps in developing valves with larger orifices, higher pressures and smaller coils.
  • Normally closed (N.C.) means that when the solenoid valve is not energised the supply pressure port is closed off. In the case of 3 way valves the downstream port is open to the exhaust port.
  • Normally open (N.O.) means that when the solenoid valve is not energised the supply pressure port is open to the downstream port. In the case of 3 way valves the downstream port is closed to the exhaust port.
  • IP rating is an international standard to denote the degree of protection against water and solid objects. All of our electrical coils with DIN plugs have an IP65 rating. The '6' denotes a complete protection against items as small as dust and '5' is protection against low pressure jets of water from all directions.
  • Flame proof relates to the electrical part of a solenoid valve only (usually the coil and operator assembly) and is a way of making the valve safe to use in an explosive atmosphere. These valves must be installed in compliance to the wiring standards for this type of approval and in a zone compatible to the approved code and temperature rating.
  • D.I.P rating relates to Dust and Ignition Proof.
  • N.B. Bar relates to pressure: 1 Bar = 14.7psi = 100KPA = 1 atmosphere.

 

Ball Valve Terminology
Now is a good time to explain some of the terminology used in order to help you with your selection.

Components
2 Way Valves

  • 2 piece - Body manufactured from two castings and threaded together.
    Advantage: Lower cost
    Disadvantage: Difficult to remove from the pipe work, usually non-replaceable
  • 3 piece - Body manufactured from three castings and clamped with tie rods.
    Advantage: Able to be removed from the pipework without disruption, repairable, usually a higher spec valve
    Disadvantage: Usually more expensive

3 Way Valves

  • 4 piece - Body manufactured from four castings and threaded together.

Function
2 Way / 2 position

  • Two port valve that turns the flow ON or OFF

3 Way / 2 position

  • Three port valve that is available in two configurations
    1. L-port - commonly used as a flow diverter. In one position port C is connected to port A, in the second position port C is connected to port B.
    2. T-port - commonly used as a valve for draining or relieving the downstream pressure. In one position port C is connected to port A, in the second position port A is connected to port B.

L or T port

Actuators
Pneumatic

  • Double Acting (DA) - pneumatic actuator that requires an air signal to turn it ON and a second signal to turn it OFF
    Advantage: Quick operation and lower cost
  • Spring Return (SR) - pneumatic actuator with spring return that requires an air signal to actuate - spring to close (also known as single acting). Advantage: Only a single signal required to operate - fail safe in the event of a power or air supply failure

Electric

  • A motorised gearbox drives the valve. Commonly used where compressed air is not available. Slower operation - usually 12 to 15 seconds. They are available in Spring Return as well.

 

Pressure/ Vacuum Switches

Now is a good time to explain some of the terminology used with Pressure Switches in order to help you with your selection.

 

Single Pole Double Throw (SPDT)
With this type of switch the electrical circuit can be "made" when the switch is activated (common to N.O.) or "broken" when the switch is activated (common to N.C.).

Single Pole Double Throw

Single Pole Single Throw (SPST) Normally Closed
With this type of switch the electrical circuit will be "broken" when the switch is activated.

Single Pole Single Throw Normally Closed

Single Pole Single Throw (SPST) Normally Open
With this type of switch the electrical circuit will be "made" when the switch is activated.

Single Pole Single Throw Normally Open

Deadband/Hysterisis/Differential are all terms used to describe the difference between when a switch activates and when it resets. Because of the mechanics of the micro-switch this is seldom at the same setting. Some of our switches have fixed deadbands (Series PMM, VCM) and others have limited adjustable deadbands (Series PSM, PSP, VSM, adjustable up to 30% of full scale).

Set Point is the setting at which the switch will activate.

 

Measures of Flow

Cv Imperial measure flow of vale US gallons per minute of water at 60° fahrenheit with pressure drop of 1 psi across the valve

Kv Metric measure flow of valve m³ per hour of water at temperature between 5°C & 40°C with rpessure drop of 1 Bar across valve

Qn Pneumatic flow of valve litres of air per minute at 20°C input pressure 6 Bar pressure drop of 1 Bar

 

Flow through a valve is calculated by the following formula;

 

1. Fluid

Q = 14.28cv √?P/r

where

Q = Flow (L/min)

?P = Pressure Drop

r = Density of Fluid (kg/dm^3) (water = 1kg/dm^3)

cv = Flow rating of valve

 

2. Gases

Q = 400cv √(P2 + 1.013) x ?P x √273/273+t

where

P2 = Outlet Pressure

t = Gases Temperature

 

Working out Amps/Volts or Watts

Amps = Watts/Volts

Volts = Amps x Ohms

 

Duty Cycle - compliance to IEC standard

Duty cylce means the starting frequency. The formula for calculating it is as follows;

Running Time / (Running Time + Rest Time) x 100% = Duty Cycle

Rest Time = Runnng Time x (1 - Duty Cycle) / Duty Cycle

For exampel the running time for 0M-2 is 15 seconds.

1. 30% duty cycle   15 x (1 - 30%) / 30% = 35 seconds rest time

2. 75% duty cycle   15 x (1 - 75%) / 75% = 5 seconds rest time.

The higher the duty cycle, the shorter the rest time.