Solenoid Valve Terminology D

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Solenoid Valve Terminology D

Diaphragm : A diaphragm is a round or square sheet of elastomer rubber compound typically sandwiched between the upper and lower valve body made from either NBR, EPDM or FKM that rests across a sealing face inside the valve that either directly or indirectly allows or prevents the flow of media though the valve. Typically reinforced with Nylon and supported by either an external stainless steel disc or internal metal support to give additional strength to withstand the pressure of media trying to pass through the solenoid valve.

De-energised : The de-energised state of a solenoid valve is with no electrical power supplied to the solenoid valve also known as a fail-safe position.

Degreased : Degreased solenoid valves are typically used for oxygen service, these valves are either manufactured in clean grease and oil free environments or have been disassembled and cleaned in a special non flammable water based solvent to remove any traces of grease, oil or lubricant that could ignite within the oxygen.

Delrin (POM) : Delrin is barnd of Dupint it is a strong thermoplastic used for seal and some plastic valve body materials. It is a type of Polyoxymethylene (acetal, polyacetal and polyformaldehyde). Delrin is susceptable to strong acids but offers good heat resistance and low water absorbtion. Temperature range from -40C to +150C. Delrin or POM is also known as Hostaform, Celecon, Kepital, Duracon, Lupital or Ultraform.

Delta P ΔP : Pressure differential or pressure drop being the pressure difference between the inlet port and outlet port of a valve.

Density : Density of liquid or gas is the mass per unit volume or thickness. The density of water for example is 1 Kg/m³, the thicker the liquid or gas the slower it will move through a solenoid valve. Flow is directly affected by density of media and the flow of liquids can be calculated where:

  • Q = Flow litres a minute
  • ΔP = Pressure drop
  • d = density
  • Kv = flow coefficient of solenoid valve (litres a minute)
  • Q = Kv x √(ΔP/d)²

Devlon : A molecular weight polyamide banded by Devol, designed for high pressure temperature applications. There are various grades of Devlon, the most popular of which is V-API, which is a lightweight,acid, alkai and impart resistant material. Temperature range -40C to +93C.

Dezincification : Dezincification is a form of pitting or corrosion that attacks certain zinc bearing copper-based alloys, often called "yellow brass", when in contact with sea water or fresh water that is high in oxygen and carbon dioxide. ASTM B61 and B62 are "red brass" and are not susceptible to dezincification.

Diaphragm : A round or square thin flexible elastomer seal secured and sealed around the outer edge or occasionally centrally with its unsupported area free to flex and move. Typically controlling the flow of media through a valve by lifting away from a sealing face, or seating back again to prevent flow.

Differential Pressure : A solenoid valve differential pressure is the pressure difference between the valve pressure at the inlet port and the valve pressure at the outlet port. For example a pressure assisted valve that requires a pressure differential of 0.5 bar (7PSI) means that the pressure at the inlet port must be 0.5 bar higher than the back pressure or outlet pressure say 5 bar at inlet and 4.5 bar at outlet would give the same ΔP (delta P = pressure differential).

Dip Tube : A dip tube extending the blow down valve on large gate valves requires a tube which is located inside of the valve. This tube is called the "dip tube" and extends through the bonnet to the bottom of the valve body cavity.

Direct Acting : Direct acting solenoid valves utilise the armature assembly to "directly" open or close the valve by either covering or exposing a flow path to allow or prevent the flow of liquid or gaseous media.

Disc : Disc or valve poppet or plug is the closing element of a globe, gate or regulator valve, moves to and from the valve seat in a direction 90° to the face by means a rotating threaded stem.

Distribution Line : A pipeline which distributes gas or liquid to individual locations, commonly smaller in diameter than the supply line (6" or less) and low pressure under 10 bar

Diverting Valve : A diverting valve is a valve that diverts the flow or liquid or gas media, rather than simple On/Off or open/closed control. Diverting valve examples would be:

  • to divert compressed air to or away from a pneumatic cylinder or actuator
  • to divert from diesel to vegetable oil for a car or lorry.

DOT regulations. Department of Transport : A code of federal regulations setting out the minimum safety requirements for the transportation of hazardous gases or liquids by a pipeline system.

Double Acting : A double acting valve will have two points of control, either two solenoids or two compressed air inlets. There is no fail-safe or automatic full return back as each side will need to be actuated to move the valve fully into the direction of activation.

Double Block and Bleed Valve : The capability of a valve in a pipeline that is under pressure, to have its body cavity pressure bled down or drained to down to atmospheric pressure when the valve is in either the fully closed or fully open position.

DPDT : Double pole double throw electrical switch.

DPST : Double pole single throw electrical switch.

Drain Plug : A fitting located at the bottom or base of a valve, the removal of which allows the draining and flushing the body pressure cavity.

Draw Off Tap : Valves capable of controlling fluids by opening and closing the valve parallel to the seat orifice.

Dry Armature : A dry armature solenoid valve, sometimes called an isolated diaphragm valve is a valve where the media passing through the valve will ONLY come into contact with the valve body material and the sealing material. Dry armature solenoid control valves are used to control very aggressive and corrosive acids and alkali's.

Dry Lube : Dry-film moly disulphide applied as a coating to sliding or rotating parts to reduce frictional drag. Also available is in liquid form that can be mixed with lubricating oils that stick or coats all metal parts to provide fail safe and increased lubrication, will provide continued lubrication for a short time if the oil is removed.

Dynamic Seal : A seal or gasket used to seal between two moving metal parts such as a stem seal, piston seal or shaft 0 ring.

Durometer : A durometer is an instrument for measuring the hardness for synthetic rubber or elastomer seals, measured on a SHORE Hardness scale. For example a WRAS approved EPDM rubber would have a shore hardness of 72, being soft and pliable yet strong enough to withstand mains water pressures.

Duty Ratings : A solenoid duty rating is defined as the electrical power ON time compared to the electrical power OFF time for a solenoid coil. For example a solenoid coil powered ON for 1 minute and then power OFF for 4 minutes would be 1/4 or 25%. If a coil is shown as having a 100% duty cycle rating then the coil can be powered ON 100% of the time but as with all solenoid coils they can only be energised when correctly fitted to the solenoid valve.