Solenoid Valve Terminology P - R

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Solenoid Valve terminology P

Parallel Thread : A parallel thread is a straight thread sealing is by O ring or bonded washer between the two flat surfaces of the male threaded fitting being screwed in and the female threaded flat face.

Pilot Assisted : See pressure assisted

Pin Hole : A small hole typically though the thickest part of the valve body casting or just below the surface caused by gases trapped in the molten metal during cooling.

Pinion Shaft : An external gear drive shaft typically with a hand wheel or actuator connected to it, that will drive an internal reduction gear for valve actuation.

Plastic : A generic term for a non metallic material such as PVC, PP, PVDF, Nylon, Delrin or PTFE used in the construction of water and aggressive media solenoid valves and sometimes used as a protective coating for other valve types.

Plug : An electrical connector that allows for an electric cable or power supply to be easily connected to or removed from an electrically actuated valve or controller. Sometimes referred to as DIN 43650 electrical connectors.

Plunger : The solenoid plunger sometimes referred to as the armature is the magnetic stainless steel part that moves when the solenoid coil is activated, which in turn either directly or indirectly changes the sate of the solenoid valve.

PMI - Positive Material Identification : Positive material identification is a system for checking the identity of a valve material.

Pneumatic : Pneumatic means an air or gas media that is compressed and piped to an air operated system or valve. Pneumatic typically means air.

Pneumatic Test : A pneumatic test is typically a valve tested with compressed clean dry air. Typically valves are tested in the closed position to ensure leak tightness and can be tested in both open and closed positions to test the valve is functioning and working correctly.

Porosity : Porosity is a defect in valve body castings caused by gas bubbles or open spaces (voids) in the metal, main the valve body porous.

Port : A port is the connecting point of a valve, a valve with two ports will have one inlet and one outlet, a valve with three ports will be a diverting valve diverting flow to one of two pipelines. A port can be threaded, flanged or weld end.

Port Size : Solenoid valve port or connection size are most commonly measured by thread or flange connection.

Position Indicator : A position indicator is typically a visual position flag or grommet within a clear protective window that gives visual indication of the mechanical open or closed position of a valve.

Position Switches : Position switches are used to provide a volt free mechanical or proximity electrical switch that is triggered when the valve is in the open or closed position, for remote confirmation of valve position. An open position or signal feedback switch will confirm by switch contact the valve open position, a closed position switch will confirm by switch contact the valve closed position. Either one or both can be used with various solenoid or coaxial valves.

Power Ratings : Power rating typically refers to the electrical supply power rating or Watts (watts = volts multiplied by amperes). A transformer or power supply may have a Amperes rating. For example a power rating of 1 Amp would be sufficient to power 1 220vAC solenoid valve with a 17 Watt coil, as the current consumption would be Amps = 17watt/ 220volt = 0.077 Amps, but when used with 12vDC 15 watts would give a valve power consumption of 17watt / 12vdc = 1.1466 Amps being more than the available power (current) supply. See coil power ratings.

Pressure : Pressure is measured in terms of units of force against area, for example 15 PSI or 15 pounds force on every every square inch. Another measurement of pressure commonly used is Bar, 1 bar = 1 atmosphere or 14.71 PSI so 10 bar would equate to 147.1 psi, another term kg/cm2 or kilograms force per square centimetre 1 Kg/cm²=1.0197 Bar but safe enough to assume bar = kg/cm² . Pressures and vacuum can be easily converted from Torr, mmHGa, PSI, Hgv, Atm, H2o, Kg/cm2, kPa, Bar and mBar.

Pressure Assisted : Pressure assisted also known as pilot operated means that the pressure difference across the valve is being used to open or close the valve. Pressure difference is the difference between the inlet pressure to the valve and the outlet pressure from the valve, known as ΔP.

Pressure Differential : Pressure differential is required for some types of solenoid valves, such as pilot operated valves servo assisted valves, floating diaphragm valves and pressure assisted valves. Pressure differential is the pressure difference between the inlet and outlet ports of the valve. For example a valve with 2 bar inlet and open ended to atmosphere would have a pressure differential (difference) of 2 bar but small gravity fed solenoid operated or solenoid actuated valves piped into closed loop systems would have a low pressure differential.

  • 1 bar = 14.71 PSI
  • 1 bar = 100 kPa (kilo-pascal)
  • 1 PSI = 6.9 KPa
  • 1 Kg/cm² = 0.98 bar
  • 1 atmosphere = 1.013 bar
  • 1mm Mercury = 1.33 mbar
  • 1 Ton /in² = 154 bar

Pressure Drop : Pressure drop is the difference in pressure between two points. A pressure drop of a valve is the pressure difference between inlet and outlet ports. Pressure drop will occur along any pipe or through any valve as is caused by friction, restrictions and change in flow direction.

Pressure Gauge : A pressure gauge is a pressure measurement device that indicates the pressure at the point at which it is connected to the pipeline system. Pressure gauges are typically threaded at the base or rear and can be glycerine filled to prevent the pressure indicator needle vibration.

Pressure Rating : Pressure rating is the maximum allowable working pressure the equipment is designed to operate. This can be a minimum or maximum pressure rating.

Pressure Switch : An electrical volt free switch connected into a pipeline that will open or close according to its setting and the pipeline pressure. Used for simple ON/OFF control and monitoring of pipeline pressures.

Proof Pressure : a liquid or water hydrostatic pressure test typically 150% of rated maximum working pressure applied to a valve in the closed position to test the structural integrity of the pressure bearing shell or valve body.

Proximity Switch : A proximity switch is a volt free valve position indication switch that utilises magnetic field disruption or something metallic close to its "Proximity"to switch. For example an open proximity switch in an angle seat piston valve will react (switch and make circuit) when the valve piston lifts open and the metal stem is close to or within the proximity of the switch. A control panel will know by break or make electrical circuit if a valve is mechanically fully OPEN or CLOSED.

PRV - Pressure Reducing Valve : Pressure reducing valves are designed to reduce and maintain a pre-set outlet pressure regardless up inlet or upstream pressure variations caused by other process demands, valve or pump changes. Pressure reducing valves are available in direct acting and pilot operated operation.

PSI - Pounds per Square Inch Pressure : PSI is a measurement of applied pressure measured in pound force per square inch. For example one atmosphere is 14.71 psi being 14.71 pounds force applied to each square inch so a pressure vessel with 10 square inches of surface area would have an applied force measured at 10 x 14.71 = 147.1 pounds of force or 66.86 Kg.

PTFE seal : PTFE or Polytetrafluoroethylene) is also known as Teflon®, Teflon is a trade mark of Dupont. PTFE offers excellent chemical resistance to most liquids and temperatures up to +230°C and down to -200°C for cryogenic applications. PTFE has good resistance to most liquids and gases. PTFE has poor sealing characteristics as it is a hard material without the elasticity of NBR, EPDM, FKM, which will cause leakage or sealing difficulties if the media being controlled is not clean.

PU220™ : PU220® is a zero rated 2/2 way brass solenoid valve and is also a registered class 9 trade mark number 2456842 for Connexion Developments Ltd.

PU225™ : PU225® is a pressure assisted 2/2 way brass solenoid valve and is a registered class 9 trade mark number 2456841 for Connexion Developments Ltd.

Pump Control Valve : A specialised check valve to control flow and prevent cavitation and water hammer in or from pumps and liquid flow lines.

Solenoid Valve Terminology R

Radiographic Inspection : Radiographic inspection is the X ray analysis for checking welds, metal castings and metallic fabricated parts for flaws, cracks and potential weaknesses.

Rectified : A rectified coil or connector will typically include a bridge rectified or full bridge rectified circuit that will convert AC 50/60Hz alternating current input into DC direct current output.

Rectified Coil : A rectified coil converts the AC (alternating current) 50/60Hz into DC (direct current) typically by an internal full bridge rectified circuit to allow for a DC coil to be used. DC coils generally offer quieter operation without the 50/60Hz Buzz normally associated with AC applications, but typically can offer a reduced pressure range in accordance with DC valve pressure range if used for direct acting or assisted lift zero rated solenoid valves.

Reduced Bore : A solenoid valve or gate, ball or globe valve those port or connecting point is smaller than the pipeline internal or bore diameter, hence reduced bore.

Regulator : A pressure control valve that automatically regulates, reduces and controls a pre-set sometimes manually adjustable outlet pressure, regardless of upstream or inlet pressure increases or changes.

Relief Valve : A safety pressure release valve designed to automatically release fluid pressure to protect pressure bearing equipment from over pressure damage. Regulations ensure that pressure relief valves are fitted to all pressure vessels to ensure that their maximum design pressure is not exceeded.

Relieving : A relieving valve or pressure regulator will vent excess downstream system pressure if the pressure exceeds the set pressure or the pressure setting is reduced. A relieving air pressure regulator will vent excess downstream air pressure externally.

Response Time : The response time is the time required by a solenoid valve to completely change its state from Open position to Closed position or visa versa. Typical response times are around 20 to 50 milliseconds (0.05 seconds) for miniature solenoid valves up to 1/2" and from 100 - 5000 milliseconds (0.1 to 5 seconds) for larger valves. Larger valves operate more slowly to avoid the effects of water hammer and internal damage.

RF - Raised Face : A raised area on the face of a flange where the sealing gasket will fit. The reduced sealing face means that a higher applied pressure is applied to a smaller surface area and any minor damage to the flange face edges due to transportation or installation will not inhibit sealing.

Rising Stem : A gate or globe valve whose stem will rise out of the valve body when the valve is opened. Typically the stem is not in contact with the media passing through the valve.

RO Water : RO or reverse osmosis water is a water purification process where water is forced through semi permeable membranes which remove between 90% to 99% of tap water impurities, producing water that is free from minerals and other impurities.

Rockwell Hardness Number : A measurement of metal hardness by a Rockwell Hardness Tester. Rockwell scale B for soft metals, Rockwell scale C for hard metals.

Rohs Compliance Definition : ROHS definition and aim is to restrict certain dangerous substances commonly used in electronic and electronic equipment. An RoHS compliant component or product is tested for the presence of Lead (Pb), Cadmium (Cd), Mercury (Hg), Hexavalent Chromium (Hex-Cr), Polybrominated Biphenyls (PBB), and Polybrominated Diphenyl Ethers (PBDE). For Cadmium and Hexavalent chromium, there must be less than 0.01% of the substance by weight, for Lead, PBB, and PBDE there must be no more than 0.1% of the material, when calculated by weight. Any RoHS compliant component must have 100 parts per million or less of mercury and the mercury must not have been intentionally added to the product or component. In the EU, some military and medical equipment are exempt from RoHS compliance.

RPM - Revolutions Per Minute : RPM or revolutions per minute is a measure of rotating speed of a shaft or wheel given as complete turns over a one minute measured time interval.

RTJ - Ring Type Joint : A ring type joint or flange connection with metal metal sealing that are used on high pressure applications such as the gas and oil exploration and production. R.T.J joints excel in sealing for high pressure pipelines and fittings.

Rupture Disc : A thin metal disc on a pressurised system designed to break or rupture at a specific pressure, much like a pressure relief valve but in this case will vent all pressure and will need to be replaced if ruptured.