New gas valve offers greater precision

Jon Lawson

Up to now, users who wanted to meter very small quantities of gas precisely had hardly any choice but to use a needle valve. Witt now presents the PMV Precision Metering Valve as an alternative, with a two-fold benefit.

Very small gas flow rates down to 30ml/min can be metered by the PMV. The precise flow adjustments can be made in the pressure range up to 20 bar using a rotary knob. Its spindle with 14 full rotations is generously sized to allow very fine flow gradations and has virtually no hysteresis. An alternative is a digital knob with 1499 divisions and a locking ring. This allows any target value to be set rapidly, precisely and with high repeatability. Witt can also supply the valve as simply a valve cartridge for installing in machines and other apparatus. All commercially available gas types can be used – including hydrogen and oxygen.
The high precision of metering even the smallest gas quantities is however only one of the special features. "We have redeveloped precision metering technology from scratch" explained valve specialist Andreas Heyer. "A hollow-cylinder, sintered body forms the regulating core element."  
The PMV is superior to the needle valve in terms of service life. "The porous structure of the sintered body filters out unwanted particles from the gas as a side-benefit." continued Heyer. Static sintered bodies are not only insensitive to dirt but are also self-cleaning when the valve is being set. Rapid clogging, as occurs with a needle piston, is rare. This has meant a corresponding lengthening of the fault-free service life.
Witt supplies the PMV fine-metering valve as a straight flow valve in block design with two rotary knob variants or simply as the valve cartridge.  A choice of eight sinter inserts with different flow ranges and degrees of fineness is available. The valve is manufactured from brass and stainless steel, with nitrile rubber (NBR) seals. The design is extremely compact – the valve cartridge is less than 70mm long and weighs only 54 grams.

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