Proportional relief valve is PED-certified

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Parker Instrumentation has developed a PED-certified proportional relief valve for process instrumentation applications with the ability to provide protection over a broad 10.3-414bar (150-6000psig) pressure range.

CE-marked and certified to category IV of the Pressure Equipment Directive (PED), which covers a wide range of applications including hydraulic fluid power equipment, the new valve will be set and tested at the Parker factory for specific application pressures. Its body will be laser-etched with the cracking pressure. The new valve is a simple fit-and-forget device that needs no testing or calibration by the end user, therefore adding reliable safety as well as environmental and/or equipment protection to a wide variety of process and laboratory instrumentation applications.

Designated the HPRV valve, it is available with 3.6mm/0.142inch flow ports. The novel captured seat design is blow-out and chip-resistant and works across the entire operating pressure range (the valve will handle pressures up to 552bar (8000psig) during relief). A range of colour-coded springs configure the valve for eight cracking pressure ranges from 10.3-24.1bar (345-414, 150-375, 325-775, 725-1525, 1475-2275, 2225-3025, 2975-4025, 3975-5025 and 4975-6000psig). The end user can then adjust the valve more finely using an external nut, which is secured in position by Parker's Tru-Loc mechanism as well as a lock wire to eliminate the possibility of accidental movement and to guard against tampering.

Good resolution

Compared with some competitive relief valves, this arrangement provides excellent resolution over crack pressure settings. Furthermore, a low-friction stem seal design helps control the cracking pressure, which is maintained to within 3 per cent of the setting. The valve's balanced poppet design also ensures consistent cracking operation regardless of system back pressures up to 138bar (2000psig).

As standard, the valve is provided with integral A-Lok compression tube ends, which eliminates threaded connections and the potential problems associated with thread sealants such as PTFE tape. Other end styles can also be specified to suit the installation and include single-ferrule CPI end connectors for imperial and metric tube sizes as well as male or female NPT threaded inlet/outlet ports. The valve's outlet port can be configured to duct media to a safe place or release over-pressures to atmosphere.

O-ring seals adapt the valve for use with different types of media over temperatures from -57 to +204degC (-70 to +400degF). Five choices of material are available: fluorocarbon rubber and nitrile rubber for general-purpose use; ethylene propylene or neoprene rubber for compatibility with a wider range of chemicals; or highly fluorinated fluorocarbon rubber, which is compatible with a very wide range of chemicals.

Each HPRV valve is provided as a complete item including spring under a single order number to simplify purchasing. The valve is 100 per cent PED-certified and requires no additional paperwork or approval before use. Parker has additionally set up its manufacturing and assembly process to ensure short lead times and can supply the valve anywhere in Europe within five working days.

Mat Davis, of Parker Instrumentation, says: "For this relief valve design, we went back to the drawing board and created a universal product that will function at pressures up to 6000psi, which accounts for the vast majority of instrumentation applications. We believe it will simplify life for both users and purchasers."

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