Types 7608 – 7668
Precision relief valves


Types 7608–7668 relief valves offer a choice of three orifice sizes, each with either 1/4" NPT female, or 1/2" NPT male, inlet connections. The valve is of the direct acting type, comprising a hexagonal section body in which a piston is spring loaded against a seat formed on the inner end of an inlet orifice. Spring loading, and hence valve cracking pressure, is adjustable by means of a screw at the upper end of the body.
The loading spring is immersed in the valve operating fluid, the spring chamber being connected to the valve outlet port		 through a fluid way in the piston. The possibility of fluid leakage via the threads of the spring adjusting screw is prevented by a sealing/locking cap fitted over the protruding end of the screw.
Special manufacturing materials ensure that the valve complies with NACE Standard MR-01-75 (latest revision as applicable) and is thus suitable for use in most fluid systems. It should be noted, however, that the valve is designed to function as a safety device and should not be used to control fluid pressure within a system.

This relief valve conforms to Directive 94/9/EC relating to equipment intended for use in potentially explosive atmospheres and is ATEX (ATmosphere EXplosible) certified.

These valves also conform to the Pressure Equipment Directive 97/23/EC. All valves are CE marked and supplied with a test certificate plus a declaration of conformity.
Marshalsea Hydraulics has been assessed by SGS Société Générale de Surveillance SA and certified as meeting the requirements of ISO 9001:2000 for the design, development, manufacture and servicing of hydraulic pumps, relief valves and intensifiers.

Type numbers and specifications

Part
number		  
Orifice		 Pressure range
(bar)(psi)		 Inlet
connection
7608 5/32" 90–620 1,300–9,000 1/4" NPT female
7618 1/8" 90–932 1,300–13,500 1/4" NPT female
7628 5/32" 90–620 1,300–9,000 1/2" NPT male
7638 1/8" 90–932 1,300–13,500 1/2" NPT male
7648 3/16" 69–414 1,000–6,000 1/4" NPT female
7668 3/16" 69–414 1,000–6,000 1/2" NPT male
Operating parameters
Pressure range   1/8" orifice – 90 to 932 bar (1,300 to 13,500 psi)
5/32" orifice – 90 to 620 bar (1,300 to 9,000 psi)
3/16" orifice – 69 to 414 bar (1,000 to 6,000 psi)
Reseal pressure   92% cracking pressure or better.
Operating media   Mineral oils, water, water-glycol mixtures with corrosion inhibitor.
Inlet connection   1/4" NPT female standard
1/2" NPT male optional.
Working temperature   standard: –20°C to + 150°C.
arctic: available on request.
Recommended filtration
   10 micron.
Weight   1.25 Kg.