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Introduction
In general, all systems where pressure is contained must have some form of pressure relief,
which is often mandated and regulated by local authorities. The design of such systems is
dependent on a complex range of factors including, but not limited to, the potential for
pressures increases, the volumes which must be passed by the pressure relief equipment
in operation and the capacity of the system to contain pressures.
Typical tank and pressure vessel systems are required to release pressure without passing
large volumes of liquid. Usually these systems operate to relieve vapor from the space
above the liquid using self acting pressure relief valves.
Although these valves are commonly used as pressure relief devices, the nozzle size is
quite small and hence, the capacity for passing liquids is extremely limited. Therefore, such
designs are often limited to tank and vessel protection, where overpressure is readily
relieved without the need to pass significant quantities of liquid.
1.2.2
Control valve application
The Daniel Models 762, 763, 765, 766 and 767 Gas Loaded Relief/Back Pressure Control
Valves are specifically designed to regulate and control maximum pipeline pressures or to
maintain a minimum back pressure in a system. They have proven to be reliable, rugged
and very responsive in controlling pipeline surges and pressures. The Daniel Models 762,
763, 765, 766 and 767 Gas Loaded Relief/Back Pressure Control Valves are not pilot
operated. They incorporate an integral oil reservoir mounted on the external surface of the
valve cylinder head, which upon installation, is partially filled with a light oil. Gas under
pressure is then applied to the reservoir. The oil is a moveable barrier between the gas and
the valve piston. This insures that nitrogen gas does not permeate the piston seals which
would result in nitrogen consumption and the need to constantly replenish the system. A
major benefit of the valve design is that all internal parts, including cylinder, piston and
seat ring are removed as a cartridge assembly which keeps line connections intact.
Applications
•
Back pressure control
•
Pipeline pump station by-pass
•
Pipeline pressure and surge relief
•
By-pass pressure control
Features and benefits
•
Modular construction
•
No diaphragms or stuffing boxes
•
Linear control characteristics
•
Exceptionally fast response speed
•
Positive shut-off
•
High flow capacity
•
Balanced piston design
•
No pilot controls
•
Can pass dirty or viscous products
4
Daniel Models 762, 763, 765, 766 and 767 Control Valves
USER MANUAL
11
www.Daniel.com
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