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User manual
P/N 3-9008-553
8
Operation parameters
8.1
Control valve normal operation
Models 700 Control Valve is versatile valve in the market. It can incorporate any single or
multiple control function(s) to meet the exact requirements for on - off in modulating
control of liquid products. Control combinations are virtually unlimited.
All series 700 control valves are pressure balanced, single-seated piston operated with 45°
body construction. The valves are hydraulically operated and use the flowing stream as the
power medium. All are equipped with a needle valve in the pilot supply line for adjusting
the closing rate and for sensitivity control. A strainer is also incorporated in the pilot flow
line, upstream of the needle valve.
Unique design features and unit-built construction ensures positive leak-proof
performance. In addition, the basic valves body and internals are the same throughout the
line, simplifying spare parts inventory and reducing costs.
8.2
Operation accessories
•
Opening speed control: Device installed in the Y port of the valve to control opening
speed
•
Thermal relief: It is the pressure differential safety device use to eliminate excessive
pressures caused by thermal expansion.
•
Block or isolation valve for X, Y, Z ports
•
Manual override: Device used to by-pass the pilot module
•
Valve position indicator
•
Limit switches: The sequential switches convert the mechanical motion of the batch
controlling mechanism of the preset counter to electrical signals used to control the
solenoid pilots of the control valve for low flow position-shut down and/or start-up.
•
Orifice flanges
It is recommended to ensure that both the line and the product are clean before the valve
is installed. Small particles of foreign material usually will not effect the performance of
the valve, although larger particles may damage the valve piston and its seat.
8.3
Operation overview
Operation of the Model 700 Control Valve is based on a balanced piston principle.
When pressure on both sides of the main valve piston are equal, a spring (located on the
top of the piston) acts as a differential force and closed the main valve piston. As pressure
against the bottom of the piston increases and exceeds the pressure exerted against the
top of the piston, plus the force of the spring, spring tension is overcome and the valve
opens.
User manual
Operation parameters
November 2020
45
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