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1
Introduction
Topics covered in this chapter:
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1.1
Purpose of this manual
Daniel Measurement and Control Inc. designed this manual to guide owners and personnel
in the installation, operation and maintenance of the Daniel
and Models 1770 and 2770 Pilots Manual, 3-9008-608. It is imperative that product owners
and operation personnel read and follow the information contained in this manual to
ensure that the control valve is installed correctly and is operating according to the design
certifications and safety considerations.
1.2
Description of the Model 770 control valve
1.2.1
Control valve general features
The Model 770 (normally closed) differential control valve is designed to maintain a
controlled pressure differential within +/-2 psi of the pilot set point, regardless of
variations in upstream or downstream pressure. The pilots are balanced, single seated with
large ports and operate on a differential as low as 5 psi (34.5 kPa).
1.2.2
Control valve applications
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1.2.3
Operation overview of the control valve
The Daniel Differential Control Valve operates on a balance-piston principle. When
pressures on both sides of the valve piston are equalized, a spring (located on the top of
the piston) acts as a differential force and closes the main valve piston. When the pressure
against the bottom of the piston exceeds the pressure (plus the force of the spring)
exerted against the top of the piston, spring tension is overcome and the valve opens. It is
from this principle of operation that all variations of control, with the use of pilot valves
User Manual
Purpose of this manual
Description of the Model 770 control valve
Agency certifications for the Model 770 Control Valves
Maintains system pressure at a predetermined level above product pressure
Vapor pressure control on LPG, NH3 and similar products
Pump differential pressure control
Provides constant pump discharge flow rate by controlling differential pressure
across an orifice plate
Introduction
TM
Differential Control Valve 770
3
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