Emerson Daniel 762, User Manual

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• Screwed seat rings on all sizes
• No consumption of nitrogen gas
NOTICE
The Daniel Models do not comply with any internationally over-pressurization protection
recognized codes. What the Daniel Models do is to allow the movement of an undetermined
amount of substance
within a pressurized system, not from a pressurized system.
1.2.3 Operation overview of the control valve
The Daniel Models 762, 763, 765, 766 and 767 control valves are normally closed and
open on increasing inlet pressure. The basic valve is of the balanced piston operated
design. Pressure applied to the inlet side of the piston is equally transmitted to the spring
side of the piston. When the line pressure on the inlet side exceeds the gas pressure plus
the pressure exerted by the spring, the moveable barrier of oil compresses the gas and the
valve opens. As line pressure falls below set point, the gas pressure, added to the spring
pressure, closes the valve and it remains closed as long as gas pressure is greater than the
line pressure. Opening and closing speeds are controlled by a check valve mounted to the
internal surface of the cylinder head as shown in
Figure 1-1 .
Check valve Figure 1-1:
Opening speed is relatively unrestricted which results in very fast opening speed. Closing
speed is controlled by the fixed orifice in the check valve.
These valves are normally closed and open on increasing inlet pressure. The basic valve is
the balanced piston design. Nitrogen gas is used to pressurize the valve piston to keep it in
the closed position. The valve incorporates an integral oil reservoir mounted on the
external surface of the cylinder head, which upon installation, is partially filled with a light
oil. Gas under pressure is applied to the reservoir. The pressure of the nitrogen gas, minus
the 4 psi (force of the valve spring) is the effective set point of the valve. When the pipeline
pressure is less than this total force, the valve will be tightly closed. As pipeline pressure
increases the spring and gas pressure is overcome and the valve opens. The oil is a
moveable barrier between the gas and the valve piston. This should eliminate any
possibility of gas permeating the piston seal which would result in gas bypassing the piston
and gas consumption.
The valve may be mounted in a 45° angle position, horizontally or vertically. Whichever
orientation is specified, the oil reservoir must be vertical.
Introduction
User manual 5