Emerson Y690A Datový list stáhnout pdf (Strana 4)

Bulletin 74.1:Y690A

SLIDING PUSHER POST

OVERPRESSURE SPRING

VALVE DISK

VALVE STEM

LEVER

DOWNSTREAM CONTROL LINE FOR

TYPES Y690AM AND Y690AHM

PITOT TUBE FOR

TYPES Y690A

AND Y690AH

INLET PRESSURE

OUTLET PRESSURE

ATMOSPHERIC PRESSURE

B2625

Figure 2. Y690A Series Operational Schematic

Principle of Operation

With Internal Registration

(Refer to Figure 3)

Types Y690A and Y690AH are direct-operated

regulators with internal registration (see Figures 2

and 3). It provides a constant set pressure for

accurate gas blanketing. When vessel pressure

decreases below the control spring setpoint, the force

of the spring moves the disk away from the orice

allowing gas to ow into the vessel. As the vessel

pressure increases, the increase is sensed by the

diaphragm through the pitot tube. This movement

of the diaphragm causes the disk to move toward the

orice, decreasing the ow of blanketing gas. When

the vessel pressure reaches the system setpoint,

the disk will seat against the orice shutting off the

ow of gas.

With External Registration

(Refer to Figure 4)

Types Y690AM and Y690AHM Gas Blanketing

Regulators reduce a higher-pressure gas to maintain

a positive low pressure of blanket gas over a stored

liquid. Also when the vessel (or tank) is suddenly

cooled, causing vapors to contract, the regulator

replaces the volume of contracting vapors with a

volume of blanketing gas to prevent the internal vessel

pressure from decreasing. In both cases, a positive

vessel pressure prevents outside air from entering the

vessel and reduces the possibility of atmospheric

pressure collapsing the vessel.

Gas blanketing regulators respond to a slight decrease

in internal vessel pressure (caused by pump out or

atmospheric cooling) by throttling open to increase the

ow rate of gas into the vessel. When the vessel’s

liquid level has been lowered to the desired point

and the vapor pressure has been reestablished, the

regulator throttles close.

When the liquid level drops and vessel pressure

decreases below the setting of the control spring,

the spring force on the diaphragm opens the disk

assembly to supply the required ow of gas to the

vessel. When vessel pressure has been satised,

outlet pressure tends to increase slightly, acting on

the diaphragm. When the outlet pressure exceeds

the control spring setting, the diaphragm moves to

close the disk assembly.

1 2 3 4 5 6 7 8 9 ... 15 16

Bulletin 74.1:Y690A 1

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