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Bulletin 74.1:Y692

Principle of Operation

The Type Y692 Gas Blanketing Regulator reduces a

high-pressure gas to maintain a positive low-pressure

of blanket gas over a stored liquid when the liquid

is being pumped out of the vessel (see Figure 2).

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 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 re-established, the

regulator throttles closed.

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,

control pressure tends to increase slightly, acting on

the diaphragm. When the control (vessel) pressure

exceeds the control spring setting, the diaphragm

moves to close the disk assembly.

The Type Y692 Gas Blanketing Regulator 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 or

control line. 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.

Installation

Install the Type Y692 regulator with the spring case

barrel pointed down. This will assure that the lowest

set pressure shown in Table 1 is achieved. Flow

through the regulator body is indicated by the ow

arrow cast on the body. If a block valve is required,

install a full ow valve between the regulator and the

blanketed vessel.

Sizing Tank Blanketing Systems

When sizing a gas blanketing regulator system for a

low pressure blanketing application, you must consider

the replacement of blanketing gas required for the

liquid loss during pump out of the vessel and also

the condensation/contraction of vessel vapors during

atmospheric thermal cooling.

Direct Displacement

The direct displacement method should be used

with extreme caution. The direct displacement

method determines the amount of blanketing gas

required to replace liquid pumped out of the tank.

Direct displacement does not allow for uctuating

temperature or other factors that may affect pressure

in the vapor space. This method is typically applied

to tanks operating at constant temperature and

containing non-ammable, non-volatile products.

total

= Q

pump

where,

total

= Required Flow Rate

pump

= Required Flow Rate to replace pumped out

liquid from Table 1

1 2 3 4 5 6 7 8 9 10 11 12

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Emerson Y692 Scheda Tecnica Pagina 5

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