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Bulletin 71.1:627W

Figure 3. Monitor Regulator Schematic

A6623

CONTROL LINE

WORKING REGULATOR

MONITOR

TYPE 627W

SET HIGHER

THAN WORKING

REGULATOR

TYPE 627W TYPE 627W

INLET

Capacity Information

Tables 4 and 5 give regulating capacities in U.S. GPM of

water (multiply by 0.2271 to convert to m

/h of water).

To determine regulating capacities at pressure settings not

given in Tables 4 and 5 or to determine wide-open capacities

for relief sizing at any inlet pressure, use the Catalog 10 liquid

sizing procedures in conjunction with the appropriate liquid

sizing coefcients (C

and K

, see Tables 6 through 8). Convert

to m

/h according to the preceding paragraph if necessary.

Liquid Sizing for Liquids Other

than Water

∆P

where:

= Flow in GPM

∆P

= Value differential in psi

= Valve sizing coefcient (see Tables 6 and 7)

G = Specic Gravity

Example:

NPS 1 (DN 25) body

1/4-inch (6,3 mm) orice

Glycol (Specic Gravity) = 1.11

inlet

= 200 psig (13,8 bar)

out

(setpoint) = 100 psig (6,9 bar)

Capacity based on 20% Droop from setpoint

out

at full ow = 100 psi setpoint – 20 psi Droop = 80 psi

∆P = 200 – 80 = 120 psi

= 1.18 from Table 6

120

1.11

1.18

= 12.2 GPM Glycol

= 46,2 l/min Glycol

Maximum Allowable Pressure Drop for

Liquid Service

Pressure drops in excess of allowable will result in choked ow

and possible cavitation damage.

Choked ow is the formation of vapor bubbles in the liquid

owstream causing a crowding condition at the vena

contracta which tends to limit ow through the regulator.

The vena contracta is the minimum cross-sectional area

of the ow stream occurring just downstream of the actual

physical restriction.

Cavitation and ashing are physical changes in the process

uid. The change is from the liquid state to the vapor state and

results from the increase in uid velocity at or just downstream

of the greatest ow restriction, normally the regulator orice.

To determine the maximum allowable pressure drop for water:

∆P

(allow)

= K

)

where:

∆P = Valve differential in psi

= Valve recovery coefcient from Table 8

= Valve inlet pressure in psia

To determine maximum allowable pressure drop for uids other

than water, see Fisher

Catalog 10.

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

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