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Lock-up Pressure Parameters
Per ANSI Z21.80, lock-up is defined as an outlet pressure not
more than 150 % or 5 in. W.C, whichever is greater, above the
setpoint after a downstream safety shutoff valve closes within
2 seconds, and the two following conditions exist:
1. outlet pressure is set to the highest set point of the spring,
and
2. the regulator is set to maximum capacity or flow at which
the regulator will control lockup pressure within the ac-
ceptable limits.
This means that in a given application, a lockup greater than
150% or 5 in. W.C could occur, depending out the inlet pres-
sure, the outlet pressure of the regulator, the flow rate of the
regulator, and the pipe volume downstream the regulator and
upstream the safety shutoff valve.
Regulator Orifice Diameters
Regulator Type
FRI 705/6
FRI 707/6
FRI 710/6
FRI 712/6
Mounting
Recommended Mounting Procedure
Regulator dome from vertically upright to lying horizontally
If the flow is not in the same direction of the
arrows, the regulator will not operate properly.
3 ... 10
Orifice Diameter (mm)
17.0
24.0
29.0
37.5
Per DUNGS, lock-up is +30% of the outlet pressure set-
ting after downstream shutoff valve slowly closes within 30
seconds. Therefore, in a given application, a lockup greater
than +30% or 5 in. W.C could occur, depending on the inlet
pressure, the outlet pressure of the regulator, the flow rate of
the regulator, and the pipe volume downstream the regulator
and upstream the safety shutoff valve.
If in a given application the lock-up pressure is too high,
employing one or more of the following should reduce the
lock-up pressure:
1. Increase the size of the regulator.
2. Increase the pipe volume downstream the regulator and
upstream the safety shutoff valve.
3. Decrease the inlet pressure.
4. Decrease the oulet pressure.
5. Reduce the flow rate.
6. Remove vent line, if installed.
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