Groth 1401E - Manual (Page 12)

11
SETTING AND TESTING PROCEDURE
SERIES 1401 PILOT VALVES
TESTING PILOT VALVE ALONE
NOTE: See pressure relief valve manual for procedure for
setting and testing the pilot valve/relief valve assembly.
1.0 Equipment
1.1 Test apparatus per Fig. 13.
1.2 Test gauges must be selected to suit the specified set
pressure. The set pressure should be between 20% and
80% of the full scale reading of the gauge.
2.0 Test procedure and acceptance criteria
2.1 To determine set pressure, slowly increase pilot inlet
pressure. Simulated actuator pressure will rise with inlet.
As set pressure is approached, the actuator pressure will
begin to decrease. Continue to increase inlet pressure
slowly until actuator pressure is 15% (+/- 10%) of inlet
pressure. This is the set pressure.
2.2 Rotate set pressure adjusting screw [2] clockwise to
increase set pressure or counter clockwise to decrease.
Adjust screw and repeat above test (2.1) until the specified
set pressure is achieved.
2.3 To determine reseat pressure, slowly decrease the inlet
pressure and the actuator pressure will begin to increase.
Reseat occurs when the actuator pressure equals the inlet
pressure.
2.4 The difference between set and reseat pressure,
"blowdown", can be adjusted with the blowdown needle
[20]. Maximum clockwise rotation provides rapid relief
valve opening, "snap action", and maximum blowdown.
Standard blowdown, unless otherwise specified is 7-10% of
set pressure.
2.5 Increased counter clockwise rotation of blowdown
screw provides "modulating" action and minimum (zero)
blowdown. Reseat pressure is the same as set pressure.
NOTE: The blowdown needle is located in a pressure
containing chamber, and is retained by the blowdown
bushing. DO NOT remove the blowdown bushing while
under pressure.
2.6 Remove body vent and install a flexible tube in this
port. Immerse this pilot discharge bubble tube in water
approximately 1/4" below surface to detect cracking and
reseat pressure. See Warning on page 6.
2.7 A small interaction occurs between set pressure and
blowdown adjustments. Readjustment of both may be
required until the specified set pressure and blowdown are
achieved. After completion, lock both screws with
locknuts and replace cap on set pressure screw.
2.8 Hold the valve at set pressure while soap bubble
testing all bolted, flanged and threaded connections.
2.9 Standard setting specifications
TABLE 5
SETTING SPECIFICATIONS - PILOT VALVE
Pilot
Action
Set
Pressure
Set
Pressure
Limits
Maximum
Cracking
Pressure
% of Set
Reseat
Pressure
% of Set
Snap 2"-8" WC +/- 0.2" 75 90 +/- 3
Snap 8" WC -
1.0 PSIG
+/- 3% 90 90 +/- 3
Snap 1.0 - 15.0
PSIG
+/- 3% 95 93 +/- 3
Modulating 2" - 8" WC +/- 0.2" 75 100
Modulating 8" WC -
1.0 PSIG
+/- 3% 90 100
Modulating 1.0 - 15.0
PSIG
+/- 3% 95 100
3.0 Test report data
3.1 Record the following data for future reference:
Model, tag & serial numbers
Test medium
Set pressure
Blowdown pressure
Cracking pressure
Bubble tight reseat pressure
Fig. 13 Pilot Valve Alone
ACTUATOR VESSEL
APPROX 0.1 CU FT
25 PSI MAWP
AIR
SUPPLY
LET PRESSURE
ACTUATOR
PRESSURE