Cashco 1000 HP Differential - Manual (Page 9)

9 IOM-1000HP-Dif fer en tial
13. Bench test unit for suitable operation and
seat leak age. NOTE: Regulators are not
normally tight shutoff devices. Pressure
must build above setpoint for best shutoff.
1. Erratic operation; chattering.
Possible Causes Remedies
A. Oversized regulator; inadequate rangeability. A1. Check actual fl ow conditions, resize regulator for
minimum and maximum fl ow.
A2. Increase fl ow rate.
A3. Decrease regulator pressure drop; decrease inlet
pressure by placing a throttling orifi ce in inlet
piping union.
A4. Replace full orifi ce with reduced orifi ce; i.e. new
cylinder required.
B. Worn piston/cylinder; inadequate guiding. B. Replace trim.
C. Flow induced instability. C1. Get straight runs of piping (5 diameters upstream,
10 downstream) to and from regulator.
C2. Ensure outlet velocity is not excessive; use pipe
reducer close to regulator outlet.
C3. Add next higher range spring. Contact factory.
C4. If composition diaphragm, switch to metal
diaphragm.
D. Improper (oversized) jet. D. Replace existing piston with new piston with
proper jet.
E. Plugged trim. E. Remove trim and check for plugged holes in
piston, or debris in guide zone or jet zone.
F. Unstable loading pressure. F1. Stabilize loading pressure; i.e. pump, control
valve, etc.
F2. Air in loading piping. Vent spring chamber.
VII. TROUBLE SHOOTING GUIDE
SECTION VII
14. Soap solution test around cylinder (21)-to-
body (1) connection for leakage. Test pres-
sure should be a min i mum of 100 psig at the
inlet or actual service con di tions if higher.