User Guide

Troubleshooting Guide Continued
Symptom #5 Cause: Solution:
First check pressure drop is low
(less than 5 psid) during fi eld testing
A. Debris fouling fi rst check seat
B. Debris fouling second seat with
backpressure
C. Inlet pressure variations causing
inaccurate gauge reading
D. Disc does not move freely in arm.
(Therefore, disc not parallel to
seat ring)
E. Damaged seat or seat disk
F. Worn guide, bushing or stem
G. Bearing not properly seated in cover
Inspect and clean
Inspect and clean
Eliminate pressure variations.
(see symptom 2A)
Inspect and clean if required
Inspect and replace as required
Inspect and replace as required
Inspect and reassemble
Symptom #6 Cause: Solution:
Second check fails to hold back
pressure during fi eld testing
A. Outlet gate valve not closed completely
B. Debris fouling second check seat
C. Disc not moving freely in assembly
D. Damaged seat or seat disk
E. Worn guide, bushings or stem
F. Bearing not properly seated in cover
Check for debris blocking gate valve
Inspect for dirt or other foreign debris
Inspect and clean
Inspect and replace if required
Inspect and replace if required
Inspect and replace if required
Inspect and reassemble
Symptom #4 Cause: Solution:
Relief valve does not open above
2.0 psid during fi eld testing
A. Outlet gate valve not closed completely
B. Plugged low pressure hydraulic passage
(from "ZONE" to inner diaphragm)
C. Improper alignment of internal parts
during reassembly (causing high
resistance to movement)
D. Jammed main stem due to debris
Check for debris blocking gate valve
Inspect and clean
Reassemble
Clean
Note: If check valve seat disc has been severely cut at the seat ring diameter, the assembly is being subjected
to extremely high and repeated back pressure. Either thermal water expansion or water hammer are the
most likely causes.
5
MAINTENANCE MANUAL MODELS 860 & 880V 2
1
/2" – 10"
IOM-F-860_880V.indd 5 7/11/08 10:45:27 AM