5
MAINTENANCE MANUAL: MODELS 860, LF860, 860U & LF860U
1
/
2
"- 2" (15 – 50mm)
Troubleshooting Guide (Continued)
SyMpTOM #3
CauSe:
SOluTIOn:
Continuous discharge from relief valve during
A. Seat disc dislodged from cavity in
Reposition disc in main stem cavity
FLOW and NO FLOW conditions
the main stem. (This can be caused
Repressurize system slowly
With this symptom, the pressure drop across
by pressure surges during initial filling of
the #1 check valve would be
system lines.)
7 psid or more at all times
B. Debris fouling the relief valve seat
Inspect and clean
C. Debris blocking the relief valve
Inspect and clean
sensing passage
D. Dirt or scale jamming main stem
Inspect and clean, or replace
E. Leakage at main stem
Inspect and clean, or replace
SyMpTOM #4
CauSe:
SOluTIOn:
Relief valve does not open above
A. Outlet gate valve not closed completely
Inspect and clean
2.0 psid during field testing
B. Plugged low pressure hydraulic passage
Inspect and clean
(from “ZONE” to inner diaphragm)
C. Improper alignment of internal parts during
Reassemble
reassembly (causing high resistance to movement)
D. Jammed main stem due to debris
Clean
Check for debris blocking gate valve
SyMpTOM #5
CauSe:
SOluTIOn:
First check pressure drop is low
A. Debris fouling first check seat
Inspect and clean
(less than 5 psid) during field testing
B. Debris fouling second seat with backpressure
Inspect and clean
C. Inlet pressure variations causing
Eliminate pressure variations
inaccurate gauge reading
(see symptom #2A)
D. Damaged seat or seat disc
Inspect and clean as required
E. Worn guide, bushing or stem
Inspect and replace as required
SyMpTOM #6
CauSe:
SOluTIOn:
Second check fails to hold back
A. Outlet gate valve not closed completely
Inspect and clean
pressure during field testing
B. Debris fouling second check seat
Inspect and clean
C. Damaged seat or seat disc
Inspect and replace if required
D. Worn guide, bushing or stem
Inspect and replace if required
