8
MAINTENANCE MANUAL MODELS 825Y, 825YA, 825, 825D, 825YD & 826YD
Troubleshooting Guide (Continued)
SYMPTOM:
CAUSE:
SOLUTION:
4. Relief valve does not open above 2.0 psid during
fi eld testing.
a. Outlet gate valve not closed completely.
a. Check for debris blocking gate.
b. Plugged low pressure hydraulic passage
(from “ZONE” to inner diaphragm).
b. Inspect and clean.
c. Improper alignment of internal parts during
reassembly (causing high resistance to
movement).
c. Disassemble and center the button, spring and
main stem.
d. Jammed main stem due to excessive torque on
center bolt (825 and 825D only).
d. Do not exceed 15 inch-pound torque on main stem
center bolt.
5. First check pressure drop is low
(less than 5 psid) during fi eld testing.
a. Debris fouling fi rst check seat.
a. Inspect and clean.
b. Debris fouling second check seat with
backpressure.
b. Inspect and clean.
c. Inlet pressure variations causing inaccurate gauge
reading.
c. Eliminate pressure variations.
d. Disc holder not perpendicular to stem
(therefore, disc not parallel to seat ring)
(825, 825D and 825YD).
d. Inspect and reassemble if required. NOTE: Spring
must be removed when tightening disc holder to
stem.
e. Damaged seat or seat disc.
e. Inspect and replace as required.
f. Worn guide, bushings or stem.
f. Inspect and replace as required.
g. Guide not properly seated in cover (825, 825D and
825YD only).
g. Inspect and reassemble.
6. Discharge from drain hole in relief valve spacer
(825 and 825D only).
a. Leakage under diaphragm retaining screw (8
places).
a. Apply thin layer of sealant around each thread,
insert on bottom and reassemble.
b. Leakage under diaphragm at main stem diameter.
b. Apply thin layer of sealant
on button at the main stem
diameter. DO NOT EXCEED 15 INCH POUNDS
when tightening center bolt.
c. Hole in diaphragm.
c. Replace diaphragm with fabric side towards the
button.
7.
Second check fails to hold back pressure during
fi eld testing.
a. Outlet gate valve not closed completely.
a. Check for debris blocking gate.
b. Debris fouling second check seat.
b. Inspect and clean.
c. Disc holder/stem not moving freely in guide(s).
c. Inspect for dirt or other foreign material.
d. Disc holder not perpendicular to stem
(therefore, disc not parallel to seat ring)
(825, 825D & 825YD).
d. Inspect and reassemble if required. NOTE: SPRING
MUST BE REMOVED WHEN TIGHTENING DISC
HOLDER TO STEM.
e. Damaged seat or seat disc.
e. Inspect and replace as required.
f. Worn guide, bushings or stem.
f. Inspect and replace as required.
g. Guide not properly seated in cover (825, 825D &
825YD only).
g. Inspect and reassemble.
Note:
If check valve seat disc has been severely cut at the seat ring diameter, the assembly is being subject to extremely
high and repeated back pressure. Either thermal water expansion or water hammer are the most likely causes.
