Watson McDaniel HSP Series, Installation & Maintenance Manual, Page: 11 / 13

11 Watson McDaniel Company HSP Valve Manual Rev3 2415800
System Troubleshooting
PROBLEM POSSIBLE CAUSE CORRECTION
1. Cannot set valve to
give high enough
downstream
pressure
requirements
a) Valve undersized a) Check capacity of valve against load
b) Downstream piping undersize b) Check velocity of steam in piping
system
c) Pilot valve spring not adjusted properly c) Readjust desired reduced pressure
d) Pilot adjusting spring not correct d) Check color code of spring against
spring range in literature
e) Inlet or outlet gate valve partially closed e) Open valves
f) Upstream pipeline strainer blocked f) Clean strainer screen
g) Pilot screen clogged g) Clean screen
h) Inlet pressure too low causing reduced
capacity thru valve
h) Check with gage and correct as
required
i) Diaphragm orifice blocked i) Check and clean orifice, Do not
remove clean-out wire
j) Bleed orifice fitting missing, installed
wrong or eroded
j) Inspect and check against cut-away
drawing
k) Main valve diaphragms failed k) Replace diaphragms
2. Downstream
pressure over rides
set pressure under
load conditions
a) Valve is extremely oversized a) Check catalog for rated capacities
b) Bypass valve open b) Close valve
c) Pilot valve adjusting spring set too high c) Readjust to desired reduced
pressure
d) Bleed orifice blocked d) Inspect and clean
e) Dirt in pilot seat or stem guide e) Clean pilot head and seat assembly
f) Foreign object lodged between main valve
disc and seat
f) Check main valve disc and seat.
Check stem guide bushing for
binding
g) Pilot diaphragms ruptured g) Replace pilot diaphragms
h) Main valve seat thread leaking h) Check body in seat ring area for
erosion
3. Valve will not open a) Adjusting spring not set a) Adjust setting
b) Upstream isolation valve closed b) Check and open valve
c) Upstream pipeline strainer blocked c) Clean strainer screen
d) Pilot screen blocked d) Remove and clean
e) Pilot stem and guide bound with dirt e) Inspect and clean
f) Bleed orifice missing or installed wrong f) Inspect and check against cut-away
drawing
g) Diaphragm orifice blocked g) Inspect and clean. Do not remove
clean out wire
h) Main valve diaphragms ruptured h) Replace main valve diaphragms
4. Valve will not close a) Bypass valve open a) Close bypass valve
b) Pilot sensing line not installed b) Install pilot sensing line
c) Bleed orifice blocked c) Inspect and clean
d) Dirt in pilot seat or guide d) Inspect and clean
e) Inspect and clean e) Replace pilot diaphragms
f) Foreign object lodged between main valve
disc and seat
f) Inspect, clean and repair