14
TROUBLE SHOOTING GUIDE
PROBLEM: ERRATIC CONTROL
CAUSES
CORRECTIONS
1.
Bent or binding valve stem.
1.
Replace with free running stem.
2.
Packing binding valve stem.
2.
Replace packing set.
3.
Poor bulb location.
3.
Relocate bulb to more representative
average temperature location or add
agitation.
4.
Sudden load changes requiring greater
capacity then valve size can handle.
4.
Replace with proper size.
5.
Wide changes in valve inlet pressure-more
pronounced with unbalanced single seal
valve.
5.
Maintain more stable inlet pressure.
6.
Over sized valve.
6.
Replace with proper size.
PROBLEM: TEMPERATURE EXCEEDS THE DESIRED CONTROL POINT
CAUSES
CORRECTIONS
1.
Adjustment setting too high.
1.
Lower setting.
2.
Bulb at cold location.
2.
Relocate bulb to more representative
average temperature location or add
agitation.
3.
Tube system assembly has lost pressure
fill.
3.
Replace the thermal actuator.
4.
Stem adjustment too small.
4.
Readjust.
(Closes with temperature increase.)
5.
Foreign material under seats holding valve
open.
5.
Cool the bulb to open the valve and allow
flow to flush seats.
6.
Erosion of seats with resulting high
leakage.
6.
Repair or replace valve body assembly.
7.
Pressure drop across valve is too high.
7.
Reduce pressure drop or replace single
seated valve with a double seated valve.
8.
Stem moves into body to open valve.
8.
Change to stem moves into body to open
valve.
(Opens with temperature increase.)
9.
Valve size too small.
9.
Increase supply pressure of replace valve
with larger size.
10.
Valve inlet pressure too low.
10.
Increase supply pressure or replace valve
with larger size.
11.
Heat exchanger is not large enough.
11.
Replace with proper capacity.
12.
Stem moves into body to close valve.
12.
Stem moves into body to open valve.
13.
No flow or temperature to bulb.
13.
Add by-pass flow line.
