Powers 595 Series 11 Self-Operating Temperature Regulators - Type DB & DS Double Seat, Balanced - Manual (Page 10)

Preventive Maintenance
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Once every three months, inspect the Regulator
as follows:
1. Visually check for leaks from the valve body joints, piping-to-
valve connections, packing and stem areas
2. Visually check for excessive corrosion on the regulator,
including the bellows, capillary, bulb, thermal system legs,
bridge, and yoke. Also check for excessive corrosion on the
valve body.
3. Perform the instructions in Testing the Thermal System Less
than full valve travel may indicate a leak in the bellows, capil-
lary, or bulb, or other problems. This may result in excessive
temperature in the process.
4. Test the temperature adjusting nut assembly for freedom of
movement (see Adjust Set Point for instructions).
5. Remove bulb from the process fluid and check for excessive
corrosion, or erosion that may weaken the bulb and/or cause
thermal system failure.
Troubleshooting
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• Erratic temperature control (valve cycles too hot/cold)
1. Valve sized incorrectly. Verify valve selection.
2. Regulator is controlling at incorrect set point. Refer
to Adjust Set Point.
3. Bulb is poorly positioned and/or oriented, and will not control
the actual temperature of the heating/cooling medium. Refer
to Install Bulb.
4. Incorrect type of bulb is being used. See Table on page 15.
5. The valve stem is sticking. Lubricate the stem.
6. The valve stem is bent. Refer to Maintenance for disassem-
bly instructions and replace.
7. Packing gland assembly too tight. Loosen packing gland nut.
8. Faulty or incorrect steam traps. Replace with correct
steam trap.
9. Very wet steam. Install a high pressure steam trap just ahead
of the valve to drain off condensate that collects in the
steam line.
• Regulator does not shut off
1. Pressure differential is greater than allowable pressure drop.
Refer to Water Capacities and Steam Capacities tables.
2. Plug and/or seat is worn. Refer to Maintenance. Replace
seat and/or valve body plug.
3. Foreign material between the plug and seat. Refer to
Maintenance. Clean.
4. Bulb is poorly positioned and/or oriented, and will not control
the actual temperature of the heating/cooling medium. Refer
to Install Bulb.
5. Incorrect type of bulb is being used. See Table on page 15.
6. Valve sized incorrectly, causing wire drawing and leakage.
Refer to Sizing Information.
7. Packing gland assembly is too tight, locking valve stem.
Loosen packing gland assembly and lubricate if desired.
8. Bent valve stem; need to replace. Refer to Maintenance
for disassembly instructions.
9. Thermal system failure. Refer to Testing the Thermal System.
10. Temperature adjusting nut assembly raised too high. Refer to
Adjust Set Point.
• Regulator controlling at too low a temperature
1. Temperature adjusting nut assembly raised too high. Refer to
Adjust Set Point.
2. Pressure differential is greater than allowable pressure drop.
Refer to Water Capacities and Steam Capacities tables.
• Valve "chatters"
1. Regulator installed with the flow of the control medium in
reverse of arrow direction on valve body.
2. Pressure differential too high, refer Water Capacities and
Steam Capacities tables for correct range.
3. Trapped condensate in line. Install a steam trap just ahead of
the regulator to drain off condensate that collects in the
steam line.
• Constant rise in process fl uid temperature
1. DA (Heating Valve): A constant rise in temperature may indi-
cate the thermal system is leaking charge and/or the valve
has failed in a partially or fully open position. This would
allow a constant flow of heating medium, which would over-
heat the fluid which you are trying to control.
2. RA (Cooling Valve): A constant rise in temperature may indi-
cate the thermal system is leaking charge, and or the valve
has failed in a partially or fully closed position. This would
slow or stop the flow of cooling medium which would over-
heat the fluid which you are trying to control.
WARNING: Failure of the thermal system will result in a
constant rise in temperature (or constant high temperature)
of the fluid which you are trying to control.
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