Bell & Gossett HS 601G Pilot Operated Pressure and/or Temperature Steam Regulators Series 2000 - Manual (Page 12)

TROUBLESHOOTING
Replace the regulator or pilot(s) when parts no longer
operate properly. A new regulator is more economical
than replacing individual parts, and will provide greater
reliability.
General Series 2000 Regulator System
Troubleshooting Guidelines
Dead End Service
The seat leakage rate for metal single seated valves is
.01% of rated flow, which is the industry standard. In
applications where .01% flow will cause pressure or tem-
perature override, seat lapping may be required. (See
"Seat Lapping Procedure", page 14.)
Lifts in the Return Line on Heat Exchanger
Applications
An elevated return line on a heat exchanger requires
steam pressure to lift condensate. Condensate cannot
drain from the heat exchanger shell until the internal pres-
sure is sufficient to lift the condensate. The steam pres-
sure required to lift the condensate remains in the heat
exchanger shell. This can then cause a temperature
overshoot and wide swings in temperature.
Steam Traps Undersized
Undersized steam traps can cause condensate to back up
in a heat exchanger shell. Backed up condensate covers
some of the tubes, reducing the heat transfer surface. If
condensate backs up it may appear that the regulator is
undersized.
When a temperature regulator is installed in
the steam supply, size the steam trap based on 1/2 psig
pressure differential.
Failure to Install System Recirculation Pumps
A system without a recirculation pump will have wide tem-
perature fluctuations during start-up. The regulator will
also overshoot the temperature when system steam flow
stops, trapping steam in the heat exchanger shell due to
the response time required to close the regulator.
Low or Improper Outlet Pressure
Cause:
Low inlet pressure
Solution: Correct supply pressure from the boiler.
Fully open supply valve.
Check for upstream blockage.
Cause: The regulator is not properly adjusted.
Solution: Readjust the pilot to desired operating pressure.
Cause: Feedback control line plugged.
Solution: Remove and clean.
Cause: Bleed orifice missing or worn.
Solution: Replace with new bleed orifice.
Cause: Main valve undersized.
Solution: Check valve capacity against system load.
Replace with correct size valve.
Cause: Strainer plugged.
Solution: Blow down strainer screen or remove and
clean screen.
Delivery Pressure High or Overrides
Cause:
Bypass valve is open.
Solution: Close bypass valve.
Cause: The regulator is not properly adjusted.
Solution: Readjust the pilot to desired operating
pressure.
Cause: Bleed orifice plugged.
Solution: Clean or replace with new bleed orifice.
Cause: Dirt under the seat of main valve.
Solution: Remove top cover plate and clean the seat
surfaces.
Cause: Pilot valve malfunction.
Solution: Refer to pilot valve test and repair procedures.
Cause: Main valve oversized.
Solution: Check valve capacity against system load.
Replace with correct size valve.
Delivery Pressure or Temperature Erratic
Cause:
Pressure momentarily overshoots and then
recedes to set pressure.
Solution: Valve is not responding fast enough to react to
the system. Drilling the bleed orifice out to
3/32" can increase the valve closing response
time.
(Do not drill bleed orifice if a temperature
pilot is used, as temperature accuracy will be
decreased. Do not drill bleed orifice if differen-
tial pressure across the main valve is less than
40 psi as the valve may not fully open).
Cause: Sensing line improperly located in the system.
Solution: Relocate the sensing line to stable pressure
area.
Cause: Temperature bulb improperly located.
Solution: Relocate sensing bulb to make sure it is fully
inserted into the system flow path.
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