Cashco DA8 Differential - Manual (Page 12)

IOM-DA8/9 12
4. Diaphragm continually breaks (steam service regulators).
Possible Causes Remedies
A. Stem seals, which protect fl uorocarbon elastomer in
diaphragm assembly, may have deteriorated.
A. Replace with new stem seals.
B. Diaphragm nut may not be torqued to proper value.
B. Confi rm torque value in accordance with Section VII, paragraph
E-15.
C. Diaphragm too stiff causing it to crack in service.
C. Follow proper preforming and air pressure to underside of dia-
phragm techniques during diaphragm installation in accordance
with Section VII, paragraph F-9.
5. Diaphragm continually breaks (all regulators).
Possible Causes Remedies
A. Differential pressure across diaphragm may have
exceeded limits. A. Reference limits as recorded in technical bulletin DA8/9-TB, as
well as where the various pressures are acting.
• Fluid (with fl uid properties)
• Range of fl ow rate
• Range of inlet pressure
• Range of outlet pressure
• Range of fl uid temperature
• Range of ambient temperature
Pressure readings should be taken at every location that pressure plays a role - i.e., regulator inlet (as close as
possible to inlet port), regulator outlet (as close as possible to outlet port), etc.
Following are some of the more common com plaints along with possible causes and remedies.
SECTION VIII
Possible Causes Remedies
A. Sticking of internal parts. A. Remove internals, clean and if necessary, replace.
B. Load changes are too quick for system.
B. Convert to external sensing (if necessary) and install an
orifi ce or needle valve in external sensing line.
C. Oversized regulator.
C. Check actual fl ow conditions; resize regulator for minimum
and maximum fl ow; if necessary, replace with smaller regulator.
D. Unstable loading pressure.
D1. Stabilize loading pressure; i.e. pump, control valve, etc.
D2. Air in loading piping. Vent spring chamber.
Possible Causes Remedies
A. Air trapped under diaphragm.
A. Install valve on external sensing port and bleed off air.
(Install regulator upside down to help prevent reoccurrence.)
2. Erratic regulation, instability or hunting (liquid service).
1. Erratic regulation, instability or hunting.
Possible Causes Remedies
A. Debris in trim preventing movement. A. Clean unit of debris.
B. Undersized regulator.
B. Check actual fl ow conditions; resize regulator for minimum and
maximum fl ow; if necessary, replace with larger regulator.
3. Upstream pressure too high.