Installation, Operation & Maintenance Instructions
5
API PLAN 74
SEAL SYSTEMS
7.3 Signals and alarms
A sudden or noticeably steady increase in the gas consumption should
be considered abnormal and may indicate a deteriorating seal. The
instrumentation on the system has the specific purpose of signalling
eventual malfunction of the mechanical seals. Possible alarm signals
indicating a malfunction are as shown in Table 2.
TABLE 2. Possible Alarm Signals Indicating a Malfunction
Effect
Instrument
Action
Cause
Falling Pressure
Pressure Gauge (PG)
or Pressure Indicating
Transmitter (PIT)
A
D to G
Low Pressure/
Shutdown Required
Pressure Indicating
Transmitter (PIT) or
Pressure Switch (PS)
B
D to G
Falling Flow
Flow Indicating
Transmitter (FIT) or
Flow Indicator (FI)
C
F or G
Rising Flow
Flow Indicating
Transmitter (FIT) or
Flow Indicator (FI)
A
D or E
Pulsations
in the Flow
Flow Indicating
Transmitter (FIT) or
Flow Indicator (FI)
—
H
High Flow Alert
Flow Indicating
Transmitter (FIT) or
Flow Switch (FS)
B
D, E or H
Actions
A
Investigate cause and monitor to ensure values do not breach
safe limits
B
Shut down machine to prevent damage or loss of containment
C
Check coalescing filter and gas supply
Causes
D
Excessive leakage across the inboard seal or outboard seal
E
Pipe work/joint failure
F
Drop in the barrier gas supply pressure/flow
G
Blockage of the coalescing filter
H
Actuation of the check valve – see Section 6.2
The signal from the pressure transmitter can be used either:
•
LOCALLY (with a Klaxon and/or beacon)
•
REMOTELY (in the control room)
Consult the specific instrument manufacturers manual should there be a
malfunction.
If necessary for safety, the process the alarm signals could be used as a
trip function.
7.4 Instrument maintenance
All instruments require regular calibration, following local processes
and regulations. See the supplier's instruction manual for and additional
instructions for maintenance of electrical instruments.
7.5 Spare parts
Spare parts must conform to the established technical specifications of the
manufacturer. This is guaranteed with John Crane spare parts.
You are advised to stock the most important wear parts on site.
The following data is necessary for spare part orders:
•
John Crane code/part number
•
John Crane order/ref no.
•
Part description
•
Quantity
7.6 Annual maintenance checks
Disconnection shall be made by plant person in charge of authorization.
Before any maintenance operation the system, the machine must be
stopped and depressurized, then the barrier gas pressure must be fully
discharged, and the equipment allowed to cool to ambient temperature. A
suitable container should be available to contain any liquid drained from
the barrier system.
All parts requiring maintenance must be thoroughly decontaminated prior
to any work commencing.
All joints should be checked for tightness and signs of barrier gas leakage.
If present, all flange joints should be checked for tightness and, if
necessary, gaskets changed using replacements available from John Crane.
8. Accompanying Documents
Installation Drawing (job specific) or Typical Drawing and Operational
Data Sheet.
A name and data plate is fitted to each Plan 74 control panel. It contains
references and part numbers which must be quoted in any communication.
For replacement parts please contact your local John Crane
office, quoting the system code number.
9. Cold Environments
For environments with low ambient temperatures, winterization features
may be added to the Plan 74. These may include:
•
The Plan 74 control panel may be supplied mounted in a heated
enclosure. The heating element requires electrical connection as part
of the installation and assembly procedure (see Section 6.2)
•
Heat tracing and/or insulation may be required to maintain the
temperature of the barrier gas in the Plan 74. This heat tracing and/or
insulation may be supplied with the Plan 74 control panel, or may be
applied on site around all pipework and components during installation
and assembly, leaving room to read instruments and operative valves.
•
Care must be taken during commissioning and operation, that the
Plan 74 is brought up to operating temperature before the machine is
started, and the correct temperature is maintained throughout operation.
