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Model 351/352/353 Liquid Level Systems
Section 3
Section 4—Operation, Maintenance, and Calibration
Startup
Startup and operating instructions for an instrument actuated by the Liquid
Level System are presented in the installation and operation manual for that
instrument.
General Field and Periodic Maintenance
The sensor is basically maintenance-free. If installed in an application where
sediment can accumulate in the bel lows convolutions, periodic inspection and
cleaning may be required.
CAUTION:
The sensor bellows can be damaged by contact with the housing.
When removing the sensor assembly, avoid unnecessary contact
with the housing.
Model 351 Sensor Inspection and Cleaning
1.
Remove the sensor from the housing. The 500 psi (3.5 MPa) sensor is
connected by a retainer ring; the 3000 psi (20.7 MPa) sensor is connected
by 6 bolts. Carefully separate the sensor from the housing assembly.
2. Remove any accumulated material from between the bellows convolu-
tions, using a soft brush and solvent as required.
3. Inspect the O-rings and seals before reassembly. Replace as necessary
).
4. Replace the housing over the sensor bellows. For 3000 psi (20.7 MPa)
sensors, lubricate the bolt threads and seat the bolts at 34 to 35 ft-lb (46
to 48 N-m). For 500 psi (3.5 MPa) sensors, install the retaining ring.
Model 353 Sensor Inspection and Cleaning
1. Remove the 12 bolts connecting the sensor to the housing, and carefully
separate the sensor from the housing assembly.
2. Remove any accumulated material from between the bellows convolu-
tions, using a soft brush and solvent as required.
3.
Inspect the bellows for damage. Free-length should be 2-1/4 in. (57 mm)
(see Figure 1.2). Length may vary by 1/8 in. (3 mm) due to system tem
-
perature-effects. Press lightly (by hand) on the free end of the bellows;
the bellows should be “incom pressible”
if the system is liquid filled.
4.
Inspect the O-ring, backup ring, and nickel gasket before reassembly.
Replace as necessary (see note on
5.
Carefully replace the sensor in the housing assembly. Lubricate the bolts
lightly and torque uniformly to approximately 34 to 35 ft-lb (46 to 48
N-m).
