15
Model 351/352/353 Liquid Level Systems
Section 4
Figure 4.2—Model 353 sensor bellows and bottom plate assembly
To install the sensor bellows, perform the following steps:
4.
Inspect the sensor bellows to verify that the bellows is undamaged and
the guide stem is in place.
IMPORTANT: This inspection should be performed whether the old bellows or a
replacement bellows is to be installed.
5. Inspect the two O-rings in the valve seat, the O-ring and the backup ring
in the bottom plate, and the nickel gasket to verify there is no dam-
age (see note on
). Install the nickel gasket on the bottom plate.
Lubricate the O-rings and backup ring lightly with lubricant (part number
9A-C0002-1003U) and insert in the appropriate grooves.
6. Engage the valve seat to the bottom plate. The guide stem must enter the
capillary tubing without restric tion.
IMPORTANT: To prevent loss of the O-rings in the valve seat, invert the bellows and
bottom plate during this step.
7. Tighten the valve seat with the sensor bellows wrench to approximately
39 to 40 ft-lb (53 to 55 N-m). Verify that a metal-to-metal fit is obtained
between the valve seat and the bottom plate (zero clearance).
8. After the sensor bellows and capillary tubing are filled with liquid, care
-
fully insert the plate and bellows assembly into the housing. Uniformly
tighten the 12 housing bolts to 34 to 35 ft-lb (46 to 48 N-m).
