YOKOGAWA ZR202S, User Manual, Page: 133 / 163

<11.Inspection and Maintenance>
11-4
IM 11M13A01-04E
1. Identifying parts to be replaced
In order not to lose or damage disassembled parts, identify the parts to be replaced from among all the
parts in the sensor assembly. Normally, replace the sensor (cell), metal O-ring and contact together at
the same time. If required, also replace the U-shaped pipe, bolts, filter and associated spring washers.
2. Removal procedures
(1) Remove the flame arrestor assembly using a special pin spanner (P/N: K9471UX).
(2) Remove the four bolts and associated washers from the tip of the detector probe.
(3) Remove the U-shaped pipe support together with the U-shaped pipe. Remove the filter also.
(4) Pull the sensor assembly toward you while turning it clockwise. Also, remove the metal O-ring
between the assembly and the probe. (When replacing the assembly, be careful not to allow any
flaws on the tip of the probe with which the metal O-ring comes in contact (the surface with which
the sensor flange also comes in contact. Otherwise, the sample gas will not be sealed.)
(5) Use tweezers to pull the contact out of the groove.
(6) Clean the sensor assembly, especially the metal O-ring contact surface to remove any
contaminants adhering to that part. If you can use any of the parts from among those removed,
also clean them up to remove any contaminants adhering to them.
(Once the metal O-ring has been tightened, it can no longer be used. So, be sure to replace it.)
3. Part assembly procedure
(1) First, install the contact. Being careful not to cause irregularities in the pitch of the coil spirals
(i.e., not to bend the coil out of shape), place it in the ringed groove properly so that it forms a
solid contact.
Groove in which the contact (E7042BS) is placed
F11-3E.ai
Figure 11.3 Installing the Contact
(2) Next, make sure that the O-ring groove on the flange surface of the sensor (cell) is clean. Install
the metal O-ring in that O-ring groove, and then insert the sensor (cell) in the probe while turning
it clockwise. After inserting it until the metal O-ring comes in contact with the probe’s O-ring
contact surface, properly align the U-shaped-pipe insertion holes with the bolt openings.
(3) Attach the U-shaped pipe to its support, then fully insert the U-shaped pipe, filter and its support
into the probe.
(4) Coat the threads of the four bolts with anti-seize grease and then screw them in along with the
washers. First, tighten the four bolts uniformly by hand, and then use a torque wrench to tighten all
areas of the metal O-ring uniformly, that is, to make sure the sensor flange is perfectly horizontal to
the O-ring’s working face in the probe. This is done by tightening first one bolt and then its opposing
bolt each 1/8 turn, and then one of the other bolts followed by its opposing bolt, each also 1/8 turn.
This continues in rotating fashion until they are all fully tightened with the torque wrench preset to
approximately 5.9 N•m. If they are not uniformly tightened, the sensor or heater may be damaged.
Replacement of the sensor assembly is now complete. Attach and fix the flame arrestor assembly.
Install the detector and restart operation. Calibrate the instrument before making a measurement.