Baker Hughes Pneumatic Positioners 4700P/4800P

- It may be necessary to remove positioner from valve to assemble bypass.

1. Remove air connections, vent plug, and instrument gauge.

2. Clean surface of body and remove any thread sealant left in threaded ports.

3. Install O-rings (50) in each of the four recesses on the rear surface of the module (45), making sure they are seated in the bottom of the recess.

4. Assemble to positioner using four 8-32 x 1.25” long screws (21).

5. Reinstall vent plug, instrument gauge, and air connections.

1. To remove from positioner, reverse assembly steps 5 and 4.

- Replacement of the I/P module requires removal of electrical connections, including conduit if used. Remove positioner from valve if module mounting screws are not accessible. Remove and replace module as outlined under.;

- If the diaphragm has deteriorated, replace the diaphragm assembly. This requires separation of the body and case subassemblies as outlined under.;

- To clean or replace deteriorated parts, the valve must be isolated from process. Shut off air supply. To minimize maintenance time, it is recommended that the entire pilot subassembly (11) be replaced by a new subassembly, so that the old unit can be worked on when time permits.

Disassembly 1. Unscrew the pilot subassembly (11) and disengage it from the body (1). Note: Turn the pilot subassembly while removing it to prevent damage to the O-rings.

2. Remove end plug and withdraw the spring, plug and extension pin. If necessary, use a penetrating oil to free parts.

3. Wipe the parts with a clean soft lint free cloth and blow compressed air through the orifices. Use isopropyl alcohol to clean. Do not use chloride based solvents.

1. Install three new O-rings on the pilot spool. Put a light coating of silicone grease on each O-ring.

2. Replace the extension pin and the plug, countersunk end first into the pilot spool. The plug should slide into the pilot spool by its own weight.

3. Install the spring in the pilot spool. The end having the smallest diameter must be in contact with the plug. Screw the pilot end plug into the pilot spool.

4. Install the pilot subassembly (11) into the body (1).;

- Shut off the air supply. Disconnect air lines, linkage if reciprocating, and electrical connections if 4700E/4800E. If positioner is reverse acting, refer to applicable section under “Cam Lobe Change” on page 38 to safely remove cam. Remove screw (28), washer (27), cam (26). Separate positioner from actuator by removing screws (29) and washers (30).

See Figure 18 (page 56) and Figure 19 (page 58).

1. Remove pressure gauges (12) (13), and on 4700P/4800P only (14).

2. Remove the pilot subassembly (11).

3. Remove retaining ring (17), washer (16), lever S/A (3), and spring (5).

4. On 4700E/4800E only, remove 4 screws (21) to separate I/P module from body.

5. Remove cap screws (10) and separate body S/A from the case S/A.

6. Remove the diaphragm assembly (9), and reducer plate if 6-30 psi range 4700P/4800P.