Fisher 399A - Page 4

Type 399A-161-112
3
• Replace the Type 161Y and 161YM Pilot Maintenance section beginning on page 23 with the following:
Type 161AY or 161AYM Pilot
Key numbers are referenced in figure 23.
Body Area
1. Remove the cap screws (key 2) and separate the diaphragm casing (key 4) from the body (key 1).
2. Remove the body seal O-ring (key 11) and the backup ring (key 50) from the body (key 1). Inspect the body seal
O-ring and replace if necessary. See the expanded view of the body area in figure 23.
3. Inspect and replace the orifice (key 5) if necessary. Lubricate the threads of the replacement orifice with a good
grade of light grease and install with 29 to 37 foot-pounds (39 to 50 N•m) of torque.
4. Remove the cotter pin (key 15) if it is necessary to replace the disk assembly (key 13) or throat seal of a
Type 161AYM.
5. For a Type 161AYM, inspect the throat seal O-ring (key 31) and remove the machine screw (key 33). Replace the
O-ring if necessary.
6. Install the disk assembly (key 13) and secure it with the cotter pin (key 15).
7. Place the backup ring (key 50) into the body (key 1). Next, place the body seal O-ring (key 11) into the body.
8. Place the diaphragm casing (key 4) on the body (key 1). Secure the diaphragm casing to the body with the cap
screws (key 2).
Diaphragm and Spring Case Area
To change the control spring:
1. Remove the closing cap (key 22), and turn the adjusting screw (key 35) counterclockwise until all compression is
removed from the control spring (key 6).
2. Change the control spring (key 6) to match the desired spring range.
3. Replace the adjusting screw (key 35).
4. Install the replacement closing cap gasket (key 25) if necessary and reinstall the closing cap (key 22).
5. If the spring was changed, be sure to change the stamped spring range on the nameplate.
To disassemble and reassemble the diaphragm parts:
1. Remove the closing cap (key 22), and turn the adjusting screw (key 35) counterclockwise to remove the adjusting
screw, baffle plate (key 56) and the control spring (key 6).
2. Remove the spring case hex nuts (key 23, not shown), cap screws (key 24), and spring case (key 3).
3. Remove the diaphragm (key 10) plus attached parts by tilting them so that the pusher post (key 8) slips off the
lever assembly (key 16). To separate the diaphragm (key 10) from the attached parts, unscrew the machine screw
(key 38) from the pusher post (key 8).
4. Inspect the pusher post (key 8) and the body seal O-ring (key 11), replace if required.
5. Remove hex nut (key 21) to separate the diaphragm (key 10) and attached parts.