Product Overview

Spirax Sarco PN9000 stem seal kit is a genuine factory replacement service pack engineered to maintain dynamic pressure containment and spindle guidance across PN9000 series pneumatic actuators. In control valve assemblies, pneumatic actuators convert motive air signals into linear thrust; the lower diaphragm chamber requires continuous sealing along the reciprocating spindle (Item 6) to prevent control air loss and ensure consistent valve stroke positioning.

This replacement kit supplies common wearing components across both spring-extend (E) and spring-retract (R) variants of the PN9100, PN9200, and PN9300 actuators, as well as designated configurations for the PN9400. Replacing the seal, bearing, and lower gasket restores factory containment integrity and eliminates air bypassing along the actuator yoke.

Key Features

• Common spare parts package engineered for both spring-extend (suffix E) and spring-retract (suffix R) linear actuators.
• Low-friction PTFE and steel composite bearing (Item 17) provides rigid mechanical alignment and prevents spindle galling during continuous cycling.
• Standard polyurethane dynamic seal (Item 18) maintains positive pneumatic sealing across an operating range of -20 °C to +110 °C.
• High-temperature configuration (T version) incorporates an FKM fluorocarbon seal rated for media exposures up to +130 °C.
• Reinforced graphite gasket (Item 30) ensures durable static sealing between the lower diaphragm housing and the actuator yoke assembly.
• Direct compatibility with PN9000 actuators mounted on Spirax Sarco Spira-trol K, L, and J series control valves.

Technical Specifications

Specification	PN9100, PN9200, PN9300 Kit	PN9400 Kit	High Temperature (T Version)
Bearing Item Number	Item 17	Item 3	Item 17 / Item 3
Bearing Material	PTFE / steel composite	PTFE / steel composite	PTFE / steel composite
Seal Item Number	Item 18	Item 4	Item 18 / Item 4
Dynamic Seal Material	Polyurethane	Polyurethane	FKM (Fluorocarbon)
Gasket Item Number	Item 30	Item 5	Item 30 / Item 5
Gasket Material	Reinforced graphite	High-strength graphite	Reinforced graphite
Operating Temperature Range	-20 °C to +110 °C	-20 °C to +110 °C	-20 °C to +130 °C
Motive Pressure Capability	Up to 6 bar g (actuator dependent)	Up to 6 bar g	Up to 6 bar g
Actuator Action Compatibility	Spring-extend (E) and Spring-retract (R)	Spring-extend (E) and Spring-retract (R)	Spring-extend (E) and Spring-retract (R)

Applications

• Scheduled preventative maintenance and scheduled overhaul of Spirax Sarco PN9100, PN9200, PN9300, and PN9400 linear pneumatic actuators.
• Remediation of pneumatic leaks originating around the actuator spindle yoke aperture.
• Refurbishment of Spira-trol two-port control valve packages operating in steam, condensate, and industrial gas pipelines.
• Upgrading standard actuators to high-temperature trim (T version) for high-ambient process environments.

Installation and Maintenance

Stem Seal Replacement Procedure

Before undertaking maintenance, verify that the control valve is fully isolated, motive air lines are disconnected, and actuator chambers are completely depressurized.

1. Remove the actuator from the valve body: drive the spindle to approximately mid-travel using regulated air, loosen locking screws (26), decouple valve adaptor (11), unscrew the clamping nut from the bonnet shoulder, and disconnect air supply.
2. Disassemble the diaphragm housing according to Section 5.3.1 (spring-extend) or Section 5.4.1 (spring-retract). Observe safety warnings regarding pre-compressed springs: lubricate the three long decompression hex screws (23) with PTFE grease, loosen short screws (22) first, and slowly back off the three long screws in alternating rotations to release internal spring pre-load evenly.
3. Remove the springs (5), secure the spindle (6) with a spanner, remove retaining bolt (21), spacer (8), washer (28), diaphragm plate (3), and diaphragm (4).
4. Withdraw the actuator spindle (6) upward out of the lower diaphragm housing.
5. Extract the worn stem seal (18), stem bearing (17), and reinforced graphite gasket (30). Dispose of used PTFE and elastomer elements in accordance with local environmental regulations.
6. Press the replacement stem bearing (17) and stem seal (18) into the housing bore, ensuring correct orientation. Insert the replacement gasket (30).
7. Carefully insert the actuator spindle (6) back through the newly installed seal and bearing assembly without scoring the sealing lip.
8. Reassemble the diaphragm (4), plate (3), spacer (8), and secure bolt (21) using Loctite 243 on the upper spindle threads. Tighten bolt (21) to 50 Nm (36.9 lbf ft) for PN9100, PN9200, and PN9300 models (40 Nm for PN9400).
9. Reinstall housing cover (2) and secure nuts (24) and screws (22, 23). Tighten housing fasteners evenly in a criss-cross pattern to 12 Nm (8.9 lbf ft) for M6 hardware on PN9100, or 35 Nm (26.0 lbf ft) for M10 hardware on PN9200 and PN9300.

Ordering Information

When ordering replacement stem seal kits, specify the exact description and host actuator model:

• Description: Stem seal kit
• Actuator model designation: state full model number, such as PN9120, PN9123E, PN9220E, PN9330E, PN9483E, or high-temperature designation with suffix T.
• Example: 1 - Stem seal kit for a PN9120 pneumatic actuator.