ARI Armaturen STEVI BBD 415 DN 25-50 EN - Manual (Page 9)

Rev. 0040321000 0714 Page 2-9
Operating and Installation Instructions
Straight-through blow-down valves - STEVI
®
BBD 415
7.0 Care and maintenance
Maintenance work and intervals must be defined by the operator according to the service
conditions.
7.1 Replacing the valve stem seals
7.1.1 PTFE V-ring unit design
PTFE V-ring unit (pos. 12) consisting of:
1 backing ring
4 sealing rings
1 cover ring
This stem seal is self-adjusting owing to the built-in
compression spring (pos. 15). If the stem begins to
leak, the seal pack is worn out and must be replaced.
To replace the PTFE V-ring unit:
- Remove the actuator (refer to section 10.1).
- When replacing the PTFE V-ring unit (pos. 12), make
sure that all parts are installed in the correct order
and position (refer to Fig. 4).
- The gasket (pos. 17) must be replaced.
Note:
Damaged stems must also be replaced (refer to
section 7.2 for instructions) because a new seal pack
will soon begin to leak again if the stem is no longer
intact.
- To assemble the actuator, refer to section 7.5.
ATTENTION !
Refer to sections 10.0 and 11.0 before
dismantling the valve.
Fig. 4: PTFE V-ring unit