Valve Leakage - Metso Neles L4 Series Intallation, Maintenance And Operating Instructions

2 L6 70 en
dia
h
h
1
2
disc spring set (43)
packing (20)
V-ring set or
graphite packing
anti-extrusion ring (22)
Fig. 11. Gland packing; L6C, L6D, L6F/D and L4F/D

If the leakage still occurs when the valve is pressur-
ized, re-tighten the nuts but don't exceed the values
in the Tables 7 and 8 by 50 % or do not fully com-
press the disc springs.
5.3.2 L6F

Make sure the valve is not pressurized.

Unfasten the nuts (25) and remove the disc spring
(TA-Luft) kits (43), the gland (9a), the retainer ring
(42) and the compression ring (9b).

Remove old packing rings (20). Do not damage the
surfaces of the packing ring counterbore and shaft.

Clean the gland and packing ring counterbore.
Install new set of packings (V-ring or graphite). Slip
the rings onto the shaft. Ensure that there are no
burrs in the keyway groove which could damage the
packing. Position the cut ends of the graphite rings
at a 90° angle to each other.

Mount the compression ring.

Slip the retainer ring on the shaft and push it against
the compression ring, see Fig. 12.

Install the gland.

Mount the disc spring kits.

Place the nuts on the studs.

Pre-compress the gland packing by tightening the
nuts with a tool until the disc springs have value of
compression (h –h
1

Carry out 3...5 operation cycles with the valve. Suita-
ble range of movement is about 80 %.
It is not necessary to fully close or open the valve
during the operation.

Unfasten the nuts and disc springs.

Measure the height h
these values as a basis when defining the final
height of the springs (as compressed condition).

Re-install the disc springs and tighten the nuts with
the tool. Tighten the nuts until the set value of com-
pression (h –h ) of disc springs is achieved, see
1 2
Table 9.

If the leakage still occurs when the valve is pressur-
ized, re-tighten the nuts but don't exceed the value
in the Table 9 by 50 % or do not fully compress the
disc springs.
stud (24)
hexagon nut (25)
retainer plate (42)
gland (9)
) as in Table 9.
2
of the disc springs and use
1
Table 9. Tightening of gland packing, L6F
L6F Spring set dia
DN mm
200 31.5
250 35.5
300 40
350 40
400 50
450 50
500 50
600 71
700, 750 71
800 80
900 80
Fig. 12. Mounting the retainer ring
dia
h
h
1
2
disc spring set (43)
compression ring (9b)
packing (20)
V-ring set or
graphite packing
Fig. 13. Gland packing, L6F
5.4

Valve leakage

Valve leakage is not always caused by a damaged seat ring
or disc. The reason can also be that the disc is not in the
closed position.

Check the position of the actuator relative to the
valve. The screws may be loose or the bracket dam-
aged.

Check the adjustment in the closed position (see
Section 6.4).
The marking line parallel to the disc on the valve shaft head
shows roughly the closed position of the disc (see Fig. 14).
Pressure shocks can cause loosening of the pin connection
between disc and shaft; consequently the shaft moves
while the disc remains in place and this prevents full closing
of the disc.
Compression (h -h
1
Thread Packing ring material
Graphite
No of studs 4
M12 3.2
M14 4.4
M16 4.3
M16 4.7
M20 3.8
M20 4.6
M20 4.6
M30 6.1
M30 6.7
M36 5.5
M36 8.4
stud (24)
hexagon nut (25)
retainer ring (42)
gland (9a)
9
) mm
2
PTFE
4
1.1
1.5
1.5
1.6
1.3
1.6
1.6
2.1
2.3
1.9
2.9