VAG Operating and Maintenance Instructions • 8
After the pressure test, the tension of the lateral seal must be relie-
ved to achieve its original state as otherwise the multiturn actuator
may be overloaded due to increased operating forces.
In general the tension of the lateral seal can be released to adjust
it to the actual operating pressure (see Section 3.1). This reduces
the wear of the seal during operation and lowers the operating
forces of the valve. It also increases the useful life of the valve and
reduces maintenance work on the lateral seal.
6 Maintenance and service
6.1 General safety instruction
Before the performance of inspection and maintenance work on
the valve or on parts mounted to it the pressurised pipeline must
be shut off, depressurised and protected against unintentional re-
start.
Depending on the kind and dangerousness of the medium con-
veyed, all the relevant safety regulations must be com plied with!
After completing the maintenance work and before restart, all con-
nections must be checked for proper and close fit and for leak-
freeness. For restart, perform the steps described under Section
5 for initial startup.
6.2 Inspection- and operation intervals
Due to its mode of operation, it is advisable to operate the valve
over its entire stroke at least four times per year and to check its
components for proper function. Under extreme operation con-
ditions and in case of operation with heavily soiled media, these
operation and function checks are to be performed more frequent-
ly in accordance with the operator‘s experience.
6.3 Maintenance and replacement of spare
parts
6.3.1 Testing for easy movement
During maintenance work performed according to the recom-
mended intervals, the valve should be operated over its entire
stroke. In case of difficult movement, clean and lubricate the stem
and knife.
6.3.2 Repairing a leak at the outlet of the knife
After longer shut-down periods, the seal may be slightly leaky. If
leaks persist even after the valve has been operated several times,
the lateral seal (10) can be easily re-tensioned without dismantling
the valve. To do this, evenly turn the screws of the thrust piece (2)
by approx. ½ turn each until the leaking stops. If it is not possible
to re-tension the thrust piece (2) via the screws, the ent- ire lateral
seal unit (Kit 1, items 10 and 11) has to be replaced. How often the
lateral seal requires readjustment depends on the degree of soiling
of the medium and on the operating conditions. The fact that the
seal has to be readjusted does not constitute a material defect.
Picture 5: Single parts, position
7.2
7.1
6
4
5
3
2
1
9
10
11
8
14
6.3.3 Repairing a leak at the knife passage
If the knife passage leaks, this is mostly due to damage or irre-
parable wear of the U-profiled gasket (9). In this case, the parts of
the entire unit 2 should be replaced. This can only be done when
the valve is dismantled.
6.3.4 Cleaning and lubricating
The rising stem (4) must always be kept free from dirt and well
lubricated.
Depending on the operating conditions, the knife must be clea-
ned and lightly relubricated.
The lubricator of the output drive Shape A (7.1) must be relubri-
cated using a grease gun.
The rising stem moves in axial direction through the casing of the
multiturn actuator. Depending on the nominal width or the length
of stroke, the upper opening of the casing is closed either by a
black threaded cap or a stem protection tube (15). VAG does not
assume any liability for failures resulting from modified or remo-
ved protective devices.
Recommended lubricants::
• Knife and seals: Fuchs Chemplex Si 2; Fuchs Notropeen Si 1;
Klüber Unisilikon L 641
• Stem and stem nut: KLÜBERPLEX BE 31-502 for electric
drives
Manufacturer: Klüber Lubrication München AG, Germany
