Siemens PGC 302 Edition II Manual page 136

IMPORTANT: Do not grind!
Never treat the tappet with emery paper or a
dry polishing cloth. The surface must be free
of furrows to ensure that the injection vol-
ume is correctly sealed and that the piston
can move smoothly.
Replacing the Teflon gasket
Replace the Teflon gaskets if collars are present as a re-
sult of deformation or wear.
n
Remove the lenticular gasket (6) from the adjust-
ment assembly and vaporizer. To do this, gently in-
sert the tappet approx. 5 mm into the gasket and then
tip to the side until the gasket is loose and can be
pulled out with the tappet.
Caution: do not damage the tappet in the process!
n
Insert new lenticular gaskets into the adjustment as-
sembly and vaporizer, and install with sample flow
unit.
IMPORTANT:
Select a gasket according to the application
and temperature class.
There should be no play between the new
gasket and the injection tappet. It should be
extremely difficult to move the gasket.
Teflon is always recommended because the
gasket in the adjustment assembly is always
operated below 200°C.
Rulon is better than Teflon with 25% glass
filling in some cases because it does not
generate as much abrasion.
Replacement of O-rings
n
Remove the two large O-rings and the small O-ring
out of the valve body using a small screwdriver or a
needle.
n Insert new O-rings
IMPORTANT:
Only use silicone O-rings, temperature class
-40 °C to +200 °C.
n Well grease the new O-rings and the sliding surfaces
of the control cylinder and the piston guide. We rec-
ommend DOW CORNING 111 with a temperature
range from -40 to +260 °C or Dow Corning 44
grease with a temperature range from -40 to
+200 °C.
Register8.vp Stand: 20.11.2000
Replacing the injection tappet
The injection tappet should be replaced when its sur-
face is scratched.
Assembly of valve
IMPORTANT: Valve body
The thread for the screw and flange plate
must be freely movable. Grease if neces-
sary.
The piston guide hole must have a diameter
of 5.7 mm and be smooth. Treat the hole us-
ing a drill/reamer if there are traces of wear
on the piston shaft. First remove the internal
O-ring and subsequently reinsert.
The adjustment
smoothly down to the end.
The side with the O-ring seat must slide
smoothly into the cylinder (without O-ring).
IMPORTANT: Grease!
Before assembling the liquid injection valve,
you must apply a thin film of fresh grease to
the following:
- Internal cylinder wall
- Piston shaft
- Guide hole of small O-ring
- Outside of O-rings following reassembly of
valve body and piston
For appropriate types of grease, refer to
Replacement of O-rings.
n
Insert the piston with tappet into the valve body such
that the tappet does not become greasy.
n Drop 8 plate springs next to one another over the
tappet into the valve body such that the two outer
springs support one another.
IMPORTANT: Plate springs
7 or 8 springs are permissible.
With 7 springs: support on valve body in-
side, on adjustment assembly outside.
With 8 springs: support on valve body and
on adjustment assembly outside. This is
standard with the glass vaporizer.
Liquid injection valve
assembly must slide
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