Waters Prep Series Installation And Maintenance Manual page 158

Fixing rotor seal leakage
If you see liquid leak between the stator and stator ring, tighten the pressure
adjusting screw. If you see it leak from the needle port or vent tube, replace
the rotor seal.
To tighten the pressure adjusting screw:
1. Locate the pressure adjusting screw on the injector shaft (see the
"Rheodyne 7725i injector: exploded view" on page
adjustment is set so that spring force between the valve rotor and stator
is enough to hold 4000 psi (40.8 MPa).
2. Remove the injector knob.
3. Slip the pressure adjusting nut onto the shaft so the tabs on the nut slip
into the slots in the adjusting screw.
4. Use a wrench to tighten the adjusting screw approximately 1/20th of a
turn. Use the 20 dial markings on the body and the painted spot on the
adjusting screw to gauge how far to tighten the screw.
5. If the new setting fails to accomplish leak-free operation, repeat the
procedure by an additional 1/20th of a turn. Avoid excessive tightening,
which increases rotor seal wear.
6. If this fails to stop the leak, replace the rotor seal. Otherwise, finish by
removing the adjusting nut and replacing the knob.
Replacing the rotor seal
Premature rotor seal failure can be caused by any of these conditions:
• Abrasive particles in the sample or mobile phase that scratch the rotor
seal surface.
• A wrong needle tip that chips the ceramic stator face, scoring of the rotor
seal surface.
• Buffer or salt crystallization, caused by a failure to flush the flow
passages and needle port with water after using aqueous buffers or salt
solutions. The abrasive particles scratch the rotor seal surface, resulting
in leakage.
Caution:
3-74 Troubleshooting, Testing, and Maintenance
After using buffer solutions, flush the valve with water.
figure
3-73). The pressure