Maintenance and adjustment tips on BZO-242-3 contact rod penetration adjustment

04/01/2004 - Volume I - Issue II



We have received a number of requests for additional bumper spacers and occasionally for longer threaded studs for the bumper. These requests are the result of difficulty in achieving the "Upper contact rod penetration" adjustment.


Adjustment tip


If contact penetration is not enough and the length of the bumper stud item 403 is not long enough to add shims, the "pull rod turnbuckle" adjustment will usually solve the problem. The "pull rod turnbuckle" adjustment is used to reduce the crosshead clearance to 1.25 +/-.25" (this is a change from the instruction book). The .25" +/- .1 should be reset to achieve the desired crosshead clearance.




After installing the bushings, adapters, interrupters and movable member, if not already assembled, check the alignment of the interrupters by slowly jacking the breaker closed.

1. Make a preliminary check on the contact penetration.


2. Make a secondary check on contact penetration by jacking the breaker to a point where the lower contact rods are about flush with the bottom platform and observe:


     a. If both lower contact rods In the same tank are entering the interrupter at the same time.


     b. If both bumpers in the same tank have about the same clearance to the upper contact rod assembly.


NOTE: The difference from one side to the other should not exceed .25 inch. Adjust if required.


3. If the preliminary measurements indicate that more spacers have to be added and the stud length available on the bumper is too short, then a pull rod adjustment will be necessary.


4. The pull rod forward of the phase needing adjustment should be reset. Note that all phases behind this pull rod will be affected and will need adjustment.


CAUTION: before making this adjustment, raise the overtravel stops for each phase behind the pull rod being reset.


5. Loosen the check nuts on the pull rod to be reset


6. Turn the pull rod in a direction to shorten the rod. The rod ends have right and left threads. A full turn of the pull rod will increase the pull rod adjustment by about .160" and decrease the crosshead clearance by about .50".


7. After the pull rod has been set, apply "Loctite 242" the threads and retighten the check nuts.


8. Jack the breaker closed and make a preliminary setting on the contact penetration, overtravel stop setting, toggle adjustment and alignment.


9. Final check of the above adjustments should be made after a power close at lock-out pressure.

The original instruction book should explain that operations in air are not recommended. With proper care, operations can be performed in this manner. Care should include:


     a. No personnel should be in tank.


     b. Shock absorbers should be filled with oil and the pipe plugs temporarily installed.


     c. Interrupter should be "wetted" with oil 1/2 - 1 cup of oil poured through each valve casting vent.


     d. Close at or near lock-out pressure.


Penetration, pull rod turnbuckle, overtravel stop, and bell crank toggle adjustments are not always the same when measured after slow maintenance close operation. More reliable and consistent measurements result after a power close. Therefore, power closing is recommended when taking final adjustments.