Converting a BLOCK-HEAD® Spindle to the Pneumo-Lock Mode
BLOCK-HEAD® spindles may be equipped with a porting arrangement which allows the spindle to be locked pneumatically. If there is no requirement for this locking feature, the spindle will be supplied without it.
A BLOCK-HEAD® spindle in the non-locking mode needs only two pressure lines connected to it. One is the pressure supply line connected to any one of the inlet ports. The other is for measuring the air pressure within the bearing and runs from any one of the gauge ports to a suitable pressure gauge and pressure switch.
When a BLOCK-HEAD® spindle is set up in the Pneumo-lock mode, the internal porting is split pneumatically so that one thrust and radial bearing is supplied independently of the other thrust and radial bearing. This arrangement may be used to lock the spindle by depressurizing one side while maintaining full pressure to the other side.
The two air flow paths are separated by small threaded needles which are screwed into the bearing’s internal porting. When these needles are installed, four plumbing connections must be made: two pressure-supply lines and two lines running to suitable pressure gauges. This is normally a factory-installed option, but can be retrofitted in the field.
The following procedure is recommended to minimize the introduction of harmful debris into the spindle:
- Keep the air bearing pressurized.
- Clean the outside surface of the spindle and wipe it dry. Use a cotton swab to remove any trace of liquid around the thrust plate exhaust perimeter. This is important; when the air is shut off, any liquid left at the perimeter will be drawn in by capillary action.
- Install the rotor lock which was on the bearing when it was shipped.
- Turn the air pressure down to less than 5 psi. Do not shut it off completely.
- Remove the two access screws carefully. They may pop out from the air pressure on the bearing.
- Install one needle under each access screw with the special TORX® driver supplied with the needles. They should seat with a nice solid feel. Be careful to be very clean. Introducing contaminants at this point could cause failure of the bearing.
- Replace the access screws.
- Install an additional inlet line and gauge line as shown on the Plumbing page of the BLOCK-HEAD® Operator’s Manual.
- Turn the air regulators back up to full pressure. Confirm that both sides of the bearing are receiving full pressure by observing the gauges.
- Remove the rotor lock and check for totally free rotation.
CAUTION: Never shut off air pressure or lock the bearing unless the spindle is completely stopped. Never shut off air pressure when there is liquid on the bearing.
NOTE: The bearing my be converted to the Pneumo-lock mode in a wet environment by lowering pressure on one side, but not shutting it completely off. The positive pressure will prevent intrusion of the liquid.