Power Jacks E-Series - Ball - Manual (Page 4)

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Metric Series – Ball Screw Jacks
3 General Instructions
3.1 Maintenance and Installation recommendations.
I n order to ensure that the actuators give good service over a period of years the following precautions should be
taken.
3.1.1
Select an actuator which has a rated capacity greater than the maximum load that may be imposed on it.
3.1.2 The structure on which the actuators are mounted have ample strength to carry the maximum load, and
should be rigid enough to prevent undue deflection or distortion of the actuator supporting members.
3.1.3 It is essential that the actuators be carefully aligned during installation so that the lifting screws are
vertically true and the connecting shafts are exactly in line with the worm shafts. After the actuators,
shafting, gearboxes, etc., are coupled together it should be possible to turn the main drive by hand. If
there are no signs of binding or misalignment, the actuator system is then ready for normal operation.
3.1.4 The actuators should have a greater raise than is needed in the actual installation. Should it be
necessary to operate the actuators at the extreme limits of travel it should be done cautiously.
3.1.5 It is important that the lifting screws should not be closed below the specified closed height dimension of
the actuators, otherwise serious damage may result to the worm gear. Lifting screw end stops are to
prevent over-travel or loss of screw. These are not load supporting and should be treated as an
emergency device only and must not be allowed to come into contact with the worm gears during normal
working cycles otherwise serious damage will result to worm gears and bearings.
3.1.6 The maximum worm shaft speed for these actuators should not exceed 500 R.P.M. for heavy loads.
Refer to Power Jacks Limited for higher worm shaft speeds for lighter loads.
3.1.7 The lifting screws should not be permitted to accumulate dust and grit on the threads. If possible, lifting
screws should be returned to the closed height position when not in use.
3.1.8 The ball screw should be checked periodically for excessive backlash and spalling of raceways. Note all
Power Jacks Metric ball screw actuators have an integral safety device as standard in the ball nut.
Ball Nut Safety Device provides two important safety roles:-
3.1.8.1 In the unlikely event of excessive wear in the ball screw drive, the safety ring will contact the
screw shaft, and act as an “ACME” Thread. This will provide early warning of any possible ball
screw failure, and is capable of providing drive in the event of any such failure.
3.1.8.2 It allows the ball nut on the actuator to sustain a load in the event of catastrophic ball failure. The
safety of industrial and human cargo is therefore improved. Ball screw systems without this
device would collapse under load or drop the carried load.
3.1.9 The actuators are shipped packed with grease (unless otherwise called for) which should be sufficient for
one month of normal operation. For normal operation they should be lubricated about once a month
using one of the Extreme Pressure Greases or their equivalent. See “Recommended Lubricants” Table
1.
3.1.10 For severe service conditions the actuator should be lubricated with a molybdenium disulphide type of
grease about once a week. We recommend any of the greases indicated in “Recommended Lubricants”
Table 2.
4 Recommended Lubricants
TABLE 1 – GREASE TABLE 2 – GREASE
Manufacturer Lubricant Manufacturer Lubricant
Castrol Spheerol EPL2 Castrol Spheerol EPL2
Esso Beacon EP2 Esso Beacon Q2
Gulf Gulfcrown EP2 Mobiloil Mobilgrease Special
Mobiloil Mobilux EP2 Power Petroleum BP Energrease L2 1M
Power Petroleum BP Energrease LC2 Regent Molytex 2
Regent Texaco EP2 Shell Shell Greases 5826
(Overseas)
Shell Alvania WR2 Shell Alvania 2 + MoS
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