Wood’s Powr-Grip MRPT89DC - Manual (Page 27)

Rev 24.0/12-13 25 MRPT89DC: #35062
V
ACUUM
S
WITCH
A
DJUSTMENT
Vacuum Switch Function
A vacuum switch controls the vacuum pump and the vacuum lift light for a DC lifter (see
OPERATING FEATURES for location of vacuum switch). When the lifter's power switch is in the
ON position ( ), turning the apply/release switch to the “APPLY” position activates the vacuum
pump, which evacuates the vacuum pads. After the lifter attains a vacuum level sufficient for
lifting the maximum load weight (hereafter, “minimum lifting level”), the vacuum switch
automatically turns off the pump and turns on the lift light.
18 In order to maintain sufficient
vacuum, the vacuum switch automatically turns on the pump and turns off the lift light again
before vacuum decreases to a level that is lower than the minimum lifting level.
Conditions Requiring Readjustment
At the factory, the vacuum switch is set to maintain the minimum vacuum level specified for Load
Capacity (see SPECIFICATIONS). However, shipping vibrations or shocks, normal wear, or other
conditions may adversely affect this adjustment. Periodically verify the switch adjustment by
comparing how the vacuum pump and the vacuum lift light function in relation to the vacuum
level registered on the vacuum gauge, as follows:
• If the pump
turns off and the lift light turns on before vacuum attains the minimum lifting level,
it is likely that the air filter’s element is dirty . Any filter element that obstructs airflow must
be replaced (refer to A
IR
F
ILTER
M
AINTENANCE
preceding). Otherwise, the pump would turn off
at vacuum levels that are not sufficient to lift the maximum load weight.
• If the pump turns off but the lift light does not turn on after vacuum attains the minimum lifting
level, the light bulb may be burned out. The bulb should be replaced when necessary.
Otherwise, the operator might wait unnecessarily for the lift light to turn on, after the lifter
has already attained sufficient vacuum to lift the maximum load weight.
• If the pump does not turn off and the lift light does not turn on after vacuum increases to a
level much higher than the minimum lifting level, the vacuum switch may be adjusted to
maintain a lower vacuum level. Otherwise, the pump would continue to run unnecessarily
after the lifter has attained sufficient vacuum to lift the maximum load weight.
• If the pump does not turn on and the lift light does not turn off before vacuum decreases to a
level lower than the minimum lifting level, the vacuum switch must be adjusted to
maintain a higher vacuum level . 19 Otherwise, the lifter would not maintain sufficient
vacuum to lift the maximum load weight.
18
When using the lifter at high elevations, reduced atmospheric pressure may prevent the vacuum generating system from
attaining the vacuum level set at the factory. This causes the pump to run continuously. If the ability to lift the maximum load
weight is not required, the operator can adjust the vacuum switch to maintain a lower vacuum level, allowing the pump to cycle
normally. However, be advised that
lifting capacity decreases proportionally with decreasing vacuum, based on the
vacuum level specified for the Load Capacity (see SPECIFICATIONS). For example, if a lifter's Load Capacity is rated at 16" Hg
[-54 kPa], lifting capacity decreases by 6.25% for each inch of Hg subtracted from (or for each 3.4 kPa added to) the vacuum
level. Always maintain a minimum vacuum level of 10" Hg [-34 kPa], regardless of the vacuum level specified for the
original Load Capacity. In addition, lifter markings should be adjusted to reflect the revised Load Capacity and the vacuum gauge
should be marked to indicate the revised minimum lifting level.
19
In order to observe lifter functions while vacuum is decreasing, it may be necessary to create a controlled leak in the vacuum
system (eg, by breaking the seal between one or more vacuum pads and the test surface).