Wood’s Powr-Grip EO1DCB - Manual (Page 12)

Rev 10.0/9-13 10 EO1DCB: #35191AFT
V
ACUUM
S
WITCH
A
DJUSTMENT
Vacuum Switch Function
A vacuum switch controls the vacuum pump for the DC Vacuum Back-Up System while it is activated (see
OPERATING FEATURES for location of vacuum switch). In order to maintain a vacuum level sufficient for
lifting the maximum load weight (hereafter, “minimum lifting level”), the vacuum switch automatically
turns on the Back-Up System’s pump before vacuum decreases to a level that is lower than the minimum
lifting level. After the minimum lifting level is attained, the vacuum switch automatically turns off the
pump. 4
Conditions Requiring Readjustment
The vacuum switch must be set to maintain the minimum vacuum level specified for the lifter's load
capacity (consult lifter specifications). Periodically verify the switch adjustment by comparing how the
Back-Up System’s vacuum pump functions in relation to the vacuum level registered on the lifter’s vacuum
gauge. This can be done while performing the preceding B
ACK -U P F UNCTION T EST , as follows:
• If the pump does not turn off 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 Back-Up
System’s pump would continue to run unnecessarily after attaining sufficient vacuum to lift the
maximum load weight.
• If the pump does not turn on before vacuum decreases to a level lower than the minimum lifting level,
the vacuum switch must be adjusted to maintain a higher vacuum level . Otherwise, the
vacuum generated by the Back-Up System would not be sufficient to lift the maximum load weight.
Adjustment Procedure
WARNING: Lifting capacity decreases whenever vacuum switch is adjusted to
maintain lower vacuum level.
1) Using a 1/4" open-end wrench, turn the adjustment screw about 1/6th turn at
a time (approximately one flat of the screw head).
To maintain a
lower vacuum level, turn the screw clockwise (when viewing
vacuum switch from end with electrical connectors).
To maintain a
higher vacuum level, turn the screw counter-clockwise (when
viewing vacuum switch from end with electrical connectors).
2) Recheck the vacuum switch setting by performing the preceding B
ACK
-U
P
F UNCTION T EST following each adjustment.
When the vacuum switch is adjusted correctly, the Back-Up System’s
vacuum pump turns off only after vacuum increases to a level higher
than the minimum lifting level; and the pump turns on again before
vacuum decreases to a level lower than the minimum lifting level.
4
When using the lifter at high elevations, lower atmospheric pressure may prevent the Back-Up System from attaining the
vacuum level set at the factory. This would cause 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 lifter's load capacity (see lifter 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.
1 ELECTRICAL CONNECTORS
2 ADJUSTMENT SCREW
3 TO MAINTAIN HIGHER VACUUM
4 TO MAINTAIN LOWER VACUUM