Farr HD8625, Technical Manual

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T
echnical
M
anual
hD8625 8-
5
/
8
” 35K T
ong
2.17
SHIFTING TONG WHILE ROTATING THE MOTOR AND CAGE PLATE MAY RESULT IN
CATASTROPHIC GEAR TRAIN FAILURE
I
llustratIon
2.g.4: t
ong
m
anual
s
HIft
C
ontrol
4. General Comments
a) Position rotary gear in contact with both idler gears when breaking out joints or collars where high torques are required.
b) When making-up integral (shouldered) joints, it is essential to make up the last turn of the threads in low gear. This reduces the
tendency of an instant stop or a sudden increase in torque, which induces extremely high stresses on the gear train.
c) DO NOT employ the “snap break” method of breaking-out joints when pulling a string. By definition, the “snap break” method is
a procedure used by some operators to break out connections, accomplished by leaving slack in the “jaw-pipe” engagement,
and then quickly pulling the throttle valve control lever allowing the tong to snap into its loaded or high torque condition. Although
this method is very effective in breaking out joints, the extremely high stress placed on the gear train frequently causes gear
breakage.
s
eTup
& o
peraTion
3. SHIFTING GEARS
The shifting shaft has three “detent” positions identifying the low speed/high torque position, the “neutral” or free-spinning position,
and the high speed/low torque position. The detent strength may be adjusted by releasing the locknut on the detent tube and increas-
ing or relaxing pressure on the detent spring. Ensure the locknut is tightened once the desired detent pressure has been set.
To shift to the high-speed gear, move the shifting handle downward from neutral position. To shift to the low-speed gear, move the
shifting handle up through the neutral detent to its highest position. Note that the high clutch gear or the low clutch gear may not
be exactly aligned when shifting, so the operator may need to “bump” the motor control handle slightly to turn the main clutch gear
shaft and shifting collar into alignment. This is most effective when applying a small amount of pressure on the gear shift lever in the
direction you want to shift the tong, ensuring the shifting collar will “catch” when the main clutch gear aligns with either the high or
low clutch gear (see Illustration 2.G.4).
LIFT HANDLE TO
SHIFT TO LOW GEAR
PUSH HANDLE DOWN
TO SHIFT TO HIGH GEAR