80-0420-23 POWER TONG
Manual № TM12012
Section 3
Page 3.17
©2008-2017 McCoy Global
Installation & Commissioning
3.5 EQUIPMENT CONFIGURATION AND LEVELING
3.5.1 Suspension and Restraint
Suspend the tong from a location as near to the centre of the drill rotary as possible, and from a location high
enough on the mast to ensure easy handling. Suspending the tool lower in the rig increases the effort required to
move the tong to and from the connection point.
The suspension line may be extended over a pulley and balanced by a counterweight equal to the weight of the
tong, or simply tied off in the derrick to form a dead line. When using a dead line arrangement it is necessary
to use a McCoy spring hanger assembly (see specification page for recommended spring hanger). This spring
hanger compensates for the downward movement of the casing as the thread is made-up, and imparts additional
force to the suspension cable:
• A “single spring” hanger typically applies 420 lbs (191 kg) to the suspension line for every inch of thread made
up
• A “double spring” hanger typically applies 840 lbs (382 kg) to the suspension line for every inch of thread made
up
If you do not know which specific spring hanger is in use, check the specification page in this manual for
information on the recommended spring hanger for this application. McCoy Global will not guarantee or specify
spring hangers other than what has been supplied by McCoy.
Many applications use a lift cylinder for adjusting the height of the tong. Ensure the weight of the lift cylinder is
known if it has not been included in the total weight of the tong.
All forces upon the suspension line must be considered when calculating necessary strength of the suspension
line. The weight of the tong, the weight of the lift cylinder, the weight of the spring hanger, and the force imparted
on the suspension line by the spring hanger must all be added together in order to arrive at the total force
supported by the suspension line. Select your suspension line based upon the total force and the margins of
safety dictated by the policies of your company and by established engineering practices. Ultimately, calculating
the force on the suspension line and selection of the suspension line is the complete responsibility of the customer.
McCoy Global recommends using dual backup (snub) lines of sufficient strength to withstand the force imparted
by the maximum rated torque of the tong and backup assembly in use. The snub lines will arrest uncontrolled
movement of the tong and backup in the event slipping of the backup jaws. Calculate the force on the snub lines
by dividing the maximum torque of the tong by the tong’s torque arm (expressed in feet). For example, a 80,000
lbs.-ft. tong with a 56 inch (4.67 ft.) torque arm will generate 17,143 lbs. of force against the snub line. Select your
snub lines based upon the total force and the margins of safety dictated by the policies of your company and by
established engineering practices. Ultimately, calculating the force on the snub line and selection of the snub line
is the complete responsibility of the customer.
Snub lines must be securely connected to the rear of the tong and backup assembly, and tied off to a suitably rated
anchor. When properly installed the snub line should be taut enough to allow very little movement, preventing the
tong from generating excessive force on the lines by “snapping” tight when rotation is applied.
!
DANGER
MCCOY GLOBAL ACCEPTS NO RESPONSIBILITY FOR DESIGNING AND SELECTING AN ADEQUATE
SUSPENSION AND RESTRAINT SYSTEM FOR YOUR DRILLING EQUIPMENT. FAILURE TO FOLLOW
THE INSTRUCTIONS PROVIDED IN THIS SECTION MAY RESULT IN SERIOUS INJURY TO THE
OPERATOR.
ALL SELECTED FASTENERS, SHACKLES, CLAMPS, ETC. USED FOR CONSTRUCTING THE
SUSPENSION AND SNUB LINES MUST BE RATED FOR THE CALCULATED FORCES.
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