Document 2.4.128, Revision 3
October, 2017
26
Network Transformer Instruction Manual
tank-mounted components are over tightened. Check
with the Howard Industries Transformer Division
for recommended torque values for any devices or
connections not listed below. Use manufacturer’s
recommended torque values for any user-supplied
devices.
Table 3: Torque Guidelines for External Cabinet
Fasteners
Fastener Type
Nominal
Torque
(in-lbs)
Torque
Range
(in-lbs)
Secondary throat shipping
guard bolts
80
70-90
Hand-hole cover bolts
190
170-210
Terminal and switch cham-
ber cover bolts
350
300-400
Table 4: Torque Guidelines for External Bushing
Mounting Hardware
Bushing Type
Nominal
Torque
¹
(in-lbs)
Torque
Range
Low-voltage bushing,
molded Tri-Clamp
(without clamp ring),
3/8” mounting studs
60
40-80
Low-voltage bushing,
molded (with clamp ring),
3/8” mounting studs
120
90-150
Low-voltage bushing,
porcelain (with clamp ring),
1/2” mounting studs
80
70-90
High-voltage bushing well,
molded Tri-Clamp (without
clamp ring), 3/8” mounting
studs
60
40-80
High-voltage bushing well,
molded (with clamp ring),
3/8” mounting studs
120
90-150
Notes:
¹ When checking tightness of gasketed
components, the measured torque will normally
be less than the nominal torque listed in the table
above due to relaxation of the gasket material.
Additional tightening of bushing mounting
hardware may cause the component to crack or
the gasket to become over-compressed.
Table 5: Torque Guidelines for External Bushing
Terminal Connections
Terminal Type
Nominal
Torque
²
(in-lbs)
Torque
Range (in-
lbs)
High-voltage molded
bushing insert ¹
180
156-204
Low-voltage bushing,
5/8” jam nut
600
480-720
Low-voltage bushing,
1” jam nut
600
480-720
Low-voltage bushing,
1-1/4” jam nut
720
600-840
Notes:
¹ Apply silicone grease before installation according
to the insert manufacturer’s instructions.
² When checking tightness of gasketed
components and molded busing inserts, the
measured torque will normally be less than the
nominal torque listed in the table above due to
relaxation of the gasket material. Additional
tightening of bushing mounting hardware or
bushing insert may cause the component to
crack or the gasket to become over-compressed.
