Howard HI-102 Overhead Transformer - Manual (Page 27)

Document 2.4.95, Revision 0
May, 2013
27
Fluid-Filled Overhead Distribution Transformers
Table 1: Torque Guidelines for External Fasteners
Fastener Type
Nominal Torque
(in-lbs)
Torque Range
(in-lbs)
3/8” bolt 240 220-260
Hand-hole cover
bolt
144 129-158
Fastener Type
Cover band bolt
180 170-185
Surge arrester
mounting bolts
420 372-368
Table 2: Torque Guidelines for External Bushing
Mounting Hardware
Bushing Type
Nominal
Torque
(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, porce-
lain (with clamp ring), 1/2”
mounting studs
80 70-90
High-voltage bushing, mold-
ed Tri-Clamp (without clamp
ring), 3/8” mounting studs
60 40-80
High-voltage bushing,
molded (with clamp ring),
3/8” mounting studs
120 90-150
High-voltage bushing, porce-
lain
80 70-90

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 3: Torque Guidelines for External Terminal
Connections
Terminal Type
Nominal
Torque
(in-lbs)
Torque
Range
High-voltage porcelain bush-
ing eye-bolt
210 180-240
High-voltage porcelain bush-
ing end cap
168 156-180
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
External surge arrester line
lead
180 162-198
External surge arrester
ground lead
180 162-198

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 4: Torque Guidelines for Accessories
Component
Nominal
Torque
(in-lbs)
Torque
Range
(in-lbs)
Bushing-mounted weak-
link fuse mounting bolts
85 80-90
Fluid-level sight plug 960 900-1020
Fill plug 960 900-1020
Drain plug 960 900-1020
Drain valve 600 480-720
Automatic pressure relief
device, 1/4” NPT
180 160-200
Automatic pressure relief
device, 1/2” NPT
360 324-396
Neutral strap fastener (at
ground pad)
160 140-180
Series/multiple, delta/wye
or tap switch mounting nut
120 96-144
Ground connector 160 140-180

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.