Howard HI-102 Overhead Transformer - Manual (Page 26)

Document 2.4.95, Revision 0
May. 2013
26
Fluid-Filled Overhead Distribution Transformers
Fill with fluid to fill line marked inside the
transformer tank.
Opening the Transformer Tank
Transformer tanks are shipped sealed and should
not be opened unless necessary. If it is necessary
to open the tank, follow the instructions below and
observe all safety warnings. Before removing the
transformer cover or handhole cover, de-energize
the transformer and relieve internal pressure by
operating the pressure relief valve, taking care to
avoid any hot fluid that could be expelled from the
PRV.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Before servicing the transformer, always
de-energize the transformer and then
proceed to ground all primary and secondary
transformer terminals following industry-
accepted safe grounding practices.
Grounding secondary terminals protects
against situations such as a standby
generator energizing transformer from the
secondary circuit.
• Release internal pressure by operating the
PRV with a live-line tool before opening the
tank. Be careful to avoid any hot oil that
might be expelled from the PRV.
To prevent contamination of the transformer, do
not open the transformer tank in an unprotected
area during inclement weather or where the air may
contain dirt or other particles. Any of these situations
could contaminate the insulating fluid and cause
a transformer failure. The tank opening should be
protected against entry of foreign matter. If it is
necessary to remove some fluid from the tank to
allow for inspection or other work, the transformer
must be re-filled with fluid after work is completed.
Refer to the instructions In “Removing or Lowering
the Fluid” and “Filling with Fluid.” The transformer
tank should not remain open for more than two
hours. If work is interrupted, the tank should be
resealed, evacuated, and filled with dry air or
nitrogen.
Personnel should not be permitted on top of or
inside the transformer while it is open, unless they
have emptied all pockets and checked for loose
objects that might fall into the tank. All tools should
be accounted for after work is completed. It is
recommended that any tools used on top of the
transformer or inside the tank be attached with
safety cords to prevent them from being lost inside
the transformer.
Personnel must not stand directly on any electrical
insulation. Clean drop cloths should be used under
working areas in the transformer to prevent objects
from dropping into the core/coil assembly.
The following procedure should be used to re-install
the handhole cover.
1. Place the cover gasket in its original position. If
the gasket is damaged, it should be replaced.
2. Re-install the handhole cover. Re-install and
tighten the cover bolt according to the torque
recommendations in Table 1.
3. To ensure a proper cover seal, pressurize the
headspace to 3-4 PSIG and check for leaks.
Torque Guidelines
Tables 1 through 4 below contain recommended
torque values for tightening various connections
on the transformer. Connections with gaskets will
normally relax after initial tightening. Nominal torque
values listed below include an allowance for gasket
relaxation.
Do not over-tighten any connection; otherwise,
gaskets could split due to over-compression, and
components might break. Fluid leaks could result if
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 the manufacturer’s
recommended torque values for any user-provided
devices.