Howard HI-104 Single-Phase Pad Transformer - Manual (Page 32)

Document 2.4.96, Revision 0
March, 2013
32
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
prevent aeration and the introduction of bubbles.
In the case of a double-door style transformer,
the discharge hose can be inserted through the
cover-mounted handhole and placed at the bot-
tom of the tank.
4. Fill the transformer tank slowly. Fill with fluid to
fill line marked inside the transformer tank on
the interior surface of the front panel. If the fill
line cannot be viewed, use the indication on the
fluid level gauge or sight plug (if provided) or fill
to the bottom of the fill plug.
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.
▲
! 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 from a remote
location 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.
• Never allow anyone to enter the transformer
tank until an analysis of the air inside the
tank indicates at least 19.5% oxygen.
• Whenever someone is inside the tank, a per-
son should be stationed near the handhole
to ensure the safety of the person inside the
tank.
Transformer tanks 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.
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. Should it
be 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 “Removing or Lowering the Fluid” and “Fill-
ing with Fluid.”
Personnel should not be permitted on top 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 recom-
mended that any tools used on top of the transform-
er 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.
When working on a double-door style transformer,
the following procedure should be used to remove
the handhole cover.
1. Thoroughly clean the handhole cover. Remove all
moisture, dirt, and grease to avoid contaminating
the transformer tank.
2. Relieve internal tank pressure by manually op-
erating the pressure relief valve, taking care to
avoid any hot oil that might be expelled.
3. Remove and retain cover fasteners.
4. Gently pry the cover upward, making sure that
the cover gasket does not fall into the tank. Lift
the cover vertically to prevent damage to cover,
bolts, and gasket.
5. Remove the gasket from the handhole flange.
The following procedure should be used to re-install
the handhole cover.
1. Place the gasket in its original position. If the
gasket is damaged, it should be replaced.