SSI Service Manual – 991286 Rev 3
POSSIBLE SOURCES OF ENERGY
All possible sources of energy must be identified and locked out prior to working on the equipment. The
following is a list of common sources of energy. It is possible that other sources of energy exist that are
not identified here.
Electrical Energy
Control Voltage
The voltage on the control circuit is typically 24 VDC, but could be higher. Normally, locking out the main
disconnect switch isolates this voltage from any control wiring. In some situations, the control voltage can
be fed from external circuits and will have to be locked out at its source. In some case control power from
other equipment will be present in the SSI supplied panel. Lock out all of the sources of electrical energy
before working on the electrical system.
Main Power
The main incoming power will be significantly higher than the control voltage and present a lethal shock
hazard. In most cases, locking out the main breakers on the SSI supplied panels will eliminate this
voltage from all of the circuits except the incoming leads to the breakers themselves. In other cases, the
power will have to be locked out at facility breakers feeding the equipment. Carefully determine power
sources and lock out all of them prior to working on the equipment.
On units equipped with diesel engines there are electrical heaters in the hydraulic tank and engine block
that are powered from outside sources. Disconnect (unplug) these to eliminate hazards from this source.
Potential Energy (Gravity)
If the shredder is equipped with a ram hopper, the ram itself is a source of potential energy. Lower the
ram fully or block it up in the raised position prior to working around or under it.
If the shredder is equipped with hydraulically actuated access doors or maintenance points, always lock
them in the open position or actuate them until they are over center and cannot fall closed. Do not trust
the cylinder alone to keep them open.
Falling material is a source of potential energy. Make sure that material hanging in or around the hopper
or conveyors has been secured prior to working under it.
Hydraulic Energy
The hydraulic pressure decays from all the circuits within a few seconds after the electric motor shuts
down, with the exception of any hydraulic cylinders used in ram hoppers, access doors or other devices.
These cylinders have counterbalance valves that are designed to hold the pressure in the cylinders to
prevent unintended machine motion. Support the suspended load to minimize the pressure retained, and
then carefully crack a hose fitting between the cylinder and the counterbalance valve to bleed off any
pressure prior to working on these circuits.
Thermal Energy
In addition to the above forms of energy, there are two sources of potentially dangerous temperatures:
• Hot fluids: Hydraulic fluid and gearbox lubrication can reach temperatures capable of burning or
scalding flesh.
• Hot Surfaces: The surface temperatures of hydraulic components or gearbox housings reach
temperatures capable of causing burns.
The only way to eliminate these hazards is to wait until the unit has cooled.
Other Sources
There may be sources of pneumatic energy (compressed air), compressed springs or other suspended
loads depending on the equipment configuration.
