MTS Series 244 Actuators - Manual (Page 35)

• When you charge an accumulator, follow all the charging instructions provided in the appropriate product
information manuals. When precharging accumulators, properly identify the type of gas to be used and
the type of accumulator to be precharged.
• Use only dry-pumped nitrogen to precharge nitrogen-charged accumulators. (Dry-pumped nitrogen can
also be labeled “oil pumped” or “dry water pumped.”) Do not use compressed air or oxygen for precharging:
the temperature increase caused by rapid gas compression can result in highly explosive conditions when
hydraulic fluid is in the presence of oxygen or compressed air.
• Always follow the recommended bleeding procedures before you remove or disassemble components
that contain pressurized gas. When you bleed a gas or remove a fitting, hose, or component that contains
a gas, remember that many gases cannot support life. Therefore, as the ratio of released gas to oxygen
increases, so does the potential for suffocation.
• Wear appropriate safety devices to protect your hearing. Escaping air or gas can create a noise level that
can damage your hearing.
• Ensure that all pressurized air or gas is bled out of a pneumatic or gas-charged device before you start
to disassemble it. A thorough understanding of the assembly and its pressurized areas is necessary before
you undertake any maintenance. Refer to the appropriate product information for the correct bleeding
procedure.
It may not be obvious or intuitive which bolts or fittings are used to restrain a pressurized area. On some
assemblies, you must remove a cover plate to gain access to the structural bolts. Sometimes, to protect
you from a rapid release of trapped gases, a small port is exposed when you remove this cover plate.
Exposing this port ensures that the gas precharge is fully bled before disassembly. However, this is not
the recommended procedure for bleeding a pneumatic or gas-charged device, because it can expose you
to the dangers of escaping compressed gas and particulates that are expelled from the chamber or around
the seals. Do not assume that cover plates and ports are installed in all the critical locations.
Consult MTS when in doubt about the safety or reliability of any system-related procedure or modification
that involves devices that contain any type of compressed gas.
Check bolt ratings and torques
To ensure a reliable product, fasteners (such as bolts and tie rods) used in MTS-manufactured systems are
torqued to specific requirements. If a fastener is loosened or the configuration of a component within the
system is modified, refer to the system and component assembly drawings (located on the System
Documentation CD) to determine the correct fastener, fastener rating, and torque. Over torquing or under
torquing a fastener can create a hazardous situation due to the high forces and pressures present in MTS
test systems.
On rare occasions, a fastener can fail even when it is correctly installed. Failure usually occurs during torquing,
but it can occur several days later. Failure of a fastener can result in a high velocity projectile. Therefore, it
is a good practice to avoid stationing personnel in line with or below assemblies that contain large or long
fasteners.
Practice good housekeeping
Keep the floors in the work area clean. Industrial chemicals, such as hydraulic fluid, that are spilled on any
type of floor can result in a dangerous, slippery surface. Do not leave tools, fixtures, or other items not specific
to the test, lying about on the floor, system, or decking.
Protect hoses and cables
Protect electrical cables from spilled fluids and from excessive temperatures that can cause the cables to
harden and eventually fail. Ensure that all cables have appropriate strain relief devices installed at the cable
and near the connector plug. Do not use the connector plug as a strain relief.
Series 244 Actuators Product Information 35
Safety