A manual shutoff valve assembly is mounted inside each guide arm structure. Each assembly consists of two rotary valves turned by a common operating lever (fig. 4-70). In the ON position, the valves port PA and tank fluids between the guide arm components and the hydraulic supply. These fluids can also be from the main elevation accumulator system or the guide arm exercise and emergency accumulator system. During maintenance operations or in case of a failure in one or more of the components of the guide arm, the valve may be turned to OFF. Isolating the "bad arm ensures sufficient operating pressures are still available to the other arm.

SAFETY

LEARNING OBJECTIVE: Identify safety procedures that should be used while working on power drive systems in GMLSs.

Safety is everybody's job. Awareness of danger, knowledge of how to avoid it, and constant vigilance are the three basic requirements for the prevention of accidents.

Safety is both a result and a reflection of good training. The crews of missile launching systems may be trained so that every man knows how to do his job thoroughly. However, the crew still cannot be considered well trained unless every man is safety conscious. Safe working habits must be impressed upon every crewman through proper instructions, constant drills, and continuous supervision. Carelessness, cockiness, and lack of training have led to disaster while working with all types of ordnance equipment and material.

Each piece of ordnance equipment has a specific list of safety precautions to be observed during operation and/or maintenance. Consult the safety summary of the equipment OP. Study it thoroughly before attempting to operate or repair any piece of equipment with which you are not familiar.

Any high-pressure system, hydraulic or pneumatic, is dangerous and may cause serious or fatal injuries when improperly handled. Exercise great care when operating any GMLS equipment.

Figure 4-69.-Manual transfer valve assembly; in strikedown area. 4-56

Figure 4-70.-Manual shut off valve assembly; in each guide arm.

HIGH-PRESSURE SYSTEM SAFETY RULES

The following safety rules are but a few of the many that must be observed when operating or working on hydraulic or pneumatic systems:

All hydraulic and pneumatic equipment should be installed and operated in compliance with prescribed safety precautions.

Personnel should be thoroughly trained and properly checked out on any high-pressure system before being authorized to operate the system.

Do not mix air and hydraulic fluid in a pressurized system. An explosive mixture could result (commonly known as diesel-action).

Never use oil on gauges associated with pneumatic systems. Do not use an oil gauge on an air system. Keep gauges clean at all times. Check the accuracy of gauges frequently as prescribed with maintenance requirement schedules.

Light oils, benzene, or kerosene must never be used as a cleaning or lubricating agent in a high-pressure air system. These oils vaporize easily and form a highly explosive mixture with compressed air.

Do not close or open air or hydraulic valves rapidly unless authorized to do so. Never manually actuate switches, solenoids, relays, or valves on pneumatic or hydraulic systems unless you are authorized and directed to perform these actions.

Ensure that all flexible hoses are rigidly secured to prevent them from flailing or whipping about if a connection breaks under pressure.

Inspect threads of air and hydraulic system couplings before mating. Make certain they are free of dirt, oil, and physical defects.

Adhere to test, inspection, and replacement schedules for flexible lines. Never use worn, damaged, or outdated materials.

Do not kink a high-pressure line or hose nor strike a fitting or air line that is under pressure.

Before applying air or hydraulic pressure to any connection, make sure that it is properly secured. Do not attempt to loosen or tighten any high-pressure connection while the system is under pressure.

Carefully bleed pressure from all lines before removing or loosening them. Never disconnect any pneumatic or hydraulic lines or equipment until the accumulators have been dumped to the tank and zero pressure has been verified in the system.

Immediately report any leak in an air or hydraulic system to the work center supervisor or person operating the equipment.