Most hydraulic fluids are flammable and can cause skin irritation if prolonged contact occurs. Change clothing immediately if drenched with hydraulic fluid and wash thoroughly.

Hydraulic fluid becomes a hazard if it is sprayed, heated to its flash point, or otherwise subjected to conditions that cause vaporization. Hydraulic fluid must never be stored in a missile stowage, testing, or maintenance area. Do not handle hydraulic fluid in the presence of electrical sparks or open flames. Hydraulic fluid should be kept in closed metal containers. Bulk supplies should be stored only in approved and authorized areas.

Spilled fluids make a surface slippery. Wipe up spilled or leaking fluid immediately. Oily rags and clothing should be stored in a closed metal container to avoid a potential fire hazard. They should be properly disposed of at the first opportunity.

PERSONNEL SAFETY PRECAUTIONS

When working with high-pressure equipments, you must wear approved safety glasses or face shields. Do not direct high-pressure air against the deck, workbench, or other equipments. Low-pressure air may be used for certain specified maintenance-related cleaning or drying tasks. Always obtain permission to use low-pressure air for these purposes. Never direct any pressurized air jet toward your (or a shipmate's) body.

During any GMLS equipment operation, keep all parts of the body clear of any component that moves as a result of pneumatic or hydraulic pressure.

Safety precautions must be observed and common sense used ALL THE TIME. Do not think that once you have learned all the applicable safety rules you can sit back and relax. Review them periodically, particularly for those jobs seldom performed. Try to improve upon any rules in effect. Safety is everyone's responsibility, not just those who drew up the regulations. Many accidents are caused by personnel who are so familiar with their jobs they think they can take shortcuts. Personnel who do not know the applicable safety precautions often are the cause of accidents. We also cannot forget the many tragic accidents caused by practical jokers. However, in the majority of instances, plain carelessness is the biggest threat, Stay alert!

AIR SYSTEMS

Most, if not all, ordnance systems use compressed air in one way or another. Though the compressed air supply system is not considered part of your ordnance equipment, it is a critical support element. In many cases, you may find that the lack of compressed air can stop the most carefully planned exercise. Many Gunners have learned the hard way-you need to check the availability of compressed air the day before an important exercise. It is extremely important that you know where your air comes from and who controls it.

The air supply system is operated and maintained by the ship's engineers. Air systems are classified by their operating pressures. In the ordnance world, we are concerned primarily with high-pressure (HP) air. We will briefly discuss the main applications of HP air in gun systems.

HP air plants and systems are generally designed to provide compressed air at a nominal operating pressure of 3,000 psi or 5,000 psi. They are installed when one of the ship's services requires a pressure in excess of 1,000 psi. They are also used when a ship's function requires a flow rate that cannot be readily supported by either a low-pressure or medium-pressure plant. HP compressed air plants support high flow demand systems by the addition of HP air storage flasks in the system. Once an adequate quantity of compressed air is stored in these flasks, the high flow rates and pressure demands can be supported by way of pressure reducing stations.

The primary use of HP air in a gun system is to operate the gas ejection system. The gas ejection system uses compressed air to evacuate gases and unburned solids from the bore after firing. Gas ejection is a high-flow system. The compressed air is pumped from the engineering space to a flask in the vicinity of the gun mount. The air is then routed through a reducer, where it is regulated to system pressure, then up to the gun where it is used.

SUMMARY

In this chapter, we have looked at some of the basic mechanical and hydraulic principles used in gun mount and GMLS equipment. We also discussed the Mk 75, Mk 45, Mk 13 and Mk 26 hydraulic systems-control equipment and HP air systems that support weapons systems operation. Most gun mount and GMLSs casualties are mechanical or hydraulic malfunction, therefore, a thorough understanding of mechanics and hydraulics is essential for the GM rating. In the next chapter, we will discuss the control circuits that regulate the operation of these devices. In chapter 12, we will describe maintenance and repair procedures for mechanical and hydraulic equipment.