Information Sheet Number: 1.10
Gunnery Officers are often responsible for ship's ammunition elevators and all of the associated ammunition handling equipment. A sound knowledge of this equipment as well as an awareness of the associated safety, testing, and inspection requirements is essential to the success of any Gunnery Officer.
(a) NSTM 772 Cargo and Weapons Elevators
(b) NSTM 700 Shipboard Ammunition Handling and Stowage
Ammunition, weapon, or cargo elevators are used to vertically transport material to and from magazine spaces, handling spaces, or ship's holds to various decks in support of the ship's mission.
1. Most elevator systems consist of six subsystems.
a. Trunk, including the platform. Elevators operate within an enclosed vertical trunk, which may or may not be watertight. Trunks may contain fixed guide rails, hinged guide rails, positive stop block, shock absorbers, buffer springs, ramps, barriers, platform, drain systems, and a trunk lighting system.
b. Hoist machinery. The equipment which moves the platform up and down is either electromechanical hoist, electromechanical screw, or electrohydraulic ram. The most common type is the electromechanical hoist, which consists of an electric motor, motor controller, magnetic brake assembly, speed reducer assembly, drum shaft assembly, sheaves, and wire rope.
c. Closures, including doors and hatches. Closure may provide watertight integrity, ballistic integrity, and/or gas and fire protection. They also acts as personnel, security, and equipment safety barriers. Most weatherdeck closure are equipped with a drainage system to prevent water intrusion into the elevator shaft. The simplest doors are manually operated and more complicated doors may be hydraulically powered, automatically operated assemblies.
d. Controls. The control system coordinates and controls elevator operation. It controls the direction and speed of the elevator platform and the operation of closure components. Components included in the control subsystem are the motor controller, logic controller, control stations, interlock circuits, trunk limit switches, slack rope limit switches, and door and dog limit switches.
e. Communications. The communications subsystem is used to inform elevator personnel of actions to be taken, loading requirements, platform movement, fault conditions, safety hazards, and other information. The range of equipment runs from sound powered phones to powered and amplified communications circuits.
f. Safety devices. Safety mechanisms are installed in the elevator system for the specific purpose of preventing or warning or an unsafe condition. Some safety devices include overspeed governors, slack rope devices, overtravel limit switches, emergency stop pushbuttons, personnel barriers and safety chains, audible alarms, and interlocks.
C. LOAD TESTING
1. All shipboard ammunition handling equipment shall be load tested at a minimum of every 48 months and after repair or replacement of load bearing components or after
2. Load testing is always required where the repaired or adjusted component is the last-line-of-
defense against uncontrolled movement of the load (e.g. brakes). NSTM CH 700 gives further guidance on components for testing and periodicity for testing.
3. Any qualified shipyard, industrial activity, or Intermediate Maintenance Activity may conduct load testing for ammunition handling equipment, as long as the testing is performed in accordance with NSTM CH 700 Section 4.
D. SAFETY DEVICES AND PERSONNEL SAFETY PRECAUTIONS.
1. Overspeed Governor Assembly. The overspeed governor assembly in each elevator monitors downward platform speed. When the platform exceeds 140 percent of rated speed, the governor activates by stopping the motor and setting the knurled rollers against the guide rails.
2. Overspeed Governor Slack Rope Device. A slack condition of the overspeed governor wire rope causes tension to be released from the slack rope device, which in turn opens the electrical contactors which supply power to the hoist motor and sets the brake.
3. Knurled Roller Assembly or Safety Wedges. The knurled rollers or safety wedges are driven upward, against the guide rails, in the event of uncontrolled downward movement of the platform. They jam against the guide rails, stopping downward movement of the platform. The platform must then be jogged upward to disengage the knurled rollers or safety wedges.
4. Up and Down Overtravel Limit Switches. These switches sense overtravel of the platform in one direction, either up or down (these are separate switches). In order to return the system from a down overtravel condition, the platform must be jogged up, and vice versa.
5. Emergency Stop Pushbutton. Emergency stop pushbuttons are mushroom shaped
pushbuttons installed at all master control stations and machinery rooms. Depressing the
emergency stop pushbutton deenergizes the entire elevator electrical circuit by tripping a
circuit breaker. The circuit breaker must be manually reset to restore operation.
6. Safety Barriers and Safety Chains. Liferails, lifelines, or safety nets are installed around hatches and elevator openings to prevent personnel from falling to a lower level. Guard rails are installed in trunks and around platforms to contain weapons during strike up and strike down.
7. Audible Alarms. Alarm bells or horns are normally installed on the underside of hatch covers. These are designed to warn personnel when the hatch is about to close. Some elevators use a warning bell, which sounds continuously during platform travel.
8. Interlocks. Electrical or mechanical interlocks prevent platform operation unless all doors at all levels are closed and dogged. They also prevent door opening in the event that the platform is not located at that level.
9. Safety Precautions. Some safety precautions include, but are not limited to:
a. Supervisor and operators shall be familiar with elevator capacities and limitations.
b. Operating instructions shall be posted at all control stations and machinery rooms.
c. A safety observer shall be posted when a hatch or moving component is in an area not fully visible to the operator.
d. Communications shall be established between all safety observers and all control stations prior to and throughout elevator operations.
e. No elevator shall be operated if any of the safety features are either inactivated or defective.
f. Prior to initiating any movement, the elevator operator shall visually check the area of operations for personnel or obstructions that would interfere with the safe operation of the elevator.
g. Personnel barriers shall be installed across open trunk doors and around open hatch edges.
h. Obtain permission from the elevator control authority prior to conducting any maintenance, repair, or PMS activity on the elevator. Before performing any
maintenance, the elevator system shall be deenergized and tagged OUT OF SERVICE in accordance with the current OPNAV and ship's equipment tag out instructions.
i. Do not bypass, tie off, or otherwise modify and safety equipment or interlock, except when specified for testing purposes.
j. DO NOT ALLOW PERSONNEL TO RIDE ON ANY ELEVATOR NOT DESIGNATED FOR PERSONNEL USE.
E. REPRESENTATIVE DIAGRAMS OF MAJOR TYPES OF ELEVATOR SYSTEMS
Figure 1.10-1 Amphibious (LPH) Elevator
Figure 1.10-2 Amphibious (LPH) Elevator
Figure 1.10-3 Combatant (DD/CG) Elevator
Figure 1.10-4 Aircraft Carrier Weapons Elevator