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System Preventive Maintenance

Preventive maintenance components are built into some ordnance systems to help detect faults within the systems. One of these components is a ground detection indicator.

The ground detection indicator is a continuous monitoring system designed to detect a system ground. Since most control circuits in ordnance systems are powered by ungrounded 115-volt, 60 hertz, single-phase current, the first ground is not very important from an operational point of view. However, if the first ground is not discovered and a second develops, the result could be an illogical and destructive sequence of system operation. The reason for this is that two grounds act as electrical conductor between the grounded components. When the ground detector indicates (by light or buzzer) that some of the control circuitry is grounded, you should determine the location and cause of the ground. The elimination of most grounds and potential grounds is good maintenance and housekeeping.


Most of the maintenance work on armament aboard ship is done by the strikers and Gunner's Mates themselves as part of the ship's routine. This is called ship's force maintenance.

The ship's force, however, does not have the facilities or the skills to perform certain less frequent, but equally necessary, maintenance operations. Examples of this type of operation are repair of gunsight or boresight telescopes and calibration of pressure gauges. Work of this nature is done aboard repair ships and tenders that have the equipment and skilled personnel required for this type of repair work,

Lastly, there are some jobs, like major overhaul of hydraulic systems or repair or replacement of roller paths, that are customarily completed in shipyards. Such work may be completed by yard workers, by the ship's force, or by both. Maintenance work completed in shipyards is termed navy yard maintenance.

Routine overhauls are scheduled far ahead of time at a specified navy yard for each ship. To get the most out of the overhaul work, you must keep records of mishaps, signs of defects, or poor operation of gunnery equipment so that each of the items can be taken care of during the overhaul. You must also keep records of all repair work done by the ship's force. Keeping the records is part of your job; the weapons officer must have this information to plan the overhaul work. Pending maintenance and equipment history records are maintained as part of the maintenance data system (MDS) that is a part of the 3-M Systems. 'he documentation of equipment malfunctions is briefly described in the "Common Maintenance Procedures" section of this chapter.

Work by tenders and repair ships is also scheduled, so it must be planned for ahead of time. Authorized alterations (ORDALTs) are also made aboard these ships when possible, although some may be accomplished by ship's force but supervised and verified by the appropriate Navy Sea Support Center, Atlantic or Pacific (NAVSEACENLANT/PAC). ORDALTs requiring special team efforts will be accomplished under the direction of NAVSEACEN personnel and supported, as required, by the in-service engineering agent and/or contractor representatives. ORDALTs usually state by whom the work is to be done. Changes of a minor nature are authorized by NAVSEASYSCOM instructions.

The upkeep period is time assigned to a ship while moored or anchored or when the ship's force and other forces afloat can work to perform upkeep duties without interruptions.

Special assistance in maintenance, especially for new equipment, may be obtained from contract service engineers who are specifically trained for specific equipment, or from mobile ordnance technical units (MOTUs) which consist of military personnel who have been trained to handle certain equipment and can be assigned to instruct others in its use and care.


All U.S. Navy ships are assigned regular overhaul availability cycles for the purpose of maintenance and updating/improvement of the ship and its installed equipment. The two types of availability are the Regular Overhaul (ROH), and the Phased Maintenance Program (PMP). As a leading GM, you will be closely involved with the planning and implementation of these programs. In addition, you will also have to supervise the maintenance of your assigned equipment through the use of Inactive Equipment Maintenance (IEM).

Regular Overhaul (ROH)

One of the most important considerations affecting the performance of ship's overhaul is the determination of what work is actually to be performed during the ROH. This phase of the planning process is developed into the Ship Alteration and Repair Package (SARP) or the Integrated Work Package (IWP) as applicable.

Because the SARP/IWP is both a planning and working package for ROH, it will be addressed at this time.

For most ships, a SARP is the document that defines and authorizes work to be done during the overhaul, assigns the level of accomplishing activity for each work item, and indicates cost estimates for each shipyard job. The IWP performs the same functions for small ships (ARS/AFT/MSO) when the OPNAV 4790.2K maintenance forms are arranged in order by ship system. The purposes of the SARP (or IWP) areas follows:

1. Integrates related customer work requirements

2. Resolves redundant and conflicting work requirements

3. Identifies work on a ship system basis

4. Serves as the single source document for all customer authorized work

The SARP/IWP is maintained as a continuing document that contains the information necessary for the following:

1. Estimating the overhaul cost and duration

2. Early decision making by higher levels of command concerning budgeting, finding, operating schedules, and overhaul duration

3. Commencement of additional advance planning, design work, and material procurement by those activities responsible for supporting and conducting the overhaul

Key inputs for developing the SARP/IWP are as follows:

1, The Current Ship's Maintenance Project (CSMP) as submitted by the type commander to the cognizant Planning and Engineering for Repairs and Alterations (PERA) approximately 12 months in advance of the ROH start date

2. Results of the Pre-Overhaul Tests and Inspection (POT&I)

3. Type commander Title "D" SHIPALT Authorization Letter

4. NAVSEASYSCOM Title "K" SHIPALT Advance Planning/Authorization Letter

For ships using the SARP overhaul package, the following action will be taken (approximately 90 days before the overhaul commencement or when the SARP screening action has been provided to the ship):

1. Work discovered during POT&I and designated for IMA accomplishment will be documented on an OPNAV Form 4790.2K and coded for availability.

2. Work previously documented into the CSMP file, but which was originally coded for other than IMA accomplishment, and for which subsequent screening action changed the accomplishing activity to IMA, will require submission of a correction document (OPNAV Form 4790.2K) to change the type of availability code.

The above work items, along with those already coded for IMA accomplishment in the ship's CSMP file (plus any desired master job catalog items), will form the IMA work package for preoverhaul and concurrent IMAVs.

The time between regular overhauls varies from 2 years to 5 years. The interval is the maximum period consistent with keeping the ship infighting trim.

An analysis of the problem of building, overhauling, or converting ships reveals that the following factors play essential roles:

1. The ship must be available for the uninterrupted accomplishment of yard work,

2. The contemplated work must be decided upon, arranged in order of priority of accomplishment, and actually authorized to be performed.

3. Sufficient finds must be available to cover the cost of the work

4. Material must be available.

5. Personnel must be available to do the work


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