How to test a hulls watertight integrity

Ship hulls watertight integrity
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Methods of checking watertight integrity 

Watertight integrity features are built into naval ships. There must be regular inspections conducted on the ship and its watertight integrity features. The ship’s planned maintenance system (PMS) gives specific details for conducting the compartment tests and inspections. The Naval Ships’ Technical Manual, chapter 9880, section IV, also covers various compartment tests and inspections. A Schedule of Watertight Integrity Tests and Inspections is maintained in the ship’s damage control library. Refer to the above References when you schedule and conduct the required tests and inspections.

Visual inspection 

Often you can discover holes or cracks in watertight bulkheads and decks by conducting a thorough visual inspection. If a compartment contains oil, water, or some other liquid, any leakage will be evident. Other sources for leakage include loose rivet heads, poorly caulked plate laps or stiffeners, and poorly caulked bounding angles. All leaks should be repaired as soon as possible to re-establish the ship’s watertight integrity. If the repairs are beyond the capability of the ship’s force repair personnel (Hull Technicians), the work should be included in the work package for the next shipyard, tender, or repair ship availability.

You will, at specified intervals conduct a visual inspection for light leaks within most compartments on the ship. To make this inspection, completely close off the compartment and secure all lighting within the compartment. Have another person (an observer) stay inside the darkened compartment to look for light leaks. Then you will need to ensure that lighting is on in the surrounding spaces. As a rule, the light from the surrounding compartments will allow the observer to locate any serious defects. However, you might need to use portable lights to provide a higher level of illumination in some areas. The observer will also need a portable light to transit the darkened space safely.

The visual inspection for light leaks is particularly important for those compartments that cannot be tested by air pressure because of permanent openings to the topside. Compartments that will have a visual inspection include engine rooms, firerooms, other machinery spaces, and all compartments on the main deck and above.

Compartments Air Test

The Schedule of Watertight Integrity Tests and Inspections is issued by NAVSEA for each ship. This schedule contains information on each watertight compartment and the type of test used to determine the compartment’s tightness. Compartments designated for air testing are scheduled so that all such compartments are tested once every 18 months for ships at least 12 years old. For electrical push-button alarms and remoteships that are less than 12 years old, the controlled valves for sprinkling, flooding, or compartments are tested once every 36 months, counterflooding systems if any are installed in Compartments that are designated for air testing the compartment to be tested. These devices are provided with fittings for attaching the air test have diaphragm covers and would be activated set. In the case of tanks, you may use sounding when the air test pressure is admitted to the tubes or air escapes to connect the air test set. compartment unless they had been previously Figure 3-13 shows the air test set that is provided de-energized. for shipboard use. The manufacturer’s technical All fittings that serve the compartment must manual, provided with each set, gives detailed be secured or blanked off before the air test is instructions for operating the air test set. conducted. If any rotating shafts or other moving.

The information contained in the ship’s parts penetrate the bulkheads, you must tighten Schedule of Watertight Integrity Tests and the packing before conducting the air test to Inspections must be strictly adhered to when maintain the air pressure. conducting compartment air tests. The air test Make sure that the crew is aware of the pressure listed in the schedule must NEVER be compartment air test being conducted. Post signs exceeded. You can seriously damage the structures at every possible access to the compartment(s) and boundaries of the compartment being tested if being tested. If an observer is stationed inside the the recommended pressure is exceeded. compartment during the compartment air test,

Before starting an air test, you need to each access to the compartment must have conduct a visual inspection of the compartment someone posted at the access closure. The guards and repair all the leaks that you find. Notify the are to prevent the access closure from being opened engineer officer, the DCA, and the OOD of your until the excessive pressure within the intent to conduct a compartment air test and which compartment is relieved. The air test pressure compartments will be involved. Also, have an used in a compartment air test is relatively low. Electrician’s Mate (EM) assist in de-energizing the However, a dangerous total force can be developed on quick-acting doors and hatches. Personnel should be instructed not to attempt to open quick-acting doors or hatches when a compartment is under air test. A person opening these doors or hatches while the compartment is under pressure could sustain severe injuries.

When conducting a compartment air test on a large compartment, use as many personnel as required to check for leaks. The personnel involved with the test need to maintain communication with each other. The X40J (salt and pepper) rig can be used, allowing you to have an isolated circuit without interruptions.

When you are conducting a compartment air test, any loss of pressure in excess of the allowable drop listed in the schedule over the specified period of time indicates deterioration of the watertight integrity of the compartment. If corrective measures are beyond the capacity of ship’s force, the compartment must be listed as UNSATISFACTORY. You must then request that repairs be completed during the next availability y.

While the compartment is under test, leaks will be disclosed by hissing or whistling noises as the air escapes. All leaks should be located, marked, and listed for corrective action. You should repair all leaks that you found and then test the compartment again. If the allowable pressure drop is again exceeded on this test, apply a soap solution to the boundaries of the compartment and to all joints, fittings, and closures. When the air pressure is applied, bubbles will be formed by escaping air, thus indicating the location of the leaks.

The observer inside the compartment will have a lighted candle. As the observer goes over areas where leaks are suspected, the deflection of the flame will indicate the location of leaks.

Upon completion of the compartment air test, relieve the air pressure in the compartment. Be sure that all caps for the air test fittings are replaced. These caps are classified XRAY. Ensure that all temporary closures are removed from overflows, air escapes, and air vents in magazines and fuel oil tanks. The boundaries are sure to be ruptured when the space is filled or flooded if these vents and escapes are left closed. Then make the appropriate entries in the watertight integrity log if your ship has one.

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