Battery Maintenance: Routine Maintenance on the Emergency Diesel Start Batteries - Assignment Example

Battery Maintenance Battery Maintenance: Routine Maintenance on the Emergency Diesel Start Batteries An emergency power system in ships is an independent and immediate source of electrical power which supports the various important electrical systems if normal power supply is lost. The electrical power systems are installed for purposes of protecting life and property in the case where the primary source of power fails for example in case there is a black out. This standby power system consists of a standby generator, batteries and other various components. The system is usually self-contained and independent from any of the other engine room systems. The system has its own independent systems for starting, cooling, fuel oil, preheating and lubrication oil. The main electrical systems supplied by the emergency power supply include navigation and communication equipment, emergency lighting, the fire and sprinkler pumps, the water tight doors and lifts, the steer gear and bilge pump. The system is automatically connected to the emergency switchboard and is automatically started if the main power source goes off. The system is always located higher up and outside the engine room spaces. This insulates them from any damage and / or fire to the engine room. Batteries in ships are backup source of power as an emergency system or form part of the standby power system installed to protect property and life from the various consequences of loss of primary power supply. They are an excellent source and store for electrical power since they are used as instant supply source of available energy. They are also used to provide low voltage direct current supply on regular basis to various machines on the deck and engine. Generally, there are two types of batteries used onboard a ship; the lead acid batteries and the alkaline batteries. The Lead – Acid batteries also known accumulators consist of six separate cells in a series and each cell contains a lead peroxide plate as the positive terminal and a lead plate as the negative terminal which are both immersed in dilute sulphuric acid, the two plates are known as electrodes and the sulphuric acid is known as the electrolyte. This whole arrangement is kept in a leak proof casing. The two plates are joined by a wire and this develops a potential across this wire which eventually ensures current starts flowing through it. These batteries develop a total output of 12 volts since each cell in the series has a potential of producing 2 volts. The Lead Acid accumulators used currently has many plates which are interleaved in one cell. For proper insulation the whole arrangement is usually surrounded by heavy duty plastic, a bitumen case or hard rubber casing. This produces a greater capacity due to its compact nature The alkaline batteries used on board a ship consist of a positive plate made of Nickel Hydroxide and a negative plate made of cadmium and iron. These are the electrodes. The two electrodes are immersed in an electrolyte; potassium hydroxide solution. These batteries consist of 5 cells which produce a total of 7 volts since each cell produces a voltage of about 1.4 volts. The currently used alkaline batteries consist of cells which are arranged in series and mounted in hardwood crates but with spaces in between the cells. There are made of several plates which are interleaved for purposes of producing higher capacity. The choice of the battery to be used is dependent on the advantages and disadvantages of each of the batteries. For the case of the lead acid accumulators, they require few cells to reach a particular voltage and they are reasonably cheap. However its life span is limited and it requires regular attention and charging to keep it going since it discharges on an open circuit. Additionally to get uninterrupted and smooth flow, it should always be fully charged and it becomes useless in left discharged for any period of time. Alkaline batteries on the other hand retain charge for open circuits and rarely get affected if kept for long periods if it’s discharged. Additionally it retains its charge fully in an open circuit. They require less attention and can stay for hours without continuous charging. However they are comparatively expensive and a greater number of cells are needed to produce a particular voltage since they have a smaller nominal valve per cell. Despite the differences the two types of batteries are widely used from the same basic function though Lead acid accumulators are preferred due to cost implications and discharge capacities. All the batteries that are used on the onboard in ships should be effectively maintained in order to prevent various kinds of problems which include leakage. The maintenance of batteries is very important task on a ship and should be carried out in a diligent manner. All the batteries should be maintained in a fully charged condition. The maintenance of the battery depends on the type and capacity of the battery. On discharge the battery is recharged by providing electrical power according to the capacity of the battery. During the charging process, some energy is lost due to battery heating and therefore extra energy is provided to fully re-charge the battery. This can be prevented by charging with low current value. The three main types of charging methods are; constant current in which a series resistance is reduced. This increases the charging voltage, constant voltage in which there is a high value of current being provided and it reduces gradually as the battery charges and the initial current is prevented from getting too high by the resistance of the circuit and the lately the trickle charging method in which a low current value is usually passed through the battery continuously to keep the battery at the peak condition and fully charged. The conditions of the batteries are measured using basing on two parameters; the voltage and the specific gravity. The instrument used to measure specific gravity is the hydrometer and the voltage is measured used a voltage meter. To measure charge using a hydrometer an electrolyte from each cell is taken and placed in the glass tubing found in hydrometers and the specific gravity is taken. The cells should have the same charge and the specific gravity reading must be corrected for the temperature of the electrolyte. The specific gravity is related to the charge of the battery. For the case of lead acid accumulators the specific gravity is 1.280 for a fully charged one at 150C and its 1.120 if it’s fully discharged therefore a narrow range between the two spectra. The voltage of the batteries must also be checked and in most cases the battery should show a voltage slightly higher than the rated voltage. In the case of lead acid accumulators a fully charged one has a voltage of approximately 12.60V. On the other hand any discharging value should be approximately less than the rated voltage of 12.0V. Both the specific gravity and voltage are not done in isolation and are usually checked and compared with the standard value provided by the manufacturer. In addition to checking the charge which is a major maintenance procedure; there are other maintenance practices which include; the battery should be kept clean and dry, the electrolyte levels in batteries should be kept just above the top of the plate, distilled water should be added in case there is reduction in level of the electrolyte due to evaporation or chemical reactions. The inner part of the battery should always remain clean and there should be no dirt deposits on the battery casing like electrolytes since this spilled electrolytes lead to corrosion and random battery discharge due to flowing of stray currents. Additionally the battery terminals should be kept clean and petroleum jelly applied. Clearing off the small vents in the caps of the cells should be done and the voltage of the cells taken during discharging at regular intervals of time. The specific gravity should remain between a range of 1.280 and 1.225 and not to be allowed because the plates start getting destroyed by saltation. These practices are recommended for the systems in any cruise ships ranging from few hundred kilowatts to several megawatts provided the systems are regulated as per the National Fire Protection Association. Generally there should be visual inspection of the areas around the batteries to ensure that they are kept debris free and there is enough ventilation during operations. In the case of extreme changes in environmental conditions for example extreme temperatures exposure, salt water exposure, and excessive exposure to various debris for example dust or sand frequent inspections must be done. This maintenance programs are in accordance to the manufacturers’ manual. A maintenance log should be kept and a record of all maintenance programs and tests should be made to allow for future maintenance plans. Well maintained logs and records are also important for warranty and insurance purposes. A simple checklist for monthly maintenance can be illustrated as; Procedure Repairs (if necessary) Pass / fail test Date of inspection Battery electrolyte level correct Pass 08/05/2015 Battery terminals Apply jelly Fail 08/05/2015 Cell caps Clean Pass 08/05/2015 Lead Acid Accumulators Alkaline batteries Examples of manual There are safety considerations associated with the systems and this are covered as part of the rules and regulations governing emergency battery systems. These regulations are in accordance to International Safety Management code for safe management and operation of ships and pollution prevention (ISM), Marine Pollution (MARPOL) and Safety of life at Sea (SOLAS) All the battery systems are certified and tested in accordance with the approved test performance at the manufacturer. The designs of the battery and the system shall not render any main functions unavailable for more than the stipulated period of time. An operation manual for the battery system should be kept on board in several areas and it should include the various components recorded before the ship leaves the port, that is; The charging procedure, normal and emergency operational procedures and the battery discharge and deterioration rates. The maintenance schedule and logs should be made available The battery spaces arrangement must be in a way that in case there is hazardous situation that may be caused by a breakdown of these batteries for example gassing fire or explosion cannot lead to loss of propulsion of the ship or auxiliary power for essential or important users and that the safety of everyone on board is ensured. The safety assessment should take into account other external hazards such as water ingress. If the battery is the main source of power it shall be located in the machinery space and it shall follow modifications in parallel strings with separate short circuit protection. The battery system must be installed in environmentally controlled space unless it’s designed from environmental conditions All battery casings shall be made of flame resistant material and a test program for functional and safety tests shall be submitted before testing. In the case the government of the flag state has not authorized issuance of SOLAS certificates of safety on their behalf, the SOLAS will only require written confirmation of the same and that a copy will be submitted. However the ship will be assigned as main class ships. In the event that the Government of the flag state give authority SOLAS gives certification in accordance to SOLAS Chapter II-2 Additionally any abnormality in the system shall initiate an alarm in the main vessel alarm system targeting individual response and/or group response. The abnormality shall include failure, high cell temperature, battery breakers tripping and high battery space ambient temperature. Protective safety functions with regards to emergency shutdown of the system shall give alarm and arrangement of battery system shut down. Reference Downward J.M: Managing ships: Ship Management Series; Miami, Fairplay Publications Read More