List of Important and Not-So-Famous Tanks on a Ship

Fuel oil, diesel oil, and lubricating oil tanks are the names of tanks everyone is aware of. But there are several tanks apart from them which also play an important part in the overall working of the ship. Moreover, there are also tanks of which many people are not aware of. In this article we will have a look at some important and some not-so-famous tanks present on the ship.

Hydraulic Oil Tanks

Hydraulic oil tanks for valves

Separate tanks are used to store oil which is used for different valves on the ship. Valves such as ballast valves, fuel valves etc. are remotely operated by hydraulic oil.

Hydraulic oil tanks for Winches

Tanks for hydraulic oil are located outside the engine room to store winches oil.

Hydraulic oil tanks for Steering gear

Steering gear hydraulic oil tank is normally located in the steering room and is used as a storage tank to receive bulk oil.

Water tanks

Fresh water tanks

Fresh water tanks present onboard may be two or more in numbers, depending upon the size of vessel. They are used to store sanitary water for accommodation, engine room and deck use.

Drinking water tank

A separate drinking water tank may be present to store drinkable water received from shore or to store water produced by fresh water generator (F.W.G).

Distilled Feed water tank

A ship’s boiler needs distilled water to produce steam, and therefore water from fresh water generator (F.W.G) is stored in distilled water tank.

Boiler feed water tank

The boiler feed water system consist of a separate tank which receives water from distilled water tank.

Cascade tank

Cascade tank, also known as hot well, is a part of boiler feed water system. Water is pumped into the cascade tank from the feed water tank. The boiler water is treated in the cascade tank and the return from the steam heating system is also connected to the hot well.

Ballast water tanks

Ballast water tanks are present all over the ship for ballasting and de-ballasting purpose for stabilizing the ship and for acquiring correct draught for port and canal crossing etc. Double bottom tanks are generally located outside the engine room.

Stern tube cooling water tank

This tank is located around the stern tube of the propeller and acts as a cooling media for the same. It can be used as a fresh water water tank of the ship.

Slop tanks

Slop tank in tanker

Slop tanks are present onboard tanker to store oily water mixture from cargo tank washing. The number of slop tanks depends on the Dead weight Tonnage (DWT) of the vessel.

Sludge tank

Located in engine room, this tank is used to store sludge produced after treating fuel or lube oil through purifiers.

Bilge tank

The water and oil leakage in the engine room is collected in bilge wells and this oily water mixture is then transferred to primary bilge tank or bilge holding tank, where the mixture is settled down and then is transferred to secondary bilge tank.

The oily water separator is supplied through secondary or separated bilge tank and a shore connection is also connected to this tank to dispose off all the collected bilge to shore.

Scavenge drain tank

The sludge produced by the main engine in the scavenge area is collected in the small capacity scavenge drain tank.

Oily Water Separator (O.W.S) Sludge tank

When oily water separator operates, it separates oil from water and that oil is collected and discharged into a separate tank known as O.W.S sludge tank.

Other Not-So-Famous yet Important Tanks

Drain tank

The drain tank is located in the engine room. All drip trays and other drains are connected to this tank.

Leak off tank

This is a small tank separately fitted in the main engine and all auxiliary engines to detect any fuel leakage. The tank consists of an orifice and a float. If the leak is very small, it will pass through the orifice; but if leakage increases, the oil will not be able to pass through the orifice and tank level would increase, rising the float and thus giving an alarm.

Stuffing Box Tank

The main engine stuffing box scraps the impure lubricating oil, which is collected in a separate tank known as stuffing box tank.

Stern tube gravity tank

The stern tube system oil is circulated in the system by means of two tanks, lower gravity and upper gravity tanks.

Waste oil tank

The waste oil tank is a separate tank used to collect waste and impure oil produced onboard ship.

Soot collecting tank

When the economiser tube washing is done, the soot water is collected in a soot collecting tank.

Sewage holding tank

The sewage produced from the onboard crew is collected in a common tank known as sewage collecting tank. The sewage plant takes intake from the sewage holding tank.

Expansion tanks

The jacket water system of main engine, auxiliary engine and some times main air compressor are provided with individual expansion to provide provision to compensate change in volume and maintaining positive pressure.

Jacket water drain tank

When any maintenance is to be done on the main engine, the jacket water is drained and collected into the jacket water drain tank.

Rocker arm tank

Many diesel generators are provided with separate rocker arm lubricating oil tank to avoid contamination.

Sourced by : http://www.ekomeri.com/

The post List of Important and Not-So-Famous Tanks on a Ship appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2ifhda1
via IFTTT

Fresh water Generator on Ships_2

Plate Type Fresh Water Generator

Working principle of plate type fresh water generator is same as that of submerged tube type. Only difference is the type of heat exchangers used. Here plate type heat exchangers are used for condenser and evaporator unit. Heat from the diesel engine cooling water is used to evaporate a small fraction of the seawater feed in the plate type freshwater generator or evaporator. Unevaporated water is discharged as brine (by combined air /brine ejector). The evaporated water passes through the demister to the plate type vapour condenser. Here, after condensation it is discharged to fresh water storage tank by fresh water distillate pump. During entire operation the feed rate to the evaporator is fixed by the orifice plate at the feed inlet to evaporator. A typical plate type freshwater generator line diagram is shown below.

In the event of salinity of fresh water exceeding a predetermined value (maximum usually 10 ppm) the solenoid controlled dump valve diverts the flow back to the shell. This prevent contamination of the made water. Excess salinity could be used by many factors include leakage of seawater at condenser or priming of evaporator or malfunctioning of demister, or many other reasons.

What cannot be condensed at the condenser are called ‘incondensable gases’ like air and these gases are continuously ejected out by air/brine ejector. This way the shell of fresh water generator is maintained at high vacuum, a must requirement to boil water at low temperatures.

Materials of Construction for Fresh Water Generator

The shell is usually fabricated steel (or non-ferrous metal like cupro-nickels) which has been shot blasted then coated with some form of protective. One type of coating is sheet rubber which is rolled and bonded to the plate then hardened afterwards by heat treatment. The important points about protective coatings are:

They must be inert and prevent corrosion. They must resist the effect of acid cleaning and water treatment chemicals They must have a good bond with the metal

Heat exchangers use aluminium brass tubes and muntz netal tube plate in the case of tube type fresh water generator. For plate type, titanium plates are used for condenser and evaporator. Demister is made of layered knitted wire of monel metal.

Operation

Extreme care must be taken during the operation of fresh water generator onboard ships. Operate all the valves gradually. Sudden opening and closing of valves may result in thermal shock to the main engine. Also make sure that distillate pump never runs dry.

Fresh water Generator Starting Procedure  Make sure seawater ejector pump suction, discharge and overboard valves are open. Start the ejector pump. Seawater pressure at the air ejector must be 3 bar or more. Wait for vacuum to build up inside fresh water generator shell. (About 92 % vacuum). Open the feed water valve to feed seawater to the evaporator. Adjust the feed water pressure. Normally marking is provided on the pressure gauge for desired feed water pressure. Open main engine jacket cooling water inlet and outlet to the evaporator gradually. Open the air vent clock at the top of the evaporator to make sure the evaporator is filled with jacket cooling water. Air must be purged out if any. Switch on the salinity alarm panel for measuring purity of the freshwater produced. There will be a sight glass provided at the suction line for the distillate pump. Make sure condensed water is coming to the suction line. Now start the distillate pump and open discharge valve to lead generated water to specified storage tanks. Do checks While Running Fresh water Generator Through the sight glass provided in the evaporator shell, observe flashing of water. Also check for the brine level inside. It should not be too high or too low. Shell temperature must be around 50 deg cel. Make sure shell vacuum is more than 90% from the vacuum gauge. Check seawater inlet and outlet temperature to the condenser. Ensure seawater pressure at air ejector inlet more than 3 bars. Check for distillate pump pressure and water flow meter. Check salinity of fresh water produced. Check level and flow of dosing chemical. Check ampere of ejector pump and distillate pump motor. Regulating the Capacity of Fresh water Generator

Capacity of a fresh water generator means the quantity of fresh water produced by it per day. The capacity of fresh water generator can be varied by reducing or increasing the amount of jacket cooling water to the evaporator. The quantity of jacket cooling water to the evaporator can be adjusted by adjusting the bypass valve provided. When the temperature of jacket cooling water is comparatively low, the quantity to the evaporator to be increased a bit. At the same time cooling seawater pressure to the condenser also to be regulated accordingly.

During very low seawater temperatures, evaporation temperature can falls to a lower value. In that case, adjust vacuum adjusting valve to control vacuum inside the shell. Cooling seawater quantity to the condenser also can be reduced to increase the evaporator temperature. During high seawater temperatures, evaporation temperature can go up. In that case, increase the quantity of seawater to the condenser for reducing evaporation temperature.

Too high evaporation temperature causes scale formation in the heat exchanger. On the other hand, too low evaporation temperature results in seawater carry over which increases salinity of fresh water produced.

The distillate pump discharge to be throttled so that pump should not run dry. The rate of distillate pump discharge and rate fresh water produced in the condenser should match. When distillate pump is not able to extract the freshwater at the rate of production, level of freshwater increases in the condenser and effective cooling area of the condenser reduces. This finally results in reduced evaporation quantity.

Fresh water Generator Stopping Procedure

When ship approaches port, shallow water, etc. it is desirable to stop the fresh water generator. This is because the seawater may contain harmful bacteria which can enter the freshwater produced. Operation of freshwater should be carried out in consultation with bridge watch keeper. Following procedure may be adopted for stopping fresh water generator.

Slowly open bypass valve for main engine jacket cooling water. Ensure that main engine jacket cooling water temperature is within normal limits. Close jacket cooling water inlet and outlet valves for the freshwater generator respectively. Close the feed water chemical dosing valve. Stop the distillate pump and shut discharge valve. Switch off salinity meter. Close filling valve to freshwater tanks. Wait for evaporator shell temperature to drop below 50 deg cel. Close the feed water valve to evaporator. Stop ejector pump. Shut fresh water generator overboard valve. Open the vacuum breaker valve to make shell side pressure equal to atmospheric pressure. Open the drain valve of the evaporator to drain all the seawater from the fresh water generator. Precautions for Operation of Fresh water Generator Seawater pressure at the inlet of air ejector must be 3 bar or more. The pressure at ejector outlet should not exceed 0.8 bar. Never start fresh water generator distillate pump in dry condition. Operate jacket cooling water valves to the fresh water generator gradually to avoid thermal shock to the main engine. Feed water to be supplied for a few minutes to cool down the evaporator before stopping. Never open the drain valve of evaporator before opening vacuum breaker. Otherwise atmospheric pressure causes seawater inside to hit the deflector.

Sourced by : http://www.ekomeri.com/

The post Fresh water Generator on Ships_2 appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2hLH1d3
via IFTTT

Fresh water Generator on Ships

Fresh water production from sea water for domestic and auxiliary purposes is an essential requirement aboard ships. A considerable amount of fresh water is consumed in a ship. The crew consumes an average 100 liter/head/day. In a steam ship (a ship whose main propulsion unit is steam turbine or a ship which is a large tanker having steam turbine driven cargo oil pumps) the consumption for the boiler can be as high as 30 tonnes/day.

Sufficient potable water may be taken on in port to meet crew and passenger requirement. But the quality of this water will be too poor for use in water tube boilers and for filling expansion tanks. It is common practice to take on only a minimum supply of potable water and make up the rest by distillation of sea water. The stowage space that would have been used for fresh water can hence be utilized for fuel or extra space made available for cargo when fresh water generator is installed on a ship. It is statutory requirement to have a distillation plant for emergency use if otherwise ship has carried sufficient potable water. The equipment used on board for the production of freshwater from seawater is known as fresh water generator.

Various types of fresh water generators used on board ships are mainly:

Submerged tube type fresh water generator Plate type fresh water generator, and Reverse osmosis plant

What ever type of plant is used, essential requirement of any fresh water generator is that it should produce fresh water as economically as possible.

Submerged Tube Type Fresh Water Generator

The shell and tube freshwater generator consist of heat exchanger, separator shell and condenser. In addition to this water ejector, ejector pump, distillate pump, salinity indicator, demister or mesh separator, solenoid valve and water flow meter are also fitted as accessories.

Fresh Water Generator Working Principle

Basic principle of all low pressure freshwater generator is that, boiling point of water can be reduced by reducing the pressure of the atmosphere surrounding it. By maintaining a low pressure, water can be boiled at low temperatures say 50 degree Celsius. The source of heat for the fresh water generator could be waste heat rejected by main engine jacket cooling water.

Hence using energy from a heating coil, and by reducing pressure in the evaporator shell, boiling can takes place at about 40 to 60 degree Celsius. This type of single effect plant is designed to give better economy than obsolete Boiling Evaporators.

The submerged tube type fresh water generator explained below uses the heat from main engine jacket cooling water to produce drinkable water by evaporating seawater due to the high vacuum, which enables the feed water to evaporate at a comparative low temperature. Steam can also be used as a heat source instead of main engine jacket cooling water.

This type of fresh water generator is based on two sets of shell and tube heat exchangers, one acting as evaporator or heater and other as condenser.

The combined air/brine ejector creates evaporator chamber vacuum condition by driving sea water pass through air/brine ejector, and sea water supplied by the ejector pump to be delivered to ejector for taking out the brine (concentrated seawater) and air. A simple fresh water generator diagram is shown below.

While entering to the evaporator chamber temperature of feed water will be around 50 degree Celsius. Feed water supply rate to the evaporator is fixed by an orifice fitted at the feed inlet. Because of the vacuum condition inside evaporator feed water evaporates at this temperature. The water spray and droplets are partly removed from the vapour by the deflector mounted on top of the evaporator and partly by a build in demister. The separated water droplets fall back into the brine, which is extracted by the water ejector.

The desalted vapour, which passes through the demister, will come in contact with the condenser, where it will be condensed by means of incoming cold seawater.

The distilled water is then taken out by integral freshwater pump (distillate pump) and controlled by salinometer and solenoid valve. If the salt content of produced water is high, solenoid valve diverts the freshwater to the shell side of freshwater generator, and issues an alarm signal. In order to get better suction head, distillate pump is placed at the lowest possible location in the fresh water generator plant. This is because the fresh water generator shell is at a lower pressure. Distillate pump get maximum net positive suction head with the height of liquid column in the suction line.

Thermometers are installed for control of seawater to the condenser and jacket cooling water to the evaporator. These thermometers permit control of both heating and cooling of these units. The salinometer or salinity indicator is connected to remote alarm so that very high salinity is immediately registered at the engine control room of the ship.

A detailed line diagram of a tube type fresh water generator on board ship is shown below. Click on the diagram to enlarge.

Sourced by : http://www.ekomeri.com/

The post Fresh water Generator on Ships appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2gHWlnB
via IFTTT

How to Choose the Best Boiler Feed Water Treatment Technologies for Your Plant

When it comes to choosing technology for boiler feed water treatment, knowing the feed water source quality in relation to the water quality required for your specific boiler is essential, as inadequate water treatment can lead to the scaling, corrosion, and fouling of the boiler and downstream equipment. We’ve mentioned this before in some of our previous boiler feed water treatment articles, but this bears repeating as some of these issues, if neglected, can be pretty serious.

Although the water quality and makeup quantity is a complex calculation that needs to be analyzed by a boiler feed water treatment expert, there are some common characteristics for boilers and their recommended feed water treatments that can indicate different technologies that might be useful in your system.

Here’s how to be sure you choose the best boiler feed water treatment technologies for your plant:

Know the quality of water feeding your boiler

Since water absorbs more heat than any other inorganic substance, it is often used to create energy. However, when water is being used in a boiler to create a large amount energy in the form of steam, any impurities in the water can be a detriment to the boiler itself and equipment down the line. For this reason, it’s essential to know the impurities present in the water and treat them accordingly.

Boiler feed water is a combination of the boiler makeup water (what is required to replace any lost water in the boiler due to evaporation or water loss in blowdown and processing steam) and condensate return water (the distilled water created when the boiler is producing steam that condensates on the internal areas of the boiler):

Boiler makeup water

Depending on how often your boiler is blown down (rid of any impurities that occur as a result of the steam-making process) or how much water is lost to evaporation and steam generation, the quantity of makeup water needed to replenish this loss might fluctuate.

Pretreatment of makeup water is important, though, especially in the case of higher-pressure boilers that require extremely pure water.

Choosing your boiler makeup water source critical in determining the treatment options that will go into the makeup of your system. These sources might include city water, city-treated effluent, in-plant wastewater recycle (cooling tower blowdown recycle), well water, or any other surface water source.

Some common impurities include:

Iron Copper Silica Calcium Magnesium Aluminum Hardness Dissolved gasses Total dissolved solids Suspended solids and organic material

The presence of these contaminants can cause a scale to form inside the boiler pipes and parts. This is a hard deposit that can decrease the efficiency of the boiler, promote local overheating, and be extremely damaging to the system. Others promote corrosion, fouling, and loss of steam purity and need to be removed to maintain the integrity of the system.

Some common treatments to remove these types of contaminants include:

Coagulation/chemical precipitation filtration and ultrafiltration deaeration/degasification ion exchange/softening membrane processes such as reverse osmosis and nanofiltration

So, again, depending on the impurities present in your water, any combination of these treatments might best suit your facility and makeup your treatment system.

Condensate return water

When steam is produced inside the boiler, the water particles collect and condense, then are recycled and used as part of the boiler feed water again. Technically, the condensate that the steam-making process produces is distilled, pure water, but dissolved gases such as oxygen and carbon dioxide are sometimes present. The chemical reactions due to the presence of these dissolved gases can cause severe corrosion on boiler pipes and parts.

The gases are typically removed with deminerization, advanced deaeration devices, or chemical scavengers, so if you have these present, chances are your boiler feed water system will incorporate some form of these technologies.

Know the quality of water needed for your boiler

The quality of feed water needed for your individual boiler depends on many factors, but the primary element to consider is the pressure at which you need to run your boiler in relation to the amount of water you need to process per day and how fast (this is your required peak gallons per minute, or GPM). For certain pressures, there is a maximum level of contaminants to you can feed into the boiler, and as you increase the pressure in your boiler, it becomes more critical for thorough water treatment that yields higher quality water.

Low-pressure boilers (600 PSI and lower) and water with a low amount of total dissolved solids. Typically the technology used for lower-pressure boilers includes simple filtration to make sure no dirt gets into the boiler and a water softener to take out the hardness. As the water chemistry might dictate, or as the pressure increases, you might use a water softener in addition to a dealkalizer for a lower alkalinity feed. High-pressure boilers (600 PSI and higher). Treating your feed water for a higher-pressure boiler usually requires some type of demineralization, ion exchange, or electrodeionization (EDI) polishing. Resin-based sandwich or mixed-bed polishing devices can also be used, and these technologies can be permanent (regenerable in place) or portable (requiring an exchange service from an outside provider). Reverse Osmosis is a very popular technology for power plants when used in combination with a polishing technology. They are typically used on high-pressure boilers in power plants or refineries where extremely high purity water is desired.

Also note that boiler/turbine manufacturers each have their own requirements for water quality, so be sure to check with your manufacturer what their recommendations are.

Sourced by : http://www.ekomeri.com/

The post How to Choose the Best Boiler Feed Water Treatment Technologies for Your Plant appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2fOn2pt
via IFTTT

2 Important Drains in the Ship’s Engine Room

There are several drains provided in the ship’s engine room in order to prevent water clogging and damage to any machinery. Though all these are equally important, there are few that require regular attention.

Two most important drains in engine room are:

The Air bottle moisture drains and Water Drains from fuel oil settling and service tanks

Most of you would know this for sure, but the fact remains that several mishaps happen due to improper handling and infrequent draining of these tanks. Mentioned below are two instances which explain the importance of these drains in ship’s operations.

Lesson 1

On one of our previous ships, we had an anchorage of 24 days and in this period everyone in the engine room forgot to drain the water from Fuel Oil settling and service tanks in the ship’s engine room.

We then suddenly received orders to move the ship. After a few hours, the engine slowed down and an overload alarm appeared on the engine control room panel.

We immediately tried to find out the reasons for the overload alarm and realized that the viscometer was showing “high viscosity” level. After some brain-storming, it was decided to check the service tank drains.

The junior engineer, who was assigned the task of checking the drains, came back saying that oil and not water was coming from the drains. However, when asked to drain more, a large amount of water discharge was found.

Luckily the generators were on Diesel oil (D.O) which helped prevent the blackout on the ship. Moreover, we had two settling tanks, so removal of water was much faster, but we missed the convoy at Suez as the engine RPM did not increase until “good quality” oil came in the line and the viscosity reached near normal.

Lessons Learnt:

We should have drained the tanks every day until we saw (Collecting the drain in suitable container- half cut soft drink can) no water coming. In our case, the drain pipe end was ending too deep in the funnel so the contents could not actually be seen. It is thus extremely important that what is coming out of the drain is clearly seen.

In dry dock, while cleaning Fuel Oil service tanks, a senior engineer must carefully check the drain from both inside and outside. The steam heating coils must also be pressure tested at this occasion.

Lesson 2

Air bottles are important for supplying air to the marine engine air starting system and for other important purposes. On a new ship, it was found that we were draining water not from the Air bottle bottom drain but from a drain on the filling line.

Below the filling line drain, a funnel was installed which was quite familiar to the air bottle drain funnel. The motorman was so sure about the drain that no senior officer bothered to cross check. Then, one day we got a doubt about the quantity of water draining from the funnel, which was of course not of the quality we expected.

Upon opening the air bottle manhole door it was found that the water was filled up to quite a high level and luckily it did not find its way into the main engine, else there could have been a massive damage to the engine or even injury due to water hammer. The Air bottle was then cleaned and the defect was rectified.

Lessons Learnt

Nowadays, it is often seen that the tracing of pipelines in ship engine room is not done properly, mainly because of shortage of crew members and fast turnarounds. Efforts should thus be made to trace the pipelines once in a while.

While opening air to main engine, moisture must be drained from the bottom most point of the line. Air driers and control air line filters must also be regularly checked.

These days quarantine inspection has also become important. The cold room holding provisions thus must be kept clean. Meat room and fish room drains should be checked (put a handful of salt in them), along with the unit cooler pan heater and drain.

Sourced by : http://www.ekomeri.com/

The post 2 Important Drains in the Ship’s Engine Room appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2f0LEzQ
via IFTTT

Procedure for Starting and Stopping of Sewage Treatment Plant on a Ship

Any machine on the ship requires a proper procedure to be followed for starting and stopping it. Failure to follow this step-by-step procedure will lead to either failure in starting or stopping the machine or lead to some fault.  

Sewage treatment plant is one such equipment on the ship which requires a step-by-step procedure to be followed for starting and stopping it. In this article we will go through the procedure of starting and stopping a sewage treatment plant.

Starting of a Sewage Plant

Sewage plant is generally running all the time during sailing, but it might need to be started when the ship is installed with a new sewage treat plant which needs to be stopped at regular interval of time for improving its performance and maintenance procedures. Below are the points that need to be followed for starting a sewage treatment plant.

1. Make sure if any maintenance is carried out on the sewage treatment system, all the openings have been closed properly before starting.

2. The sewage plant is be filled with fresh water inside the chamber.

3. At this stage, there are no aerobic bacteria inside the chamber, but the sewage has started coming to the plant. Thus, in order to increase efficiency and starting rate of the plant bio pac is added to the plant by flushing the amount specified in the manual.  This bio pac is mixed with warm water which helps in growth of these bacteria and also efficient functioning of the plant.

4. If the bio pac is not added, the plant might take up to 5 to 7 days to be completely functional. However, with the bio pac it becomes functional within 24 hours.

5. Start the air compressor or open the air valve as per the design of the plant. The pressure is maintained as per the manual. Generally 0.3-0.4 bars.

6. Open the sewage overboard valve and close holding tank valve when the ship is out of restricted waters.

7. The plant is continuously monitored and checked for the flow through the transparent plastic tubes.

8. The sample is taken for checking for suspended solids and chlorine content.

Stopping of the plant

Stopping of the sewage treatment plant is generally done either before entering the dry dock or in case some maintenance has to be carried out inside the treatment plant.

1. For stopping the system, close the inlet valve to the sewage plant and close the overboard valve and let the sewage go overboard.

2. Empty all the three chambers of the plant i.e. aeration, settling and chlorination chambers. If the chambers are not emptied, it will lead to growth of anaerobic bacteria which forms the toxic H2S gas.

3. If entry has to be made inside the tank, the later should be checked for hydrogen sulphide gas H2S with the help of dragor tube by taking a continuous sample from the plant. Entry is made with the help of mask and rubber gloves should be put on.

4. In case the ship is going to dry dock the overboard should be connected to shore reception facilities.

Sourced by ekomeri.com

The post Procedure for Starting and Stopping of Sewage Treatment Plant on a Ship appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://hosent.co.kr/news/procedure-for-starting-and-stopping-of-sewage-treatment-plant-on-a-ship/
via IFTTT

Maintenance and Checks for Sewage Treatment Plant on Ship

An efficient running of a sewage treatment plant on a ship requires periodic maintenance and daily checks of the system. Failure to do so can lead to an output that cannot be discharged into the sea, blockage of pipelines, and even failure of some parts.

There are several factors that results in smooth working of a sewage treatment plant on a ship and this article enumerates all the maintenance and checks for that smooth running.

Routine Checks

1. During daily rounds the pressure of the system should be checked and should be within the limits.

2. The air lift return should be checked to make sure the system is working properly. This is usually checked by the flow through the clear plastic pipe present on the installation. A clear sludge can be seen flowing through the tubes back to the aeration chamber.

3. Over a period of time, the sludge content in the aeration tank due to the recycling of the sludge from settling tank and fresh sewage increases. This sludge content or suspended solid particle is measured in mg/liter. The method of checking it is to take sample in a conical flask provided by the manufacturer and filling it up to 1000ml mark. The sample is then allowed to be settled and reading of sludge content is checked.

 

The sludge content should not be above the 200 mark, but if it is above the 200 mark, the tank has to be emptied for increasing the performance. In some ships this is checked by filtering the sample through a pre-weighed pad which is dried and re-weighed. This also depends from manufacturer to manufacturer, but is done every week.

4. Also the bio-pac is added every week to the plant to increase efficiency. The bio-pac contains aerobic bacteria which get activated when mixed with hot water.

5. The chlorination of the sample should be between 1-5 ppm and accordingly the dosing has to be increased or decreased.

6. The level of biological oxygen demand (BOD) is also checked and it should not be above 50 mg/liter. The sample is checked by incubating the sample at 20 degrees and well oxygenating the same. The amount of oxygen absorbed over a period of five days is measured. This is done to check the oxygen required for full breakdown of sewage after it has been treated by aerobic bacteria.

7. The internal coating of the sewage treatment plant should be checked for cracking and blistering. If any kind of damage is found then we first need to empty the tanks and then necessary repairs to be performed. Special precautions should be taken before entering the tank as it may contain toxic gases that cause suffocation. The gases should be checked by dragor tube, a special tube in which samples of various gases are taken before entering.

When it is made sure of the absence of toxic gases, entry is made with the mask and gloves. After completion of work the area has to be disinfected. Later, hands should be properly scrubbed and overalls be thoroughly washed.

8. If the sewage treatment plant is fitted with UV disinfectant system instead of the chlorination system, the UV lamp has to be changed as recommended by the manufacturer.

9. High and low level limit switches should be checked for auto cut-in and cut-out of the discharge to over-board pump.

10. Make sure the stand-by sewage discharge pump is put on auto during the working of the sewage treatment plant.

Maintenance

In case of a blockage of the sewage line there is a connection for back flushing which uses sea water. This is to be used to unclog the sewage pipelines; however, it is to note that all valves are closed and only the necessary valves are open, for it might back flush from WC of the cabins.

Generally, stewards are instructed for using chemicals provided by various manufacturers such as Drew Marine and Unitor during washing so that no blockages of lines are caused. However, there shouldn’t be any overuse of these chemical as it would lead to killing of aerobic bacteria which will decrease the efficiency of the plant and other problems.  The amount of chemicals is to be as per manufacturer recommendation.

Reference: From marine auxiliary machinery by Mc George

Sourced by ekomeri.com

The post Maintenance and Checks for Sewage Treatment Plant on Ship appeared first on Shipbuilding Equipment and materials - HOSEUNG Ent Co., Ltd.

from WordPress http://ift.tt/2e7dYQB
via IFTTT