Advantages of screw pumps and Disadvantages of Propeller / Centrifugal Pumps

Advantages of screw pumps:

+ Slow Speed, Simple and Rugged design

Probably the main and overall advantage of a screw pump is its superb reliability. The simple design, open structure and slow rotation speed makes it a heavy duty pump with minimal wear that operates for years without trouble.

+ Pumps raw water with heavy solids and floating debris

Because of the open structure and large passage between the flights a screw pump can pump raw sewage without the need for a coarse screen before the pump. Both floating debris and heavy solids are simply lifted up. This saves considerably on equipment costs for a coarse screen or maintenance!

+ Can run without water

A screw pump can operate even when there is no water in the inlet. Therefore it is not necessary to install expensive measures (level control etc) to prevent ‘dry-running’’. The lower bearing does not need cooling.

+ No collection sump required = minimum head

A screw pump ‘scoops’ the water directly from the surface and does not need a collection sump. This keeps the pump head to a minimum.

+ Constant high efficiency with variable capacity

The efficiency-curve of a screw pump is flat on the top. Due to that efficiency characteristic, the screw pump offers even high efficiency when it works at 50% of its capacity.

+ Pump capacity is self-regulating with incoming level

When incoming water-level goes down, at dry weather flow, the screw pump ‘automatically’ pumps less water. Ergo: no control system required to adapt pump performance.

+ 'Gentle handling' of biological flock

The activated return sludge on STP’s is a delicate biological substance. Because of the low rotational speed and large opening between the flights, screw pumps do not damage this biological flock (whereas the high speed rotating centrifugal pumps will completely shred the biological flock).

+ Easy maintenance (no 'high skilled' staff required)

A screw pump requires very little maintenance. Compared to (submersed) centrifugal pumps it is next to nothing. Besides that no ‘highly skilled’ maintenance staff are required which makes this type of pump very suitable for remote locations.

+Long lifetime ( > 20-40 years)

Screw pumps with typical lifetimes of between 20-40 years are not unusual.

Disadvantages of Propeller / Centrifugal Pumps:

- High speed = increased wear

The relatively high operational speed (450 – 950 rpm) causes wear and damage in the pump housing, this is particularly so when pumping waste water containing sand and stones. This wear results in regular expensive repairs to the housings.

-Possible blockages at reduced capacities

At reduced capacities the speed in the vertical pipe reduces to such an extent that the solids fall out of suspension to the bottom of the pipe causing blockages which eventually stop the pump.

- Heavy solids cannot be pumped

Heavy solids cannot be pumped; the sump eventually fills with the solids which have to be removed by hand by maintenance staff. Alternatively a coarse screen would need to be installed which increases the total equipment costs!

- Floating debris is not pumped

Floating debris is not removed; this collects in the sump and has to be removed by hand. Moreover, at lower water levels in the sump when the spirals of the pump are not completely covered, floating (wooden) debris can enter the conical spiral causing the pump to block. Repair is difficult necessitating complete dismantling of the pump.

- Dry running is fatal

A centrifugal pump will be severely damaged when running dry; it is therefore necessary to install expensive measures (level control etc) to prevent ‘dry-running’.

- High friction losses in pipes

High speed is required in the vertical discharge pipe in order to lift the solids with the waste water, obtaining this high speed requires the use of small diameter piping. Using small diameter piping causes high friction losses in the pipe which increases energy consumption.

- Mechanical seals need regular adjustment

The mechanical seal between the pump and motor requires regular adjustment or replacement which is time consuming (isolation and wash down required) and hence expensive.

- Lifting facilities required with each maintenance

Even low capacity pumps (100 l/s) are too heavy to lift by hand, therefore every time repair is required a mobile crane must be used or permanent lifting facilities must be installed – either option being expensive.

- Higher skilled maintenance staff required

The submerged pumps and motors require higher educational skill of both operators and maintenance staff.

- Submerged motors cause more trouble than dry motors

The nature of the design requires the use of submerged motors; problems are encountered with leakage and short circuiting.

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The advantages and disadvantages of screw pumps

Advantages of screw pumps and Disadvantages of Propeller / Centrifugal Pumps
What is the difference between pumps?
How is the screw pump? Advantages of screw pump:
1. Wide range of flows and pressures
2. Wide range of liquids and viscosities
3. Built-in variable capacity
4. High speed capability for freedom of driver selection
5. Low internal velocities
6. Self-priming with good suction characteristics
7. High tolerance for entrained air and other gases
8. Minimum churning or foaming
9. Low mechanical vibration, pulsation-free flow, and quiet operation
10. Rugged, compact design - easy to install and maintain
11. High tolerance to contamination in comparison with other rotary pumps

Disadvantages of screw pump:
1. Relatively high cost because of close tolerances and running clearances 
2. Performance characteristics sensitive to viscosity change
3. High pressure capability requires long pumping elements    

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What is the difference between pumps?

Construction - Advantages and disadvantages of Globe valves

Construction - Advantages and disadvantages of Gate valves

Installation Procedures Butterfly valves???

Some note when installing and using the Butterfly valves

Hello friend! Today I would like introduce for you: " What is the difference between pumps?"

There are many different types of pumps on the market, this article will help you understand the differences between each pump type.

The type of pump you'll need will depend on your application, including:

• The type of liquid you wish to pump
• The distance you wish to move the liquid
• The volume you need to achieve over a specific time frame

But it can be difficult to know exactly which pump you should choose. There are so many designs and niches that identifying the pump which will meet these three needs can be confusing. To simplify things when trying to select your pump, there are two types of pump which work in very different ways and broadly encapsulate most pump designs.

Centrifugal Pumps

This type of pump is one of the most common in use today. Like other pump designs, it uses an impeller, which is a rotating blade to generate suction which then moves fluid through pipes. The rotating impeller creates what is known as centrifugal force, giving this pump design its name. The pump can be driven by an electric motor or engine.

Centrifugal pumps are usually used for liquids which are low in viscosity and low in solid concentration. However, there is a centrifugal slurry pump which can move liquids with a large amount of particles.  

The PIA Australian Pump Technical Handbook (2007, p.30) classifies impellers into three designs:

• Axial Flow: The axial flow impeller discharges fluid along the shaft axis. For this reason an axial flow pump is by definition not "centrifugal" in its pumping action.
• Radial Flow: The radial flow impeller discharges the fluid radially at 90° to the shaft axis. 
• Mixed Flow: The mixed flow impeller discharges fluid in a conical direction using a combined radial and axial pumping action – as suggest by the title
• Positive Displacement Pumps
• This type of pump creates an expanding cavity on the suction side of the pump and a contracting cavity on the discharge outlet. This difference creates pressure which pulls and pushes a fluid simultaneously, exerting enough force to create flow.
  Positive displacement pumps come in two designs:
  • Reciprocating: In this design, the suction is created by a piston which plunges into and pulls out of the material. Valves are used to ensure that the flow only moves in one direction. A reciprocating design therefore pulses the liquid at identical intervals
  • Rotary: A rotary design uses two gears which mesh together. The movement of the gears creates high pressure on the discharge side which creates flow
  • Due to the design, positive displacement pumps are better at handling viscous material. There are many different types of positive displacement pumps, such as:
    • Rotary lobe pump
    • Progressing cavity pump
    • Rotary gear pump
    • Piston pump
    • Diaphragm pump
    • Screw pump
    • Gear pump
    • Vane pump
    • Peristaltic hose

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How is the screw pump?

Hi friend! Today I would like introduce for you: "How is the screw pump?"

Construction - Advantages and disadvantages of Globe valves

Construction - Advantages and disadvantages of Gate valves

Installation Procedures Butterfly valves???

Some note when installing and using the Butterfly valves

A screw pump is a positive-displacement (PD) pump that use one or several screws to move fluids or solids along the screw(s) axis. In its simplest form (the Archimedes' screw pump), a single screw rotates in a cylindrical cavity, thereby moving the material along the screw's spindle. This ancient construction is still used in many low-tech applications, such as irrigation systems and in agricultural machinery for transporting grain and other solids.

Development of the screw pump has led to a variety of multiple-axis technologies where carefully crafted screws rotate in opposite directions or remains stationary within a cavity. The cavity can be profiled, thereby creating cavities where the pumped material is "trapped".

In offshore and marine installations, a three-spindle screw pump is often used to pump high-pressure viscous fluids. Three screws drive the pumped liquid forth in a closed chamber. As the screws rotate in opposite directions, the pumped liquid moves along the screws' spindles.

Three-spindle screw pumps are used for transport of viscous fluids with lubricating properties. They are suited for a variety of applications such as fuel-injection, oil burners, boosting, hydraulics, fuel, lubrication, circulating, feed and so on.

Compared to centrifugal pumps, positive-displacement pumps have several advantages. The pumped fluid is moving axially without turbulence which eliminates foaming that would otherwise occur in viscous fluids. They are also able to pump fluids of higher viscosity without losing flow rate. Also, changes in the pressure difference have little impact on PD pumps compared to centrifugal pumps.

The term ‘screw pump' is often used generically. However, this generalization can be a pitfall as it fails to recognize the different product or ‘screw' configurations, as well as the uses, advantages and design considerations for each. The design differences of each screw configuration and pump type make each suitable for different applications and handling fluids with varying characteristics.

Each ‘screw pump' operates on the same basic principle of a screw turning to isolate a volume of fluid and convey it. However, the mechanical design of each is different. The primary difference is the number of screws: one, two, three or more

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Short circuit events occur in electrical systems on ship

Advantages of screw pumps and Disadvantages of Propeller / Centrifugal Pumps
What is the difference between pumps?
How is the screw pump?
Short circuit: a type of incident in the electrical system due to the phenomenon of short-circuit between the phase is not in the normal mode.

In neutral grounded systems (or 4 wires), one phase or phase-to-ground contact (or neutral wire) is also called a short circuit.

- In neutral or earthed neutral systems through compensation equipment, the phenomenon of single-phase contact with ground is called ground contact. Ground currents are mainly due to the phase capacitance to ground.


short circuit in electrical system

Indirect short circuit: It is short-circuited through an intermediate resistor, consisting of the resistor by the electric arc and the resistance of the other elements in the path of the current from one phase to another or from phase to ground.

Electric arc resistance varies over time, which is often complicated and difficult to determine accurately. Experimental:

                                     R = 1000.lI [Ω]

         Where: I - short circuit current [A]

                                 l - electric arc length [m]

Direct Short Circuit: It is short-circuited through a very small, ignorable intermediate resistor (also known as a short circuit).

Short circuit symmetry: the short circuit still maintain the system, three-phase voltage in symmetry.

Short circuit asymmetry: short circuit makes the line system, three-phase voltage is not symmetrical.

- Horizontal non-symmetry: when the incident occurs at one point, the sum of the phases at that point is the same.

- Vertical symmetry: when the incident occurs, the total phase impedance at one point is not the same.

Complex faults are the occurrence of many asymmetric short circuit transients along the electrical system.

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How do diesel generators and gasoline generators differ?

Generators are composed of two components: the engine and the generator.
Principal of Centrifugal pumps
Operation of generators on ships
Differences Between Diesel Engines and Gasoline Engines
Advantages of screw pumps and Disadvantages of Propeller / Centrifugal Pumps
What is the difference between pumps?
How is the screw pump?

Most generators on the market today use two types of engines: diesel engines (petrol engines) and gasoline engines (gasoline engines for fuel). To understand the difference between these two generators or the differences between the two types of engines, let us highlight the following differences:
So where are gasoline engines and diesel engines different?

First of all, these two engines have in common the use of liquid fuels, are internal combustion engines and complete tasks in four periods: loading - compression - explode - discharge corresponding to two revolutions of the crankshaft engine.


The basic difference between a gasoline engine and a diesel engine lies in three characteristics: the type of fuel used, the fuel supply system and the fuel type.
Gasoline fueled gasoline engines are characterized by the octane value (anti-knock value), the higher this value, the higher the anti-knock factor.


Currently, there are four types of petrol with different octane values ​​in our country: A95 has 95 octane rating for gasoline engines with a compression ratio above 9.5: 1; The A92 has an octane rating of 92 for engines with a compression ratio of 9.5: 1; The A83 has an 83 octane rating for engines with a compression ratio of 8: 1, but this type of gas is not currently used; The last category is E5 biofuel, a mixture of 5% ethanol A95 gasoline.


Meanwhile, diesel diesel engines are characterized by cetane value (fire rating) and in the market today the commonly used type is DO 0.5% S. The different characteristics of gasoline and diesel that fuel systems of the two types of engines differ fundamentally.
The petrol engine's fuel supply system is a combustion mixture (including gasoline and air) on the intake manifold (including carburetor and electronic fuel injection). Directly to the air right in the cylinder. However, on newer generation vehicles (such as the new Ford Focus), the direct injection system (GDI) has the same basic principle as diesel engines.


At the gasoline engine, the combustion mixture is introduced into the engine to perform the compression stroke and is detonated by the spark ignition for combustion, expansion and work. Due to such characteristics, the gasoline engine has an additional ignition system. For diesel engines, after injection the fuel injected at high speed and pressure combined with the vortex chamber on the top of the piston produces the combustion mixture. The mixture is compressed with high compression ratio and self-igniting, expanding and producing.


In the same vehicle of a manufacturer, if there are two choices of gasoline and diesel engines with equivalent cylinder capacity, each has its own advantages. Gasoline engines often achieve faster turnaround times and larger capacity, thus accelerating better. On the other hand, diesel engines generally have a lower number of revolutions, with lower acceleration than gasoline engines, but with higher torque, which results in lower traction at lower rpm.
The performance of the diesel engine is about 1.5 times larger than that of a gasoline engine. Diesel fuel is generally cheaper than gasoline, 1 liter of diesel when fully burned gets about 8,55 calories while 1 liter of gasoline burns completely for about 8,140 calories. The fuel consumption of the diesel engine is 200-285g / kWh smaller than the gasoline engine's 260-380g / kWh.


However, in addition to the above advantages, diesel engines have some limitations compared to gasoline engines: If you compare two types of gasoline and diesel engines with the same capacity, the diesel engine weight is greater than the gasoline engine. The High-Diesel fuel injection material and technology require higher fuel consumption, so diesel engines are more expensive than gasoline engines; lower speed diesel engine than gasoline engine; The high noise and exhaust gas of the diesel engine contains more carbon black than the gasoline engine.


In the future, in the luxury car, the use of gasoline engine is mainly due to the superiority is the engine smooth operation, great acceleration. Research to improve fuel efficiency and efficiency on gasoline engines is increasingly being completed such as direct injection gasoline (GDI) system, multiple ignition system, intelligent air distribution mechanism. In addition, a trend is also developing quite strong is the use of hybrid engines.
Diesel engines, with their outstanding advantages, are large traction, especially engine components with longevity and durability, so diesel engines are always targeted by scientists to overcome the dangers. processing.


The main research directions for completing the diesel engine focus on increasing power, increasing the maximum number of revolutions and reducing vibration. To achieve this goal, experts put turbocharger systems in place to increase the pressure and air volume in the combustion chamber, thereby increasing the engine's capacity. On the other hand, the Common Rail (CDI) system (as on the Mercedes GLK or Mitsubishi Triton) is capable of completing the electronic injection process and increasing the injection pressure will help make the combustion process more complete.

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Differences Between Diesel Engines and Gasoline Engines

Construction - Advantages and disadvantages of Globe valves

Construction - Advantages and disadvantages of Gate valves

Installation Procedures Butterfly valves???

Some note when installing and using the Butterfly valves

What is the difference between a gasoline engine and a diesel engine? Which one is better? Why do people use diesel without using gasoline ... This problem is always used by many users to question and debate. So what's the difference between these two engines? Advantages and disadvantages of gasoline engines and Diesel how? The following article outlines the differences, advantages and disadvantages of these two types of engines to give the reader a more general look at the two types of engines.

Differences Between Diesel Engines and Gasoline Engines:
The diesel engine uses diesel fuel, no spark plugs, engine powered by the compression of fuel mixture and air in the cylinder.

Gasoline engines use fuel as fuel, resulting in the combustion of a mixture of air fuel in the cylinder thanks to spark plugs.

Advantages of Diesel Engines versus Gasoline Engines:
Advantages:

- Diesel engine performance is higher than petrol engine (1.5 times).

- Diesel oil is cheaper than gasoline.

- Diesel engine's own fuel consumption is lower than that of gasoline engine.

- Diesel oil does not burn at normal temperature so it is less dangerous.

- Due to the lack of carburetor and ignition parts, the diesel engine is less damaged.

- Diesel engines outperform better gasoline engines.

Disadvantages:

- At the same capacity, diesel engines are heavier than gasoline engines.

- The higher compression ratio of the diesel engine requires the engine parts to be good resulting in more expensive fabrication.

- The details of the fuel system in diesel engines are very high accuracy (error 1 / 100mm) as high pressure pump, injectors, so the cost of manufacturing and repair higher.

- Repair parts of the diesel fuel system must have specialized machines, expensive tools and skilled workers.

- Diesel engine speed is lower than petrol engine speed.

- Diesel engines cause more noise and "foul" than gasoline engines. (This has been overcome with many advanced technologies)

Diesel engines and gasoline engines have their own advantages and disadvantages. However, the manufacturer has applied two types of engines on the car to suit the purpose of each vehicle separately. Feeling and enjoying a smooth, petrol-like, gas-powered, or powerful, diesel-powered vehicle depends on the preferences and needs of each person. In this article, we hope people will have more knowledge about these two types of engines and easier to choose for the purpose of using their vehicles.

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Operation diesel generators on ships

Construction - Advantages and disadvantages of Globe valves

Construction - Advantages and disadvantages of Gate valves

Installation Procedures Butterfly valves???

Some note when installing and using the Butterfly valves

Hi friend! Today I would like introduce for you : "Operation of generators on ships"
Generator Engine (G / E) have the function, the task of generating electricity to supply electrical appliances on board. Speaking of light, we often think of a combination of diesel (diesel engine) hybrid generator (Alternator).

 1. Prepare to start the machine

- Check and open the DO oil valves, lubricants, water cooling properly;

- Checking the viscosity of sand oil, speed regulator, turbocharger, generator base oil ...

- Check and add to the expansion tank;

- Check the oil level, (FO) in the service tank, filter full of oil tank, water discharge, oil tank;

- Filling up the starter bottle, flushing water and wind system;

- Hand pump (or pump) about 10 minutes;

- Via machine by hand via about 8 loops;

- open-drain on the cylinder cover;

- Open the wind start, turn the engine by the wind start (tread-machine), observe when the discharge is anything unusual. If it is normal, it should be flushed;

- Start the machine at low rev. Monitoring the engine parameters, if normal, increase the rotation slowly to the revolutions;

- Wait for the exhaust gas temperature of the cylinder to stabilize (the machine for about 10 minutes), conduct electricity into the grid. Adjusting and increasing the load gradually for new machines;

- Oil FO and change to oil FO for the machine (if the equipment running FO).


   2. Monitor and care when the machine is operating

- Check the status of the machine: sound and vibration.

- Check the exhaust temperature, coolant temperature from the cylinder;

- Check the level and temperature of the exhaust gas turbine lubricant;

- Checking the temperature and pressure of the turbocharged air;

- Check the temperature, lubricant pressure (Lub.Oil), cooling water (CFW), cooling water (SW), fuel DO (FO);

- Check the load of the generator (kW) on the main electrical panel and its parameters such as voltage, frequency and current. Depending on the load of the ship, one or two generators may operate simultaneously:

- Record the parameters every 2 hours;

- Keep clean and clean outside of the machine before delivery to the next shift.

(Note: There are parameters to note, should notify the following, write on the board for everyone to know).


  Steps to turn off the lights.

- Perform oil change from FO to DO and run for about 15 minutes to fully utilize DO (if running FO);

- Reduce the load to the machine until the power meter indicator is about 5 kW, the load is completely off;

- Reduces the rotation of the machine to near the revolving revolutions;

- Run for about 10 minutes to cool down, then turn off the computer;

- open the flush-case on the cylinder;

- Turn the air blow (blow air) to scavenge the gas and blowing the soot clean the combustion chamber;

- Lubricating pump and machine via 10 rounds;

- Close the starter valves, lubricants, coolant and related valves (if needed).


     4. Synchronous 2 generators

4.1 Synchronization condition Two synchronous generators operate in parallel:

(1) The voltage of two generators must be equal (U1 = U2)

(2) The frequency (Hz) of the two transmitters must be equal (F1 = F2)

(3) The phase voltages of two generators must coincide (angle U1, U2 = 0)

(4) Correct order of phase

In practice on ships, when synchronizing two generators by hand or by automatic air conditioning must also check the above conditions. People use the method of light (off lights or rotors) or use "synchronous" combined with the "voltmeter".


4.2 Synchronized steps

- Adjust the rotation (Hz) of two machines equally

- Check the voltage of two generators equally (if deviation, must adjust)

- If automatic "automatic" only to turn on the "select" switch to the machine needs to (new) and press the "parallel" button, the system will automatically adjust and network for two machine working in parallel

- In the case of "manual" connection: After adjusting the two machines in terms of frequency and voltage, turn on the "select" switch to the air conditioner, followed by the "synchronous clock". When seeing three lights with the same brightness and needles of the "synchronous" only 12 hours then quickly shut off the two-transmitter. Then adjust the parameters of the two machines to match each other.



4.3 Disconnect one machine

When the two machines are working in parallel, to cancel the load must do the following:

- Change the oil to DO for load-breaker (if the machine runs FO).

- The transmitter's output switches off for the active machine.

- When the load of the machine is about 5 Kw off the main bridge or press the "OFF"

- Reduce the rotation of the machine to turn off and to run about 10 minutes for the machine to reduce the temperature.

- Turn off the machine completely and take the rest of the machine.

Generator Engine (G / E) are an important device on board, most of the equipment on board is powered by light sources. The fuel used for lighters is usually DO, some of which are HFOs, but when stopped, they switch to DO. For the purpose of making the Generator Engine (G / E) work safely, stably and efficiently, the operator needs to look after the equipment while the machine is operating, periodically maintenance Generator Engine (G / E) according to the manual and the manual. And it is important to start, synchronize, change oil and stop the engine according to the steps mentioned.


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101 Important Things to Check While Starting Fuel Oil Purifier on Ships???

Hi friends! Today I would like introduce for you "101 Important Things to Check While Starting Fuel Oil Purifier on Ships".

Every engine room machinery system needs systematic step-by-step starting and stopping procedures to ensure smooth running. The number of things to consider while handling ship’s machinery system, depends on aspects such as equipment type, making etc.

Starting a fuel oil purifier also involves several important steps and checks. Mentioned below are ten most important things that must be checked while starting fuel oil purifier on ships.

1. Check Oil Level in the Purifier Gear Case – Don’t forget to check the level of the oil in the purifier gear case before starting the purifier. If the oil is not up to the required level, insufficient lubrication will damage the the gears and other rotating parts (shaft, bearings etc.) in the purifier gear case. 

2. Ensure Break is in Release Position – The purifier break, which is provided near the gear at the bottom of the purifier, must be in release position. If the break is not released, the purifier will not reach its required speed and the motor current will increase. Moreover, this will also cause wear down of brakes.

3. Open Inlet and Outlet Valves – Ensure that both inlet and outlet valves of the purifier are in open position. If the discharge valve is not open, the purifier will overflow resulting in oil in the sludge side. Similarly, if the suction valve is not open, the purifier will not get the necessary oil supply.

4. Open the Tank Valves – Check the valves of the specific tank (service or settling) where the discharge from the purifier is to be sent. If the tank valve is not open, the back pressure in the line will increase leading to overflowing of the purifier.

5. Check the Level of Operating Water –  If there is a separate operating water tank provided, check the water level in the same. If the operating water is not sufficient, the purifier bowl will not lift, resulting in the sludge ports to remain in open position.

6. Check Feed Pump– Check that the purifier feed pump is running properly, along with oil pressure and temperature. Some purifiers are provided with attached gear pumps for supplying fuel to the purifier. In such cases, ensure that the oil temperature is enough to ensure smooth running of the gear pump attached (via shaft and key) . If the temperature is low, the oil viscosity will be high, which may lead to breaking of the key that connects the shaft and the gear pump, thus stopping the oil supply.

7. Ensure Heater Valves are Open – Ensure that the fuel oil valves to the steam heater are opened before opening the the steam line valve near the heater. If the steam is opened first, the tubes can get damaged, leading to ingress of water in the oil.

8. Increase the temperature  – Increase temperature of the fuel oil to the limit provided in the digital control panel of the purifier. In all automated purifiers, the control panel is provided with a pre-set minimum temperature limit. The purifier will not start until the fuel oil reaches this temperature.

9. Check for any abnormal sound or vibration– If you know your machinery extremely well, you will be able to tell if there is any abnormal vibration or sound during starting. Shut the purifier immediately in such conditions and rectify the fault completely before starting it again.

How to check? – Take a screw driver, touch the metal end to the purifier body, and the second end to your ear. You will be able to hear the smooth running of the inside parts more clearly.

10. Check Solenoid Valves – Check all solenoid valves are operating properly by checking the lights on the solenoid valves. If the lights are not working properly, take a screw driver and bring it near to the top surface of the solenoid valves. When the solenoid starts working, the screw driver will be attracted to the valve body due to magnetic effect.

If solenoid valves are not working properly, the purifier will also stop operating. For e.g. if the operating water line solenoid valve is not working properly, the bowl will not lift, or if the high pressure water line solenoid is not working, then the purifier will not de-sludge.

The Ultimate Guide to Operating Engine Room Machinery is a premium ebook which explains starting and stopping procedures of all engine room machinery and systems on ships.

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How to operation centrifugal oil purifier?

Hello friend!  Today I would like to introduce for you: "How to operation centrifugal oil purifier?".

Principal of Centrifugal pumps

Operation of generators on ships

Differences Between Diesel Engines and Gasoline Engines

We have already discussed the basic principle of operation of purifiers. Lets learn how to start and stop purifiers, and about necessary safety precautions before starting, de-sludging procedures, and emergency stopping.

• We all know that centrifuges are an important type of auxiliary equipment on board ships and that they are classified into two operating functions. One is a clarifier, which separates solids from liquids. The other type is a purifier, which separates liquids of different density. The Purifier operates on the principle of separation by centrifugal force. But in order to optimize the purification process, certain parameters should be adjusted before the purifier is started. Out of those parameters, very important parameters are:

  1. Feed inlet oil temperature
  2. Density of Oil
  3. RPM of the rotating bowl
  4. Back Pressure
  5. Throughput of oil feed

• Understanding the Parameters

  1. Feed inlet oil temperature: Before entering the purifier, the dirty oil passes through the heater. This increases the temperature, thus reducing the viscosity of the oil to be purified. The lower the viscosity, the better will be the purification.

  2. Density of Oil: As the dirty oil entering the purifier is heated to reduce the viscosity, the density also reduces. The lower the density, the better the separation.

  
  

  3. R.P.M of the rotating bowl: If the purifier has not achieved full RPM (revolutions per second), then the centrifugal force will not be sufficient enough to aid the separation.

  4. Back Pressure: The back pressure should be adjusted after the purifier is started. The back pressure varies as the temperature, density, viscosity of feed oil inlet varies. The back pressure ensures that the oil paring disc is immersed in the clean oil on the way of pumping to the clean oil tank.

  5. Throughput of oil feed: Throughput means the quantity of oil pumped into the purifier/hr. In order to optimize the purification, the throughput must be minimum.

• Pre-checks before starting a Purifier

  Before starting a Purifier, following checks are very essential:

  1. If the Purifier is started after a overhaul, then check all fittings are fiited in right manner. The bowl frame hood locked with hinges.

  2. Check the Oil level in the gear case. Ensure that it is exactly half in the sight glass. Also ensure the sight glass is in vertical position, as there is a common mistake of fixing it in horizontal position.

  3. check the direction of rotation of the seperator, by just starting and stopping the purifier motor.

  4. Check whether the brake is in released position.

• Starting the Purifier

  1. Ensure the lines are set and respective valves are open. Usually the lines are set from settling tank to service tank.

  2. Start the purifier feed pump with the 3-way re-circulation valve in a position leading to settling tank.

  3. Open the steam to the heater slightly ensuring the drains are open so that the condensate drains. close the drains once steam appears.

  4. Start the Purifier.

  5. Check for vibrations, check the gear case for noise and abnormal heating.

  6. Note the current (amps) during starting. It goes high during starting and then when the purifier bowl picks-up speed and when it reaches the rated speed, the current drawn drops to normal value.

  7. Ensure the feed inlet temperature has reached optimum temperature for separation as stated in the Bunker report and nomogram ( bunker delivery note gives the density of the fuel and using this we can get the separation temperature and gravity disc size from the nomogram)

  8. Now check whether the bowl has reached the rated speed by looking at the revolution counter. The revolution counter gives the scaled down speed of the bowl. The ratio for calculation can be obtained from the manual.

  9. Now, after the bowl reaching the rated RPM, check for the current attaining its normal value.

• De-sludge Procedure

  10. Open the bowl closing water/operating water, which closes the bowl. (Ensure sufficient water is present in the operating water tank)

  11. Now after 10 seconds, open the sealing water to the bowl.

  12. The sealing water should be kept open till the water comes out of the waste water outlet.

  13. Once the water overflows through the waste water outlet, stop the sealing water.

  14. Now open the de-sludge water/bowl opening water. (This is done to ensure the bowl has closed properly). During de-sludge we can hear a characteristic sound at the opening of the bowl.

  15. Repeat the steps 10, 11 ,12 & 13.

  16. Open the 3-way re-circulation valve such that the dirty oil feed is fed into the purifier.

  17. Wait for the back pressure to build up.

  18. Check for overflowing of dirty-oil through waste water outlet & sludge port.

  19. Now adjust the throughput to a value specified in the manual. Correspondingly adjust the back pressure, too.

  20. Now the purifier is put into operation. Change over the clean-oil filling valve to service tank.

• After-Checks and Stopping the Purifier

  Checks after starting the purifier during regular watches:

  1. Adjust the throughput, back pressure, temperature of feed inlet if necessary

  2. gear case oil level, motor amps, general leakages, vibration have to be monitored3. De-sludge every 2 hours for heavy oil purifiers & every 4 hours for lubricating oil purifiers. (Rrefer to the manual or chief engineer instructions.)

  Stopping of Purifiers:

  1. De-sludge the purifier after stopping the feed inlet.

  2. Shut down the steam inlet to the oil.

  3. Stop the purifier after filling up the bowl with water.

  4. Apply brakes and bring up the purifier to complete rest.

  5. If any emergency, the purifiers has emergency stops, on pressing it, will stop the purifiers immediately shutting off the feed.

  Thus we have seen in detail how to start the purifier after carrying out all safety checks and we have also seen how to stop it.
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