Mechanical Auxillaries

8/14/2019 Mechanical Auxillaries

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WORKING PRINCIPLES,CHARACTERISTICS AND OPERATION OF

AUXILIARY SYSTEMS.

1. UNIT AUXILIARIES:-

1.1 OIL PRESSURE UNIT:-

The oil pressure unit(OPU) stores the energy used for automatic speed regulation ofthe generating set, its automatic control during starting, varying the load(including

changeover to operation as synchronous phase modifier), and ordinary or emergency

shutdown of the set. The turbine gates are usually operated by separate OPU.

Energy is supplied to the OPU through the oil pressure in an air-oil (pressure) tank,

which is continuously maintained by pumps. The pressure tank is filled with air and

oil in a certain ratio. The oil is thus pressurized, so that energy is stored in the tank.

This pressure permits the operation of the power members of the regulation andcontrol system, such as distributor and runner servomotors, as well as the servomotors

actuating the nozzle needle in a pelton turbine and the ideal-discharge outlet, at anytime and under all operating conditions.

The quantity of air in the tank and its pressure must not decrease. However,

unavoidable leakage of air from the pressure tank necessitates periodical delivery ofair into it. This is carried out by a separate compressor or from the common air

receiver.

The duty of the OPU is to continuously restore and maintain an energy reserve in the

pressure tank through periodic topping-up with oil by means of the pumps, as well aswith air from the high-pressure main air line. The normally stored energy in thepressure tank is determined by the initial oil pressure and air volume. The working oil

pressure is 25 to 60 kg/cm2. The initial air volume is usually between 60 to 70 % of

the volume of the pressure tank.

Certain deviations from the working oil pressure and air values are permitted, in

view of the unavoidable losses of oil and air in the hydraulic and pneumatic systems.

These deviations must not affect the correct operation of the OPU. Pressuredeviations of 6 to 8 % of the nominal value are permissible; the fluctations of the

amount of air in the tank should not exceed 2% of the initial quantity.

The theoretical work capacity of the pressure tank is thus determined by two

magnitudes, viz., the working oil pressure and the design oil level. The principal

process for restoring the work capacity of the OPU is, therefore, the automatictopping-up of the pressure tank with oil and air.


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1.2WORKING OF OPU SYSTEM:-

The OPU system has been shown in the figure.

Important components as indicated in the figure are:-

1)Air-oil Tank; 2) pressure pickups;3) non return valves; 4) Oil-level indicator;

5) Oil pumps;6) level pickups; 7) Relief valve;8) leakage-oil tank;9)leakage-oil

pump; 10) electric motors.

The oil pump is switched on when the pressure in tank has dropped to a

predetermined level; it is switched off when this pressure has regained its nominalvalue. Switching on and off is performed by pressure pickups. The pump works

without interruption in case of continuous operation. Oil is delivered into the pressure

tank when the pressure in the tank has dropped below the nominal value. The bypass

valve is opened when the pressure in the air-oil tank has attained its nominal value,and the oil is returned to the sump. Delivery of air into the pressure tank may be

automatic or not, depending on the degree of automation and the power of the plantequipment.

Automatic control of the OPU, ensuring its reliable and uninterrupted operation,

consists in maintaining oil pressure and level in the pressure tank withinpredetermined limits, as well as the emitting of warning signals when operation of the

OPU is faulty.

Figure shows schematically the working of OPU. the system is equipped with two oil

pumps. One of these is normally in service, while the other acts as standby. The

motors driving the pumps are controlled by the pressure pickups 3PP to 7PP.

Under normal operating conditions the pump is switched on when pickup 3PP is

energized. This pickup is set to respond at the minimum pressure level in the tank.The pump is switched off when the pressure in tank reaches the maximum value at

which pickup 5PP responds. Pickups 3PP and 5PP are adjusted so that the pressure

drop in tank does not exceed the permissible limit, and that the pump in service is not

switched on more frequently than ever y 10 to 15 min.

The standby pump is switched on by pressure pickup 4PP when the pump in service

has failed or when very frequent regulation of the turbine is necessary. Pressurepickup 4PP is set to respond at a pressure which is 1 to 2 kg/cm below that at which

pickup 3PP responds, The standby pump is switched off by pressure pickup 5PP.

Excessive pressure rises in the OPU are prevented by relief valves which causesurplus oil to be discharged into the sump. Pressure pickup 6PP fitted to tank (1)

emits a warning signal when the pressure drops below the permissible limit. Pressure

pickup 7PP when the pressure has dropped to an emergency level at which the

generating set has to be shutdown.


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2. HP LUBRICATION SYSTEM:-

The purpose of high-pressure oil lubrication is to build up an oil film between the

thrust pads and the bearing runner when starting the machine and stopping of unit.

The oil pressure pump set shall, therefore, be switched on both during start and

retardation and shall remain in operation while the machine is revolving at low speed,

up to 30 percent of its rated speed.

The arrangement of HP lubrication system has been shown in figure. The oil pressure

system generally incorporates a multiple-stage gear pump in which the requisite oil

pressure is generated by 2 gear set operating in series. The pump unit is mounted onthe motor via flanged adapter. Oil is drawn by the pump from a filter and forced out

to the bearing. A pressure operated switch and a pressure gauge are mounted on this

pipe, the former for the purpose of blocking turbine starting circuit in case the oil

pressure should fail reach a pre-set value. A bypass valve connecting the high-pressure pipe with the oil pot allows the oil pressure to be adjusted to the desired

value.

This valve returns excess oil to the oil pot and thus also prevents excessive back

pressure when the pump is started up. A filter and a check valve are inserted in the

high-pressure pipe at a point before the distribution pipe encircling the bearing.Branch pipes and high-pressure hoses carry the oil to the bearing thrust pads and are

coupled to individual check valves screwed into the oil duct in each pad. These ducts

enter in a circular depression machined in centre of the babbitted surface of the pad.

3. BRAKING AND JACKING SYSTEM:-

3.1 BRAKES:

Brakes are installed on large hydro machines solely for two functions:

(a) On normal shut down, to bring the rotor quickly to standstill to reduce wear of the

thrust pads after lubrication ceases.

(b) In emergency to stop the machine in case of bearing failure or electrical fault that

might lead to fire.

Brakes are designed for application at 50% of rated speed but practically brakes are set

to apply when speed has fallen to 25-30% of the rated value. In emergency, brakes are

applied even at higher speeds. The brake application is carried automatically by aprogrammable control system based on feedback obtained from the speed sensor.

However, emergency braking is done manually.


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Brakes are operated by air pressure at 5 to 15 kg/cm2 which depends upon the mass

and speed of machine. The air braking purpose is kept in a common reservoir of

sufficient capacity charged by an electrically driven compressor controlled by apressure switch.

An electrically controlled valve for each machine admits air to a series of brakecylinders. The pistons lift rectangular brake shoes, retained against the peripheral drag

by links, and fitted with renewable friction blocks of bonded asbestos. On release of

brake, pistons are pulled down by springs.

The brakes bear on a polished mild-steel track mounted on the underside of the rotor

rim. Most of the heat developed passes into the track, which must be designed for a

very considerable rise of temperature in an emergency stop. Unless, in small sizes, itcan be a one-piece (floating) ring. The track consists of segments with oblique joints

and due allowance for expansion. To avoid thermal distortion, the segments are

necessarily thick, and at over speed impose a severe load on the rotor spider.

3.2 JACKS:-

The same brake mechanism is used for jacking the machine by applying large air

pressure at 100-150 Kg/cm2. Jacking has three applications:

(a) For removal of the thrust pads.(b) For the initial operation of new thrust pads, to ensure flooding of the bearing

surfaces immediately before starting,

(c) For starting the machine to create oil film over bearing surface of thrust pads in theabsence of hydro static lubrication system.

For jacking, the cylinders are filled with oil and actuated by a small motor-drivenpump. A convenient arrangement for alternative braking and jacking is to connect all

the cylinders in series as an open ring, to one end of which is connected the low-

pressure air supply, and to the other end the high-pressure oil pump, with appropriatestop-valves. The air supply can then be used to clear the system of oil when jacking is

no longer needed.

4. CENTRALIZED GREASE LUBRICATION SYSTEM(CGL SYSTEM):-

To facilitate grease lubrication of every moving part Centralized grease lubrication

system is provided. This system gives grease to all moving parts, joints & linkage forsmooth operation. Automatic centralized system of grease lubrication is meant for the

lubrication of rubbing parts of the guide apparatus (Guide vane lower, middle, and

upper bushes, regulating ring, servomotors and other). Once it is switched on, it feedsgrease to all points. Different feeders are used to distribute amount of grease to

different lubricating points. The greasing can be done even when the machine is

running. The system consists of a grease reservoir, reciprocating motor driven plunger


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type pump, a change over type distribution valve, a set of dose feeders, pressure relays,

etc. all units are interconnected.

The Centralized grease lubrication system basically comprises of a pump with

lubricant container, a pressure operated reversing valve, two main lines with branch

lines strategically placed to serve a number of metering elements, placed adjacent tobearing points and an electrical control panel.

4.1 OPERATION:-

The pump is driven by an electric motor, and delivers the lubricant from the container

to the reversing valve by pressure supply line. The reversing valve directs the lubricant

to one of the main lines, depending on the valves spool position, both main linesconstitute main alternating supply and return circuits from which branches are taken to

the metering element. These dual line elements meter the lubricant to the points of

application via feed lines of small bore tube.

The schematic diagram of typical Centralized Grease Lubrication System is shown

in the figure.

Various parts are:

1. Pump Unit,2.Pressure Relief Valve, 3. Pressure Supply Line,4. Return Line,5.Hydraulic Reversing Valve,6. Main Line No.1,7. Main Line No. 2, 8. Metering

elements,9.End of line pressure Gauge, 10. Electrical Control Panel.

5.DUST COLLECTION SYSTEM:-

With the latest design of the generator, the magnetic poles of the generator are mountedon the rotor. The excitation control sub-system i.e. excitation transformer, rectifier bridge,

excitation-current auto control panel, etc. have to be provided outside the generator.

Hence the excitation system output current is carried/ fed to the magnetic field- coilsthrough slip rings. Slip rings enable to keep on feeding the excitation-current from a

stationary part of excitation control sub-system to the moving part of magnetic-field-

coils.

During the operation as carbon brushes keep on rubbing/touching the slip rings with

certain pressure, this also result into spreading of the dust of the carbon on the slip rings

and around the slip ring area.

The dust acts as an electrical conductor and the insulation-blocks on which the slip rings

are mounted start earthing the excitation current resulting in giving alarm of the' fieldearthing. Hence the obstruction in operation is there.

During the shutdown of the generating unit, at about 20% to 25% speed of the machine,

brakes are applied till the standstill of the rotation of the machine. The braking action is


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the chances of rotor-field-earthing increases. Overall effect: reduces the life of the

insulation of winding/busbars and chances of accident due to rotor-field-earthing

increases.

5.3 GENERATOR AIR COOLERS:-

Dust layer acts as thermal insulation on the cooling fins of the generator-air-coolers and

the cooling-area-pockets are filled with the dust thereby cooling becomes inefficient.

Corrosion on the generator-air-cooling-surfaces accelerates more due to the presence ofdust & moisture.

5.3.1EFFECT:

Higher operating temperature of the generator reduces the operating life of the generator.

Overall effect, reduced life of the generator-winding/bus-bars due to inefficient cooling

and the reduced life of the generator-air-coolers.

5.4BEARING OIL-BATH:-

With the increase of the dust level in the generator cooling air circulation current, the dust

also passes in to upper guide bearing oil bath and lower guide bearing oil bath and thrust

bearing(depending on its location)- oil bath. The dust gets start dissolved in the oil bath

of the bearings. By the increased dust level in the oil, the lubricating quality is decreasedresulting into the extra rubbing of the bearing surfaces and high operating temperatures of

the bearings.

5.4.1 EFFECT:

Operating temperatures of the bearings before higher, life of the lubricating oil and life ofthe bearing pads reduced, enhanced maintenance required. Overall effect, equipments

need more maintenance and more O&M expenditure is there.

5.5 INSTRUMENTATION AND PROTECTION INSIDE THE GENERATOR

BARREL:-

The dust deposit on the probe and on the terminal blocks of the instrumentation systemsportion provided inside the generator barrel might start erratic/malfunctioning behavior

thereby, the protection and the control on the important parts of the generator may

become extremely bad. C.T. provided in the generator barrel is an example of thiscategory.

5.5.1EFFECT:

More maintenance required for the instrumentation systems. Overall effect, more O&M

expenditure and reduced productivity of the power station.


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5.6PRINCIPLE OF OPERATION OF THE DUST COLLECTOR:-

With air blow of suitable velocity the carbon dust is taken away from the place where it

is formed/released and then collected in a chamber and precipitated by various methods.

alternatively, if the air is sucked by some system, the dust particles present in the air atthe air-suction point are also driven along with the air. This air is taken to place/container

where the dust particles are settled down or precipitated. Finally the precipitated dust is

taken for disposal outside the power station, keeping ready the chamber to receive more

dust further operation of the dust collector.

-When brakes are applied, pads put pressure on the brake track.

- The rubbing of the pad-surface and the brake track surface takes place.-Dust D mostly liberated at the trailing end(with reference to the rotation

direction of annular brake track of the brake pad.- The dust collector chamber placed just next to the trailing end of the brake

pad.

- Dust collector chamber kept at negative air pressure to suck air during its

action.- The dust along with sucked air is collected in the chamber.

- Each dust collector chamber is provided with an exhaust pipe to carry

further the air dust mixture to precipitator chamber.

Further details piping and dust precipitation chamber are followed:

-All the outlet pipes are connected to the main pipe header.

- The main pipe header is led to the inlet of vaccum pump which creates the negativepressure to suck the air.

-The output of vaccum pump is connected to the precipitation chamber. The velocity of the

air is reduced and dust is collected by the filter placed in side on the perforated walls.

- The diameters of all the pipes are designed so that, suction pressure in all the dust

collection chamber remain the same.

6.COOLING WATER SYSTEM:-

In a hydro station, water is required for the cooling of the following units:-

6.1GENERATOR STATOR WINDINGS:-


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The heat exchangers, generally of the finned copper tube type, may be attached to the stator

frame, but separate exchangers external to the machine are sometimes installed with

suitable air ducting formed either in the concrete work or by independent sheet-metaltrunking. In all cases the air is circulated by fans on the generator rotor.

6.2 THRUST & GUIDE BEARINGS OF MACHINES:-

Heat exchangers are installed in the outer periphery of the bearing housing filled with

bearing oil. Water while passing through this heat exchangers, cools the bearing oil whichin turn cools down the bearing temperature.

6.3SHAFT SEALS:-

Where the shaft emerges from the turbine cover, a suitable sealing arrangement is fitted to

prevent water escaping or air entering. The shaft seal is generally rubber gland pressed over

the shaft sleeve fitted on turbine shaft. In case the shaft gland is too tight pressed or

machine at partial or no load, the rubber seal tends to become overheated. In these caseswater is fed in shaft seal for cooling to avoid the damage of seal due to high temperature.

6.4TRANSFORMER COOLING:-

The oil used in transformers may be cooled in a number of ways. Cooling by water is not

always the most economical method but is frequently adopted as an extension of waterservices required for other purposes. The heat exchangers are then supplied integrally with

the transformers, and special care is taken to ensure that the total loss of head through the

transformer heat exchangers does not differ reatly from that through the generator heatexchangers, otherwise the cooling system will be hydraulically uneconomical.

The water for the cooling purpose may be tapped from penstock, tail race or from tube wellin open or close circuit.

6.5OPEN LOOP COOLING WATER SYSTEM:-

In a open cycle water is tapped from penstock and fed to various heat exchangers by means

of booster cooling pumps and the water after cooling the machine is discharged in tailrace.

the design of this system is simple and economical as least number of booster pumps arerequired. Also, it gives good cooling effect. But during the monsoon period, river water

contains lot of silt and while passing through the heat exchangers, silt chokes the Cu-Ni

tubes of heat exchangers. Therefore, closed loop cooling water system is preferable forhydro stations located in silt laden areas.

6.6CLOSE LOOP COOLING WATER SYSTEM:-

In order to avoid the from the river water, in close loop system a cooling water pond of

sufficient size is constructed and in it underground water is fed from tube well. The water,

after cooling is sprinkled in the pond through a sprinkler system installed above water pond


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and is again recovered back in pond. While sprinkling, the water loses its heat while

coming in contact with the atmosphere. The make up water as and when required is poured

in pond through tube well. This system is successfully operating in tanakpur hydro powerstation.

However, at the locations where it is difficult to bore the well and create a pond, a systemconsisting of closed loop primary water system with potable make up water supply is a

better alternative. Water from the tail pool/ penstock is circulated for heat exchanger as a

secondary cooling water system to transfer the heat of primary cooling system.

In all the above cases the cooling water should be passed through duplex type strainer so

that one section can be kept in service whilst the other is being flushed. Also the hardness

of cooling water should be treated (if possible) to avoid scale formation on the innersurface of Cu-Ni tubes. Inclusion of cyclone separators in the cooling water circuit is also

becoming popular and has been found to be effective in silt laden areas.

In addition to the supply for cooling, water may have to be provided for fire hydrants, fixedfire-fighting installations of the emulsifier or water-spray type. The pressures which the

different services require vary considerably and consequently it is difficult to devise acombined system which is at once effective and inexpensive.

7.SAFETY PRECAUTIONS FOR CENTRIFUGAL SEPERATORS :

The bowl of a centrifugal separator rotates at a very high speed & great forces aregenerated. to ensure our own safety, always carefully follow the instruction book(s)

concerning installation, assembly of the components, operation and regular maintenance.

Always use specified company spare parts & tools supplied with the machine.

Never start the machine before the lock rings of the bowl inlet, outlet & otherfastenings have been securely tightened. note that the assembly marks (arrowed)must

be aligned or pass each other (due to thread wear) when the lock ring is fully tightened.

If excessive vibration occurs, immediately fill & keep the bowl full of liquid whilststopping. switch off & apply brakes, if fitted. after the bowl has stopped; dismantle, clean

& check all parts carefully.

Never loosen any part of the machine until the bowl has completely stopped.

Never heat the bowl body, bowl hood or lock ring with a naked flame.

Never carry out any welding work on the components that rotate.


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Never operate the machine when the assembly mark on the lock ring can pass the

corresponding mark on bowl body/bowl hood by more than 25 degrees.

Check at regular intervals for damage due to corrosion/or erosion.

Switch off and disconnect the power supply to the machine before starting any dismantlingwork.

Never use the machine for separating a liquid that is more corrosive or has a higherdensity, temperature, different characteristics of the solids, etc. than that for which the

machine has been purchased.

A separator bowl is balanced as a complete unit. do not interchange the components of abowl with those of any other machine, even if it is the same type. make sure that no parts

are left out at assembly.

Follow the safety instructions concerning inflammable, toxic or corrosive process media& cleaning agents.

7.1THROUGHPUT:-

This means the quantity of liquid supplied per unit time. the throughput is given in cu.m/h

or l/h.

7.2RECEPTION ABILITY:-

This means the largest liquid quantity that the bowl can treat per unit time, expressed in

cu.m/h or l/h.

7.3CLARIFICATION:-

A liquid- sludge separation in which the machine is used for separating off particles,normally solids, having a higher specific gravity than that of the liquid.

7.4PURIFICATION:-

A liquid-liquid separation in which the machine is used for separating two intermixed liquids,

which are insoluble in each other & have different specific gravities higher than those of the

liquids can be separated off at the same time.


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8.FACTORS INFLUENCING THE SEPERATION:

8.1DIFFERENT IN SPECIFIC GRAVITY:

The centrifugal force acts on all particles proportionately to their specific gravity. this applies

to solid particles as well as to fluid particles. the greater the difference in specific gravity, theeasier the separation.

9.SIZE & SHAPE OF PARTICLES:-

The larger the particle, the quicker the sedimentation. the particles to be separated off must notbe so small that the mixture is getting near colloidal state. the smooth & round particles are

easily separated off than the irregular & elongated one.

Rough treatment, such as in pumps, can split the particles, with reduced size &separating speedas a result.

9.1VISCOSITY:-

The more fluid a liquid is, the quicker is the separating process and the better the separation-

in other words, low viscosity improves the separation result. The viscosity can in many casesbe reduced by heating. High viscosity will reduce ability.

10.TIME IN CENTRIFUGAL FIELD:-

If the separation is not satisfactory, the throughput must be reduced. lower throughput gives,

normally, a better separation result.

11.CLARIFIER BOWL:-

This bowl has one outlet. the liquid to be treated flows through the distributor to the interspaces

between the bowl discs. the heavy particles move by the centrifugal force along the underside

of the discs towards the periphery of the bowl, where they settle on the bowl wall. the liquid

proceeds towards the bowl centre and is discharged through the bowl hood.

The separation procedure can be influenced by e.g. changes in the viscosity (raise in separating

temperature) or in the throughput.

12.PURIFIER BOWL:-

This bowl has two outlets. the liquid mixture to be treated flows through the distributor to the

interspaces between the bowl discs, where the liquid phases are separated from each other by

action of the centrifugal force. the heavy phase & any solids move along the underside of the

bowl discs towards the periphery of the bowl,where the solids settle on the bowl wall.


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The heavy phase proceeds along the upper side of the top disc towards the neck of the bowl

hood and discharges over the gravity disc- the outer way.

The light phase moves along the upper side of the bowl discs towards the bowl centre &

discharges via the hole in the top disc neck- the inner way.

In a purifier bowl the so-called seal prevents the light phase from passing the outer edge of the

top disc, i.e. taking the outer way. thus the bowl must be filled with sealing liquid before theliquid to be treated is supplied. the sealing liquid is subsequently forced towards the bowl

periphery so as to form a liquid ring confined inwardly by the so-called interface between the

light phase & the heavy one. the Position of the interface will depend partly on the ratio

between the specific gravities of the two liquid of the two liquid phases, partly on the size ofthe diameters in the outer & the inner outlet (D2 & D1 respectively).

The sealing liquid:

Must be insoluble in the light phase.

May be soluble in the heavy phase.

Must not be heavier than the heavy phase.

Normally, the heavy phase is used as sealing liquid.

12.1 NOTE:-

Provided the content of heavy phase in the liquid mixture is sufficiently high (min 25%) , it

may in some cases do to feed the liquid mixture to be treated to the bowl. the liquid seal willthen build up automatically in some time.

13.HYDROSTATIC BALANCE:-

If the specific gravity of the light phase is S1 & the specific gravity of the heavy phase is S2,

the hydrostatic balance can be expressed as follows:-

S1 D32 - D2

2

______ = _____________

S2 D32- D1

2

13.1DISPOSITION OF THE INTERFACE:-

The purifier bowl is adjusted for separation of liquid mixtures with various specific gravity ratios

by altering the diameter of the outlet for the heavy phase (D2). the heavier or more viscous the


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light phase & the larger the liquid feed the smaller the diameter should be. for this purpose a

number of gravity discs with various hole diameters are delivered with the machine.

Where to dispose the interface depends on which phase should be delivered pure & on the

proportions between the amounts of the two phases as well.

If the light phase is wanted more free from the heavy one, the interface should be placed nearer

the bowl periphery, however not so far from the bowl centre that the liquid seal breaks (the

gravity disc is too large).

If the heavy phase is wanted more free from the light one, the interface should be placed nearer

the bowl centre, however not inside the outer edge of the discs (the gravity disc is too small), as

this would prevent the liquid flow.

13.2SEPERATORS:-

It is intended for the removal of impurities from fuel & lubricating oils. the separator must bestopped at regular intervals & the bowl opened for removal of sediment.

13.3MAJOR MACHINE PARTS:-

Power transmission.

Frame parts.Pump.

Bowl.

Inlet, outlet.Motor.

13.4POWER TRANSMISSION:-

Bowl spindle.

Worm wheel shaft.Worm.

Worm wheel

Friction coupling.

Top bearing.

The motor rotates the bowl through the friction coupling & worm gear.the friction coupling

ensures a gentle start & acceleration & prevents overloading of worm gear & motor. the wormgear serves to adapt the bowl speed to the motor speed. to decrease bearing wear & prevent

transmission of bowl vibrations to frame & foundation the top bearing of the bowl spindle is

isolated.


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14. BRAKE:-

When stopping the machine always apply the brake in order to reduce the retardation time ofthe bowl, thus quickly passing the critical speed.

14.1 REVOLUTION COUNTER:-

It is essential to operate the machine at the correct speed both in order to achieve the best

separating results & for reasons of safety. the proper speed appears on the name plate. count thenumber of revolutions of counter per minute.

14.2PARING DISC:-

The paring disc serves as a stationary pump wheel mounted in a chamber in the rotating bowl

neck. the paring disc dips radially into the rotating liquid ring & pares out liquid. the paring disc

is used as discharge pump.

14.3GEAR PUMP:-

The feed pump of all MAB separators is of the gear type, as is the feed & discharge pump.the

gear pump is direct-driven by the worm wheel shaft.

14.4BOWL:-

The bowl body & bowl hood constituting the bowl casing are held together by the large lock

ring. In the bowl are the distributor & the disc set through which the process liquid (oil/water) ispassed & where in the separation takes place. Uppermost in the disc set lies the top disc. The top

disc neck forms a discharge chamber from which the processed, light liquid phase (oil) is

discharged by the paring disc. The heavy liquid phase (water) leaves the bowl through thegravity disc, which is clamped to the bowl hood top by the small rock ring.

14.4.1 BOWL PARTS:-

1. Gravity Disc.

2. Bowl Hood.

3. Top Disc.4. Large lock Ring.

5. Distributor.

6. Small lock ring.7. Paring Disc

8. Bowl Disc Set.

9. Bowl Body.10. Level Ring.


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15.CENTRIFUGAL FORCE:-

In all centrifugal separators the bowl is running at a very high speed, normally between 5000 &9000 r.p.m.

Great forces are generated, subjecting the machined heavy stress. It is essential to followexactly the erection given in the instruction book concerning assembly of bowl operation, &

overhaul, & thesafety precautions as well. The bowl is a balanced unit, which will get out of

balance when incorrectly assembled or insufficiently cleaned.

16.CHECKING THREAD CONDITION:-

The threads of the large bowl lock ring & bowl body should be checked for wearat least once a year.

remove the bowl hood seal ring, put the hood on the empty bowl body ( disc set removed) and

tighten the lock ring until the hood lies tightly against the bowl body. If the mark on the lockring has passed the stationary mark by more than 25, consult.

16.1 DISC PRESSURE:-

If the lock ring can be screwed down without resistance until tight contact between bowl hood

& bowl body is obtained; increase the pressure by adding the spare bowl disc to the top of thebowl disc set (beneath top disc).

16.2GUIDE MEANS:-

When assembling, make certain that the bowl part guide means are in the proper position to

assure correct bowl assembly. take care not to damage the guides when assembling.

16.3HEIGHT ADJUSTMENT:-

The maintenance & repair manual (MR) contains information on height adjustment measures

checking & adjusting procedure.

It is essential that this stationary paring disc should be correctly positioned relative to the rotary

parts.

17.PURIFICATION:-

A separator is arranged for purification-liquid/liquid/solids separation. The process liquid is

pumped by means of the valve. The liquid can be brought to recirculate through the heater until it

has obtained the correct separating temperature.the purified oil leaves the separator through the outlet & the water separated out through the outlet.


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18.LIQUID FLOW:-

The purifier bowl has two outlets. The process liquid9oil/water mixture) flows through thedistributor C to the space between the bowl discs D. The water and any solids move towards the

bowl periphery where the solids settle on the bowl wall E. The water leaves the bowl through the

outlet. The oil moves towards the bowl centre & discharges through the outlet.

18.1LIQUID SEAL- IN PURIFICATION:-

To prevent the oil from passing the outer edge of the top disc & escaping the outer way with the

water through, a liquid seal must be provided in the bowl. to this end the bowl must be filled with

water through before the process liquid is supplied. the latter will then force the water towards the

bowl periphery. An interface will form between the water & the oil. Its position can be adjusted byaltering the diameter of the water outlet. i.e. by exchanging the so-called gravity disc.

19.CLARIFICATION:-

A separator is arranged for clarification- liquid/solids separation. The process liquid is pumped by

the feed pump through a heater to the separator. By means of the valve the liquid can be broughtto recirculate through the heater until it has obtained the correct separating temperature. The

clarified liquid (oil) leaves the separator through the outlet.

19.1LIQUID FLOW:-

The clarifier bowl has one outlet. The process liquid (oil/solids) flows through the distributor C to

the spaces between the bowl discs D. The solids move towards the bowl periphery & settle on thebowl wall E. The liquid (oil) moves towards the bowl centre & discharges through the outlet.


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Fig.: Aerial view of Centrifugal separator.

Mechanical Auxillaries

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Transcript of Mechanical Auxillaries