PAVAN K. SHARMAAddl. MANAGER (OPERATION)

Boiler Feed Pump Hydraulic Coupling

Boiler Feed Pump

Motor Speed-1493 rpmGear ratio -165/41Primary speed -6008 rpmFull load slip -3 %Max. O/P speed of geared variable speed coupling -5829 rpmRegulating range -5780 to 1200 rpmPumps- 1) Working oil pump (Centrifugal)

2) Lub oil pump (Gear Pump)Both driven from I/P shaft of geared variable speed coupling.

3) Aux. oil pump (Electrical Motor driven)Lub Oil pressure (Normal) -2.5 bar, at 1.5 bar-alarm & at 1.2-AOP starts.Control oil pressure -3.5 BAR & alarm -2.2 bar.Working oil pump pressure -1.6 to 2.1 barWorking oil upstream of control valve -1.0 to 1.8 barWorking oil flow rate -1068 Litre/min.

Geared variable speed turbo coupling:

The variable speed turbo coupling and step up gear are incorporated in a common housing, while the lower section serves as an oil tank.

Flexible connecting couplings are applied for power transmissionfrom the motor to the geared variable speed turbo coupling and from there to industrial machine. The speed is increased between I/P and primary shaft by means of a gear stage(165/41). Torque is transmitted hydro dynamically from the primary wheel to the secondary wheel by working oil.

The torque generated by the driving machine is provided to accelerate the fluid in primary wheel (Pump Impeller) This is delayed in the secondary wheel (Turbine Wheel) to produce an equal torque. The fluid can only circulate by a pressure drop between the primary and secondary wheel. This requires that the secondary wheel speed is lower than that of the primary wheel. Thus a slip is required for power transmission.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

The coupling size is selected so that the full power can be transmitted with a low slip, the “full load slip” (at max. filling). The O/P speed can be regulated infinitely by changing the oil filling in the working chamber between the primary and secondary wheel. This isaccomplished by positioning the scoop tube accordingly which will determine the oil filling of the working chamber.

The power loss caused by slip will heat up the working oil. The heat is then dissipated in the working oil cooler.

Oil circuits:The same oil is used as working and lub oil. The working oil

pump and main lub oil pump are combined to form a pump set and are driven by the I/P shaft of the geared variable speed turbo coupling.

The electric motor driven AOP lubricates the unit at start up, during rundown and in case of interferences.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

Working oil circuit:The working oil circuit consists of a closed circuit superposed by an

open circuit so that the filling can be changed.

In the Closed circuit, the oil which flows into the coupling via the circulating control valve(32) for power transmission and heat dissipation, is removed by the displaceable scoop tube. Under the action of dynamic pressure the oil flows through the scoop tube housing, working oil cooler and circulating control valve(32) back into the coupling.

The Open circuit is made up of the working oil pump, throttle and pressure relief valve. The coupling is filled by oil flowing from the open to the closed circuit. Excess oil supplied by the working oil pump flows through the pressure relief valve back into the sump. The same applies when the coupling filling is reduced.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

The connecting line with orifice plate between lube and working oil circuit is provided for faster filling of working oil circuit during start up. The operating pressure of working oil is set on the pressure relief valve.

If the closed circuit interrupted and the geared variable speed turbo coupling oil temperature rises to 160 deg cent the fusible plug blow. Bores in the fusible plugs are thereby released and the coupling drains.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

Lub oil and control oil circuit:The main lub oil pump pumps oil out of the sump through the non

return valve, pressure relief valve(24), lub oil cooler, and reversible double filter to the bearing points, pressure switches and gear wheels.

Oil for hydraulic scoop tube control is branched off upstream of the adjustable orifice plate(22). The control oil pressure is approximately 3.5 to 4.0 bar.

The lub oil pressure is set about 2.5 bar. Control oil pressure and lub oil pressure are set on the pressure relief valve(24) and on the adjustable orifice plate(22) as a function of each other.

To ensure the bearings are coated with oil during coupling start up, rundown and failure they are supplied with oil by the aux. oil pump before the drive motor is switched on and after it is switched off.

The aux. lub oil pump which is driven by the electric motor draws lub oil out of the sump and pump it back through a non return valve into the lub oil circuit.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

External Oil supply:Lub oil for external units is taken from the coupling’s lub oil circuit

and returned to the oil sump. Pilot bored orifice plates are fitted at the lub oil outlets of geared variable speed turbo coupling to the motor and to the driven machine.

Control:The output speed is controlled by an actuator adjusting the scoop

tube and thus the filling in the geared variable speed coupling. The cam disc serves for linearization the angle of adjustment of actuator as a function of the controlled variable speed.

Scoop Tube Positioning:The scoop tube which regulates the amount of oil in the coupling is

controlled by turning the cam disc by means of actuator. The control valve(46) is actuated by roller which is held by spring pressure against the cam disc.

If the cam disc is moved in the direction of “full output speed” the control valve(46) opens the pressure oil flow into the chamber(49) of the double acting positioning cylinder. The scoop tube which is connected to piston(48) is moved in the direction “full O/P speed” and the degree of filling in the coupling is increased. Simultaneously the control valve(46) is returned to its starting position by a spring load roller which presses against the slope of the scoop tube and shuts off the oil feed as soon as the scoop tube position preset by the actuator is reached.

When cam disc is turned in direction “min O/P speed “ control valve opens the oil flow into the chamber(47) and the scoop tube is moved in the direction “min O/P speed”.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

Oil throughput control:The duty of circulating control valve(32) is to supply the coupling with

enough working oil to compensate for the losses. A cam disc controls the circulating control valve as a function of the scoop tube position.

Rapid positioning of scoop tube:Using this arrangement the scoop tube is moved from any position

towards “zero O/P speed” and back in the direction “full O/P speed” more rapidly than is possible with the actuator. Normal coupling emptying and filling time with up to 75 mm2/s oil viscosity are around 5 to 10 sec. Rapid regulation is used for example in the following cases.

1) Quick run up of drive motor and driven m/c by rapid draining of the geared variable speed turbo coupling:

The two solenoid valve(43 &45) are energized for rapid run up of main motor under no load. The energized solenoid valve(43) lets pressure oil flow into the chamber(47) of the scoop tube positioning cylinderirrespective of the position of control valve(46). At the same time solenoid valve(45) stops the supply of oil….

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

…and allows the oil in the chamber(49) to flow unhindered into the oil sump. The scoop tube moves in the position 0% filling.

After run up of drive motor (With approximately 95% normal speed) the solenoid valve are de energized and the scoop tube moves at once to the position fixed by the actuator. The coupling fills within the specified time the driven machine runs up to the corresponding speed.

2) Quick run down of drive motor and driven machine by rapid draining of geared variable speed coupling:

The two solenoid valve(43 & 45) are energized for rapid draining of the coupling. The scoop tube moves in the position of 0% filling as per description in section-1. The coupling drains and power transmission from drive motor to driven machine is interrupted.

M

B1

B3/4

B2

B5 B6 B7B8/9

B10

4643

45

44

49

47

PRV-31

PRV-24

48

LUB OIL

WORKING OIL

CONTROL OIL

I/P SHAFT

LOP

WOP

AOP

32

Thank You