CHAPTER – 1 DESCRIPTION

LIST OF CONTENTS

1 Introduction

2 Technical Data

2.1 Motor Driven pump

2.2 Turbine driven pumps

2.3 Driver / Pump flexible coupling 3 Description

3.1 Pump casing

3.2 Rotating assembly

3.3 Journal and thrust bearings

3.4 Bearing housings

3.5 Mechanical Seals

3.6 Driver / pump coupling

CHAPTER – 1

DESCRIPTION

1. INTRODUCTION :

Three Booster Stage Pumps are supplied to each 500 MW Unit. Each pump consists of FA1B75 type Booster Stage Pump, two are driven by turbine through gear box and one is Motor Driven.

The FA1B75 type Booster stage pump is a single stage, horizontal, axial split casing type, having the suction and discharge branches on the casing bottom half, thus allowing the pump internals to be removed without disturbing the suction and discharge pipe work or the alignment between the pump and driving motor.

The pump shaft is sealed at the drive and non-drive end by mechanical seals which are flushed by boiler feed water pumped round a closed circuit. The rotating assembly is supported by plain white metal lined journal bearing sand axially located by a double thrust bearing.

The bearings in the pump are lubricated by forced oil lubrication system.

2. TECHNICAL DATA :

2.1 Motor Driven Pump 2.1.1 Pump

Manufacturer BHEL

Type FA1B75

Direction of rotation Anti-Clockwise (Viewed on non-drive end)

Liquid pumped Boiler feed water 2.2 Turbine Driven Pump

2.1.2 Pump

Type FA1B75

Direction of rotation Clockwise (Viewed on non-drive end)

Liquid pumped Boiler feed water

2.3 Thrust Bearing

Manufacturer Michell Bearing / Glacier

Type Double thrust

2.4 Mechanical seal

Manufacturer BURGMANN, Germany 2.5 Driver/Pump Flexible Coupling

Manufacturer Euroflex, India

3. DESCRIPTION : 3.1 Pump Casing :

The cast steel pump casing is of the double volute type, split on the horizontal center line. The top and bottom half casing are located to each other by dowel pins and secured by the studs and nuts, sealing at the axial split being effected by a two-ply brown paper joint.

The bottom half pump casing has the suction and discharge branches and support feet, cast integrally.

The pump casing is machined internally to accept the casing rings and stuffing boxes are also formed at each end of the casing to accommodate the water jackets and the mechanical seals, thus preventing leakage along the pump shaft.

The interface of the casing and base plate supports is near the shaft axis. Dowels and a guide key are arranged to maintain longitudinal and transverse alignments whilst accommodating thermal expansion.

A tapped air vent connection is provided on the top half casing. Connections are also provided on the suction and discharge branches for pressure gauges and a drain.

3.2 Rotating Assembly :

The rotating assembly consists of the shaft, impellers, nuts, keys, seal sleeves, thrust collar, the rotating parts of the mechanical seals and pump half coupling.

The double entry impeller is keyed to the shaft and is located axially by an impeller nut on each side of the impeller hub. The impeller is fitted with a wear ring on each shroud, the rings being retained by grub screws.

The seal sleeves are keyed to the shaft and are located and secured by grub screws. Leakage between the shaft and sleeve is prevented by an ‘O’ ring fitted in a groove machined in the bore of the sleeve. The thrust collar is keyed to the shaft and is secured against a shoulder on the shaft by the thrust collar nut. The pump half coupling is keyed to the tapered end of the shaft and is secured by a coupling nut, locked by a lock screw.

3.3 Journal and Thrust Bearings :

The rotating assembly is supported at each end of the shaft by a white metal lined journal bearing and the residual axial thrust is taken up by a tilting pad double thrust bearing mounted at the non-drive end of the pump.

The journal bearing shells are of mild steel, white metal lined, thick wall type, and are split on the horizontal plane through the shaft axis. Each bearing is prevented from rotating by a dowel pin located in a recess in the top half bearing housing.

The thrust bearing is fitted at the non-drive end of the pump and has eight titling pads in a split carrier ring on each slide of a thrust collar, which is keyed to the pump shaft and secured by a nut and lock-washer. The carrier rings are held in non-drive end bearing housing and are prevented from turning with the thrust collar by dowels locating in slots in the top half of the housing. The thrust pads are retained on the carrier rings by special pad stops screwed into the rings. Machined spacers are fitted behind each carrier ring during manufacturer to effect the axial running position of the rotating assembly. The thrust bearing is provided with for resistance temperature detectors.

A split floating oil seal is fitted in a groove in the housing to maintain a level of lubricating oil with in the housing, around the thrust bearing, when the pump is stopped. The floating seal is prevented from turning by an anti-rotation pin fitted in a slot in the bottom half of the housing. An orifice plug fitted at the thrust bearing lubricating oil outlet ensures a flooded bearing housing when the pump is stationary. The bearing are supplied with lubricating oil from the forced lubricating oil system.

For further information on the bearings references should be made to be bearing manufacturer’s instructions at Chapter 4.

3.4 Bearing Housings :

The bearing housings are in the form of cylindrical castings, split horizontally, secured to each bracket, by set screws and dowels located. Each housing is provided with lubricating oil inlet and outlet connections, vent connections and instrument entry points.

The top and the bottom halves of the drive end bearing housings are secured together by studs and nuts, and the housing is closed at the drive end by a cover plate. An oil retaining shield at each end of the housing prevents oil leakage from the housing when the pump is running.

The top and the bottom halves of the non-drive end bearing housing are secured together by studs and nuts and located by dowel pins. Leakage of lubricating oil from the non-drive end bearing housing is prevented by an oil retaining shield in the in board side of the housing and by a bearing housing end cover and joint secured to the out board side of the housing by hexagon head screws.

3.5 Mechanical seals :

The drive and non-drive end seal cooling jackets are fitted with mechanical seals mounted on seal sleeves and located within seal cooling jackets.

The cooling jacket, which provides a heat soak barrier between the pump casing and the mechanical seal, is continuously flushed with cooling water from an external source.

A pumping ring incorporated in the mechanical seal pumps a supply of boiler feed water through a heat exchanger in a closed circuit, thus keeping the seal circuit temperature at approximately 60°C.

For further information on the mechanical seals reference should be made to the manufacturer's instructions at chapter 4.

3.6 Driver / pump coupling :

The drive from the driver to the pump shaft is transmitted through a spacer flexible coupling.

SECTION – A

BOILER FEED BOOSTER PUMP

CHAPTER – 2