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Feed Pump FK6D32

key word:Heat exchange element


Product description

DG600-240 (FK6D32) feed pump (spiral seal)


1. General rules
The pump is a horizontal, centrifugal, multi-stage cylinder type, consisting of the following two main components.
1.1. Cylinder: A part of the main pressure boundary that makes up the pump is welded to the pipeline and supported on the pump base of the steel section structure at the centerline position.
1.2. Internal components of the pump: can be pumped out of the pump barrel as a whole, together with the barrel to form the main pressure boundary of the pump. This design, developed by the British senior feed pump, makes use of a spare core package, which makes maintenance time greatly reduced, and the core package includes all the wearable parts of the pump and is interchangeable.
The pump is axially positioned at the coupling end by a pair of transverse keys under the pump foot on the inlet side and a longitudinal key under the barrel. This arrangement allows the pump to remain neutral to the drive machine in all temperature conditions and to transfer the piping load to the pump seat. A brass slider is used between the pump foot and the pump seat, thus ensuring free thermal expansion and good contact.
The barrel is a manganese steel forging with good welding properties, the inlet branch pipe is a carbon steel casting welded to the barrel, and the outlet branch pipe is a forged steel piece, also welded to the barrel.
This construction makes it possible to remove the entire core package as a whole after removing the coupling and auxiliary piping and loosening the end cap bolts. Thus, in the event of a major fault shutdown, the inner core package can be removed within approximately 24 h if necessary, and a core package removal tool is provided specifically for this purpose.
The big end cap is a manganese steel forging with a stop sleeve to the final stage guide vane and an O-ring between the big end cap and the barrel to form an efficient seal, this seal is embedded in the groove of the barrel.
The bolts of the big end cap are liquid tightened by a liquid tightening device, which can give precise preloading of the big bolts. Since the load can be gradually added, the possibility of end cap deformation is minimal. With this tool, the end cap can be quickly disassembled and the entire core package can be quickly disassembled.
The joint surface of the large end cap and the barrel is machined to a good finish, and the innermost stage has a gasket between the inner pump housing and the barrel, which is a stainless steel toothed gasket.
The inner pump casing is made of corrosion and erosion resistant 13% chrome steel, the interface between adjacent inner pump casing is sleeve type until the mouth, and embedded with O-ring, the guide ring is also 13% chrome steel, and the positioning pins inside the guide vane at all levels are set on the front pump casing.
All inter-stage pins are fully enclosed and do not come into contact with the pumped liquid. In the event of pin failure or loosening, the pin will not discharge from the pump outlet.
Each inner pump casing and guide vane is equipped with a replaceable neck ring in the bore. Each neck ring is designed with a special geometry and machined to fit into each bore. This shape allows it to maintain the static pressure stiffness of the bushing and greatly reduces leakage, eliminating the need for other specialized leak prevention devices.
The internal components are the inner pump casing and the guide lobe fixed coupling, which is fixed to the barrel by a butterfly spring between the final stage guide lobe and the large outlet end cap. This spring provides sufficient static pressure to the joint surface during assembly and shutdown to allow the internal assembly to expand freely. When the pump is running, a hydraulic pressure differential is established, thus ensuring a tight seal between the joint surfaces.
The inlet guide is positioned on the inlet side of the pump by a closed stop sleeve to ensure the alignment of its internal components when the core package is installed. This stop sleeve ensures that the inlet guide can be tightly positioned on the barrel by the tensioning ring, while allowing free expansion during thermal fluctuations.
All areas of the barrel subject to high velocity water flow are coated with stainless steel austenitic plating to prevent erosion. All joint surfaces are also protected in the same way.

 

2. Rotating Elements
The pump, like many of Weir's other boiler feed pumps that have been in continuous operation in power stations, has a rigid rotor, which ensures a high degree of mechanical reliability, making the risk of over-standard vibration or internal contact negligible.
Basic design features of the rigid rotor of Weir pumps.
2.1. a minimum critical speed in the liquid exceeding 130% of the maximum operating speed.
2.2. the minimum critical speed in the liquid does not drop below 120% of the maximum operating speed even when the internal operating clearance of the pump is worn to twice the design value
2.3. the standard shaft torsional shear stress is conservative and does not exceed 60 N/mm2 (85001bf/in2).
The pump shaft is a martensitic stainless alloy steel forging, rough machined, heat treated, ground and finish machined with a chrome plating layer on the radial bearing gear to prevent shaft galling. All threads on the shaft are machined and shaped to a high standard with a single head tool, with rounded transitions at all cross-sectional changes and thread tails. All heat treatments are carried out with the shaft in vertical position.
The main components on the shaft and the rotor are balanced in accordance with the work procedures and quality levels specified in ISO 5406:1980 and ISO 1940:1973, respectively. These quality standards grades are confirmed for previous practice.

 

3. Hydraulic components
The impeller and guide vane used in the pump are 13% chromium stainless steel precision castings, and the runners are cast by the precision casting method, which results in excellent surface finish and strength, high precision lobe shape and high repeatability.
The impeller and guide vane have the same specific speed as the feed pumps already installed and used in some large power stations, so the hydraulic characteristics of the pump are established.
The radial clearance is based on efficiency, critical speed and shaft deflection criteria.
The impeller is not fitted with wear bad, but sufficient metal is left in its wear-prone parts to be turned away and fitted with rings in case of operational wear. Impeller and static wear ring materials have hardness differences.
Impeller axially by the card ring positioning, card ring for the two-piece embedded in the shaft, card ring positioned in the groove of the impeller to prevent its rotation fly out. The impeller is positioned on the hub to fix the impeller and act as an inter-stage seal for the impeller, and the torque is transmitted by the key which is matched with it. The minimum internal fillet angle of the keyway is chosen to ensure a maximum stress concentration factor of 3.0.

4. Intermediate pumping head
There is an intermediate tap on the pump casing.
It is sealed by two seals between the core package and the barrel, and forms a circumferential space outside the secondary and tertiary pump housings.
There is a radial hole in the pump casing inside the secondary or tertiary stage, which allows the pressure water to enter the circumferential space.
There is a tap port on the barrel body, so that the secondary or third stage tap water from the circumferential space to the intermediate tap connector.

 

5. Balancing device
The hydraulic balancing device of the pump is the balancing drum device, which is installed behind the final impeller of the shaft. The balance drum rotates in the throttle bushing fixed on the big end cover, which becomes a pressure-reducing device, and the outlet pressure acts on the unbalanced area of the final impeller, so that there is always a residual thrust towards the inlet end, which makes the shaft in a stretched state.
The balance drum is pressed on the shaft, axially positioned by the shaft shoulder and tightened by a nut on the low pressure side, and the balance drum is positioned on the shaft by the key and locked by the nut.
The balance drum is made of stainless steel forging material and rotates in the throttle bushing. The throttle bushing material is specially selected to keep the hardness difference between it and the balance drum the same as the hardness difference between the impeller and its bushing.
The bore of the throttle bushing is machined with a set of shallow balance grooves, and a number of swirling breaks are machined on the end face, this structure improves the hydrostatic stiffness, and at the same time greatly reduces leakage.

 

6. Bearing
Radial bearings.
The pump shaft is supported by a pair of ordinary cylindrical radial plain bearings, bearings for the eugene bushings, forced oil lubrication type, lubricating oil from the independent lubricating oil system, bearings by the bearing gland fixed, bearing gland by the bolt fixed in the lower half of the bearing bracket. When the upper half of the bearing bracket is mounted, it forms a 360o flange support and is directly connected to the inlet and outlet end caps. The entire assembly is positioned by pins to ensure accurate reassembly, and the bearing can be disassembled together with the shaft during overhaul.
Self-aligning tile type thrust bearings.
Self-positioning tile type thrust bearings have the same capacity to carry thrust loads in both directions and are suitable for both directions of rotation.
The thrust ring assembly consists of a support ring, the tiles are evenly distributed between the individual locating pieces on the support ring, the outer diameter of the tiles are embedded in the flange of the support ring, the tiles are loosely positioned by the heads of the locating pieces embedded in the grooves on both sides, so that the tiles can be freely tilted during operation but will not fall off.
The thrust bearing is designed to have the smallest possible power loss without reducing the load carrying capacity.
The thrust bearing is mounted in an axially centered bearing cavity within the free end bearing chamber, which is itself axially centered.
This arrangement has the following advantages.
a. The thrust disc can be mounted on the shaft before the bearing chamber is fitted, enabling accurate checking of the drift and axial positioning of the inner (load side) face.
b. Enables inspection of groups of thrust bearings by simply removing the upper half of the cavity without removing the thrust disc, thus allowing in-situ inspection and replacement of tiles without removing the thrust disc, leaving little risk of misfitting this critical component.
c. Enables visual inspection of bearing assemblies.
The thrust bearing is designed and proven to be reliable based on measuring the axial thrust characteristics of equipment that has previously used the same hydraulic components.

 

7. Shaft End Seals
The pump is equipped with a fixed bushing injection seal water unloading type labyrinth seal to ensure that seal water does not enter the pump while the pump is operating and pumping water does not leak out. Condensate is injected into the seal chamber to flow in the direction of the pumping water, and meets the pumping water leaking out in the unloading ring, where it is reconnected by a pipe to the front pump inlet, and as long as the seal water pressure is kept higher than the front pump inlet pressure, no hot water will leak out from the seal chamber.
There is also some condensate seal water leaking along the labyrinth seal via a U-shaped tube to the condenser.
The labyrinth seal is a parallel single diameter arrangement, and the seal sleeve and bushing are machined separately with reversed double-headed spiral grooves.
The seal can be removed as a sub-sleeve with only a small amount of disassembly work.

 

8. Pump seat
The pump seat is a welded structure of rolled section steel, arranged to support the pump at the centerline. The entire structure of the pump base is designed to be both rigid and free of deformation.

9. Parameters of the pump

Model  DG600-240(FK6D32
Type Cylinder core package, horizontal
Pumping medium Boiler feedwater
Number of stages 6-stage impeller
  Unit Rated working condition Maximum continuous working condition
Inlet flow rate m3/h 552.4 600.23
Outlet flow rate m3/h 529.42 577.14
Head m 2156.5 2239.9
Efficiency % 82.58 82.55
Pumping head pressure MPa 11.06 11.43
Pumping head flow rate m3/h 22.98 23.09
Shaft power kW 3429.3 3859.6
Inlet water temperature 175 179
Intake water density kg/m3 892 888
Cavitation allowance (required) m 27.39 30.97
Rotational speed r/min 5068 5248
Maximum overrun speed r/min 5700
Inlet pipe specification mm φ273×7
Intermediate tap pipe specification mm φ89×7
Outlet pipe specification mm φ244.5×20
Direction of rotation   Clockwise (looking from drive end to free end)
Weight kg 6960

 

10. Main spare parts of the pump

 

No. Parts name Drawing No. Unit Quantity
1 O-Rings and Sealing Retainers ALL SPECIFICATIONS Unit 1
2 Graphite Gasket 105*125*10 PCS 1
3 Inlet end cap bushings 600-240-4-3 PCS 1
4 Pump casing bushings 600-240-4-16 PCS 5
5 Guide vane bushings 600-240-4-17 PCS 5
6 Balance Drum 600-240-3-14 PCS 1
7 Pump casing screws 600-240-4-24 PCS 6
8 Pump casing screws 600-240-4-25 PCS 6
9 Pump casing screws 600-240-4-26 PCS 18
10 Pump casing screws 600-240-4-28 PCS 6
11 Spring Retainer 600-240-4-15 PCS 6
12 Seal Washer 600-240-04-06 PCS 1
13 Thrust tile block 600-240-06-03 GROUP 1
14 Cooling sleeve 600-240IIM-05-01 PCS 1
15 Cooling sleeve 600-240IIM-05-02 PCS 1
16 Sealing chamber 750-180-05-04 PCS 1
17 Sealing chamber 750-180-05-03 PCS 1
18 Balance drum nut 600-240-03-19 PCS 1
19 Bushing Nut 600-240IIM-03-04 PCS 1
20 Lock nut 600-240IIM-03-02 PCS 1
21 Shaft sleeve nut 600-240IIM-03-05 PCS 1
22 Lock nut 600-240IIM-03-06 PCS 1
23 Dynamic and static ring L270-99 PCS 2
24 Balancing drum bushings 600-240-04-20 PCS 1
25 Balancing drum locking washer 600-240-03-18 PCS 1
26 Big End Cap Repair 600-240M SET 1
27 Thrust disc 600-240-03-22A PCS 1
28 Repair Fee 600-240M SET 1