DG type multi-stage boiler feed pump
DG type multi-stage boiler feed pump is a horizontal multi-stage single-suction segment centrifugal pump, suitable for conveying clean water with a temperature not higher than 250 ° C, or non-corrosive liquids with physical and chemical properties similar to water, widely used in Boiler feed water in power plants, metallurgy, heating and other industries has a maximum lift of 1800 meters. The casing of the boiler feed pump can be disassembled axially at the axis. The suction port of the DG85-80×8 type pump is vertically upward, and the discharge outlet is vertically upward, which is vertical to the axis line. From the direction of the driving end, the rotation direction of the water pump is clockwise. According to the user’s needs, it can also produce counterclockwise rotation, and the user can make a special request when ordering.
Parameter range and model description of DG type multi-stage boiler feed pump:
Flow rate Q 3.7-1350m³/h
Head H 49-1800m
DG — Multistage boiler feed water pump
12—The flow rate at the design point is 12.5m3/h
50—The single-stage lift at the design point is 50m
3—The number of levels is 3
DG type multi-stage boiler feed pump structure type:
This type of multi-stage boiler pump is a single-shell, single-suction, multi-stage segmental centrifugal pump structure. The multi-stage pump has a vertical inlet and a vertical outlet. The specific structure is as follows:
Stator part: It is mainly composed of front section, middle section, guide vane, rear section, bearing frame and balance chamber cover. The parts are connected by rods and nuts. The front and rear sections are fixed on the pump seat with bolts and nuts.
Rotor parts: mainly the impeller, impeller retaining sleeve, balance retaining sleeve, balance disc and shaft sleeve parts are tightened with small round nuts, and fixed on the shaft with flat keys to prevent rotation. The entire rotor is supported on bearings at both ends. The rotor is directly connected to the motor with an elastic pin coupling. To compensate for the expansion, a toothed pad is installed between the last stage and the balance sleeve, which should be replaced when the pump is overhauled.
Balance mechanism: The pump adopts a balance plate hydraulic balance device that can completely and automatically balance the axial force. The device consists of four parts: balance plate, balance plate, balance sleeve and balance block.
Rotation direction: Seen from the motor end, the pump rotates clockwise.
Material of main parts: Except for DG85-80 and 200DG43, the overcurrent parts of the pump are made of cast steel, and the rest of the pump is made of cast iron.
Scope of complete sets: complete sets of supply pumps, motors, check valves, gate valves, common bases or their own bases.
The material of the main parts of the pump:
Inlet and outlet section: ZG230-450
Middle section: ZG230-450
Guide vane: QT450
Sealing ring: QT450
Balance plate: ZG2Cr13
Gimbal: Tin bronze
Pump installation steps:
1.1.1 Before assembly, all pump parts, especially the mating finishing surfaces, must be thoroughly cleaned.
1.1.2 Count all the parts, and classify and number the parts according to the assembly order.
1.2 Assembly of pump parts
1.2.1 Pay attention to install the sealing ring in the middle section to prevent it from falling off.
1.2.2 Pay attention to the guide vane anti-rotation pin.
1.2.3 Tighten the nut of the pump body through the rod symmetrically to maintain a proper tightening force. If it is too loose, it will cause leakage of the joint surface of the middle section. If it is too tight, it will cause deformation of the stator parts. Tighten the threaded rod symmetrically.
1.2.4 After the threaded rod is basically tightened, use a dial indicator to find out that the front and rear sections are not parallel. 1.3 Measure the total string volume of the rotor, which should meet the requirements of the drawing.
1.4 Install the front cover and low pressure end cover bearing and lower shoe, and lift the shaft to the center position.
1.5 Use a special lifting tool and a dial gauge to check the runout of the end face of the balance sleeve, which should meet the requirements of the general assembly drawing.
1.6 Assemble the rotor parts and tighten the lock nut. The measured string quantity after the balance plate is installed shall meet the requirements of the general assembly drawing.
1.7 Install the head cover, tail cover, bearing body and the top of the bearing pad and the clearance on both sides, which should meet the specified value of the bearing pad quality requirements.
1.8 Adjust the center of the bearing bush on both sides, and lock the adjusting nut after adjustment.
1.9 Assembling the thrust bearing
1.9.1 For the assembly of the thrust bearing components, scrape and grind the black pads according to the requirements of the bearing components, and the thrust pads should rotate flexibly during assembly. 1.9.2 After the thrust bearing is installed, the axial gap between the balance disc and the balance sleeve should be 0.04~0.08mm according to the requirements of the general assembly drawing, and the adjustment of the gap is realized by the adjusting ring.
1.9.3 After adjusting the clearance, install the thrust bearing and thrust plate, and lock the lock nut.
The pump body and the pump cover constitute the working chamber of the impeller. The inlet and outlet flanges are provided with pipe screw holes for installing vacuum gauges and pressure gauges, and the lower part of the pump body is provided with pipe screw holes for discharging residual water.
The impeller is single-suction closed type. A balance disc is set to balance most of the axial force. At the same time, a thrust bearing is provided to bear a small part of the axial thrust that may remain. The arrangement of the bearing keeps the shaft in a stable pulling rod state. The impeller must be strictly checked for static balance before assembly to ensure smooth operation.
The pump shaft is supported by two babbitt alloy sliding bearings, which are installed in the bearing body in the pump suspension and lubricated with thin oil.
There is a sealing ring on the pump body, which can improve the volumetric efficiency of the pump. On the other hand, it can also prevent high-pressure water from flowing back into the suction chamber, disturbing the water inlet flow field, and ensuring the suction performance of the pump.
The shaft seal is generally a soft packing seal. When the pump is working, a small amount of medium can be introduced to the stuffing box, and cooling and lubricating water can also be externally connected to play the role of water seal and cooling and lubrication. According to the user’s needs, the packing seal can be changed to a mechanical seal.
1.9.4 Adjust the clearance between the thrust bearing seat and the push plate by the cushion to ensure the clearance requirements of the thrust bearing in the assembly drawing.