Product description

　　The medium pressure boiler feed pump DG is suitable for transporting clean water with a medium temperature of -20℃ to 160℃ (the medium pressure does not exceed 105℃), or non-corrosive liquids with physical-chemical properties similar to water. The pump's inlet pressure should not exceed 0.59M (6kgf/cm2). It is widely used in power plants, metallurgy, heating, and other sectors for boiler feeding, and is also suitable for boiler feed systems of units and main pipeline systems in power plants of various capacities. The maximum height can reach 1800 meters. The medium pressure boiler feed pump DG, as a high-pressure boiler feed pump or another high-pressure feed pump, is an efficient and energy-saving product specially designed for the upgrading and modernization of new series of industrial steam boilers. It is not only suitable for medium and low pressure boiler feeding but also for transporting water to great heights in factories and cities.

↑Medium pressure boiler feed pump series DG280-65×6↑

　　The high pressure boiler feed pump DG is a multi-stage centrifugal pump with single suction, belonging to the series of multi-stage high pressure pumps. The pump casing can be axially disassembled along the axis line. The model DG85-80×8 pump has its suction inlet oriented vertically upwards and the outlet also vertically upwards, perpendicular to the axis. From the drive side, the pump rotates clockwise; it can also be manufactured with counterclockwise rotation according to user needs, which must be specified when ordering.

Explanation of the medium pressure boiler feed pump model DG

Example of model: DG45-80×6

DG — medium pressure boiler feed pump with single suction and multiple stages

45 — design flow rate of the pump

80 — lift height per stage of the pump

6 — number of stages of the pump

Structural characteristics of the medium pressure boiler feed pump DG

　　Bearing balance: The rotor of the high pressure boiler pump DG is supported by ball bearings at both ends of the pump shaft. Lubrication with fine oil and cooling with circulating water; the axial force of the rotor is automatically balanced by a balance disk. The balance water returns to the suction section of the pump through the balance return pipe. The rotor of the medium pressure pump DG is supported by sliding bearings at both ends of the pump shaft. Lubrication with fine oil and cooling with circulating water; the axial force of the rotor is balanced by a balance disk. Between the balance chamber and the front section, a water return pipe is installed. The rotor of the high pressure boiler pump DG is supported by sliding bearings at both ends of the pump shaft. The bearings have forced lubrication, the pump is equipped with an oil system, and the axial force of the rotor is balanced by a balance disk. In addition, it has a thrust bearing to support the residual axial force generated by changes in working conditions. Between the balance chamber and the suction pipe, a water return pipe is installed.

　　Transmission: The medium and medium-high pressure multi-stage pumps are driven by a motor through an elastic coupling. From the transmission direction, the pump rotates clockwise. The high pressure pumps are also driven by a motor through an elastic coupling, and according to user needs, they can be equipped with toothed couplings, diaphragm couplings, or hydraulic couplings. The motor can be a small steam turbine or an electric motor. From the transmission direction, the pump rotates clockwise. The casing and cover of the boiler feed pump form the working chamber of the impeller. On the water inlet and outlet flanges, there are threads to install vacuum and pressure gauges. At the bottom of the casing, there are threads to drain the residual water.

　　The impeller is of single suction and closed type, equipped with a balance disk to balance most of the axial force, and also has a thrust bearing to support the small residual part of the axial force. The arrangement of the bearings keeps the shaft in a stable state of tension bar. Before assembly, the impeller must undergo strict static balance verification to ensure stable operation.

　　The pump shaft is supported by two Babbitt alloy sliding bearings, installed in the bearing housing of the pump support and lubricated with fine oil.

　　In the pump casing, there is a sealing ring that can improve the volumetric efficiency of the pump and, on the other hand, prevent the backflow of high-pressure water into the suction chamber, disturbing the inlet flow field, thus ensuring the suction performance of the pump.

　　The shaft seal is generally a soft packing seal. During the operation of the pump, a small amount of medium can be led into the packing box, and external cooling and lubrication water can also be connected to fulfill water sealing and lubrication functions. According to user needs, the packing seal can be replaced with a mechanical seal.

Main materials of the parts of the medium pressure boiler feed pump DG

Kind notice: The user can communicate with the technical staff of Zhonglian Pump Industry to make a reasonable configuration according to the site conditions and needs.

Steps for installing the medium pressure boiler feed pump DG

1. Preparation

Before assembly, all pump parts, especially the finishing surfaces that fit together, must be thoroughly cleaned.

Count all parts and classify and number them according to the assembly order.

2. Assembly of the pump parts

Pay attention to correctly install the sealing ring of the middle section to prevent it from falling off.

Pay attention to correctly align the anti-rotation pin of the guide vanes.

Tighten the nuts of the through bolt of the pump body symmetrically to maintain proper tension; if it is too loose, it may cause leaks at the joint surface of the middle section; if it is too tight, it may deform the stator parts. The tightening torque during assembly is approximately 5550 Nm. Tighten the through bolt symmetrically.

After basically tightening the through bolt, use an indicator to check that the non-parallelism between the front and rear sections is ≤0.1mm. Measure the total eccentricity of the rotor, which must meet the requirements of the drawing.

Install the front cover bearing and the low-pressure end cover and the lower support, and raise the shaft to the central position.

Use special tools and a micrometer to check the oscillation of the balance sleeve end, it must meet the requirements of the general assembly drawing.

Assemble the rotor parts and tighten the locking nut. The measurement of misalignment after installing the balance disc must meet the requirements of the general assembly drawing.

Install the front and rear covers at both ends, the bearing body, and the space on the top and sides of the bushings, it must meet the specified values in the bushing quality requirements.

Adjust the center of the bushings on both sides, and after adjusting, tighten the adjusting nut.

3. Assembly of the thrust bearing

The assembly of the thrust bearing parts must scrape and sand the black metal sheets according to the requirements of the bearing parts; during assembly, the thrust sheets must rotate flexibly. 1.9.2 After installing the thrust bearing, the axial space between the balance disc and the balance sleeve must be 0.04 to 0.08 mm according to the requirements of the general assembly drawing, the adjustment of the space is done with an adjustment ring.

After adjusting the space, install the thrust bearing and the thrust disc, and tighten the locking nut.

The pump body and the cover form the working chamber of the impeller; on the water inlet and outlet flanges, there are threaded holes to install vacuum and pressure gauges; at the bottom of the pump body, there are threaded holes to drain the wastewater.

The impeller is of single suction and closed type, equipped with a balance disk to balance most of the axial force, and also has a thrust bearing to support the small residual part of the axial force. The arrangement of the bearings keeps the shaft in a stable state of tension bar. Before assembly, the impeller must undergo strict static balance verification to ensure stable operation.

The pump shaft is supported by two Babbitt alloy sliding bearings, installed in the bearing housing of the pump support and lubricated with fine oil.

In the pump casing, there is a sealing ring that can improve the volumetric efficiency of the pump and, on the other hand, prevent the backflow of high-pressure water into the suction chamber, disturbing the inlet flow field, thus ensuring the suction performance of the pump.

The shaft seal is generally a soft packing seal. During the operation of the pump, a small amount of medium can be led into the packing box, and external cooling and lubrication water can also be connected to fulfill water sealing and lubrication functions. According to user needs, the packing seal can be replaced with a mechanical seal.

The space between the thrust bearing seat and the thrust disc is adjusted with wedges to ensure that the thrust bearing space requirements are met according to the general assembly drawing.

Instructions for use of the high-pressure boiler feed pump type DG

1. Start-up

Before starting the pump, rotate the pump rotor to check if the rotor rotates flexibly;

Check that the motor direction matches the pump rotation direction;

Open the pump suction valve, close the gate valve and the gauge plug in the outlet pipe to fill the pump with liquid, or use a vacuum system to remove air from the suction pipe and the pump;

Check the tightening of the connection bolts between the pump and the motor and the safety around the pump to ensure it is ready to start;

Start the motor, when the pump is running normally, slowly open the gauge plug and gradually open the outlet gate valve until the gauge needle indicates the required pressure (control the lift height given by the pump according to the reading of the outlet gauge).

2. Operation

This pump balances axial force through an internal balancing mechanism; the balancing liquid flows from the balancing device to the inlet section through a balancing pipe, or a short tube is designed outside the balancing chamber for the balancing liquid to flow outside the pump. To ensure the normal operation of the pump, the balancing pipe must not be blocked under any circumstances;

During start-up and operation, carefully observe the instrument readings, bearing heating, leakage, and packing heating, as well as the vibration and sound of the pump; if any anomalies are detected, they must be addressed promptly;

The increase in bearing temperature reflects the quality of the pump assembly; the bearing temperature must not exceed 35℃ above ambient temperature, and the maximum bearing temperature must not exceed 75℃;

The pump rotor exhibits some axial movement during operation, the axial movement must be within the allowed range, ensuring the space between the faces of the motor and pump couplings;

During operation, periodically inspect the wear of parts such as the impeller, sealing ring, guide sleeve, shaft sleeve, and balance disc; if the wear is excessive, they must be replaced in time.

3. Stopping

Before stopping the pump, first close the gauge plug, slowly close the outlet gate valve, after completely closing the outlet valve, stop the motor, and once the pump is stopped, close the suction valve; drain the water inside the pump; if it is to be left unused for a long time, disassemble, clean, lubricate, and store the pump.

Assembly and disassembly of the high-pressure boiler feed pump type DG

1. Precautions when disassembling the pump

Stop the pump following the stopping order;

Drain the liquid inside the pump housing (including cooling water); if the bearings are lubricated with light oil, drain the lubricating oil;

Disassemble auxiliary pipes that hinder disassembly, such as balancing pipes, water seal pipes, and cables;

Disassembly must strictly protect the manufacturing precision of the parts to avoid damage; when disassembling the through shaft, the middle sections must be supported with blocks to prevent the housings from loosening and sinking, which could bend the shaft.

2. Disassembly order of the pump

Unscrew the bolts of the bearing cover on the discharge side and the connection bolts between the outlet section, the rear cover, and the bearing body, remove the bearing cover, the bearing body, and other bearing parts;

Unscrew the round nut of the shaft and sequentially remove the inner ring of the bearing, the bearing cover, and the retaining ring, then remove the packing body (including the packing cover, the packing ring, and the packing);

Sequentially remove the O-ring seal, the shaft sleeve, the balance disc, and the shaft key, then disassemble the outlet section, the last guide, and the balance ring sleeve;

After removing the last stage impeller and the key, disassemble the middle section and the guide; continue disassembling the impellers of each stage, the middle section, and the guide until the first stage impeller is disassembled;

After disassembling the pump coupling, unscrew the connection nut between the inlet section and the bearing body and the bolts of the bearing cover, then disassemble the bearing parts on the inlet side;

Extract the shaft from the inlet section, unscrew the fixed nut of the shaft and sequentially remove the inner ring of the bearing, the O-ring seal, and the shaft sleeve;

For pumps with sliding bearings, the disassembly order is basically the same, except that the disassembly of the bearing parts is slightly different.

3. Assembly of the pump

The assembly order of the pump is generally done in the reverse order of disassembly. The quality of the assembly directly affects whether the pump can operate normally, as well as the lifespan and performance parameters of the pump. During assembly, the following points must be considered:

The machining accuracy and surface roughness of the parts must be protected, and damages such as dents or scratches are not allowed; the molybdenum disulfide used for sealing must be clean, and the screws and fastening bolts must be evenly tightened.

The alignment between the outlet duct of the impeller and the inlet duct of the guide is guaranteed according to the axial dimensions of each part; the quality of this alignment directly affects the performance of the pump, so the dimensions of the pump should not be adjusted arbitrarily.

After assembling the pump, before installing the packing, manually rotate the pump rotor to check if it rotates smoothly and if the axial play meets the specified requirements.

After passing inspection, press the packing and pay attention to the relative position of the packing ring in the packing chamber.