Assembly process of centrifugal pump

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The components of the pump must be qualified products and have undergone various rust prevention treatments. The components should be cleaned thoroughly during assembly, and there should be no oil stains, dirt, or iron filings present. Exposed machined surfaces of carbon steel and cast iron components should be coated with rust proof oil or grease.

Assembly process of centrifugal pump

1、Assembly process rules

1. General requirements during assembly

1.1 The components of the pump must be qualified products and have undergone various rust prevention treatments.

1.2 The components should be cleaned thoroughly during assembly, and there should be no oil stains, dirt, or iron filings present.

1.3 Exposed machining surfaces of carbon steel and cast iron components should be coated with rust proof oil or grease.

1.4 After pump assembly, there must be arrow markings indicating the direction of pump rotation.

1.5 After passing the performance test of the 1.5 pump, the accumulated water inside the pump should be removed, and anti rust oil or grease should be applied to the carbon steel pump body flow channel, carbon steel impeller flow channel, outer surface, carbon steel pump shaft and other components.

1.6 Before packaging the pump, a 5mm thick Q235-A material blind plate should be installed at the inlet and outlet of the pump body. If there is a matching flange, it should also be installed on the blind plate.

2. Requirements for partial and final assembly

2.1 When assembling flat keys and bearings, it is not allowed to directly strike them with an iron hammer. Instead, wooden hammers, copper bars, or special assembly tools should be used for assembly.

2.2 When the inner diameter of the bearing is an interference fit of r6 and s6, hot fitting should be carried out at a temperature of 80-120 ℃

2.3 The joint end between the double headed bolt and the mother body should be coated with dry oil, ensuring consistent length and even tightening.

2.4 During the assembly process, it is strictly prohibited to scratch the surface of the components, especially the mating and sealing surfaces, to avoid affecting the assembly quality.

3、Assembly of mechanical seals

3.1 During assembly, each joint surface should be strictly adhered, and the friction surface should be coated with industrial Vaseline lubricating oil.


4.1 During the assembly of the coupling, lubricating oil should be applied to the inner hole, shaft neck, and keys. The force should be evenly applied during assembly to prevent damage to the parts due to impact.


1、Cleaning:The components must pass the inspection, the material code meets the drawing requirements, the surface is cleaned clean, and the mating surface is coated with engine oil. The bearing box should be cleaned thoroughly and coated with oil resistant enamel. It should be naturally dried for 24 hours and can only be assembled after passing the inspection.

2、Assembly of bearings and shafts:

The bearing is heated in the heating furnace to 90 ℃ -110 ℃ and installed on the shaft for cooling. First, install the bearing cover on the left side of the bearing box, then install the components of the bearing and shaft into the bearing box, lean against the left bearing cover, and measure the size of the drive end bearing cover and the outer ring end face of the bearing. The clearance is 0.30-0.70mm for CZ pump and 0-0.42mm for ZA pump. If the bearings of the ZA pump are used in pairs, install and use a tightening nut to lock the bearings until the outer rings of the two bearings can rotate relatively slightly to obtain an ideal clearance.

3、Assembly of mouth ring, impeller, and pump body

When assembling the mouth ring with the impeller or pump body, attention should be paid to evenly installing the mouth ring around the impeller or pump body to minimize the shape error of the mouth ring. After installing the set screws or welding them, measure the radial runout and clearance between the impeller and the ring. The measured values should comply with the general technical conditions for pump assembly, and any parts that exceed the tolerance should be repaired.

4. Sealing installation

4.1 Installation of containerized mechanical seals

When installing containerized mechanical seals, first use double headed bolts and nuts to install the seal onto the pump cover. After the pump shaft is inserted into the sealing shaft sleeve and the bearing housing is connected to the pump body, move the stop gasket on the seal away from the shaft sleeve.

To reduce the wear of the O-ring during installation, the area where the O-ring passes can be lubricated, but the ethylene propylene rubber ring should be lubricated with soap solution or water.

4.2 Packing Seal Installation

Before installing the packing seal, the length of each circle should be determined based on the outer diameter of the shaft sleeve. After slightly flattening, it should be wrapped around the shaft sleeve and pushed into the packing box. If there is a water seal ring, it should be installed together as required. After filling, press evenly with the packing cover.

5. Install impeller

For single-stage pumps, the impeller should undergo a static balance test and meet the technical requirements. After installing the impeller on the shaft and tightening it with a nut, install the entire rotor into the pump body and tighten it with the nut.

For multi-stage pumps, in addition to conducting static balance tests on the impeller, a trial assembly of the rotor components should also be carried out. The impellers and shafts should be installed together, marked, and dynamic balance tests should be conducted. The experimental results should meet the technical requirements.

During installation, push the balance drum, shaft sleeve, and all impellers to the right until the first stage impeller and shaft sleeve are against the shaft shoulder. Measure the gap between the shaft sleeve and the balance drum to ensure it is ≥ 0.5. If the gap is too small, adjust the balance drum to meet the requirements. Then install the shaft with the first stage impeller onto the inlet housing, and gradually install the impeller and the middle section housing with guide vanes onto the shaft until the outlet section. Fix the pump components with screws, install balance devices, seals, and bearing components, determine the correct middle position of the rotor, and adjust the axial clearance of the tapered bearing to 0.04-0.06mm

6. Adjustment of the bearing housing of a horizontal multi-stage pump

The bearing housing of multistage pump with non lip positioning shall be aligned and adjusted during installation. Rotate the adjustment bolt to make the bearing housing move vertically and horizontally. Measure the limit positions of the bearing housing in both directions, take the average value, and finally lock it with a locking nut. Fix the positioning pin, then install the seal and bearing. Adjust the axial direction of the rotor.

7. Coupling installation (pump head fixed)

Installation of membrane coupling:

Install the pump end and motor end couplings onto the corresponding shafts, and use a dial gauge to align the coaxiality of the two shafts (adjust the motor position vertically with a gasket) so that the radial runout between the two shafts is ≤ 0.1 and the end runout is ≤ 0.05. Once the requirements are met, install the intermediate coupling part. At speeds greater than 3600 rpm, radial runout ≤ 0.05 and end runout ≤ 0.03. If using high temperatures (approximately greater than 130 ℃), final calibration should be carried out under high temperature conditions during pump operation.

Installation of claw coupling:

Similar to membrane coupling, install the two flanges of the coupling onto the corresponding shaft and adjust their positions with a ruler. If the speed is ≥ 3600 rpm, it should be aligned according to the membrane alignment method.

8. Painting

Painting should be carried out in a clean and dry place, with an ambient temperature of no less than 5 ℃ and a relative humidity of no more than 70%. If the relative humidity is greater than 70%, an appropriate amount of moisture-proof agent should be added to the coating to prevent whitening of the film.

Non steel metal parts, stainless steel parts, chrome plated, nickel, cadmium, silver, tin and other parts: sliding parts, fitting parts, sealing surfaces, ribbed surfaces, signs and steering signs are not painted.

All non machined surfaces and non mating surfaces of pump components other than those mentioned above should be painted.



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