Disassembly of large circulating pump impeller

Abstract: The structure of circulating pump rotor is huge and the shape error exists locally. Impeller disassembly is difficult. This article describes the structural characteristics and removal of special tools.

1 Overview

Our circulating pump is produced by the Changsha Pump Factory single-stage double-suction centrifugal pump, model 32SHA-10, medium for ammonia and urea production of recycled water. The pump rotor by the impeller, shaft, flat key, left and right positioning sleeve and threaded sleeve composition, size and structure shown in Figure 1. Although the fit of the impeller and the shaft is a clearance fit (φ165D / d), the tolerance of the impeller hole, the shaft and the key has an error due to the large tolerance of the impeller and the shaft (181335 mm2), which makes the impeller disassembly difficult. At the same time as the rotor running time is longer, the gap between the positioning sleeve and the shaft has been media corrosion and dirt deposition filling dead, positioning sleeve can not be removed alone, only with the impeller together to remove, so that more impeller The difficulty of demolition. In view of the rotor structure and the actual use of the situation, we use the top pressure method and the temperature difference method and the demolition program, and achieved good results.

The demolition of the basic process is: First, the rotor placed on a demolition tire, so that the impeller fixed, and then apply a certain amount of top pressure on the shaft, while the impeller hub to be heated to expand, the shaft under the action of force and Impeller hole from.

2 removal of the design of the tire

According to the rotor structure and stress analysis, taking into account the stability of the tire, bearing capacity and ease of production, the framework of the tire welded with 16 channel steel, the bottom frame with a thickness of δ35 Q235 steel reinforcement , The upper part of the two force beams using movable push-pull structure, the material with heavy rail 14.

In the demolition, the first rotor on the tire, and then the beam placed on the inlet end of the impeller, jack pressure on the shaft, the entire rotor vertical upward movement, when the beam and the upper frame on both sides of the tire Fixed beam contact, it will play to limit the role of the impeller to move up. As the jack below the rotor continues to pressurize, when the top pressure exceeds the combined resistance between the impeller and the shaft, the impeller and shaft will slip until they fall off.

3 top pressure and heating method to determine

With the gap (mm) Jack (t) Heating time t (min)

t1 t2

0.03 to 0.0550 6 3

0.06 ~ 0.08 505 2

0.08 ~ 0.130 5 1

Rotor in the demolition of the top of the pressure of the size of the heating temperature level and the length of time are the key to influence the rotor can be successfully removed.

3.1 pressure to determine the top

Using assembly theory to calculate, the removal force is:

P = πDL · q · f

Where: D-mating surface diameter, m;

L- with the inclusive length, m;

q-shaped position error should be positive pressure, Pa;

f-coefficient of friction.

Calculated: removal force P = 181335 × 10-6qf.

It can be seen from the above equation, shape and position error caused by the positive pressure q and friction coefficient f of small changes, will lead to large differences in disassembly force, the practice concluded that long-term operation in the medium circulation pump rotor, the impeller Friction is quite large demolition, the general f to take 2 to 8, q to 9.8 × 104 ~ 1.47 × 105, so Pmax = 213249.96N.

3.2 Determination of heating method

For the structure of the impeller, combined with the actual production, we use two gas welding at the same time the impeller hub heating gas welding flame form of oxidation flame. Heating time should be strictly controlled, if the heating time is short, the expansion of the hole is not enough, the impeller and the shaft can not slip; If the heating time is too long, the impeller heat quickly passed to the shaft, the shaft get too much heat, local heating, Axis diameter increases, in theory, the axis of the heating rate is accelerated, the hub temperature slowed down by the temperature difference between the wheel hole and the shaft is not increased but decreased, it is likely to have interference fit , So that disassembly can not be carried out.

4 Conclusion

Circulating pump impeller demolition, the use of top pressure and temperature difference method combined with the practice proved to be a safe and reliable, easy to use, but also greatly improve the efficiency of disassembly methods. Its small footprint, compact structure, flexible mobile, can be used at the production site or repair shop, laid the foundation for the overhaul of the circulating pump in the future.

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