Figure 1. Scheme of the vacuum pumps balancing stand

Vacuum pumps balancing stand

Vacuum pumps balancing stands were developed in 2002 and 2009.

The main requirement in developing these stands was to ensure high quality balancing of assembled pump high-speed turbine rotors (in their own bearings) at the operating speed, which can be 42,000 – 60,000 rpm for various types of pumps.

The actual value of the residual rotor imbalance had to meet the requirements for rotors of the 1st accuracy class in accordance with the GOST 22061-76.

The design of the stands under consideration is schematically presented in Fig. 1

As in the previous case, the stand is executed in the form of a rectangular platform 1 installed on 4 cylindrical springs 2.

It should be noted that the design and manufacture of the platform provided the longitudinal and transverse ribs, which contributed to the highest rigidity while minimizing the platform weight.

This resulted into high stand vulnerability to the imbalance forces with simultaneous eliminating danger of platform resonance oscillations (bending, torsional, etc.) in the whole rotation rate range of the pumps when balancing.

The platform has a fixed cylindrical base 3, onto which a balanced pump 4 is mounted.

The pump is closed with a special cover 5, with the phase angle sensor 6, which is part of the measuring system of the stand.

Besides, the measuring system includes two vibration sensors 7 and 8, installed on the base and the cover respectively.

All the sensors are connected to the corresponding inputs of the measuring and computing unit 9, which carry out vibration measurements and adjusting weights characteristics calculation.

Apart from the stand development, to achieve the required quality of vacuum pumps rotors balancing, a special technology was required, which included two main stages.

At the first stage, when the pump rotor rotation rate does not exceed 8,000 rpm with the rotor being rigid, the main components of its power and couple imbalance are compensated. At the same time, our devices help to reach the level of residual vibration of no more than 0.01 mm/s in the frequency range from 3,500 to 8,000 rpm.

After that, at the second stage, the rotor is balanced again at an operating frequency of 42,000 or 60,000 rpm, depending on the pump design.

At this rate, exceeding the critical rotation rate, the pump rotor becomes flexible and deformed.

As a result, the additional balancing is required to compensate for the imbalance occurred.

The level of rotor residual vibration, after additional balancing, does not exceed 0.3 mm/s at a rotation rate of 42,000 (60,000) rpm, which guarantees a long-term trouble-free vacuum pump operation.

The time for full balancing cycle of this unique device usually does not exceed 30 minutes.