In-Situ Balancing vs. Workshop Balancing: Which to Choose for Your Equipment?

Method 1: Balancing on a balancing machine (in the workshop)

How it works

The component (rotor, shaft or impeller) is removed from the main equipment and taken to a dedicated balancing centre. There it is mounted on a high-precision balancing machine, which spins the rotor up to the required speed and performs all the necessary measurements and calculations.

Advantages

• High balancing accuracy for an individual component: balancing machines provide precise measurement and make it possible to bring the residual imbalance below the tolerances set by the standards.
• Controlled conditions: all operations are carried out in the workshop at an optimal temperature, free from external vibration and interference.
• The option of accompanying work: turning, welding and the replacement of worn parts can be done at the same time.
• A standardised process: especially useful when balancing series-produced parts.

Disadvantages

• Long equipment downtime: it requires complete dismantling, transport and subsequent reassembly of the component. This can take days or even weeks.
• High total cost: the price includes not only the balancing but also the dismantling, transport and reassembly.
• It does not account for the system's influence: a rotor balanced perfectly on the machine may vibrate once installed in the unit, owing to the influence of couplings, bearings, the foundation or alignment.
• Size limitations: not every machine is suitable for large or heavy rotors.

Method 2: In-situ balancing (where the equipment is installed)

How it works

Balancing is carried out directly on the customer's equipment, in its own bearings, without removing the rotor. A specialist with a portable vibration measurement system and a laser tachometer balances the unit at its working speed, right where it operates.

Fig. 1. Sensor installation for in-situ balancing: 1, 2 - vibration sensors on the bearings, 3 - laser speed sensor, 4 - measurement unit, 5 - laptop with the software

Advantages

• Minimal downtime: the work often takes just a few hours. No dismantling of the unit is required.
• Substantial cost savings: there is no expenditure on dismantling, transport and reassembly.
• Balancing the system as a whole: the main advantage — it takes account of real conditions: the stiffness of the foundation, the state of the bearings, the couplings and shaft alignment.
• Versatility: suitable for large equipment and equipment that is difficult to dismantle.
• Work on site: the specialist comes to you, with no need to transport the rotor anywhere.

Disadvantages

• It requires access to the rotor: there must be a way to fit the correction weights.
• Starts and stops are required: the process needs 3-4 start-up cycles of the equipment for measurement.
• The influence of external factors: vibration from neighbouring equipment or unstable speed can complicate the work.

A detailed comparison table

How to choose the optimal method: a decision checklist

Choose WORKSHOP balancing if:

• You are balancing a new part before installation.
• The rotor is fresh from an overhaul or manufacture.
• The part is small and easy to remove.
• You require very high accuracy (grade G1.0 or better).
• Accompanying mechanical work is needed (turning, weld build-up).
• Downtime is not critical.

Choose IN-SITU balancing (on site) if:

• The equipment is large (big fans, induced-draught fans).
• Dismantling is difficult, expensive or impossible.
• Downtime is critical (production cannot wait).
• The rotor operates as part of a complex system (couplings, drive).
• Real installation conditions need to be taken into account.
• You need to eliminate vibration in the whole unit, not just the rotor.

Practical application examples

Example 1: a boiler induced-draught fan

The task: elevated vibration in a 200 kW induced-draught fan.

The solution: in-situ balancing of the impeller.

The rationale: removing the impeller would have meant shutting the boiler down for several days. The in-situ balancing was completed in 3 hours during a planned shutdown.

Example 2: an electric-motor armature after rewinding

The task: balancing a 30 kW armature after the winding was rewound.

The solution: workshop balancing in the repair shop.

The rationale: the armature had already been removed for repair. Workshop balancing provides high accuracy and is convenient, since the part is already in the workshop.