Sulzer often works with hospitals on planned maintenance tasks, repairing and replacing fans, motors and other equipment as the need arises. Through these partnerships, the company was recently asked to assist with an urgent repair.
Maintenance engineers at the hospital had investigated a vibration problem with an air handling unit that supplied emergency theaters. Having identified a catastrophic bearing failure, they realized that an immediate repair was required and called the local Sulzer Service Center.

Emergency entrance of hospital.
The emergency theaters were only out of action over the weekend, as planned

Diagnosing the issue

The initial site visit was made on the Saturday when they assessed the damage and checked the dimensions of the shaft. The fan within the air handling unit, which was originally manufactured in 1970, measured approximately 1.5 meters in diameter and was supported by a 1½ inch (38 mm) shaft. The original bearings were non-lubricating pillow block bearings which had been recommended by a local supplier. These had failed due to a lack of lubrication, which resulted in damage to the shaft and a considerable amount of vibration in the fan unit.

Sulzer proposed the manufacture of a new shaft and the installation on new split bearings that would improve the performance of the fan and reduce the maintenance requirements for the future.

Recommended treatment

The duty engineer at the hospital approved the suggested solution and urged the repair to be completed at the earliest opportunity. Sulzer immediately ordered the new bearings and the replacement shaft was manufactured at the local service center overnight.

On Sunday, the engineers returned to the hospital with all the new components and installed the shaft and bearings. With the new parts in place, the fan was checked and dynamically adjusted for balance and the final vibration results were sent directly to the duty engineer as confirmation of the completion of the repair.

“This repair was all about speed and delivering a robust solution that would last for many years to come. Understanding the needs of the customer and the importance of completing the repair on time is a specialty of ours.”

Paul Stevens - Sulzer sales engineer

Technical information

Sulzer uses a variety of balancing equipment and vibration analysis software to ensure comprehensive data is provided to the customer. Following guidance from ISO 2372 (10816), the vibration testing results are categorized into one of three groups which are prioritized using a ‘traffic light’ sequence:

  • Critical – Red – above 7.1 mm/sec – Immediate attention is required
  • Warning – Amber – Above 3.5 mm/sec – Attention is required at the earliest opportunity
  • Normal – Green – Machinery is operating in a satisfactory condition
Reception area in a hospital.
Overnight repairs ensured the emergency theaters were ready for operations on Monday morning

Saving costs and time

For every hour that the emergency theaters are out of action, there is a cost of GBP 2’500 (USD 3’200) per hour as well as the inconvenience to patients of having to rearrange operations. By completing the repair over the weekend during a planned maintenance period, Sulzer helped the hospital to avoid these costs and return the operating theaters to the medical staff.

Since the repair, the slightly smaller AHU for other theaters at this hospital was also inspected, identifying a similar level of vibration. To resolve this, Sulzer proposed a replacement shaft and split bearings to be installed during a planned maintenance period, minimizing downtime within the department.

Paul Stevens, concludes: “The repair of the shaft and bearings was completed by 5 p.m. on Sunday and the speed of the repair was very much appreciated. In fact, the Theater Manager advised us that we had avoided having to cancel up to nine operations that were planned for Monday.”

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