A Retrofit Solution to the Failure of a Swimming Pool Lane Divider Storage Reel
A Retrofit Solution to the Failure of a Swimming Pool Lane Divider Storage Reel from Barry Sunderland
A Retrofit Solution to the Failure of a Swimming Pool Lane Divider Storage Reel

Storage reels are used to retrieve, store and deploy lane dividers in the University of Limerick 50 m swimming pool. Many of the reels began to fail at the welded joint between the crossbars and the frame. An investigation was carried out that measured the forces applied to the reels, calculated the stresses on the welded joints using Finite Element Analysis and hand calculations.
It was judged that the joints were failing due to high cycle fatigue cracks that were initiated by corrosion pits at the weld site.
A number of different solutions were explored which aimed to provide a low cost design that could be retrofitted to the existing reels. An AISI 304 stainless steel bracket was designed, This bracket can be slotted between the bars and rotated into position. The bracket would be welded to the frame and would ensure that the weight of the lane divider is shared between the three crossbars at all times.

Lane divider storage reels are used on the pool side in the University Arena 50m Swimming Pool to recoil, store and redeploy the lane dividers. The hooked end of a lane divider is slotted in between the three crossbars and the reel is turned manually to wrap the lane divider around the crossbars. These reels are used almost hourly to either place lane dividers in the pool or to take them out to facilitate the needs of different pool users.
Many of the storage reels, which had been in service for ten years, began to fail at the welded joints. The storage reels were still in use after the crossbars began to fail. This put more stress on the remaining crossbars which subsequently failed. A section was taken from a failed crossbar for inspection. The storage reel was fabricated from AISI 304 stainless steel. This is an austenitic CR-Ni stainless steel that has high weldability and is widely used for general stainless steel fabrications. Inspecting the material surface showed that due to the high moisture, chlorinated environment there was widespread pitting corrosion on the surface of the bars and on the weld.
It was also clear that the weld was of low quality and was considerably undercut. This occurs when the parent metal is flushed away during the welding operation due to the welding current being too high or poor operator technique. This causes a higher stress concentration at the joint than would be expected. A force gauge was connected in line with a lane divider and the lane divider was reeled in a number of times. This allowed us to get an approximate value for the force that is applied to the cross bars during operation. The loading pattern on the cross bar is reasonably complex but was simplified into two situations. A point load that occurs when the lane is being wound in and the evenly distributed load when the lanes are stored on the reels.
The design of the storage reel causes the forces during retrieval and storage to be applied to the crossbars individually. A bracket was designed that would divide the load between the three crossbars. The geometry of the bracket would allow it to be slotted between the existing crossbars, rotated and then welded into position. This reduces labor costs and provides a fast solution to the reel failures.
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A Retrofit Solution to the Failure of a Swimming Pool Lane Divider Storage Reel

Storage reels are used to retrieve, store and deploy lane dividers in the University of Limerick 50 m swimming pool. Many of the reels began to fail at the welded joint between the crossbars and the frame. An investigation was carried out that measured the forces applied to the reels, calculated the stresses on the welded joints using Finite Element Analysis and hand calculations.
It was judged that the joints were failing due to high cycle fatigue cracks that were initiated by corrosion pits at the weld site.
A number of different solutions were explored which aimed to provide a low cost design that could be retrofitted to the existing reels. An AISI 304 stainless steel bracket was designed, This bracket can be slotted between the bars and rotated into position. The bracket would be welded to the frame and would ensure that the weight of the lane divider is shared between the three crossbars at all times.

Barry Sunderland
Mechanical Engineer actively seeking employment in the NW United States Bozeman, MT