Brevini gears up to protect Hull from flooding

© Copyright Paul Glazzard

Approaching its mouth at the Humber Estuary, much of the river Hull’s course is through extremely flat land that is just above sea level. This means that the river’s height is affected by the tide as it winds through the city and even into the surrounding countryside. Ever since the City was built flooding has posed a threat to properties as large seasonal tides have caused the river to overtop its banks. Records of attempted flood defence systems date all the way back to the 1700’s. The most recent, and most successful, is the Hull Tidal Surge Barrier which was constructed in 1980.

The tidal barrier features a 212 tonne gate which spans 30 meters between two towers that house its mechanics. The gate sits across the mouth of the river Hull and can be lowered when an exceptionally high tide is predicted. Once closed, the sea water is prevented from surging up the river and flooding nearby properties. Since its construction the barrier has proven extremely effective and is closed approximately 12 times each year; in November, 2013, it protected an estimated 17,000 properties from a 5.85 meter record high tide.

Regular maintenance and improvements are made to the flood defence to make sure it remains as reliable as ever. To this end a recent refurbishment project was carried out which included a complete replacement of the operating system, consisting of mechanical, electrical and hydraulic equipment. Brevini supplied the complex gear system, which was designed to safely position the barrier during tidal swells and then lift it back safely.

Dave Brown, Brevini Sales Manager explains: “The renovation of the Hull Tidal Surge Barrier was an extremely important project, if the barrier fails then thousands of lives will be impacted upon. The drive system needed to operate in the worst conditions that nature could throw at it. The project managers approached us as we specialise in designing gearboxes which can deliver high reduction ratios for slow and steady movement on high-torque, heavy applications.

“The nature of this application requires a high degree of precision and reliability; the potential damage that a failure could cause doesn’t bare thinking about. We worked closely with the project managers to understand what the duties may be, given different scenarios and designed a system that would be capable of moving the gate, even in the event of a drive failure. Reliability was definitely the name of the game in this application as failure to either open or close the gate as desired could result in large scale flooding across Hull.”

Due to the fact that the drive system had to physically fit in a pre-defined and very tight space envelope while accommodating very specific operational needs, a standard proprietary gearbox was never an option. Both of the towers’ drives consist of a large 3:1 Posicross bevel gearbox connected to a triple input Posired 2 bevel helical unit with reduction ratio of 25.6:1. This in turn is combined with a two stage Positorque planetary gearbox with a reduction ratio of 20.238:1. The innovative arrangement allows for mechanically linking both drives with the option to hydraulically or hand drive the gate from either tower, also while keeping dimensions to a minimum.

Dave Brown continues: “We worked out the possible requirements given different scenarios – such as lifting the gate when it is subjected to mud suction. From there we were able to design a solution that would fit within the confines of the tower and operate safely even in the event of a drive or a complete power failure. Everyone was happy with the solution and it has been operating reliably despite the severe flood event the country has suffered in recent years.”

© Copyright Bernard Sharp