How to drain almost 10 million gallons of water in just 14 hours
Trollhätte canal, located in the Southwest part of Sweden, has a difference in altitude of 145 ft, handled by six locks. One single lock demands 2.1-3.2 million gallons of water. In May 2009, the lock system was closed down for maintenance and repair; this required four of the locks to be drained and kept dry for four days. Grindex pumps in the sizes Matador and Maxi were rented for the task. During 14 hours, a total of almost 10 million gallons of water were drained away.
A 200-year-old canal with 145 ft. of difference in altitude
Trollhätte canal was opened for traffic for the first time back in the year 1800. This allowed sailing ships to pass through the river Göta älv all the way from Gothenburg up to Lake Vänern. The river has been widened several times since the opening. The canal is 50 miles long; 6 miles of these are excavated while the rest is a natural part of the river. The difference in altitude is 145 ft. and is managed with locks in three places: One lock in Lilla Edet is managing 18 ft. and in Trollhättan are four locks with a total difference in altitude of 105 ft. The last lock is located in Brinkebergskulle and manages 20 ft.
At every lockage, 2.1-3.2 million gallons water is demanded. 
Every lock contains 2.5 million gallons of water; this is equal to nine seconds of flow in the Göta Älv River. Despite their 200 years of age, the locks are modern with electric and mechanical operation of the locks. Double lock floors gives calmer movement of water during both filling and emptying of the locks.
Ships up to 4000 metric tonnes can pass the locks; the limits are 290 ft. of length, 43 ft. width and 17.7 ft. depth.
Service and repair
With intervals of a few years, the locks are closed down for service and repair. In May 2009 four lock chambers were scheduled for an overhaul. From May 9 at 6:00 a.m. to May 12 at 8:00 p.m., they needed to be completely drained. And we are talking about big amounts of water; as every lock chamber is 295 ft. long, 43 ft. wide and 26 ft. deep, you end up with a total of almost 10 million gallons or 37 million of litres with water. All this must be drained away in less than 24 hours.
Renting pumps from Grindex
The Swedish Maritime Administration is responsible for the locks. As they were planning the service and repair of the locks, they contacted the local supplier, Sjuntorps Industrisupport, who helps them with pumps in other applications with pump rental requests. As the time frame was narrow it was imperative the whole operation went according to schedule. Staff from Grindex technical department assisted with sizing of the pumps. With facts from earlier lock chamber emptying projects using Grindex pumps, a time between nine 9 and 16 hours was estimated. For this task the pump models Matador and Maxi were recommended. At the pressure height of 20 ft., the pumps have a flow of 81,000 and 181,000 gallons per hour.
A total of 17 pumps were rented, including backup pumps.
A service deal between the Swedish Maritime Administration and Sjuntorps Industrisupport was also closed, guaranteeing service around the clock, together with spare pumps if necessary. Everything was working as planned and the staff from the Maritime Administration could focus on their task without bothering about the pumps. The time frame for the draining of the lock chambers was set to 24 hours. After only 14 hours it was dried out and ready for work.
This case story can also be downloaded from Grindex Press site together with high resolution images. The address is www.grindex.com/press