Proven corrosion protection in salt water environments is also finding its way into inland applications. The second chamber of the new twin lock was put into operation in Münster in April 2014.

The annual cargo guided through here corresponds to a traffic volume of more than half a million trucks. An electro-hydraulic system solution from Rexroth generates and regulates all of the motion required for the locking processes. The hydraulic cylinders are equipped with the long-lasting corrosion protection, Enduroq, and a new generation of the contactless position measurement system, CIMS.Since the construction of the Dortmund-Ems Canal in 1899, initially one and then a total of three locks as of 1913 and 1926 have been surmounting a height difference of 6.2 meters in the southern section near Münster. Inland water transport has changed considerably in the past decades, however. In the past, shipping traffic was characterized by towboats, but today, large motor vessels and push-towing units with lengths of up to 189 meters are the standard. This presents new requirements for modern locks and made a new construction of the locks in Münster necessary.

Half of the water remains in the system
The Münster I and Münster II twin locks exchange 8,000 cubic meters of water per lock process – half of the required quantity per chamber. This provides savings in water consumption. The lock process begins once the flap gates at the upstream head and the miter gates at the downstream head are closed. The water flows via two longitudinal channels on both sides of each chamber and through two transverse channels into the chamber with the lower water level. Through this exchange, both chambers reach the same level in the middle between the respective target marks. While the remaining water is drained downwards in the chamber for the descent, the other chamber is filled up by the water intake structure. A total of ten closures in the channels regulate the water level.

Electro-hydraulic drive solution: intelligent and reliable
Electro-hydraulic drives from Rexroth generate all the motion required for the locking processes, the opening and closing of the flap and miter gates, as well as the eight circulating closures in the longitudinal channels and the two transverse closures. For decades, the company has been equipping locks with drive and control technology all over the world. In addition to numerous constructions in Germany, Rexroth solutions are also being used in the Panama Canal, for example.

The hydraulics have a major advantage in that the modular design enables the spatial separation of thrust and drive cylinders. This meant the hydraulic power units for the new Münster I and II locks could be placed below the locks, protected in caverns. Only the cylinders directly at the gates and closures are exposed to splashing.

Environmentally friendly, rapidly biodegradable hydraulic fluid
The 16 hydraulic power units each consist of two redundant motor-pump groups, with an installed output power of 2×15 kW for the roller gates and miter gates as well as 2×7.5 kW for the flap gates. The A10VSO axial piston pumps used from Rexroth are particularly quiet and achieve a level of efficiency which is well over 90 percent. They are able to generate the required flow by means of the swivel angle adjusting mechanism. A special feature of the Rexroth axial piston pumps is that the service life is independent of the hydraulic fluid. With the environmentally friendly, rapidly biodegradable hydraulic fluid based on synthetic ester which is used in Münster, the components used are also able to achieve the same service life as with mineral oil. The electronic components of the hydraulic power units open up many possibilities for diagnosis and permanent condition monitoring. Technicians can call up operating states and change parameters at any time.

Proven corrosion protection in salt water
Cylinders with a stroke of 2,200 mm open and close the 52-ton miter gates with a traction force of up to 450 kN. The cylinder stroke for the 13.2-meter wide flap gates at the upstream head is 8,100 mm. The 10 roller gates for the longitudinal and transverse channels are opened and closed by hydraulic cylinders with a stroke of 3,000 mm. All cylinders have corrosion protection for a long service life. Reliable corrosion protection involves more than the coating of the piston rod. Only the application-specific interaction of coating, tribology, and sealing technology ensures comprehensive, long-term protection. Rexroth provides such coordinated system solutions on the basis of its Enduroq surface technology. The Enduroq coatings have already proven themselves worldwide in numerous maritime and offshore applications. The empirical values in these harsh environments convinced WNA Datteln to also use this corrosion protection on the Münster lock.

Highlight of the expansion program
The new construction of the Münster I and II twin locks ranks among the outstanding measures undertaken in the expansion program of the southern stretch of the Dortmund-Ems Canal and ensures that considerably more than the average of 16,000 vessels and push-towing units to date will be handled every year.

Author: Bosch Rexroth AG, Arnold Habermann
Department: Sales Steel Construction for Hydraulic Engineering