The Krammer Locks (Krammersluizen)
The highlight of the Philips Dam is formed by the two shipping locks. These locks were essential because the Philips Dam found itself on the shipping link between the Scheldt and the Rhine. They have a unique system by which saltwater and freshwater can be separated. It was intended to prevent too much salt water from the Oosterschelde flowing into the freshwater Volkerak or too much freshwater flowing into the Oosterschelde when ships were passing. Experience had already been gained with a salt-fresh separation system at the Kreekrak locks further south on the Scheldt-Rhine Link. The locks were built with a length of 280 metres and a width of 24 metres in order to make room for inland vessels with four tug-pushed lighters. Outports, with a length of 1.3 kilometres where ships could moor, were built in front of the locks. An additional yacht lock was built north of the two locks with its own 75 metre long outport. Space was reserved for additional locks if the shipping industry or pleasure cruising should increase in the future.
The Scheldt-Rhine Link
The Scheldt-Rhine Link (or Scheldt-Rhine Canal) was opened in 1975 for shipping traffic between the Scheldt and the Volkerak. The canal is 38 kilometres long and starts in the harbour area of Antwerp. From there it goes through Zuid-Beveland to the Kreekrak locks in the Oosterschelde, followed by the dredged channel through the Oosterschelde and the broadened river Eendracht. It then continues through Sint-Philipsland and ends up at the Volkerak. When ships pass the Krammer Locks of the Philips Dam, they arrive on the Hollandsch Diep. The river Waal can be reached through the Merwede. Push-tow combinations with a maximum of 9,000 tons are allowed on the Scheldt-Rhine Canal.
Separate salt and fresh water
The fact that salt water has a higher density than fresh water (1.03 kg/dm³ <-> 1.00 kg/dm³) had an influence on the design of the locks. When fresh and salt water are mixed, salt water sinks to the bottom. Suppose a ship sails from the Oosterschelde into the lock. First of all the lock gates are closed behind the ship. Then the salt water (situated at the bottom) gets pumped out underneath. At the top fresh water is pumped into the lock. When the water level has fallen far enough and the salt water is pumped out, the lock opens. When a ship wants to sail into the Oosterschelde from the Volkerak, almost the same thing happens: once the ship is inside the lock, the lock gates will close behind the ship. A large amount of the fresh water gets pumped away at the top and at the bottom salt water is pumped in. When the water level is equal to the water level on the Oosterschelde, the lock gates at the front of the ship will be opened. It is inevitable that each time some fresh water ends up in the Oosterschelde. Thankfully it has no significant influence on the salt water environment.