Special pumps for crude oil caverns
KSB Group has supplied Scandinavian Tank Storage Sweden, with pumps intended for discharging crude oil from an underground rock cavern. The oil will be pumped to the surface by three special-designed submersible borehole pumps manufactured at KSB’s Homburg site in Germany. All three pumps are equipped with a 700 kW motor and are operated at a voltage of 6,600 V.
The pumps are made of duplex stainless steel and each one has a flow rate of 2,000 cubic metres per hour. The head is around 80 metres. During testing, both pump and motor exceeded the quoted efficiencies.
Since the cavern is heated, the motors had to be equipped with an external cooling water supply system. Despite this fact, the pumps, including power cable and cooling water tube, were not allowed to exceed a given outside diameter, because they have to fit into existing caisson pipes This is the reason why standard pump/motor units could not be used for the application. Three process pumps installed above ground pump the oil to the waiting ocean-going tankers.
At the end of the 1970s, the Swedish government had four huge rock caverns built for crude oil storage in Syrhala, at the port of Gothenburg. With a storage capacity of 800,000 cubic metres of crude oil each, they were used for contingency stockpiling of the national oil reserves to prevent supply shortages. As a consequence of the changed geostrategic situation in the mid-1990s, however, the Swedish government closed all strategic oil storage plants.
The existing caverns will now be used for interim storage of the crude oil shipped on smaller vessels through the Baltic Sea from Russia to Sweden, where it is then pumped onto ocean-going vessels for its onward journey to North America, Japan, Singapore and to the large European refineries. One of the caverns is therefore being prepared for reuse as a transit crude oil storage facility.
Having completed construction phase one, the first shipload of crude oil is expected for the autumn of this year. The pump manufacturer was awarded the contract because of its reputation as a full-liner and because of its competent service team in Sweden. In addition, KSB has a history of supplying equipment to storage caverns around the world.
The plant in Syrhala is the only one of its kind in Sweden, as there is currently nowhere else where you can unload and load crude oil at the same location. The authorities hope that the new facilities will put the port in the same competitive league as large ports such as Rotterdam and Hamburg.