A ship cannot function without the various pumping systems placed in or controlled from the machinery spaces. The pumping systems are of major importance and they are many and varied. Some systems supply coolant and lubricants to the main machinery, and without their supply the main propulsion machinery will be quickly brought to a halt by safety devices in the control system. The machinery would be badly damaged if safety devices did not function to bring it to a halt. This illustrates the importance of machinery support systems, and the safety devices used to protect machinery in the event of a pumping system malfunction. An equally important pumping system is used to pump out loose water from cargo and machinery spaces, which must be kept clear of water to prevent damage. In extreme cases, if loose water is not removed it could eventually collect at some point where the stability of the ship would be adversely affected and lead to capsize or sinking. Machinery of either steam or internal combustion type requires clean fuel free of water. The fuel transfer system is used to bring fuel from the bunker storage spaces into settling tanks where water and heavy dirty material are removed. In motor ships the fuel requires further purification treatment. This treatment is carried out in the fuel cleaning or separation system. When cargo operations are in progress the ballast system may be used for ballasting or de-ballasting to maintain draught, trim, and a safe stability, and sometimes to keep hull stresses within safe limits.