An embodiment in accordance with the present invention provides a hydraulic pump including a first motor running at a fixed speed, a reservoir for fluid and a first pump operatively coupled to the motor such that the pump runs at the same speed as the motor and generates a flow of fluid from the reservoir. The heat exchanger includes an inner tube through which a heat exchanger medium can flow and a flexible outer tube that at least regionally envelops the inner tube with the formation of a flow-through intermediate space. The timer begins a countdown when the locking barrier is left in an open position. Plural buffering systems may be used as arranged in one or both of in series and in parallel.