Network and Transient Modelling of Dual Pressure Distribution Systems

There is much demand from international clients, especially in the Middle East, to reduce costs by enabling low pressure distribution networks to provide a high pressure supply to fire hydrants by operating the systems on a dual pressure basis. There are many problems associated with such an approach, and conventional steady state design approaches prove inadequate in these circumstances. Accurate modeling of the dynamic response of the network to a fire demand is necessary to ensure that the control system will respond reliably. A combination of industry standard steady state and transient modeling methods have been used to develop operational philosophies, pressure surge protection, and to design adequate security of supply. This paper describes the modeling methodology, and the design approach used to safely protect a complex network. It gives practical illustration of control, mechanical, and cost issues relating to the dual network, and provides a basis to reconsider the potential cost savings of dual pressure networks. Issues addressed include: 1) the detection of an open fire hydrant to trigger standby pumps to rapidly increase the network pressure, 2) provision of adequate surge protection, 3) coordinating surge protection with rapid response, and 4) a review of the cost implications of an adequately controlled system.