What are the requirements for the suction and discharge pipes of fire pumps?

When connecting to equipment, relatively short connecting pipes should possess a degree of flexibility or be designed to compensate for uneven foundation settlement caused by the addition of metal hoses. Remove the plug from the deep well fire pump to allow excess grease to drain automatically. For oil-lubricated pumps, drain the oil to the correct level. For fire pump automatic inspection cabinets with volute pumps, the centerline of the impeller outlet—defined as the midline of the outlet width—must align with the centerline of the volute inlet. If misaligned, adjust by adding shims between the impeller hub and shaft shoulder. Keep the deviation between the two centerlines within 0.5 mm. For pumps with high specific speed, a slight deviation has minimal impact on performance. However, for pumps with medium to low specific speed, where the impeller outlet is narrow (e.g., only 10 mm wide), a 1 mm deviation from the volute centerline significantly affects the fire pump's performance. After adjustment, it is recommended to control the deviation between the two centerlines (impeller and volute) within 5% of the impeller outlet width. Inspect and adjust the packing in the fire pump control cabinet, replacing it as required. Adjust the mechanical seal (refer to the manufacturer's instructions provided with the pump or consult the manufacturer). To prevent cavitation in the pump, the piping from the pump to the installation should taper gradually. If the intermediate section is U-shaped, install a drain valve and an air vent valve at the top.

All piping connected to the fire pump must use independently supported solid structures to minimize pipeline vibration and prevent pipe weight from affecting the pump. Double-suction pumps should be symmetrically arranged to ensure uniform flow distribution on both sides. In inlet/outlet pipelines, install adjustable pump mounts and vibration dampers to accommodate pipeline movement. Vibration supports should be installed at multiple pipeline locations to compensate for installation errors and reduce additional forces on pump connections.

The diameter of inlet/outlet pipes must not be smaller than the pump's inlet/outlet diameter. For reciprocating pumps, the pump end and drive end must not obstruct piston rod disassembly and maintenance. The pump suction piping must meet Net Positive Suction Head (NPSH) requirements, and the pump and piping should be as short as possible. When the pipe length exceeds the distance between the equipment and the pump, process system calculations should be performed. Straight pipe length must not be less than 3D times the inlet diameter.