Requirements for Suction and Discharge Piping of Fire Pumps

Fire pumps are among the most commonly used pumps in China. Their suction and discharge pipes constitute vital components of equipment deployed nationwide. Due to specific operational requirements, thorough preparation, understanding, and strict adherence to procedures are essential for ensuring efficient pump performance. For deep well fire pumps, remove the plug to allow excess grease to drain automatically. For oil-lubricated pumps, drain oil to the correct level. Diesel-powered fire pumps are categorized into different types based on various classification methods. With their fully sealed, leak-free, and corrosion-resistant characteristics, they are widely used in environmental protection, water treatment, firefighting, and other sectors for pumping various liquids. They are ideal pumps for creating leak-free, pollution-free workshops and factories. The pump types used in firefighting systems are similar, differing only in head and flow rate. For fire pump automatic inspection cabinets with volute pumps, the centerline of the impeller outlet (i.e., the centerline of the impeller outlet width) must align with the centerline of the volute inlet. If misalignment occurs, adjust by adding shims between the impeller hub and shaft shoulder. The deviation between the two centerlines should be controlled within 0.5 millimeters. For pumps with high specific speed, a slightly larger deviation has minimal impact on performance. However, for pumps with medium to low specific speed, where the impeller outlet is narrow—for example, only 10 millimeters wide—a 1-millimeter deviation from the volute centerline significantly affects the fire pump's performance. After adjustment, it is advisable to control the deviation between the two centerlines (impeller and volute) within 5% of the impeller outlet width. As is well known, certain characteristics and related piping systems have their own specific requirements.

1. The piping systems at the pump end and drive end of reciprocating pumps should be reasonably arranged to avoid obstructing the disassembly and maintenance of pistons and connecting rods.

2. All piping connected to the pump (including those subjected to burst testing) must have independent, solidly supported foundations to minimize vibration transmission and prevent pipe weight from bearing on the pump.

3. Fire pump mounting brackets should incorporate inlet and outlet vibration damping supports to correctly position piping and reduce additional forces on the pump nozzle caused by installation errors.

4. When connecting the pump to equipment on shorter, non-uniform foundations, the connecting piping system must incorporate flexibility or incorporate metal flexible hoses to compensate for differential foundation settlement.

5. The diameter of suction and discharge pipelines shall not be smaller than the inlet/outlet diameter of the fire pump.

6. The pump suction piping must satisfy the required net positive suction head (NPSH). Shorter piping is preferable, especially when redirecting flow toward the pump. When the distance between the pipe and the pump is long, the system should be designed with cavitation prevention measures.

7. To prevent pump cavitation, the elevation of the suction piping system from the equipment to the pump inlet should gradually decrease. No U-shaped sections should occur in the middle. If unavoidable, install an air vent valve at the high point and a drain valve at the low point.

8. The straight pipe section before the fire pump inlet must not be less than three times the inlet diameter.

To prevent uneven suction flow and cavitation in the pump, the suction pipe should be symmetrical on both sides to ensure uniform flow distribution.

When utilizing fire pumps, understanding their requirements for suction and discharge piping is essential. This enables efficient application of technical equipment and maximizes operational benefits. Another fundamental piping requirement is compliance with quality standards. Otherwise, even if other specifications are met, the overall effectiveness will be significantly compromised.