【Common Issues in Haichuan Pipeline Design】10 Key Requirements for Pump Pipelines, 4 Types of Auxiliary Pipelines, and 3 Typical Arrangements

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During the design, installation, and inspection of pipelines, various minor issues that have been overlooked or not taken into consideration are often identified. These issues are collected and organized into a series; this list is being updated continuously. Everyone is welcome to actively participate in discussions. This is a compilation post on common problems in Haichuan pipeline design – it’s still being updated, and discussions are welcome: https://bbs.hcbbs.com/thread-5705828-1-1.html ------------------------------------------------------------------ The 10 key requirements for pump piping, 4 types of auxiliary pipelines, and 3 typical layout patterns. “Pumps are the ‘heart’ of chemical processing units, while their inlet and outlet pipelines serve as their ‘vascular system’.” Whether a pump can operate smoothly, efficiently, and for a long period depends not only on its own quality but also on whether the design of the piping system connected to it is reasonable. This article systematically outlines the 10 core requirements for pump piping, the installation principles of the 4 types of key auxiliary pipelines (balancing/minimum return/warm pump/anti-condensation), as well as schematic diagrams and key tips for avoiding pitfalls in the three typical layout configurations: side inlet, top inlet, and top outlet. Whether you are conducting detailed design or on-site construction inspections, this is a valuable practical checklist. I. Core Principles – 10 Key Points for Pump Inlet and Outlet Pipelines. Valve Installation: Cut-off valves must be installed at both the inlet and outlet; the type of valve to use depends on the pipe diameter (gate valve/butterfly valve/sphere valve). Support and flexibility: Equipped with adjustable/vibration-damping supports to absorb pipeline stress ； When short pipes connect different base devices, flexibility (such as flexible hoses) is required to compensate for equipment settlement. Diameter principle: The diameter of the suction/discharge pipe should be ≥ the pump port diameter, with the suction pipe being 1–2 size grades larger than the discharge pipe to avoid throttling. NPSH assurance: The suction pipeline should be short and straight, with as few bends as possible, to fully meet the pump’s required net positive suction head (NPSHa > NPSHr). Requirements for straight pipe sections: There should be a straight pipe section with a length of ≥3 times the inlet diameter in front of the centrifugal pump, to ensure a stable flow velocity. Symmetry of double-suction pumps: The pipes of double-suction pumps need to be arranged symmetrically to ensure balanced flow and prevent cavitation. Backflow prevention setup: A check valve should be installed at the outlet of the centrifugal pump, as close to the pump outlet as possible to facilitate maintenance. Safety pressure relief: A safety valve must be installed in front of the outlet valve of the reciprocating pump to prevent overpressure. Monitoring and protection: A pressure gauge is installed at the outlet (between the pump outlet and the check valve) ； A filter is installed at the inlet (Y-type for ≤2″, T-type for >2″) to protect the pump body. Venting at the highest point: A vent valve should be installed at the highest point of the pipeline, especially in a \"jacking\" configuration, to release air during startup. II. Lifeline systems – Analysis of 4 types of critical auxiliary pipelines 1) Balance pipe: When vaporization of the fluid occurs easily at the pump inlet, a balance pipe that can return to the gas space of the equipment upstream of the suction side can be installed between the pump inlet nozzle and the pump inlet isolation valve, allowing the generated gas to flow back and preventing cavitation in the pump. An isolation valve should be installed on the balance pipe. 2) Minimum return pipeline: To prevent the centrifugal pump from operating at a flow rate lower than its minimum value, a minimum return pipeline for the pump should be installed, allowing a portion of the fluid to flow back from the pump’s discharge outlet to the container at the pump’s suction inlet, thereby ensuring the required flow rate of the pump. 3) Warm pump pipeline: When the temperature of the material conveyed by the centrifugal pump exceeds 200 ℃, a warm pump pipeline is required. This pipeline allows a small amount of material to flow from the discharge pipe of the operating pump to the outlet of the standby pump, then pass through the standby pump and return to the pump inlet, thereby keeping the standby pump in a heated standby state to facilitate its startup. 4) Anti-freezing pipes: Pumps handling media that tend to solidify at room temperature should be equipped with DN20–25 anti-freezing pipes, installed in the same manner as the pipes for heating pumps.