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http://mmbiz.qpic.cn/mmbiz_jpg/UnooUHhibJVSNaF3yCJyBezkm9cvUiaQ1srof9MLqj3AGk51tVkoEFyvAbsk6icytMRYLkdKHj8QrCB0dP8HMsVicQ/640?wx_fmt=jpeg&tp=webp&wxfrom=5&wx_lazy=1 1. There are 6 types of protection wires for pumps, whose purpose is to prevent damage to the pump and ensure its proper operation; the protection wires are selected based on the operating conditions. 1. Warm pump line – When transporting high-temperature oils with a temperature exceeding 200°C, a DN20–25 warm pump line should be installed if a backup pump is available ； 2. Low-flow line – When the pump’s operating flow rate is 30% below its rated flow rate, a low-flow line should be provided to allow the pump to operate normally at that lower flow rate ； http://mmbiz.qpic.cn/mmbiz_png/UnooUHhibJVSNaF3yCJyBezkm9cvUiaQ1sDAkev0Qudcav3ibmUGLYtYsp0xDc1Z69PjQRSudx1QKuJQXMYn2zIww/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=13. Balance line – For liquids whose saturated vapor pressure at room temperature is higher than atmospheric pressure, or for liquids that are in the bubble point state, a balance line must be installed to prevent vapor from forming in the liquid entering the pump or bubbles from entering the pump and causing cavitation ； http://mmbiz.qpic.cn/mmbiz_png/UnooUHhibJVSNaF3yCJyBezkm9cvUiaQ1sIibs0NHxDT9WeQLtF8sIN9hLaqapKNG288ibuRibFElfSNSU4rOKdPPbg/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=14. Bypass line – used for testing the pump or to keep it running when the main outlet valve is closed under abnormal operating conditions. Bypass valves equipped with flow-limiting orifices are generally installed in situations where the pressure difference before and after the valve is very high ； 5. Anti-condensation measures – When transporting liquids with high pour points or high freezing points that solidify at normal temperatures, anti-condensation measures should be implemented in the standby pumps and pipelines to prevent blockages (Pump Manager is worth paying attention to) ； 6. Safety valve line – For positive displacement pumps such as electric reciprocating pumps, gear pumps, and screw pumps, a safety valve line is provided on the outlet side; when the outlet pressure exceeds a set value, the safety valve opens and the fluid returns to the pump’s inlet pipe. II. The minimum flow line of a centrifugal pump serves the following purposes: 1. When the centrifugal pump operates at low flow rates, fluid separation can occur inside the pump, which can lead to vibration and noise in the pump. By setting a minimum flow rate for the pipeline, it is ensured that a certain amount of fluid flows through the pump at all times after it starts up, thereby preventing cavitation ； 2. When a centrifugal pump with high power is operated with the outlet valve closed, the fluid inside the pump becomes increasingly hot; in severe cases, this can damage the bearings. By installing a minimum flow line, it is possible to ensure that a certain amount of fluid flows through the pump at all times while it is running, thereby preventing such issues from occurring ； 3. When operating at low flow rates, the pump shaft is subject to additional radial forces. By installing a minimum flow line, it is ensured that a certain amount of fluid flows through the pump at all times during operation, thereby preventing the pump shaft from being subjected to excessive radial forces ； 4. Sometimes, a flow-limiting orifice plate is used on the pump’s minimum flow line; this ensures that the centrifugal pump can continue to operate safely even if the pump’s outlet valve is closed due to some mistake, thereby preventing damage to the pump. The advantage of using a flow-limiting orifice plate is that no manual adjustment is required; if only a shut-off valve is used to regulate the flow, it is difficult to keep it near the pump’s minimum flow rate – the flow will either be too high or too low. http://mmbiz.qpic.cn/mmbiz_png/UnooUHhibJVSNaF3yCJyBezkm9cvUiaQ1sxYzjMj7V60s9nh2yiaStpXVydwQDH8ickmGtX2XwA6IGT7rP3GlwIroA/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1 III. Differences between various traffic streams 1. Differences between low-traffic streams and circular streams. The former has a flow rate that is 30% lower than the rated flow rate during normal operation, while the latter is used in locations where frequent switching on and off is required or to prevent clogging due to condensation. Similarity: The flow rate of the pump is much higher than the flow rate required by the actual process. 2. Distinguish between the minimum continuous stable flow rate and the minimum continuous heat flow rate. The minimum continuous stable flow rate refers to the lowest flow rate at which the pump can operate properly without exceeding the specified limits for noise and vibration; this value should generally be determined by the pump manufacturer through testing and provided to the user. The minimum continuous thermal control flow rate is the lowest flow rate at which the pump can operate continuously without being impaired by the temperature rise of the liquid being pumped.