[Ocean Chemical Valve Management] Series of Posts - Talking about "running, popping, dripping and leaking of valves"”

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Good management of valves is the basis for stable operation. Welcome everyone to communicate, discuss and share [Ocean Chemical Valve Management] series of posts. https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5719309 ----------------------------------------------------------------Disclaimer: The content contained in this article is for technical communication and reference purposes only and does not constitute any form of professional engineering advice, design basis or operating guidance. ----------------------------------------------------------------------------------- In scenarios involving fluid control such as industrial production, municipal pipe networks, and energy transmission, valves serve as core actuators, and their sealing performance is directly related to the operational safety, economic benefits, and long-term stability of the system. The so-called "run, pop, drip and leak" is not a single failure mode, but a collective term for four different types of leak phenomena. They have different characteristics in terms of leakage intensity, location and degree of harm. Only by accurately distinguishing them can targeted treatment be achieved. “"Leakage" usually refers to a large and rapid leakage of media from a valve or connecting part, which is often caused by damage to the valve body, overpressure in the pipeline, operating errors, or valve body rupture. For example, when a steam valve is damaged, high-temperature steam gushes out, which not only causes a huge waste of energy, but may also cause serious consequences such as burns to personnel or equipment outage. “"Risk" specifically refers to the overflow of the medium from the top of the valve or equipment, which is common in situations such as imbalance in liquid level control, safety valve failure, or system overpressure. For example, improper feeding operation of the reactor causes liquid to emerge from the manhole, which can easily cause medium contamination and personnel contact risks. In comparison, the instantaneous leakage of "drip" and "leak" is small, but it is highly concealed and the long-term accumulated harm cannot be ignored. “"Drip" is manifested as medium seeping slowly from flange interfaces, stuffing boxes, threaded connections, etc., usually caused by sealing surface wear, gasket aging, thread looseness, etc. For example, oil droplets leak after the flange gasket is corroded. Long-term effects will accelerate equipment corrosion and pollute the environment. “"Leakage" refers to the continuous flow of media from cracks, pores or sealing failures in the valve body, mostly due to casting defects, weld cracks or packing failure. For example, if a small amount of leakage caused by the wear of natural gas valve packing is not discovered in time, explosive mixed gas may be formed, posing a major safety hazard. In addition, leakage can also be divided into external leakage and internal leakage.: External leakage refers to the direct leakage of media from inside the valve to the external environment, usually occurring in the valve stem stuffing box, flange connection surface, valve body casting or welding seam. Since the leaking medium is directly exposed to the atmosphere, leakage is often easily detected by the naked eye or detection instruments. But the harm is extremely direct and serious: If the medium is high-temperature steam, toxic gases, flammable and explosive fluids, or highly corrosive chemicals, once leaked, it will cause energy waste and equipment corrosion at least, and may cause burns, poisoning, fire or even explosion accidents at worst. In addition, leakage will also lead to loss of production materials, environmental pollution and corporate compliance risks. Especially in the context of increasingly stringent environmental protection supervision, leakage of media may directly trigger penalties or production suspension for rectification. Internal leakage occurs when the valve is closed. The medium leaks from the high-pressure side of the valve to the low-pressure side through the sealing pair, but it is always enclosed within the pipeline system and will not leak directly to the environment. Because there is no visible medium overflow, internal leakage is extremely concealed and often requires the use of temperature detection, pressure change analysis, ultrasonic leak detectors or abnormal system energy consumption to detect it. Although internal leakage does not directly threaten personal safety or cause on-site pollution, its long-term harm should not be underestimated.: It will destroy the adjustment and control accuracy of the system, causing the flow, pressure or liquid level to deviate from the set value. ； When pumps, compressors and other equipment continue to operate, internal leakage will cause ineffective circulation and significantly increase energy consumption. ； Long-term erosion may also accelerate the wear of the seal pair, causing leakage to continue to expand, eventually causing valve leakage or system failure. What's more serious is that in some key process interlocking systems, internal leakage may cause frequent tripping of safety valves, loss of control of reaction conditions or failure of emergency cut-off functions, posing potential risks for major accidents. From the perspective of causes, "running, emitting, dripping, and leaking" can be summarized into four core factors: selection, installation, operation and maintenance, and working conditions. Improper selection is the fundamental reason. For example, using ordinary seals under high temperature conditions or using conventional valve bodies in highly corrosive media can easily lead to premature seal failure. Improper installation will directly lead to hidden dangers, such as uneven packing, inconsistent tightening torque of flange bolts, coaxiality deviation between valves and pipelines, etc., which may cause leakage in the early stages of operation. Lack of operation and maintenance is the main reason for frequent leaks. Failure to inspect or replace aging packing and gaskets for a long time, and neglecting the cleaning and lubrication of valves will accelerate the wear of key components. In addition, fluctuations in working conditions, such as drastic changes in pressure and temperature, excessive impurity content in the medium, etc., will also significantly increase the loss of the seal pair and induce leakage. In view of the above causes, combined with on-site practical experience, prevention and control measures can be systematically implemented from the four dimensions of "selection, installation, maintenance and control". In the selection process, the valve material and sealing grade should be reasonably selected based on the medium characteristics, working pressure and temperature range. Metal-sealed valves should be preferred for high-temperature working conditions, and fluorine-lined valves are recommended for highly corrosive media. It is also recommended to install a filter upstream of the valve to prevent impurities from eroding the sealing surface. During the installation process, construction specifications should be strictly implemented to ensure that the valve and pipeline remain coaxial, the packing is filled in layers and the cuts are staggered, the flange sealing surface is cleaned, and the bolts are evenly tightened in diagonal order. After the installation is completed, a pressure test must be performed, and it can be put into operation only after passing the test. In the operation and maintenance process, a regular inspection and maintenance system should be established, focusing on key parts such as stuffing boxes, flange connections and sealing surfaces, and timely replacement of aging and damaged seals and gaskets. For slightly worn sealing surfaces, grinding can be used to repair them. ； Regularly clean the impurities in the valve flow channel to prevent the valve disc from getting stuck. ； At the same time, standardize the operating procedures to avoid human errors such as excessive force or improper operation. In terms of emergency response, once a leak occurs, the system should be isolated first, the source of the medium should be cut off, and temporary leak plugging measures should be taken according to the type of leak. For example, if a stuffing box leaks, the gland can be temporarily tightened. For leaks of highly toxic and high-pressure media, an emergency plan must be initiated immediately and professionals must be contacted to deal with it. The valve must be completely repaired or replaced in a timely manner afterwards. The "running, popping, dripping and leaking" of valves may seem trivial, but in fact they are related to production safety, energy conservation and comprehensive enterprise benefits. Technical personnel and operation and maintenance personnel should firmly establish the concept of "prevention is better than cure", accurately identify leakage types, systematically analyze the causes, and implement prevention and control measures into every aspect of selection, installation, and operation and maintenance. Only through scientific and rigorous full-process control can we effectively reduce media waste, reduce operation and maintenance costs, prevent safety accidents, and ensure long-term safe and stable operation of the system.