Valve Static Sealing Failure: Hidden Dangers and Remedy

In industrial production, valves, as key devices for controlling fluid flow, have a crucial role in ensuring static sealing performance. Valve static sealing failure can lead to the leakage of hazardous materials, energy loss, environmental pollution, and even safety accidents, severely affecting the safety, stability, and long-term operation of enterprises. This article will delve into the risks associated with valve static sealing failure and introduce effective measures to enhance the reliability of valve sealing.

Valve static sealing failure is a problem that cannot be ignored, as it may trigger a series of serious risks and consequences. The following sections will detail the risks associated with valve static sealing failure.

Valve static sealing failure can lead to the leakage of flammable and explosive media. When the concentration of flammable gases in the environment reaches the explosive limit, it can easily cause fire and explosion accidents. For example, in the processes of petroleum refining and chemical production, many valves are used to control the flow of flammable and explosive gases or liquids. Once the static sealing of a valve fails, the leaked medium may explode upon contact with an open flame or high temperature, causing severe casualties and property damage.

Valve static sealing failure can also lead to the leakage of toxic and harmful media. This not only causes the concentration of toxic and harmful substances in the environment to exceed the standard but also poses a serious threat to human health. For example, in some chemical enterprises, valves are used to control the flow of toxic gases such as chlorine and ammonia. If the valve seal fails, the leaked toxic gas may spread rapidly, causing great harm to surrounding personnel and the environment.

The static sealing failure of high-pressure medium valves can lead to the leakage of high-pressure media. Prolonged leakage can damage the sealing flange surface, causing permanent seal failure due to erosion and the formation of grooves on the flange sealing surface. In addition, the leakage of high-pressure media may also damage other nearby equipment and facilities, and even cause personal injury. For example, in high-pressure steam pipelines, the failure of valve sealing can lead to the leakage of high-temperature and high-pressure steam, posing a serious threat to surrounding equipment and personnel.

The static sealing failure of high-temperature medium valves can lead to the leakage of high-temperature media. This not only causes damage to other nearby equipment and facilities due to high temperatures but also poses the risk of scalding to personnel. For example, in the high-temperature steam pipelines of thermal power plants, the failure of valve sealing can lead to the leakage of high-temperature steam, causing serious harm to surrounding equipment and personnel.

The static sealing failure of critical valves can lead to unscheduled shutdowns in continuous production enterprises. This not only causes significant economic losses and resource waste but also has a major impact on the production plan and economic benefits of the enterprise. For example, in refining enterprises, the failure of critical valve seals can lead to flare emissions, which have adverse effects.

Valve static sealing failure can also lead to the phenomenon of "leakage, overflow, drip, and spill" on the plant site. This not only affects the appearance of the production equipment and the cleanliness of the site but also causes environmental pollution and accelerates the corrosion of equipment and pipelines. For example, in the production sites of some chemical enterprises, leakage caused by valve seal failure seriously affects the production environment and the service life of the equipment.

To address the risks associated with valve static sealing failure, a series of measures must be taken to enhance the reliability of valve sealing. The following are some specific methods.

Gaskets are one of the key components of valve static sealing. By improving or upgrading the types of gaskets, the reliability and service life of the seal can be significantly enhanced. Generally, metal gaskets, metal wound gaskets, metal and non-metal combination gaskets, and PTFE gaskets have better reliability and service life than rubber gaskets and synthetic fiber gaskets. When selecting gaskets, different working conditions should be considered. For example, non-metal soft sealing gaskets can be used at normal temperature and low pressure; non-metal and metal combination sealing gaskets or metal gaskets should be used at medium to high pressure and high temperature; and elastic or self-tightening gaskets, such as Belleville springs and anti-loosening nuts, should be used at sealing joints where pressure and temperature fluctuate.

With the increasing awareness of environmental protection, the selection of materials for valve sealing gaskets should also meet environmental requirements. According to environmental trends and industry requirements, gaskets made of asbestos-containing materials, including asbestos boards and asbestos ropes, are prohibited. Based on the actual site conditions, PTFE gaskets, asbestos-free synthetic fiber gaskets, metal wound gaskets, metal gaskets, and serrated gaskets are generally chosen. Except for special equipment or design requirements, rubber gaskets, asbestos rubber gaskets, PTFE-coated gaskets, flexible graphite composite gaskets, and metal-coated gaskets are generally not selected.

When selecting gaskets, high-grade gaskets can generally be used instead of low-grade gaskets, but low-grade gaskets should not be used instead of high-grade gaskets. This is because high-grade gaskets usually have better sealing performance and higher reliability, which can better meet the requirements of complex working conditions.

The quality of the flanges, gaskets, and fasteners of the valve is an important guarantee for the reliability of the seal. In addition to components provided by the original manufacturer, the selected components should be of high quality, and the manufacturers should have the necessary supply qualifications and a good track record. When receiving and using flanges, gaskets, and fasteners, the material and appearance should be inspected, and the use of defective parts should be strictly prohibited. Visual inspection items mainly include the surface precision of the flange being qualified, without casting shrinkage cavities, inclusions, forging scars or cracks, and no scratches, burrs, etc., on the sealing surface; no cracks, scratches, or impact damage on the sealing groove and sealing ring; the surface of the gasket should not have twists, deformations, cracks, delamination, scars, gaps, unevenness, rust spots, or other impurities that affect the sealing performance; the threads of the fasteners should not be deformed, bent, damaged, missing, or rusted.

When installing valves, ensure that all components are clean and free of dirt. If necessary, lubricants or anti-seize agents should be applied to the bolts. The pre-tightening force of the sealing gasket should be moderate, neither failing to achieve the sealing effect nor exceeding the design specifications to prevent the gasket from being over-compressed and losing its rebound capacity. Bolt tightening should be done using torque wrenches. For bolts larger than M24, synchronous/hydraulic or pneumatic torque wrenches should be used in principle, while manual torque wrenches should be used for bolts smaller than M24. Bolts should be tightened symmetrically in sequence, and they should not be tightened to the design value in one go. Generally, at least 2 to 3 cycles are required to ensure even force distribution on the sealing gasket.

Pressure tests should be conducted on valves that have not been tested after installation or if there is any deformation or loosening of the seal during transportation or installation. Only after passing the test can the valve be put into operation. Pressure testing is an important means of inspecting the sealing performance of valves and can effectively identify potential sealing issues, preventing leakage accidents during operation.

Production control should be strengthened to continuously improve the stability of production operations, avoiding significant fluctuations in temperature, pressure, flow, and other control indicators, and reducing vibrations and impacts on valves. Thermal tightening should be performed on the flange bolts of thermal pipelines, and 100% re-measurement of the tightening torque values should be conducted for Class A equipment and GC1 pipelines, while no less than 60% re-measurement should be done for Class B equipment and GC2 pipelines, and no less than 20% re-measurement for other equipment and pipelines. These measures can effectively reduce the risk of valve sealing failure caused by improper operations.

During each inspection, visually check the valve sealing gaskets, and regularly use instruments to detect leakage at sealing points, especially for the sealing gaskets of flammable and explosive equipment and pipeline valves. Timely identification and handling of potential hazards can prevent the escalation of faults and accidents. Regular inspection and maintenance are important means to ensure the long-term stability of valve sealing performance, effectively extending the service life of valves and reducing maintenance costs.

Valve static sealing failure is one of the common safety hazards in industrial production, which can lead to serious consequences. By implementing measures such as improving gasket types, selecting environmentally friendly gaskets, reasonably choosing gasket grades, ensuring component quality, standardizing installation operations, conducting pressure tests, strengthening production control, and regular inspection and maintenance, the reliability of valve sealing can be effectively enhanced, and the risk of valve static sealing failure can be reduced. Enterprises should place high importance on the management of valve static sealing, take scientific and rational measures, and ensure the safety, stability, and long-term operation of the production process.