Is public transportation security necessary?
The “May Day†holiday has just ended, and many people have had the experience of blocking the road. One problem that accompanies the rapid increase in traffic flow is how to ensure the safety of public travel, and the upgrading of public transport security is considered to be an effective method. However, recently launched by the Shenzhen City, Guangdong Province, a forum, "Do you think subway security work is necessary to do" survey, 62.45 percent of users said "No need, such security only for passengers increase a lot of trouble"; only 9.14 % of netizens believe that security can improve security. On April 20th, Zheng Huilong, the deputy head of the Security Department of the Shenzhen Metro Operations Management Office, responded to Shenzhen Citizen's “commentâ€: Since March 7, 2014, a comprehensive security inspection was conducted until April 15, 2015, Shenzhen Metro, Guangdong Province. The total number of inspectors was nearly 500 million. More than 150,000 contraband products were seized, including more than 90,000 pieces of inflammable and explosive materials, and nearly 60,000 pieces of controlled tools... Then, is the need for public transportation security including subways necessary? In the opinion of many experts, the answer is yes. Frequent public traffic incidents in many places across the country The reporter combed and found that since June 2013, buses in Xiamen, Guiyang, Yibin, Changsha, Hangzhou, and Guangzhou have suffered a series of accidents, and subways in Guangzhou and Beijing have also experienced repeated panic attacks. “Based on the characteristics of mobility and diversity, the public security problem of public transport can be said to have high incidence, serious losses and impacts, and even more serious harm to the community. Therefore, the issue of public transport security is very important in the prevention and control system of public security as a whole. One of the topics," said Zhang Qihuai, a researcher at the China University of Political Science and Law long-term research center for aviation and space law. “After a public transportation safety problem arises, it will cause great panic in the community. In recent years, with the acceleration of urbanization, public transportation has become denser and more crowded. The concentration of people will reduce the cost of crime and increase crimes. As a result, in the process of social development and urbanization, there will be a period of high incidence of public transportation security incidents,†said Zhang Qihuai. Some local security is in the form of In recent years, public transport in various cities has significantly increased the level of security inspections. However, the lack of hardware for public transport security inspections and their formality have triggered the public's temptation. Although Wuhan subway safety inspections are complete, there are still loopholes in human security: In individual security inspection stations, passengers' backpacks, satchels, handbags, gift boxes, stainless steel cups, etc. can be brought into the station without security inspection; the strobe light flashes on metal detection doors. In the bright case, the security inspectors were indifferent. Some security checkers were still on duty to play with their mobile phones. On April 3 this year, the issue of “individual security inspections in the Wuhan Metro†was triggered by local media and caused public concern. It is not the first time that a report similar to the security inspection of the Wuhan Metro has been issued. As early as June 13, 2013, local media in Hubei Province published a report on “Reporters carrying unannounced visits to public transport with a liter of alcohol, and the security inspections were inexplicably established and all the way to the streetsâ€. Just two weeks later, local media in Hubei issued another report on June 28th. Net exposure of two passengers carrying gas tanks to take the light rail, Wuhan Metro security worrying report. “At present, the main problem facing China’s security inspection system is inadequate equipment, and there is also no financial resources to support all-weather security inspections and security inspections of all public transport systems. Security inspections are an effective means to ensure the safety of public transportation, but they have always faced insufficient investment. Zhang Zhuting, director of the Department of Political Science and Law at the Department of Management of the Ministry of Transport, said that it is worth noting that at present, China's public transport security is preserved in a major contradiction, and public transportation is often affiliated with enterprises, and companies have many difficulties in assuming responsibility for security. Legislation to protect public transport security How to further implement the security inspection system? Zhang Qihuai suggested strengthening the legislation. “To improve safety measures and security in transportation tools, high-speed transportation tools, station terminals, and terminal buildings, we must first have laws to follow. Second, we must strengthen training for security personnel, establish specialized training institutions and schools, and finally, we must Learn from the experience of some advanced countries to implement effective measures for security inspections,†said Zhang Qihuai. Zhang Qihuai also proposed that the bus has a characteristic that is its liquidity. The establishment of an emergency team can play a role, but it can't be hydrolyzed. Therefore, based on this particularity, it is recommended that urban rail transit operators be given specific rights to ensure the safety of passengers' personal and property. In addition, Zhang Zhuting also suggested that public transportation needs innovative prevention and control system. “This system should be composed of professional teams and volunteer teams. It cannot rely solely on public transport volunteer teams. In addition, this system should be a combination of dynamic prevention and control and static prevention and control, and the combination of industry prevention and control and social prevention and control. The combination of prevention and control in China and in the future, the integration of human resources prevention and control, and the prevention and control of equipment. At the same time, local governments should give this system the necessary financial protection, said Zhang Zhuting. A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball Check Valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check Valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow. Check Valves Check Valves, Water Check Valves, Brass Check Valves, Sanitary Check Valves ZHEJIANG KINGSIR VALVE CO., LTD. , https://www.kingsirvalve.com
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with Ball Valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve or tilting disc check valve is check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains open until the tank Drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in applications such firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure. Another example is the backwater valve (for sanitary drainage system) that protects against flooding caused by return flow of sewage waters. Such risk occurs most often in sanitary drainage systems connected to combined sewerage systems and in rainwater drainage systems. It may be caused by intense rainfall, thaw or flood.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
An in-line check valve is a check valve similar to the lift check valve. However, this valve generally has a spring that will 'lift' when there is pressure on the upstream side of the valve. The pressure needed on the upstream side of the valve to overcome the spring tension is called the 'cracking pressure'. When the pressure going through the valve goes below the cracking pressure, the spring will close the valve to prevent back-flow in the process.
A duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow.
A pneumatic non-return valve.
Multiple check valves can be connected in series. For example, a double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.