Is it necessary to lock or seal the interlock emergency stop button cover?

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View 1: The emergency stop button cover needs to be locked or sealed with lead. The design of the emergency stop button cover is primarily aimed at preventing accidental activation and protecting the emergency stop button from damage and external influences. Locking can further ensure that the emergency stop button cannot be activated casually in non-emergency situations, thereby improving safety. The functions of the emergency stop button cover include preventing accidental activation, protecting the emergency stop button from damage and external influences such as dust and water. By locking it, it ensures that the emergency stop button cannot be easily activated in non-emergency situations, thereby reducing the risk of accidental operations. In accordance with relevant specifications and standards, emergency stop buttons should be equipped with protective covers and have clear markings. Although the regulations do not explicitly require that protective covers be locked, proper design and organized training can ensure that operations can be carried out quickly and effectively in emergency situations. Therefore, although locking is not necessary in all cases, it is an effective safety measure. The purpose of sealing digital switches is to ensure the effectiveness of the emergency stop button; digital switches are usually sealed with wax seals. A lead seal is a common sealing material with high corrosion resistance and sealing properties, which can effectively prevent unauthorized persons from operating the emergency stop button. Furthermore, once the seal is broken, obvious traces are left, making it easy to determine whether unauthorized access has occurred. Viewpoint 2: The emergency stop button cover should not be locked with any form of lock. The main standards referred to in China for the design of safety instrument systems in the petrochemical industry are the \"Code for Design of Safety Instrument Systems in Petrochemical Industries (GB/T50770-2013)\\" and the \"Regulations for the Design of Signal Alarm and Safety Interlock Systems (HG/T20511-2014)\“. One of them is a national standard, and the other is an industry standard for the chemical sector. Due to the high similarity between coal-to-oil and coal chemical processes and petroleum chemical processes as well as chemical plants, the design and construction of safety instrument systems in these fields also follow the relevant provisions of these two standards. Requirements for the installation of emergency stop buttons according to different standards: 1. The regulations regarding the installation of emergency stop buttons state that (1) these buttons should be placed on the auxiliary control panel. (2) The operation of the emergency stop button shall be accompanied by a turntable alarm and recording. (3) The emergency stop button shall not be equipped with a maintenance bypass switch or an operation bypass switch. 2. The settings for the emergency stop buttons specify that (1) emergency stop buttons for systems that do not have safety interlock functions can be implemented as software buttons on the BPCS operator station, while emergency stop buttons for systems with safety interlock functions should be implemented as hardware buttons on the auxiliary control panel. (2) The hardware buttons installed on the auxiliary control panel should be connected to the logic controller of the interlock system, and status alarms should be provided within the system along with recording capabilities. (3) The emergency stop button should not be equipped with a maintenance switch. (4) The emergency stop button shall be a red mushroom-shaped button with a protective cover. 3. ISO 13850 is another internationally recognized standard; in section 4.5 of its 2015 version, two functional requirements are specified for emergency stop buttons: (1) A protective cover should not be installed on emergency stop devices, unless it is necessary to prevent accidental activation and no other methods can meet the requirements. (2) For manual emergency stop devices, the measures to prevent accidental activation must not hinder or obstruct the operator or any other person who needs to perform an emergency brake from carrying out the hand movements required for such braking at any foreseeable position. 4. By comparing the different standards, it was found that there are certain differences in the technical requirements for the emergency stop button. In GB50770, there are no requirements regarding the type of emergency stop button or whether such buttons need to be equipped with protective covers; HG20511, on the other hand, has such requirements. ISO does not recommend the use of guards for emergency stop buttons, and requires that such guards must not hinder the movement of the operator’s hands. From this perspective, GB50770 does not require the installation of protective covers for emergency stop buttons, which makes it easier to understand. As for the type of protective cover for emergency stop buttons, none of the standards provide clear guidelines. Overall, the concepts behind GB50770 and ISO13850 are likely to be more similar: protective covers should be used with caution, and their presence must not cause delays in the activation of emergency braking systems. As there are currently no precise statistical data available regarding the proportion of stoppages caused by accidental presses among all stoppage incidents, nor the annual incidence rate of such accidental presses (whether or not they result in a stoppage), it is difficult to make quantitative judgments in this regard. However, in actual production processes, it is difficult to ignore the economic losses resulting from shutdowns caused by accidental triggers. Therefore, for this issue, during the design and installation phase, it is necessary first to avoid placing the emergency stop button in areas with heavy foot traffic and a large number of people; the type of structure for the emergency stop button should be carefully selected based on its functionality and the installation environment. Use color, shape, and other warning signals to draw the attention of people near the emergency stop button. 6. Fully enclosed flip-type emergency stop button cover: The button of the fully enclosed flip-type emergency stop button cover is located inside the cover, isolated from the outside world. If necessary, the operator can easily lift the outer protective cover upward and then press the button downward. Due to its enclosed structure, accidental activation of the emergency stop button inside it can be virtually completely prevented, and it also provides a certain level of protection for the emergency stop button. The process of performing an emergency brake can be simply broken down as follows: for a flip-up type cover, the time it takes to flip up the cover plus the time required to press the button equals the time needed for an emergency brake. Assuming the operator’s reaction time is 450 ms, in actual field conditions, a person’s reaction time is 550 ms. Therefore, the operators inside or outside the area must open the protective cover of the flip-type shield within 450ms/550ms and press the emergency stop button to take action. If seals or other locks are in place, attempting to unlock them in an emergency will delay the response time and may lead to further escalation of the accident. Therefore, while meeting safety requirements, the impact of the protective cover on emergency stop operations should be minimized as much as possible, to ensure that operations can be carried out quickly and effectively in emergency situations. The emergency stop button protection setting should not be locked in any form.