At the outset, I acknowledge the universal aversion to addressing safety inquiries directly. However, I seek guidance and definitive responses supported by references. My first query concerns a machine equipped with a light curtain for operator loading. The machine frame rises 2 feet from the ground before featuring a sizable opening large enough for potential entry. The light curtains detect intrusion into the load area and trigger the safety circuit, cutting power to an indexer and pneumatics. Can the light curtain automatically reset upon the operator's exit, or is manual intervention necessary? The second question pertains to a 2ft x 2ft opening outfitted with a light curtain that deactivates power when breached, ensuring safety within the immediate vicinity. Nevertheless, unauthorized entry permits access to powered devices beyond the initial breach point. Clarification on these scenarios is elusive despite my thorough search for relevant information.
1) Most safety standards require a manual reset for a safety trip, although some systems automatically reset a safety communications fault under specific conditions, such as when an AGV passes through a known roaming area. This decision places the responsibility on the system itself. 2) When a light curtain protects a large area, the entire area must be deactivated in the event of a hazard. If the hazard involves a small opening, the entire safety zone should be shutdown unless additional light curtains are used to segment the area. However, this scenario can pose a potential nightmare if someone resets the machine while someone is in the crawlspace.
In my view, in scenario 1, a manual reset of the light curtain safety circuit would be necessary if someone manages to bypass the light curtain and enter the machine. If the system resets automatically and the person gets through the light curtain, they could end up inside the machine. In scenario 2, it is important to assess the potential dangers posed by each accessible device for operators who may crawl into the machine.
I would like to mention a small side note regarding machine safety protocols. The reset function is crucial for ensuring the operator can verify the area is clear of any tools or people before resuming operations. It is recommended that reset buttons are positioned in a way that allows the operator to have a clear visual of the entire machine area. For larger machines with multiple access points, it may be necessary to have two reset buttons that need to be pressed. In some cases, machines may even require both buttons to be pressed simultaneously, especially if there are two operators involved. Consider the example of large press machines that necessitate two buttons to be pressed at once for operation. Cognex and Keyence are reputable companies that offer a wide range of safety devices and solutions for enhancing workplace safety. Explore their offerings for innovative ideas on improving machine safety.
Our system features two reset buttons for each door to ensure operator safety. The inside button is pushed, the door is closed, and then the outside button is pressed, all within a specified time frame. This process serves as a reminder for operators to confirm that the area is clear. The light curtains, which operators reach through, require manual resets. Some machines are divided into zones, and if moving parts breach these zones, they are automatically reset unless the operator's light curtain is also breached simultaneously, in which case a manual reset is necessary. Additionally, small areas within the light curtains are safeguarded with horizontal light curtains that are linked to the ones operators reach through, necessitating a manual reset. In our latest systems, we have implemented area scanners to ensure that no one is inside before the doors can be reset. In my personal opinion, it is advisable to mandate manual resets for light curtains and other presence sensing devices such as horizontal light curtains or area scanners to confirm that the space is clear. If manual resets are not feasible, the dual reset button approach (inside and outside the protected area) can be considered along with mandatory manual resets for every operation.
I implemented a safety relay with a two-handed start button to serve as a reset mechanism for operators loading a machine's light curtain station manually. Our facility had numerous two-handed start stations strategically placed to ensure operators were in a safe position when initiating the machine. The redundant light curtain was an additional safety measure to prevent any mishaps while operators were reaching into the mill. This setup successfully passed our thorough risk assessment process. In the realm of safety regulations, it is imperative that safeguards are put in place to prevent potential energy hazards. Power to drives should not be abruptly cut off to avoid long-term damage; instead, safety-rated STO signals should be utilized, which applies to robots as well. Certain inputs may still have power, such as stack lights in specific scenarios. Failure to reset a tripped light curtain, allowing movement without proper safety protocols, should raise a red flag. My experience predates the introduction of safety PLCs, requiring us to manually configure safety mechanisms to eliminate potential energy when entering a work zone. This included pneumatics releasing air, spring return valves maintaining valve positions, motor brakes automatically engaging in case of power loss, ensuring all hazardous elements were rendered safe upon entering the work area. Understanding and adhering to relevant safety standards is crucial in the industrial sector. The following codes and standards such as NEC, NPFA70, CEC, IEC, NFPA, UL, CSA, and ISO provide comprehensive guidelines for integrating safety measures into machinery design and operation. By consulting these standards, one can ensure compliance and mitigate risks effectively. Furthermore, various ISO standards like ISO 12100, 13849-1, 13850, 14119, 14122, 14122, 13857, 16092, 20607, 22400, 4413, 4414, 13849-2, 16092-1, and 16092-2 offer specific guidelines on risk assessment, machinery safety design, emergency stop functions, safeguarding devices, access to machinery, safety distances, performance indicators, hydraulic and pneumatic system safety, and validation of control systems for enhanced safety in industrial settings. Adhering to these standards ensures a systematic approach to safety implementation and reduces the likelihood of accidents or injuries.
In response to your first question, the functionality of the light curtain reset - whether it's automatic or manual - largely depends on the specific make and model of the machine. Some models may allow automatic resetting once the intrusion is no longer detected, while others might require manual intervention. Consulting the machine's user manual or reaching out to the manufacturer directly would yield the most accurate answer. As to your second query, the possible risk you've described illustrates the importance of implementing a layered approach to machine safety. While the light curtain serves as a first line of defense, you may also want to consider additional measures like safety interlocks, padlocks, and safety mats beyond the initial breach point. This ensures that unauthorized entry does not provide access to other powered devices. Remember, no single safety solution is completely foolproof, but incorporating multiple strategies could significantly limit potential risks.
In my experience, the reset behavior of the light curtain largely depends on the settings of your machine. Some machines do allow for an automatic reset once the obstruction in the light curtain is cleared, while others require manual intervention. It's crucial to check this aspect with your machine's manufacturer or refer to the equipment manual for precise details. As for your second query, it sounds like a risk for unauthorized individuals to access powered devices beyond the light curtain. To mitigate this concern, a safety interlock device could work best to cut power to all devices in the room once the light curtain is breached, or consider establishing additional levels of light curtains. This way, even after the initial breach, further intrusion will be promptly detected and subsequent devices will be powered down. Remember, each installation is unique; so, consult with a safety expert for a thorough machine-specific safety review.
It's great that you’re diving deep into safety protocol with these machines! For your first question, it often depends on the specific configuration of the safety control system used with the light curtain. Many systems allow for automatic resets once the area is clear, but it's vital that this is designed with safety in mind, ensuring there are no risks of unintended reactivation while an operator is still in danger. As for the second scenario, you're right to highlight the potential for unauthorized access—using light curtains is a solid safety measure, but further engineering solutions, like physical barriers or additional safety interlocks at the breach point, might be necessary to ensure no access to powered devices beyond that zone. It's always best to consult the machine's safety manual and relevant safety standards to ensure compliance.
Great questions! Regarding the first scenario, many light curtains do have an automatic reset feature that can be configured to allow the machine to restart once the operator exits the area, but this really depends on how the safety system is set up. It’s essential to ensure that the reset mechanism aligns with safety standards to avoid any hazards. For your second question, while the light curtain provides a first line of defense, you're right to be concerned about potential access to powered devices beyond that point. It may be worthwhile to implement additional safety measures, like physical barriers or interlocks, to prevent any unintended access to those areas. Ultimately, consulting the manufacturer’s guidelines or a safety expert can help clarify the best practices for your specific setup.
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Answer: - Light curtains can be designed to automatically reset once the operator exits the protected area. This feature enhances convenience and ensures seamless operation.
Answer: - A light curtain with a 2ft x 2ft opening is designed to cut power when breached to ensure safety in the immediate vicinity. To prevent unauthorized entry beyond the breach point, additional safety measures or physical barriers may be necessary for enhanced security.
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