Metal fabricators operate large, robust machinery every single day. So it goes without saying that it’s crucial employees are properly trained before operating said machinery. But beyond training on the equipment, employees should also be trained on the safety elements of the machine.
More often than not, metalworking machines require some type of safeguard to protect workers. Those can include hazard identifications as well as hazard reduction features and configurations along with safety-related electrical devices. A good example of a machine needing safeguarding is a gantry-style plasma cutter. With its automated motion, which operates at speeds near 1,800 ipm, a plasma cutter has the potential to seriously harm an employee.
In 2016, the U.S. Department of Labor reported 4.5 injuries per 100 full-time workers on average within the metal manufacturing industry. Despite a seemingly small percentage of the overall workforce, every effort should be made to substantially reduce the amount of workplace injuries. When choosing new machinery, it is paramount that end users evaluate the machine safety features. Injuries that could have been prevented with safeguarding devices cannot be tolerated.
The cost of accidents
When an employee is harmed, the costs associated with the accident can extend far beyond medical bills. Some are obvious, such as sick pay for injured employees while others are harder to identify and can, at times, be more expensive. The full financial impact of an accident can include an increase in insurance premiums, lost production, lost employees or customers, and even the loss of a long-standing reputation.
In the case of the fast-moving plasma machine, creating a safe working environment is two-fold. A commitment to operator safety must be accepted by the machine manufacturer, but it must also be implemented and embraced by the fabricating company and its employees.
The commitment to safety by the manufacturer and the user must also be applied throughout all stages in the life of a machine: design, manufacture, installation, adjustment, operation, maintenance and eventual scrapping.
Expectedly so, machine safety standards are available to guide manufacturers in designing machines that are safe, legal and efficient. Machines, therefore, should comply with a common set of safety requirements, thus setting a minimum level of protection for end users. Compliance to safety standards is largely for the benefit of the end user.
Functional safety
Functional safety refers to the general safety principles of machine design and the overall safety of the machinery control system, which depends on electrical safety-related systems. The goal of functional safety is to focus on reducing and eliminating risks of the machine components used, increasing the utility of the overall machine.
Risk assessment and risk reduction methods are part of the functional safety considerations. The electrical safety-related systems can include components that contribute to the performance of safety functions. Performance depends on correct selection and operation of input switches, functional controllers (including their software and firmware) and output devices, such as contactors and variable speed drives.
Functional safety standards encourage designers to focus on the functions that are necessary to reduce individual risks and the performance level required for each function, rather than simply choosing generalized components without precise requirements for the application.
Trusted machine designers offer safe machines that have undergone a risk assessment. There are various techniques for performing risk assessments and while none can say which is “the right way” it should be done; it largely depends on machine configuration or application.
Machine risk identification is defined by a series of engineering judgments by the machine manufacturer. All of the potential hazards throughout the lifecycle of the machinery with regard to any foreseeable misuse must be identified by the manufacturer.
Hazards may be found with respect to loading, material, quantity, speed, waste disposal, etc., and the risk must be reduced by eliminating them at the design stage. If the hazards cannot be eliminated by design, then extra protective measures by safety-related electrical devices may be required.
At this point, the designer must judge whether the residual risks present a need for further protective measures or simply the implementation of warning labels. This is not a perfect process because every manufacturer may take a different approach or even none at all. Ultimately, these decisions affect the functional safety of the machine, leaving the end user to deal with the repercussions.
Industry safety standards
Compliance to safety standards depends largely on applicable laws and machine manufacturer willingness. The safety of machinery is outlined in various standards, such as in the EN ISO 12100 and the European Machinery Directive. Such standards apply to create a common level of safety for machinery in the marketplace.
There are also various standards that specify principles or methodology used in the creation of machines with regard to end user safety. The safety of machine control systems is outlined in the EN 62061 or EN ISO 13849-1 standards. Although they both require a consideration of the reliability of the electrical safety-related control components per the machine architecture, they rely on different means of calculating performance.
As an example, in the EN 62061 standard, performance of safety-related electrical control systems is measured with three safety integrity levels. In EN ISO 13849-1, performance of safety-related electrical control systems is measured with five performance levels. Both performance calculations depend on system architecture and component data from manufacturers. If correctly utilized by the manufacturer, safety standards could reduce the likelihood of machine-related injuries relating to both component failures and design flaws.
Industry applications
With a commitment to workplace safety, Park Industries introduced various safeguarding features on the Kano HD plasma cutter, including the ability to disable the machine motion and plasma system operation if high-risk areas around the machine are entered. The high-risk areas are safeguarded by safety-rated sensors that connect to a dedicated failsafe controller with 150-ms cycle monitoring time.
If the light curtain, photoelectric beams, cover switch or E-stop pushbutton are triggered, the Kano HD plasma cutter’s system is placed in an E-stop state where machine motion and plasma system operations are inhibited. Then, the operator interface displays an Emergency Stop Active warning message. To return the machine to normal operations, users can easily clear the hazardous conditions and press the System Enable soft key on the custom soft operator console.
All sensors on the Kano HD are IP67-rated, which means it is dust- and water-resistant. The sensors are also wired and configured to support dual-channel integration, necessary to achieve the highest level of functional safety.
No matter the metalworking machine, business owners must place major priority on the safety features that should be involved. The safety of employees depends on it.
