Integrated safety for motor control centers demonstrates gains from overall architecture
Safety has evolved beyond protecting workers, extending to factors that include an integrated, affirmative view of product safety and brand protection. Safeguarding hands/toes/backs remains a priority, but establishing a complete safety environment has become a de facto operating priority.
Motor control centers (MCC) are more and more becoming an important element in plant safety strategies. Safe designs for elements such as equipment design and arc flash protection protect people working in and around MCCs, but safety must extend to the components operated by the MCC as well. Most controllers run several motors, so problems can show up in multiple places; when safety incidents occur, safeguards must be in place to ensure that motors won’t start unless appropriate guards are in place.
It’s increasingly important for companies to combine well-planned safety strategies for specific operations like MCCs, then combine them to ensure that activities throughout the facility are well protected. When safety steps are needed, integrated approaches ensure that all necessary equipment moves into safe modes, while other activities can continue without unnecessary stoppages.
Integrated safety drives flexibility, letting companies improve efficiency without requiring costly shop floor reconfigurations. It also eliminates costly work-arounds and lets skilled operators add or modify control parameters that comply with established quality and safety protocols.
This approach takes mundane safety chores out of the hands of operators and shifts the emphasis to a socio-technical approach that encompasses worker interactions with machinery. It includes both the technology and the productive interplay between workers, machines, and information.
Scalability in Practice
Siemens recently won a major contract at one of the world’s largest food and beverage companies, displacing an entrenched supplier during a full-site upgrade. Many different Siemens operations worked together to address the safety aspects, which were one of the customer’s key central requirements.
This holistic approach to safety let Siemens meet plant-wide goals for safety as well as productivity. The food and beverage supplier is now planning to use this model when additional plants are remodeled.
MCCs are among the elements that helped convince this global manufacturer to switch to Siemens equipment and improve safety throughout the facility. Comprehensive MCC safety goes beyond the motors and drives. State-of-the-art technology lets companies incorporate safety PLCs and use field buses such as PROFINET and PROFIBUS. Safety PLCs are an integral part of Siemens MCCs and integrated safety PLCs bring many benefits, letting customers develop safety systems that encompass the plant and allow reconfiguration when changes inevitably occur.
Many plants start their MCC security program by equipping process areas with guard interlock doors or emergency stop push button. The MCC’s safety controller monitors the button or the guard, reacting to events. The safety controller always overrides other controllers — when it senses problems, it can shut down any equipment.
As with all control systems, MCCs need to be scalable. It’s not uncommon for the number of motors to grow, so systems need to be designed for the future. Leveraging the field bus makes it simpler to upgrade, since there are no contactors to rewire.
In this era of short production times and rapid product changeovers, manufacturers need to look at getting jobs done efficiently while protecting employees, assuring product quality and optimizing plant equipment. Integrated safety systems let plants shut down some areas without impacting others, saving time and improving the return on investment. Saving even a few minutes can bring major efficiency improvements.
Those programming the safety PLC can determine which conditions will trigger a shutdown and what actions the unit should take when those conditions occur. This requirement highlights the importance of software. Programs must be foolproof, or even the best hardware will be prone to errors that can hinder efficiency programs. The code is only as safe as the ratings of the hardware. All components, from the motor to the drive to the CPU, must be able to perform the functions being asked of them.
Adding safety controls can increase some short-term costs, but the overall cost will usually be far less than the cost of an incident that could have been prevented by a holistic approach to safety controls. Safety technologies can also reduce downtime, since shutdowns often take less time to complete than the amount of time needed to recover from a preventable accident.Have an Inquiry for Siemens about this article? Click Here >>