Best practices to maintain and improve worker safety
Focus on engineering controls first in developing a safety plan in process plants.
In the process engineering world, there are many ways to maintain and improve safety for workers on the job. One way to start is to lean on others to help you come up with the solution. Enlist the help, experience, and suggestions of people in engineering, design, operations, maintenance, and site safety for their input.
Collaborating with multiple disciplines reduces the chance of important safety issues being missed, and it will help the team list the credible hazardous scenarios for all to see, evaluate, and give input to the solution. Also, working together in a larger multi-discipline team helps design and install a solution that is not only safe, but reliable, maintainable, environmentally and ergonomically friendly, and cost-effective. Multiple factors should be taken into consideration, but the emphasis always is on engineering controls first, as opposed to putting workers in personal protective equipment (PPE).
Plant and personnel safety
Safety for the plant and personnel always starts in the design phase and not when the system is already installed and running. The focus should be on engineering controls first, such as process instrumentation to measure and control key process variables and alarms if the process goes out of control. The goal is to stay within process control limits and shutdown/fix the problem when it deviates.
Once process control and monitoring is taken care of, another helpful technique to improve safety is to monitor equipment. It's been seen on the news what happens when a critical piece of equipment or monitoring instrument does not function properly.
For those critical items, it would be valuable to include data collection in the design for predictive maintenance for this equipment (also called condition-based monitoring). Logging the equipment data along with the process data helps monitor its operation unobtrusively during normal production and warn maintenance personnel when an individual component is beginning to fail or reaching the end of its lifecycle.
These include items such as counting valve or pump cycles, logging total motor hours, evaluating instrument operation, and measuring current draw/resistance of key electrical components. The experts on process safety design teams can help you identify the critical equipment or key individual components that need to be running 100% of the time for safe operation. This extra enhancement goes a long way in reducing or even eliminating, an unplanned dangerous equipment shutdown, as well as avoiding a disruptive and expensive production stop.
Identify critical variables for best safety practices
Besides equipment monitoring, another safe design practice used is identifying the top two or three variables that the group experts feel are most critical to staying away from a hazardous situation (level, flow, temperature, pressure, time, etc.), and then choosing measurement instruments of different technology and manufacturers.
For example, filling a reactor with a flammable solvent and monitoring the level in the tank. Choose a continuous level measurement device with high-level detection in the programmable logic controller (PLC) and software and use that device for normal production activity, control, data collection, and high level alarm/shutoff of the solvent addition automatic valve. Monitoring the actuator position with limit switches verify that when the control system opens/closes the valve, the switches verify that the valve truly is open/closed.
Note that in a critical operation like this, flammable solvent filling, we would also design in a hard-wired point level probe that bypasses all controls and software, shutting off that same fill valve regardless of what the control system indicates. This design provides double protection on a critical process measurement, and it does cost more money, but this design philosophy greatly reduces the risk of overfilling a vessel and running a flammable solvent onto the production floor.
Create a step-by-step commissioning plan for equipment safety
Be mindful of workplace safety at the back-end of a project, after equipment installation is complete and commissioning begins. When new equipment is integrated into an existing plant, great care needs to be taken when starting up the process, and a well-written step-by-step commissioning plan is critical to bringing equipment online safely.
The plan needs to be thought about during the initial stages of project funding, so management knows the time-frame and resources needed for start-up and to run the equipment safely, especially in an existing plant. Several things need to be taken into account including:
- The equipment that needs to be started up
- The processes that are already running in the area
- Review and specify the personnel needed
- The time-frame of the shutdown and communication plan between commissioning team members on different shifts (if applicable)
- Production or commissioning specific product/tools and utilities that are needed
- Individual component test procedures, subsystem tests, and overall production line test
- Training of plant personnel
- Final documentation for a proper hand-off to the plant operating and maintenance departments.
A good commissioning plan is typically finalized during design, since that is where most of the information about the equipment being installed and how to start up the process safely is known. Writing and following a good commissioning plan enhances the chances of a successful start-up, instills management confidence in preparedness and leadership, and will allow workers to go home safely at the end of the day.
Mark Haboian is senior program manager at Optimation Technology Inc., a certified member of the Control System Integrators Association (CSIA).