If you work with highly hazardous substances, you need to comply with the OSHA Process Safety Management Standard (PSM) (Sec. 1910.119). Here’s how.

Overview of the PSM Standard

The PSM standard is designed to prevent or minimize catastrophic releases of highly hazardous substances. It applies to chemical “processes” that involve the storage, manufacturing, handling or moving of listed toxic and reactive chemicals in amounts above specific thresholds as well as flammable liquids and gases in quantities of 10,000 pounds or more.

The standard also requires a detailed mechanical integrity program for all process equipment. In addition there are requirements regarding operating procedures, training, emergency response, compliance audits, contractor safety and process hazards analysis.

Chemical Plant Controls

Chemical plants should implement controls to ensure compliance with the PSM standard and protect workers against the risks of catastrophic incidents.

Chemical Loading: Facilities must also incorporate the following chemical handling components to ensure safe loading operations:

• Excess flow and check valves;
• Level-indicating controllers, which automatically cause lower or no flow at a setpoint, usually through pump control or valve closures; and
• Local and remote level gauges.

Chemical Movement: Facilities should implement controls to limit the risks involved in moving chemicals including:

• Pump run indication or event recorders to notify personnel when critical equipment, such as raw material feed pumps or surge tank level control pumps, are operating;
• Interlocking the pump run switch with correct valving positions downstream to ensure chemicals are pumped to the correct locations;
• Pressure relief valves as appropriate in the transfer route, and liquid pressure relief valves in lines where overpressure from thermal expansion could occur;  and
• Excess flow and check valves.

Other Controls

Chemical reactions may occur in a wide range of temperatures, pressures, rates and chemical services.  As a result, chemical releases through rupture discs, pressure relief valves and sight glasses; explosions due to excess rates of reaction (e.g., exothermic run-away reactions) and pressure elevation; and incidents relating to control of explosive conditions can occur.  These hazards can be controlled through safety devices like:

• Local and remote temperature, level and pressure indicators;
• Temperature- or pressure-indicating controllers;
• Controllers that open valves in reactor jacket cooling systems if reactor internal or jacket temperature exceeds acceptable levels;
• Interlocking agitator start-up with nitrogen supply valve to ensure reactor inerting requirements are met;
• Pump monitoring and interlocks; and
• Pressure relief devices to respond to excess vessel pressure.

Conclusion

Implementing controls for storing, handling, moving and manufacturing chemicals is essential to ensuring the safety of workers in chemical plants.  This is especially true when these chemicals meet the criteria for highly hazardous chemicals set forth in OSHA’s PSM standard. Implementing some of the above controls can help your plant not only achieve compliance but also protect workers both on- and even off-site.

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