Safeguard, Control: Know Difference

Monday, April 2, 2012 @ 06:04 PM gHale

By Gregory Hale
When it comes to process safety, everyone needs to be on the same page when it comes to differences between a control and a safeguard.

“A control will regulate or guide something within a normal range during a control process, while a safeguard is something that takes over when something moves outside the normal range,” said Lisa Long, Occupational Safety and Health Administration (OSHA) director in the office of engineering safety during the AIChE Spring Meeting and Global Congress on Process Safety in Houston Monday.

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Some areas Long said often get mistaken for safeguards, but are really control mechanisms are:
• Mechanical integrity program
• Operator training
• Normal operating procedures
• Equipment design

Simply put safety professionals need to know the difference between a control and a safeguard because the safeguards will take over when the normal process control safety mechanisms are not working.

“Safeguards should be available and effective,” Long said. She then added for emergency procedures and training you have to verify:
• Procedures accurately reflect operating practices
• Operations have proper training
• Everyone is able to follow and perform the procedures
• Safeguards also have a lifecycle and everyone needs to understand what they are.

“The PHA (Process Hazard Analysis) team needs to understand what is happening out in the field,” said Jeffrey Wanko, OSHA safety engineer at the directorate of enforcement. “They must fully understand the lifecycle of the safeguard out in the field.”

One case history Wanko pointed out was when a company was making a chlorine transfer and the hose broke and chlorine started leaking. “When that happened, the people did the right thing and pushed the kill button and the valve was supposed to shut and the leak would stop,” he said. The problem, Wanko added, was the valve suffered from corrosion and it could not close. The chlorine kept leaking.

People have to audit their safeguards to the point where they know they are physically working. Yes, people have to follow procedures, but they also have to ensure it goes beyond that.

“PHA teams really need to check that their assumptions are correct,” Long said.