When we encounter a manufacturing facility that has been pulled into OSHA’s PSM or EPA’s RMP, we are almost certain to find the same design features for the emergency stop functions (i.e., E-Stops). Most of these facilities are shocked to learn there is a big difference between the location of an E-Stop on a machine or conveyor and one on a hazardous materials process.
If we think about this, it usually becomes apparent. Still, suppose no one has experience in process safety, and a RAGAGEP states an E-Stop must be provided. In that case, the facility will most likely choose the location of this E-Stop based on their experiences with machinery safety.
For example, if we look at ANSI B11 series of safety standards and its mention of E-stops, we get the picture that these devices should be located directly on the machinery or at least very close to the machinery, such that they could be activated by the worker who needs to stop the machine or someone responding to the emergency.
But when we look at a “process safety” E-Stop, ANSI provides some very different requirements for the location of the device to activate the emergency function…
From the old ANSI ANSI K61.1-1999/CGA G-2.1-1999
5.10.8.3 Liquid Piping
…
“If an emergency shut-off valve is used, a cable or other means shall be attached to the trip arm of this valve and then laid out for at least twenty (25) feet to a remote location and
attached to a fixed object.”
The intent of this 25′ is so that a failure of the process that releases the NH3 can be put into its emergency shutdown state from a “safe location” rather than forcing the operator/truck driver from having to enter a hazardous atmosphere to close valves to isolate the leak.
Chlorine Institute, Pamphlet 1 – Chlorine Basics
8.2.2 Air Openings
Chlorine gas is heavier than air and has a tendency to collect at floor level. The exhaust air system should draw from a location at or near floor level. An elevated fresh air inlet must be provided and should be located for adequate cross ventilation. Multiple fresh air inlets and fans may be necessary to facilitate adequate ventilation. Fans, if used, should be made to start and stop from a safe, remote location.
3.4.2 ES1 and ES2 – Remote Emergency Stop Switches
At least two remote emergency stop buttons should be located strategically to shut down the system.
The US Chemical Safety Board recently released a new Safety Study titled “Remote Isolation of Process Equipment” that issues recommendations to key regulators and calls for greater use of remote isolation equipment at chemical facilities in the United States. However, this design feature has been in RAGAGEPs my entire 30+ career, and I guess I was fortunate enough to work for some great companies that used the State Fire Codes (based on the IFC) as a baseline for our process safety designs. As shown above, ANSI K61 had this requirement for a 25′ activation distance from day 1 of my career, and I always used this “approach” in my other HAZMAT processes, regardless of their PSM/RMP coverage.