recondaddy
Member
Hello all,
This is my first foray into intrinsic safety, but I feel like I designed a solid system. Inside the hazardous area, the only electrical devices are reed switches for pneumatic cylinders and RTDs for temperature monitoring. I have these interfaced with Pepperl-Fuchs Isolated Barriers and RTD Repeaters, respectively, in a control cabinet outside the hazardous area.
There are some circulating baths (120VAC) just outside the hazardous area, as well.
Whenever a hazardous condition is detected, I designed the system to go into an e-stopped condition, where I'm isolating all power leaving the panel. The circulating bath power is isolated as well as the SMC valve bank outside the hazardous area. NO POWER LEAVES THE CONTROL PANEL.
My client is telling me that this is not enough. They want ALL power inside the panel killed, as well, to include the PLC and HMI. When I explained to them that there would still be live 120VAC in the panel, they responded with, "yes, but there's no current flow."
I further explained to them that current flow is not the greatest hazard in an explosive environment but arcing, which would still be a potential threat unless they isolated all power coming into the ENTIRE ROOM. I also explained that they would essentially be unnecessarily "blind" by killing all their controls.
They remain unmoved. I'm going to give them what they want, but I just wanted to get some second opinions. Is this overkill on their part, or is my thinking correct?
Thanks for your honest opinions. I'm always open to learn.
This is my first foray into intrinsic safety, but I feel like I designed a solid system. Inside the hazardous area, the only electrical devices are reed switches for pneumatic cylinders and RTDs for temperature monitoring. I have these interfaced with Pepperl-Fuchs Isolated Barriers and RTD Repeaters, respectively, in a control cabinet outside the hazardous area.
There are some circulating baths (120VAC) just outside the hazardous area, as well.
Whenever a hazardous condition is detected, I designed the system to go into an e-stopped condition, where I'm isolating all power leaving the panel. The circulating bath power is isolated as well as the SMC valve bank outside the hazardous area. NO POWER LEAVES THE CONTROL PANEL.
My client is telling me that this is not enough. They want ALL power inside the panel killed, as well, to include the PLC and HMI. When I explained to them that there would still be live 120VAC in the panel, they responded with, "yes, but there's no current flow."
I further explained to them that current flow is not the greatest hazard in an explosive environment but arcing, which would still be a potential threat unless they isolated all power coming into the ENTIRE ROOM. I also explained that they would essentially be unnecessarily "blind" by killing all their controls.
They remain unmoved. I'm going to give them what they want, but I just wanted to get some second opinions. Is this overkill on their part, or is my thinking correct?
Thanks for your honest opinions. I'm always open to learn.