I manufacture a process control device that consists of an LED and piezobuzzer powered by 9V battery. Wired in parallel they draw 25mA, and they are housed in a NEMA 4X enclosure. I would like to offer it as an "intrinsically safe" device, and I am prepared to make any necessary modifications. However, asking agencies like UL, CSA, FM - they want $15-19K for their approval which kills the whole deal.
Does anyone know if there is any cheaper way to declare equipment as I.S., or can one self-certify?

 

Peter, you can always declare a product "self-certified," but I wouldn't.

It is less common now than it was 30 years ago, or even 20 years ago. Many companies will not permit the use of "designed to meet" products any more because of the potential for liability. Declaring your product "self certified" and "designed to meet" intrinsic safety requirements is a market limiter that could also kill the project.

Frankly, I think you can probably get your product approved by FM, UL or CSA for a lot less than the prices quoted-- it depends on how you approach them.

Here's what I used to do, when I was in product development. I'd go to Boston and sit down with the FM people, and show them the preliminary design and ask them for comments, just off the cuff, and _then_ ask for a quote. I often used the services of an ex-FM engineer to review the design before submitting. The big costs come in repeat submittals when you get rejected.

Go sit down with them, if you haven't.

If you'd like to talk further, feel free to give me a call.

Best,

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com

Mailto:[email protected]
Read my blog SoundOFF!! At www.controlglobal.com/soundoff

 

Why does it have to be IS?

There are other means of protecting hazardous area equipment like Exd. You can effectively self certify if you buy a box with an appropriate schedule permitting installation of the equipment you have in mind. Subject to you sticking to the schedule and certain procedural constraints.

Just a thought. Maybe you've considered the alternatives already.

Good luck
DaveMH

 

Dave, potential customers ask for it to be I.S. because they want to use my float switch level alarm on tanks containing flammables.
I modify the NEMA4X box with pentrations for the LED and buzzer. Everything is sealed when I'm done, but since I have modified the box I wouldn't think I can hold the box manufacturer responsible for the I.S. performance of the final product. Where can I find the Exd schedule?
Peter

 

Consider installing a Zenner type I.S. barrier between your electronics and the switch, that would be much cheaper than getting special approval. You would also need follow the special grounding techniques for the barrier.

Roy

 

Peter,

Sorry its taken a while to get back.

If I've got this right you have a device in a box which is not located in a hazardous area wired to a float switch, LED and buzzer located in a hazardous area.

If the box is in a hazardous area if find out generally what division/zone the area is if you can't move the box out (can you move the box?). This should give you a range of ways to protect the device in the box.

Fit the device in a suitable box along with "suitable" IS barriers for the inputs and outputs. I would have thought that the switch and LED would fall within the parameters of so called simple devices and therefore no product certification would be necessary. It may be possible to use a so called entity concept for IS installations. The buzzer I'm not so sure of you'd need to look at its electrical characteristics. Can you use a different IS buzzer?

Some Exd boxes used to be certified with a "flexible" so called Schedule of Limitations which you would get from the Exd box manufacturer. As long as you stay within the limits of the schedule you can have a certified box plus equipment. google some vendors for Exd boxes and ring them up if you're interested.

Hope this helps.
DaveMH