As mobility in harsh and volatile industrial and manufacturing environments has become a necessity for productivity, safety, monitoring, and management, intrinsically safe circuit design has had to meet stringent regulatory device needs. Making matters more challenging for device manufactures are the varied environments, product features, and complex requirements of meeting regulatory compliance for intrinsic safety. The definition of intrinsically safe lies at the heart of this challenge.
Intrinsic safety requirements apply to any device operated in areas where flammable gases, fuels or dust are present. The device must provide preventive protection in its electronic circuit design and physical structure when used in explosive atmospheres. These devices must be designed in such a way that they will not release enough energy to cause ignition of flammable material. Just a few of the more obvious Industries which require Intrinsically Safe devices include:
- Oil and gas
- Pharmaceutical
- Aircraft maintenance
- Chemical refining
- Power generation
- Metal smelting and refining
- Plastics manufacturers
The regulations and requirements governing intrinsic safety for any device that must be certified and manufactured for use in volatile environments are varied. There are two main regulatory bodies and certification:
- ATEX (Atmosphere Explosive)
- IECEx (International Electrotechnical Commission Explosive)
Both have complex zone requirements driving intrinsically safe circuit design standards across the globe.
While there are a number of suppliers offering tablet PCs, smart phones, handheld computing devices or cases reported to be intrinsically safe, there are vast needs for mobile handheld intrinsically safe devices for specialized use cases in highly specific environments such as complex measurement and scanning devices.
Simply repackaging a non-intrinsically safe device in an enclosure meant to provide protection from hazardous gas or dust infiltration that could be combustible is often not sufficient. Many handheld devices require an intrinsically safe circuit approach reaching the smallest aspect of the circuit board design. For example, external interface needs often prohibit the the use of such pressurized enclosures Instead, the circuitry itself must be designed, from the component level, for the target explosive environment since environmental exposure can’t be avoided. The many considerations of and the regulatory standards they must meet require a more thorough approach.
Circuit domain divisions, energy limitations often based on resistor, fuse, and diode devices, component resistance and fault condition matching, and control of spacing between metals are just some of the broad approaches to intrinsic safety circuit design. In general, total circuit capacitance and inductance must be limited to control energy storage. The device packaging must also be designed to not combust, protect the circuitry inside, and provide acceptable connectorized interfaces. To develop and design devices meeting all usage parameters and intrinsic safety regulations requires a multidisciplinary design approach.
The design of an intrinsically safe device requires detailed knowledge of circuit operation, the physics governing component operation, and the design rules that enable certification success. While most engineers can learn and understand the requirements and rules, this often requires significant time and incurs risk of design mistakes when not regularly performing intrinsically safe circuit and device level design. Many require the support of a manufacturing partner deeply experienced in:
- Ideal component selection
- Intrinsically safe circuit placement and spacing
- Cost and intrinsic safety-effective encapsulation techniques
- Whole device, interface and I/O designs meeting intrinsically safe requirements and operational needs
These partners bring the needed multidiscipline approach and the track record of whole device design consulting across differing functionalities, interconnection and interface needs. OEMs with unique product requirements around intrinsic safety can best be served by partnering with the right custom device and embedded circuit boards manufacturer. The result is an ability to develop and manufacture the most viable and usable products that meet intrinsically safe regulatory needs while also meeting operator and industry requirements.
SECO USA develops circuitry, operating system software, and fully packaged devices for rugged, environmentally challenging applications. This includes the design of intrinsically safe devices for explosive environments. Contact SECO USA for an evaluation of your product concept.
