What's the difference between an Industrial Enclosure and a Standard Off the Shelf PC

Transit Case and Rack System Integration

Difference Between Chassis Plans and Off The Shelf Standard Systems

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Commercial PCs - those desktop "white boxes" typically found at home or in the office- and industrial PCs often use similar microprocessors and motherboards. Industrial PCs may also use the same hard drives, floppy drives, and CD-ROM drives to help keep down costs. Beyond that, however, commercial and industrial PCs have little in common.

While some components used in industrial PCs are the same as those produced for the high-volume commercial market, industrial computer vendors package the components so they can operate in harsh plant floor environments.

Commercial PCs like the popular store-bought or mail-order brands are designed for distribution through retail channels and are used to run ever more bloated applications. Also, since they are rarely used outside comfortable home and office environments, commercial PCs are packaged in freestanding tower and desktop chassis made of light sheet metal and plastic, and in most cases monitors and keyboards must be attached separately.

Taken altogether, commercial PCs are increasingly built to be disposable. Industrial PCs, on the other hand, are built for longevity in harsh environments. They are packaged in rugged aluminum and stainless steel enclosures and can operate without failure in heat, cold, water, and corrosives.

Some models are wall or rack mountable, with separate monitors, but most are single panel mounted units with integral keypads and LCD displays. Commercial PCs serve perfectly well in clean, non-critical applications, thereby saving the higher costs associated with industrial computers, but critical applications on the plant floor - where down time carries significant associated costs - are best met with equipment explicitly developed to withstand these extreme conditions. Furthermore, manufacturers who are trying to control their system design and integration costs require stable, consistent product specifications from their vendors. They cannot afford to redesign and retest their manufacturing systems every time a new generation of commercial PCs is introduced.

From 1995 through 1999, commercial and industrial PCs offered very similar features, with standards for the industrial space being based on the available commercial specifications. However, over the last two years these commercial specifications have diverged from the needs of the industrial space. The push for legacy-free desktop systems has meant the elimination of technologies critical to industrial computing. Only dedicated, purpose-designed industrial PCs still offer all the features needed on the plant floor.

A multitude of industrial cards have been developed for the ISA format, including device networking and I/O, data acquisition, vision, and motion control. Very few commercial PCs still provide ISA expansion slots at all, and those that do usually provide only a single half-length slot. Industrial PCs, on the other hand, provide up to six full-length ISA slots in order to accommodate all of the manufacturer's installed networks and devices.

Built into the BIOS and system components of commercial PCs are power management functions which can interfere with industrial applications. These functions, such as OnNow and ACPI, are what let the system "spin down" or "sleep" when not active and let the user set prescheduled startup and shutdown times. While these features may be desirable in desktop commercial PCs, they cause only problems in industrial applications. Industrial PCs must be predictable, responsive, and always on. Therefore, industrial computer vendors disable these power management functions.

Many existing industrial devices depend on parallel and serial communications. These devices include PLCs, operator interfaces, barcode scanners, RF tag detectors, remote touch screen interfaces, network printers, "backpack" drives, and serial input devices. Unfortunately, parallel and serial communications are being replaced by Firewire (IEEE 1394) and USB in the latest commercial PCs. With the introduction of new device drivers in Windows 2000, industrial devices may eventually be redesigned to work with the new standards, but to date there is still not much use for USB ports in industrial applications. Industrial PCs need to work with the installed base of serial and parallel devices.

Industrial PCs must withstand many harsh plant floor conditions, including airborne dirt and chemicals, mechanical shock and vibration, electromagnetic emissions, and extreme operating temperatures and humidity. Panel-mounted units in particular use a built-in gasketing system to achieve enclosure ratings of NEMA 4, 4X, and 12 (see inset) when properly installed. Also, operator interface keypads and touch screens must allow for millions of actuations and years of non-stop operation. If the level of shock and vibration in an application is too high even for a normal industrial PC, the unit can be further ruggedized by replacing the rotating hard drive with solid-state flash memory and installing an embedded operating system. Additional upgrades to the unit's power supply, cooling system, connectors, and enclosure can ensure safe operation in even the most hazardous conditions, including the risk of explosion (Class 1, Div 1) and the presence of flammable gases (Class 1, Div 2). Even the devices and accessories attached to the computer must be able to survive harsh environments. Heavy-duty keyboards and mice are designed to resist dirt and mechanical shock, and gasketed doors over the device ports can keep out airborne substances. Needless to say, regular commercial PCs do not meet any of these standards.

While users of commercial PCs are always looking for more speed, more memory, more storage, and more features, industrial PC users require stable, consistent product specifications that can be supported for longer periods of time. OEMs must thoroughly understand a new model before integrating it into an industrial application, and maintenance personnel must be able to repair units on the plant floor with only limited training and spare parts. To satisfy these demands, microprocessor and industrial computer vendors work together to select chips and subsystems that they will support for much longer than comparable commercial PC components. Intel, for example, guarantees that they will support the processors listed on their Embedded Processors List for up to five years.

System integrators and maintenance personnel must be able to maintain and troubleshoot units quickly and without removing them from the plant floor. As such, industrial PCs incorporate several design features that make maintenance easier: front access device ports and drive bays; pop-off external fan filters; a hinged two-piece chassis allowing easy access to the LCD and backlights; and a back cover which can be removed without tools, making it possible to install additional memory and expansion cards right on the floor. When a unit absolutely must be removed from the plant floor for programming or repairs, the rear chassis can be detached entirely from the front panel without affecting the panel mounting or the enclosure rating.

Personal computers have quickly gained acceptance for use in industrial applications, by serving as platforms for Supervisory Control and Data Acquisition (SCADA) and HMI applications and by replacing more expensive PLCs in direct machine control. PCs also allow the plant floor to integrate seamlessly with the company's Manufacturing Execution Systems (MES) and front office communications. However, as OEMs and end users choose their PC platforms, they must consider the total cost of ownership. For the end user, the PC must survive the harsh environment of the plant floor and it must recover quickly should a failure ever occur. For the OEM, the PC must be a part of their ability to engineer an economical manufacturing system and consistently deliver that system over a long period of time. Many of the technologies built into commercial PCs have evolved to the point where they can also be considered for industrial applications, but commercial PCs themselves still do not satisfy the demand for higher operational performance, greater system longevity, and a more rugged environmental design. Industrial computer vendors have leveraged these technologies to reduce costs and promote compatibility, while also maintaining their high standards for quality and design. The result - the industrial PC - effectively combines the price and flexibility of the commercial desktop with the durability and performance of heavy duty industrial equipment.

Tutorial written by Nematron 2001