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Innovative Electrical Cabling Delivers Robust Protection and Simple Installation in Pharmaceutical Applications

Wed, 09/24/2008 - 8:27am
By David Fazzini
Global Pharmaceutical Director TURCK, Inc.
Manufacturing active ingredients (API) for pharmaceutical products sometimes involves volatile chemical reactions. The hazards present may be in the form of volatile gas vapors (Class I) from the raw materials used in the manufacturing process, such as acetones and toluene or dusts (Class II). Under abnormal conditions in the manufacturing process, gas vapors may ignite (Class I, Div 2). With regard to dust hazards, the chance for ignition is always present when packaging the API from the spray dryer into the storage container (Class II, Div 1). Additionally, a byproduct of the chemical reaction, emitted volatile organic compounds (VOCs), also in the form of vapors, is present within the reactor (Class I, Div 1). Protection technologies available to mitigate gas and dust hazards are explosion-proof technologies, purged systems, intrinsically safe circuits and non-incendive circuits (for Class I, Div 2 areas only).

In addition to these technologies, new technology is available that provides a cost effective alternative for installation of low power instrumentation and control circuits in this environment. Historically, pulled wire and rigid metal conduit have been used in both hazardous and non-hazardous locations. However, amendments to the National Electric Code (NEC) have permitted innovative methods to install electrical cabling and equipment in both general purpose and classified locations.

Using ITC cable as an alternative to pulled cables and conduit saves installation time and money
Instrumentation Tray Cable

Type ITC cable (Instrumentation Tray Cable) provides a cost-effective alternative for installation of low power instrumentation and control circuits. The National Electric Code defines Type ITC cable and its permitted uses, which include ordinary (non-hazardous) and classified (hazardous) locations. These environments have specific installation requirements for electrical equipment, including requirements for cabling that passes between environments (from hazardous to non-hazardous locations). Although rigid metal conduit has been used to install instrumentation and control equipment in the past, ITC cables, along with other cables, are gaining acceptance in these environments due to the many benefits they provide the user.

Type ITC cable consists of two or more insulated conductors enclosed in a nonmetallic sheath, with or without grounding conductors for instrumentation and control circuits operating at up to 150 volts and 5 amps, per NEC (National Electrical Code) Article 727. This cable can be used as an alternative to conduit in many hazardous and non-hazardous environments like those found in pharmaceutical industries, chemical plants and refineries. As with all cabling methods, the NEC requires that only qualified people service the installation, as they would notice if cables were damaged, understand associated hazards and repair the installation.

Utilizing cables like type ITC in hazardous and non-hazardous locations benefits users by decreasing costs associated with installation time, commissioning and maintenance. By nature, systems using rigid metal conduit require more time to install because wires must be pulled and cut, and the conduit must be bent and fitted. Additionally, sealing and boundary fittings may be required in hazardous locations. This is generally not an issue when using cables, and those like type ITC with quick-disconnects may not require precautionary measures (like sealing) to pass from hazardous and non-hazardous locations. Rigid metal conduit also requires hand-wiring terminations and is therefore more susceptible to human error, whereas pre-molded cables with quick-disconnects can be installed much more easily. Along with its diverse application range and compliance, ITC cables provide numerous advantages over metal conduit. In fact, ITC rated cable with quick-disconnects can result in up to 45 percent savings—with the majority of these cost reductions resulting from installation and commissioning.

Gas/vapor-tight continuous sheath in ITC cable meets NEC requirements for Division 2 locations
Installation Benefits

By nature, systems using rigid metal conduit require more time to install because wires must be pulled and cut, and the conduit must be bent and fitted—which is not the case with ITC cable. Plus, with metal conduit many installation restrictions and precautions are necessary. Conduit must be constructed so that arcing between the conduit and enclosures does not occur, which could also cause an explosion. Also, joints within the system must be wrench-tight at couplings, threaded hubs of junction boxes, conduit bodies and more. Conduit and pulled cable installations require hand terminations, making them more susceptible to human error. Due to these factors, metal conduit must be installed by trained personnel, which can add time and costs to the process. On the other hand, ITC cables can be pre-molded and used with quick-disconnects, allowing simple installation and significant time and cost savings.

For Class I, Division 2 locations, guards requiring a tool for removal must be incorporated into the quick-disconnect cable to render the connection "not normally arcing
To Seal or Not to Seal

ITC cable can be installed in classified locations, including those where fire or explosion may occur as a result of flammable gas, vapors or liquids, such as those mentioned above for pharmaceutical manufacturing processes. In these locations, sealing and boundary fittings may be required for conduit and cable systems to eliminate the propagation of an explosion or passage of flammable gases. ?Conduit entering and exiting an explosion-proof enclosure or pressurized enclosure must be sealed within 450 mm (18 in.) from the enclosure as well as when entering or exiting a hazardous location. To meet these requirements, manufacturers use different sealing compounds for diverse applications, since these compounds provide varied rates of expansion/contraction that may affect their performance within a given fitting. Still, even after the appropriate compound is determined and the conduit is sealed, it is nearly impossible to ensure the joints are gas tight in hazardous environments. Temperature fluctuations cause the conduits to expand and/or contract, permitting gases and vapors to permeate the conduit and resulting in what could be an explosive mixture.

Conversely, the gas-tight/vapor-tight continuous sheath of ITC cable, as well as the molded construction of the connector, allows its usage in hazardous locations—often without seals or fitting and with no requirement for further mechanical protection. This metal-armored cable is rated for Open Wiring Installation, making it particularly suitable for hazardous locations as allowed by the NEC. Plus, ITC cable can be used with junction bricks that offer 4 or 8-ports to further simplify installation.

ITC cable may be used where enclosed in a smooth metallic sheath, continuous corrugated metallic sheath or when interlocking tape armor is applied over the nonmetallic sheath-but it must be supported and secured every six feet
Quick Assembly with the Benefits of Quick-Disconnects

As mentioned, cabled systems may eliminate the need for seals and simplify installations. To further the benefits of a cabled system, quick-disconnect cables, which expedite installation, and glands (receptacles) may be used in hazardous locations. Cable glands are components that safely allow cable to enter an enclosure or piece of equipment. These glands are available to fit various cable diameter as well as mounting hole diameters and in a variety of materials, including aluminum, plastic, steel and stainless steel. Plus, cable glands can be simply mounted with adhesive or compound or by flanged, bolted, treaded, nut, welded or cast mount methods.

Additionally, field equipment can be specified with pre-terminated receptacles, further simplifying installations, reducing field terminations and eliminating errors associated with field terminations. To be used in Class I, Division 2 locations, guards requiring a tool for removal must be incorporated into the design of the quick-disconnects to render the connection not normally arcing. Other wiring alternatives available include explosion-proof feed-throughs for Class I, Division 2 hazardous areas, eliminating the need for a poured seal, conduit or hand wiring. The feed-through installs directly in standard conduit entries and is used with quick-disconnect cables to eliminate field terminations. Where traditional explosion-proof protection schemes required numerous parts and were labor-intensive to install, employing explosion-proof feed-throughs can eliminate many of these parts and greatly reduce installation labor. When installed in conjunction with ITC rated cable, even more time and cost savings can result.

These cabling systems, by replacing pulled wire and rigid metal conduit in pharmaceutical applications, offer a simpler, less labor intensive installation, accelerating project cycle times and reducing costs. Utilizing cabling systems also eliminates the need to seal conduit, which can improve maintenance and installation time and reduce errors. Plus, ITC cables used with junction bricks and quick-disconnect or integral home-run cable and associated receptacles can provide an integrated, code-compliant wiring method that adds the benefits of quick-disconnects to the ITC installation concept.

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