This article originally appeared in Electrical Contracting Products Magazine
Working in An Industrial Setting
By David Herres
A variety of voltages, VDV technologies, transformers and distribution channels highlight most industrial operations.
An industrial facility is typically served by large three-phase services which supply a variety of voltages. Even a relatively small set of buildings may have several customer-owned transformers and numerous distribution panels sprouting thousands of branch circuits and countless power outlets.
Since significant office space is usually involved, electrical contractors will often see customer-owned PBX (private branch exchange) telephone service emanating from a central office with a computer-controlled switch. In addition, with Internet service and an in-house Intranet, there will be a telecom room with Ethernet, wireless or optical fiber network. You don't have to look far to find a supervisory fire alarm with telephone, sprinkler and fire door interface and elevator capture. And speaking of elevators, extended downtime in this area can mean massive curtailment in productivity.
To keep all this running efficiently, an electrical maintenance department is required, complete with knowledge and expertise, tools, inventory and operating capital. When existing resources are not able to deal with an emergency situation or scheduled new construction, it is necessary to call in outside help and in these situations a pre-existing working relationship with local contractors is essential.
As an example, consider the elevator. If it goes out of service, in-house electricians are called immediately. If people are stuck between floors, the electrical personnel must certainly know how to lock out the main disconnect, get the door open and lower a stepladder so that people can get out quickly and safely. The next task is to diagnose the cause of failure. Usually, it is a door interlock adjustment, circuit board fuse or similar component failure. Then the controller can be reset and the elevator is back in service.
At times the problem eludes in-house staff and a professional elevator servicing firm has to be called in. It is vital to maintain a good working relationship with these and other outside contractors so that they will come quickly.
What to know
An area of great concern in elevator maintenance is licensing. Regulatory authority resides with State and/or Municipality and varies widely throughout the country. It is important for facility electricians to know where to draw the line in terms of permitted elevator maintenance.
In all cases, safety for company personnel and onsite visitors is the prime consideration. The National Fire Protection Association (NFPA) puts out the National Electrical Code (NEC) and the Life Safety Code (LSC), which are currently revised every three years. These two volumes, along with a number of other standards, are offered by the NFPA so that states or municipalities may adopt them into law with changes or amendments if desired.
These mandates must be followed closely by designers and installers. Good industrial maintenance electricians know these codes and keep informed of new developments.
A conscientious and knowledgeable electrical department with good outside contractors will insure the facility is a safe workplace from an electrical standpoint. Then the issues of efficiency, economy and productivity can be addressed.
It is essential to always be evaluating the overall electrical infrastructure for adequacy. With the expansion in use of sensitive electronic equipment, for example, power quality and grounding need to be watched closely. These issues are also important where large motors are in use.
Good grounding requires an adequate set of ground electrodes but it goes way beyond that. Proper non-corroded terminations and reliable bonding of cable tray segments and similar equipment are essential elements. Redundancy is helpful in insuring reliable bonding but the wrong sort of redundancy can be a fatal error. Bonding neutral and equipment grounds in more than one location can give rise to objectionable circulating currents, which are dangerous and wasteful.
If motors and other utilization equipment are removed for servicing, it is important that the equipment grounding path be reliably reconnected so that overcurrent devices will clear a fault and prevent metal casings from becoming energized.
Dangers to know
Other major concerns in an industrial setting are hazardous (classified) areas. NEC recognizes three discrete types of hazardous areas, each with different wiring requirements.
Class I locations have fire or explosion hazards due to the presence of flammable gases, vapors or liquids.
Class II locations may have fire or explosion hazards due to combustible dust.
Class III locations may have fire or explosion hazards due to ignitable fibers and flyings, as in a textile mill.
Each of these classes has two divisions. Division 1 is generally more hazardous than Division 2 because the exposure is more immediate. For example, in Class I Division 1 locations, flammable gases or liquids can exist under normal operating conditions. In Division 2, they are normally in closed containers or systems from which they may escape in case of accidental rupture or breakdown. In all classes, Division 1 carries with it more stringent wiring requirements than Division 2.
It is important that electrical maintenance workers and contractors be aware that because of changes in building usage new hazardous areas may be created and that class and division boundaries may shift so that non-compliant wiring will have to be upgraded.
A key responsibility of industrial facility electricians is in the area of emergency lighting. Most such occupancies use individual unit equipment, self-contained boxes with sealed batteries and chargers that are connected to the AC lighting branch circuits ahead of any switches. AC failure triggers a relay that actuates on-board and remote DC lights and also drives the DC portion of nearby exit lights.
The LSC mandates placement and light levels of these units and NEC sets standards for wiring them. NEC requires that emergency lights be regularly inspected and written records be kept. The LSC further requires that testing be performed for 15-seconds once every 30 days and 1 1/2 hours every year.
Maintenance electricians are expected to correct any deficiencies found during inspection, replacing bulbs, batteries and circuit boards as needed. A medium-sized industrial facility easily can have several hundred of these unit emergency lights, so just the cost of battery replacement can be significant. For this reason, it is important to keep good records. A unit that needs new batteries every month, for example, should have its charger replaced.
Industrial sites are characterized by size and complexity. Electrical loads are large, numerous and diverse. In order to maintain a safe and efficient workplace, written documentation including as-built drawings should be on file with amendments added whenever changes occur. These files can be used to generate a spare parts list so that you can decide on inventory.
Fluorescent bulb management is important. The old T-12s should be changed over to the thinner, more energy efficient T-8s. This changeover, which may be partly subsidized by utility incentives and tax credits, involves changing ballasts and bulbs, but fixtures, wiring and sockets remain unchanged. It is also a good idea to put in the new NEC mandated internal disconnects so future ballast changes do not have to be performed live.
Many organizations change bulbs only when they begin to flicker or go out completely. This is a costly error. As fluorescent bulbs age, they produce less light and more heat, and they draw more current. This causes premature ballast failure. Early pre-emptive bulb replacement saves on the energy bill and also precludes costly ballast replacement. Fluorescent bulbs that have begun to darken at the ends have seen better days. Large industrial facilities should change fluorescent bulbs according to a fixed schedule.
Undoubtedly down the road all lighting will be LED based.
Electrical work has become far more complex in this cyberworld that we now inhabit, and this is especially true in the industrial setting. Virtually all large manufacturing environments now contain Programmable Logic Controllers (PLCs). These incredible machines were first developed for General Motors in the 1960s to facilitate the automation changeover that took place annually as new models went into production. Previously, it had been necessary to rewire thousands of relays, mechanical timers and the like.
In place of hardware, this equipment consists of software instructions placed within a central processing unit. We program a PLC by plugging into it a conventional laptop and creating simple ladder schematics. Instructions are sent to complex machinery so that timing of powerful operations takes place on a microsecond level. Thus Ford's assembly line has achieved a new flexibility and versatility thanks to GM.
This new technology is now everywhere in the industrial world and maintenance electricians are key players in making it work. The individual technician has the option of accessing online knowledge bases such as PLCtutor.com in order to become a player in this arena.
Industrial electrical work is a blend of space age electronics and traditional hardwire technology. As never before, it is an open-ended situation for those who have an interest in forming the future.