Engineering systems in manufacturing, industrial buildings: Electrical, power, and lighting systems
Manufacturing and industrial facilities have some unusual engineering requirements, including demanding power requirements.
Jonathan Eisenberg, PE, Associate Manager, Rolf Jensen & Associates Inc., Boston
Brian P. Martin, PE, PDX Electrical Discipline Manager, CH2M Hill, Portland, Ore.
Peter Pobjoy, PE, LEED AP, Chief Design Officer, Southland Industries, Los Angeles
Peter Zak, PE, Principal, GRAEF USA, Milwaukee
CSE: Describe some recent electrical/power system challenges you encountered when designing a new building or updating an existing building.
Martin: With the newer facilities, the power demands and power density have increased quite a bit. Securing the capacity from the utility and designing the duct bank to dissipate the heat has been an interesting challenge. It has been common practice in the utility realm to understand the RHO of their duct bank backfill, but that hasn’t been as widely understood in the industrial market. On recent jobs, we have been requesting soil testing with a 28-day dry out. Where we are unable to do that, we’ve been specifying a concrete backfill with a controlled thermal characteristic. This helps mitigate the soil dry out and resulting thermal runaway. Even then, we have been requesting thermal resistivity testing of the concrete fill to confirm our assumptions.
CSE: Describe a recent project in which you specified back-up, standby, or emergency power in such a facility. What challenges did you face, and how did you overcome them?
Eisenberg: On our South American project, we sized the site fire water loop and fire pumps based on the largest hydraulic demand, which is an outdoor hazardous gas storage area. When the facility owner considered changing the gas storage container type, we needed to revisit our assumptions for fire pump sizing. Because the fire pumps are served by the emergency generator, the storage change caused us to verify if the generator is adequately sized to handle a larger fire pump.
Martin: On a recent project, we designed a greenfield facility with large backup power requirements. Only a small proportion of those loads were truly emergency loads. The difficulty was to distribute the emergency power to these loads that were widely dispersed throughout the site, using a set of paralleled generators and insuring that they received power within 10 seconds. The key was to be very judicious and work with the AHJ to properly classify loads that are emergency, coordinate our requirements with the generator vendor to make sure that we could sync multiple generators within 10 seconds, and then properly coordinate the restart of the equipment with the control system.
CSE: What high-voltage challenges have you encountered in these facilities, such high demand for power, demand response issues, etc.?
Eisenberg: On a hydrogen storage and fueling project, we observed high-voltage power lines that encroached on the required separation distance from the process equipment. In this case, the easiest solution was to relocate the power lines.
Martin: Nearly all of the facilities we design have a medium voltage utility service (more than 600 Vac). As we’ve seen the loads increase, we’ve been increasing the serving voltage to the site, and thus to the primary of the distribution transformers. The main issues have been making sure that owners understand the extra maintenance requirements of medium-voltage equipment, making sure that a proper protection scheme is designed and implemented, and then coordinating this scheme with the utility. This requires close collaboration with the utility, and even then, utilities typically do not ramp capacity with the same speed that industrial clients desire. We often have to design an interim protection scheme that can be in place while the utility adds capacity.
CSE: What unique lighting systems have you specified into a manufacturing or industrial facility recently? What unique demands did you meet for your client?
Martin: We’ve designed zone-based lighting controls, daylighting, and areas with occupancy sensors and have gone as far as designing networked lighting systems that allow for individually controlled luminaires. The unique demands that we have seen are trying to meet clients’ expectations for light levels while still meeting energy codes. Some states no longer provide energy code exemptions for manufacturing spaces. We have also had quite a few interesting discussions for meeting LEED criteria for an industrial building.
Eisenberg: Our industrial/chemical work often includes a review of Article 500 of the National Electrical Code to determine the delineation of Class I and II, Division 1 and 2 areas. As part of this analysis, we can be asked to look at lighting for certain areas of a facility and determine if the enclosures meet the requirements for a hazardous location as defined by the NEC.
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