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Voltage Sags, Dirty Power And Process Equipment Reliability

Mon, 06/16/2008 - 12:40pm
Is a product offering 99.999 percent reliability with a lifetime warranty a good deal? Not necessarily

The power utilities are selling just that. They call 99.999 percent “five nines” of reliability and power companies across the country are very proud of it. Some even promote “seven nines” of protection. When compared to power dependability around the world, five “nines” can be considered very good—it translates into roughly five minutes of no power each year or possibly just one hour of no power every ten years. In most industrial environments, one hour of no power every ten years would be manageable.

But when it comes to power, 99.999 percent reliability is much further from perfect than it appears. In fact, it can unknowingly cost pharmaceutical companies millions of dollars every year. A recent study by the Electronic Power Research Institute (EPRI) concluded this type of power ignorance could be costing the United States $250 billion every year.

Surely pharmaceutical processors wouldn’t need to spend tons of money to insulate themselves from only one hour of downtime every ten years unless it threatened the safety of their employees. So why do companies spend millions on premium power, multiple feeds, elaborate load-sharing switchgear, generators and uninterruptible power supplies?
Power reliability doesn’t tell the whole story

Premium power, generators and the like all seem to be viable technologies to prevent power reliability problems, especially when considering that 50 percent of unscheduled downtime is caused by power related issues. But when it comes to solving short-duration power dips, or “voltage sags” that make up 98 percent of all power glitches, these safeguards become relatively worthless. Poor power quality (PQ) or more succinctly, “Dirty Power,” causes more downtime and lost production than power reliability incidents, and often can’t be detected or prevented by typical defenses.Over the past three years several of the largest pharmaceutical manufacturers have been investigating the issue of Dirty Power and are shocked at what they’re finding. Short-duration voltage sags, cause more downtime than any other single issue in their facilities.

Voltage sags are most often caused by weather, errant rodents, mechanical failures or human error. They can be caused by problems in your facility but most often are utility “grid events” that are totally outside your jurisdiction. To further complicate matters, voltage sags are not always detectible. In a three-phase industrial environment, a voltage sag on phase “B” won’t be seen if the lights are wired on phase “A.” Some voltage sags are so short they won’t even cause the lights to flicker. Unfortunately, the downtime isn’t always as fleeting as the voltage sag. In many cases a 0.1-second voltage sag can cause hours of lost production time.
What happens to automated production processes after a voltage sag?

At most pharmaceutical manufacturing plants, voltage sags can affect the following processes;
  • all carry the potential to take the plant down for extended periods of time
  • Chillers
  • Mixers
  • Coaters
  • Compressors
  • Air Handlers
  • Catalytic Oxidizers


  • In one instance, a large pharmaceutical manufacturing facility utilized an Allen/Bradley variable frequency drive on a catalytic oxidizer to burn off excess particulates and airborne chemicals coming from the operation of a fluid bed tablet process. During voltage sag events at the manufacturing facility, the variable frequency drive would shut down and as a result, the interlocking controls shut down the Catalytic Oxidizer, which in turn shut down the Fluid Bed process. When functioning properly, this process was a necessary step to avoid dumping excess chemicals into the atmosphere; when not functioning properly, it violated EPA laws. This put the pharmaceutical manufacturer in a difficult spot every time it experienced a Dirty Power event. While shutting down the process protected the atmosphere and avoided EPA penalty, it also came at a significant production cost for the company. Incident reports had to be written and investigations conducted to assure the EPA and FDA that no contamination took place and that no product was compromised. In addition to the time and money it cost the facility to go through investigations, the product in the fluid bed had to be disposed of, and machinery had to be taken off-line to be cleaned out, costing the plant large sums of money. As would be the case with many pharmaceuticals, the scrap material cost was insignificant when compared to the lost production and resulting profits.

    Pharmaceutical processors who track the impact of voltage sags have concluded that sags account for as much as 70 percent of their total unscheduled downtime. The correlation between voltage sags and unscheduled downtime is very high from an event perspective—but the duration is not. A 0.1-second voltage sag can shut down an aseptic packaging line for 10 hours for cleaning. Many sensitive controls will actually be damaged by voltage sags as well. Variable frequency drives, custom control boards, panel PCs and other devices can be very sensitive to voltage sags. Insulating your production lines for Dirty Power can reduce damaged control equipment and cost-effectively increase your annual productivity by as much as two percent. That is a real competitive advantage.
    You might be asking, “How do we get started?”

    Once you accept that voltage sags could be one of the leading causes of unplanned downtime in your facility, what can you do about it? Believe it or not, the answer is not that complicated. It is a simple two-part process that every pharmaceutical processor should make standard practice.

    The first step is understanding the problem. Isolating the source of Dirty Power requires a power quality monitor that can distinguish between a local event and a grid event. With information from the right power quality monitor, everyone on the team can know that they just experienced a voltage sag and whether or not it can be traced outside the facility. Armed with this information, if the sag was a gridwide event, they know that simply restarting the process is all that is required. The root cause of the event is fully understood and explained. This can save thousands, and in some case millions, in unnecessary and unexplained downtime, equipment replacement and spare parts each year.
    Understanding the root cause doesn’t eliminate the problem

    The next step in the process is correction. Because voltage sags are so short in duration, power reliability technologies like generators, high-speed switchgear and standby uninterruptible power supplies are not fast enough to respond to sags and prevent downtime. Solving power quality problems requires equipment purposely built for the task. A Double Conversion UPS is an obvious choice, but not designed for the factory floor and very expensive to operate and maintain.

    A cost effective, battery-free UPS optimized for industrial power quality is perhaps a better solution to your power quality problems. To purify power in real time takes technology well beyond batteries, flywheels or even ultra-caps. In fact, to purify power doesn’t require stored energy at all; the grid can supply all the power needed to sustain operations.

    Detecting Dirty Power takes high-speed monitoring. Once detected, instantaneous response is vital. To eliminate the need for stored energy requires a technology that can harvest residual power from the grid.

    For example, a leading pharmaceutical manufacturer recently installed a power quality monitor that tracks voltage events while providing corroborative evidence to verify whether the event was internal or external to the facility. Due to the helpful nature of the power quality monitor data, the manufacturer soon became reliant on its power quality reports; in fact, this data is now regularly included in the facility’s variance reports to the FDA. Equally important is the ability it has given the manufacturer to correlate sags with machine downtime. The data has been used to create a list of the particular processes that are affected by various levels of voltage sags and the facility can now predict which machines will be down based on the phase, depth and duration data included in the reports. On a practical basis this means the company can immediately dispatch the necessary resources to the affected area and restart the machines without having to spend time troubleshooting the problem.
    A battery-free UPS optimized for industrial PQ problems

    Cost-effectively deploying PQ equipment requires careful planning. Not all pharmaceutical manufacturing operations require PQ protection. In a typical highly automated facility, less than 50 percent of the total power used drives equipment that is sensitive to Dirty Power. The nature of the business is also an important consideration. Industrials that need PQ protection include
    • Those that are production-constrained and need to optimize capital resources
    • Plants that suffer from excessive scrap expense, requiring PQ protection to remain competitive
    • Facilities that are regulated and require expensive root cause analysis for even minor anomalies
    • Factories that are time-constrained by JIT contracts, requiring PQ protection to minimize finished goods inventories and punitive back charges

      When considering PQ equipment, it is critical to take all aspects of the problem into consideration. Capital avoidance, scrap expense, rework expense, missed deliveries, idled direct expense and factory overheads are all impacted by voltage sags. The true cost of downtime is much higher than one might think.

      As pharmaceutical producers commit to tighter process controls, high-speed digital technologies will be required to meet the rigorous demands. Many pharmaceutical processing facilities already have more computers on the factory floor than in the front office. IT departments wouldn’t think of operating their mainframes without power reliability and power quality protection—shouldn’t factory automation require the same level of protection?

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