November 2002

By Mark Kestner, Ph.D

The tragic events of 9-11 lingered in the air as a great cloud of dust cast a pall over Manhattan. As New Yorkers groped for their old routines, worries about the long-term health effects of toxic dust and fumes from the disaster site have many in the medical and health care communities gravely concerned.
The health effects of dust containing asbestos, silica, and other carcinogens are very real. I know, because I grew up in the ’50s in Cleveland. At the time, Cleveland was known as a “two-shirt town.” If you had a white collar job, you changed shirts at lunchtime because the one you wore in the morning was blackened with soot from the steel mills. The Cuyahoga River, running right through the heart of the city, actually caught fire one day to the lasting disgrace of the industry that had for decades used it as a dumping ground for the most noxious oils and chemicals.
Then came the Clean Air and Clean Water Acts in the 1970s. In spite of the dire predictions of industry, environmental regulation didn’t kill the Cleveland economy — it brought my town and many other “rustbelt” cities back to life. They could breathe again.
When I was a kid, all the Lake Erie beaches were closed to swimming. Now the lakeside towns are filled with vacationers and “weary” Lake Erie has enough walleye and bass to support a tremendous sportfishing industry.
The dust that settled at Ground Zero is the target of a massive clean-up. Apartment and office buildings are going to be scrupulously cleaned to satisfy a growing chorus of property owners and the worried citizens that are afraid to move back in.
Quarries have to battle the same kind of dust every day. The stone that built the World Trade Center came out of mines in New Jersey, Connecticut, and the Hudson Valley. Many of them are the same pits that supplied the iron and lead for the guns and bullets of Washington’s army 250 years ago.
Mining is a tough business. High explosives blast rock from the ground and huge machines crush it into stone and sand. But all that processing creates dust — dust that the public doesn’t want to see and miners don’t want to breathe. “Black lung” was a rallying point for the fledgling United Mine Workers of America and John L. Lewis, who fought the early battles for better working conditions in the coalfields of Appalachia.
Today, dust emissions are regulated and strict air quality standards protect the environment. Plant operators have to satisfy the demand for more infrastructure and clean air. Quarries that were out in the New Jersey countryside 30 or 40 years ago are now ringed by “McMansions” occupied by savvy professionals who want the potholes fixed, but don’t want to see those dirty trucks.

Truck traffic has a big impact on your neighbors. Preventing noise and carryout are essential to good community relations.

What should a plant manager do?
First of all, forget about all the regulations and standards that you don’t really need to know to solve your problem. Think about dust control in terms you understand. Dust and spillage occur because material handling and processing systems leak. Plug the leaks and you’ll put more tons into trucks. When you start to think about controlling the dust by controlling the process, you are much more likely to come up with practical solutions that are easy to integrate into your operations.
Good process control and good dust control are just two sides of the same coin. I don’t use that term loosely. There are lots of ways to make more money by complying with regulation. Some customers like wetter base rock, and water going across the scale can pay for a spray system in a couple of years. I know of several examples where mines have been paid to use waste products as dust suppressants — especially for roads. This allows the chemical company to avoid the higher cost of disposal by burial or incineration. Many cement companies profit from burning hazardous wastes or tires; quarries can profit by using off-spec or waste chemicals.

Good operating and engineering practices can keep screens running efficiently without visible dust.

Understand Process and Pollution Control
If you do not understand the relationship between process and pollution control, you are much more likely to make mistakes that will ultimately cost production and lose money. One common error is to spend as little as possible on the environment. I gave a talk once to a gathering of producers and while most were attentive, there were three fellas laughing in the back of the room. “What’s so funny?” I asked. “Well, Doc,” came the reply, “We just use a hose to soak the hell outta the rock whenever the inspector shows up!” It turns out that their VE (visible emission) test took three days during which this little 500 tph plant churned out 12,000 tons of mud and off-spec rock. At $3/ton that’s about $40,000 down the drain. That’s what I call “voodoo” economics.
If you still don’t get it, you may make the other common error of waiting until you get forced to comply. That’s a sure-fire way to develop an adversarial relationship with your neighbors and the state that will add penalties and fines to your list of accomplishments. If you don’t solve the problem, the regulators will do it for you by forcing the plant to use control measures that are much more costly and cumbersome.

Turn Lemons into Lemonade
Instead of whining about environmental compliance, find ways to turn the lemon of regulation into the lemonade of profits. Believe it or not, some dust control measures are actually good for production.
For example, choke feeding a crusher not only maximizes its productivity, but also keeps the dust down because the machine is moving more rock and less air. Likewise, operating the plant smoothly at a consistent rate improves production with no down time when crushers “windmill” and really kick up some dust.
I’ve seen haul trucks race to the primary at 45 mph trailing a cloud of dust only to sit for five minutes waiting to unload. A more rational speed might have gotten the truck there just in time to unload without putting a greater burden on the plant to water the road or treat it with expensive chemicals.
There are all kinds of simple things you can do that don’t cost a dime that can have a big impact on dust levels. But it all has to come from the top down. There are many companies that peacefully co-exist with their neighbors because their owners care about the way their plant looks and want to protect worker health. Many quarries are family businesses and these smaller outfits are some of the safest and cleanest I know because no one wants to see their brother or cousin get sick or hurt. Bottom line: I’ve seen plenty of crushing plants comply with clean air standards without ruining their business.
Unfortunately, I also see plenty of plants that only turn on the water when they see the inspector coming and their operators spend their day working in dust and mud. Even in this day and age, I still encounter plant managers for some of the biggest producers who won’t spend a few minutes talking about how to control dust and improve their production. If the man at the top doesn’t value the environment, the whole plant will be corrupted by his attitude.
Several years ago, I actually had an owner tell me in all seriousness that silica dust is “good for you because it’s like that Comet cleanser and scours your lungs out.” This culture of dirt teaches that “real” men thrive in the dust and that environmental protection is the enemy of production. Likewise, many steel company executives in Cleveland took great pride in their business cards that pictured the fire and brimstone of blast furnaces as a sign of economic health and personal wealth.
They could not have been more wrong. Clean air and water are just as vital to our survival as “smart” bombs are to our security. The mining industry can be proud of the contribution it makes to the infrastructure that has made us the only superpower. When you make the commitment to control dust with improved process controls, you are on your way to a cleaner, more productive, and profitable plant. And, you can take pride in the fact that our children will have a secure and healthy country to pass to their children.
The next installment discusses one of the most effective tools to control dust — good operating practice. I’ve always been impressed by the great diversity of methods and machinery used to produce stone, sand, and gravel. Every plant seems to do something just a little bit differently. But one thing all plants that have successfully complied with air quality standards have in common are operators that have been trained to take personal responsibility for dust control. They are your front line in the battle to protect the environment and improve production.

Mark Kestner, Ph.D., is president of National Environmental Service Co., which designs and manufactures wet-suppression systems for the mining and material handling industries. He has almost 25 years of experience controlling fugitive emissions from utility, industrial, and mining operations.

In Search of Precision Blasting

A practical user’s guide to electronic blast initiation

By John Watson

For quite some time, numerous explosive manufacturers have spent untold man-hours and millions of dollars trying to develop a blast initiation technology that would, once and for all, provide users with what was once believed to be only a theoretical possibility — nominal timing. Zero “cap scatter” (the amount of variation of delay timing from the targeted nominal) has been the industry’s goal ever since delays were first introduced into the marketplace. Adding delay time between blast holes can improve blast performance. However, having the wrong delay or a poorly timed blast has proven to be very inefficient and, in many cases, hazardous.
The question of how precise a blast initiation system needs to be remains unanswered, but electronic detonator systems being used today indicate that significant improvements can be achieved over conventional pyrotechnic detonators. These systems can typically provide single digit millisecond ranges of variability, if not sub-millisecond in some cases.

Understand the differences
Several manufacturers have systems under development or in use today. It is important to understand that each system is a unique design to each manufacturer and that none of the technologies can be interchanged with the other. Unlike electric detonator systems, where a blasting machine simply provides a minimum current level to fire the blast, or non-electric detonator systems that can be initiated by standard shock tube starters, each electronic “wired” system requires a specific blasting machine designed by the manufacturer of that system. Users need to be fully trained and qualified by the manufacturer in order to operate these systems.
Each system can vary considerably in design, functionality, complexity, and capability. It is critically important that every user understands all of the design features and characteristics of his or her system to ensure safe and reliable introduction into the workplace. Design features may include the form of physical detonator construction (internal and external), software code, or system logic. Different systems will certainly have varied forms of blasting machines, controllers, programming devices, and testers. There is only one certainty with the next generation blast initiation systems: they will all have unique differences to one another.
Electronic systems vary considerably in the type and style of wire and connectors. Again, it is important to understand the proper use of these products. Each system has specific instructions for proper hook-up. Some may require a precise order of tie-in to ensure proper sequencing. Others will simply rely only on the operator’s attention to blast design for proper programming or tie-in.
One system under development uses shock tube technology for initiation and a factory programmed timing element for its delay. Hook-up would be done the same as any conventional shock tube product.
Even with all the unique features a user will have to wrestle with in choosing and using an electronic blast initiation system, there are some similarities that you’ll need to understand. Generally, electronic initiation systems can be grouped into two categories — factory programmed and field programmed systems. Factory programmed systems use detonators with fixed delay times, whereas field programmed systems use detonators that can be programmed to any delay time just prior to or after deploying the units into a borehole. Most all field-programmable electronic detonators can be re-programmed at any time prior to the blast.
One characteristic that all electronic detonators share is some type of an Integrated Circuitry (IC) or Application Specific Integrated Circuit (ASIC) as part of the timing and programming design. Another important characteristic is that they all have one or more capacitors to act as an energy storage device to run the circuits. Some detonator designs have multiple IC’s as well as capacitors built into the electronic package.
Another characteristic that all electronic detonators share relates to the bridge element or igniter. Conventional pyrotechnic designs use a bridge or igniter to start the pyrotechnic delay element burning. Electronic detonator bridges are started by the delay element or electronic timer itself. What is important about this characteristic is that with electronic detonators, the igniter as well as the electronic delay package must be capable of surviving the shot. In conventional detonator designs, only the pyrotechnic delay is exposed to the dynamic pressure and shock effects produced by a blast. Figure 1 (below) shows these fundamental construction differences.
Users should be conscious of these construction differences when designing a blast for electronic detonator systems. It is important to know the product design capability as well as what dynamic pressure level can be expected.
Even with all of the design differences, variability, and additional complexity that blasters face with these new systems, it is becoming clear to those “early adopters” in the industry that electronic initiation systems add value to the bottom line. Several recent studies have shown that productivity and other key operational improvements are clearly possible (see International Society of Explosives Engineers (ISEE) Annual Conference Proceedings; and Blasting Analysis International 10th High Tech Blasting Seminar).

Figure 1: Fundamental construction differences between pyrotechnic and electronic delays. Source: IME

Know your needs
So, you think you’re ready to try an electronic initiation system. Before you get started, it is advantageous to get an exact idea of the problem you are trying to solve. As with any new or cutting-edge technology, these systems are relatively expensive and may require some internal resources dedicated to analyzing the cost/benefit ratio to your operation. Not having a clear understanding of your needs or goals associated with the use of this technology may only prove frustrating and expensive.
Knowing your operational needs may seem quite simple, but they can easily get lost given the numerous potential approaches to applying the technology. For example, if your goal is to reduce blast-related vibration complaints, the solution may simply be related to the elimination of timing overlaps and precise detonation of the charges (peak particle velocities). Or, the need may be to increase the resultant frequencies (hz) above the response range of your neighbor’s home. Choosing the wrong approach may initially produce an even larger problem, and in the case of the later need, greater precision may only provide you with the “exact wrong time.”
Other needs may be somewhat difficult to define as well. If fragmentation improvement is your goal, have you defined the optimum size crusher feed needed for your operation and can you take advantage of the greater throughput? If the reduction of backbreak or increased wall stability is the goal, do you know exactly what delay time is needed, now that it can be achieved precisely? If increased loader efficiency is critical, do you know the exact muckpile profile required for maximum efficiency?
Without question, greater precision will provide greater control over blasting challenges. Whatever the goal, precise electronic detonator technologies will provide some level of operational improvement over conventional detonator technologies. The challenge will be understanding (and measuring) just how significant the improvement is, and taking full advantage of it.

Ready, Set, Measure

With your goals clearly set, it’s time to start measuring performance. To justify the investment of any technology, you must have a way of measuring the key factors that will help assess the value of that technology. It is equally important to design a good test plan to ensure that you come to the right conclusions and can repeat the plan.
Your plan should include a set of test blasts designed to set a baseline for the operation and quantify the current state of the problem or area of improvement. Measurements associated with the baseline-testing phase should be as comprehensive as possible to ensure that as many blast-design variables are accounted for in the evaluation as possible.
Many of the variables are not always obvious to an operator, but should be well understood by an experienced blaster. For example, if your operational goal is to reduce blast vibrations (peak particle velocity), not only should you have calibrated seismographs as a primary measurement tool, you should be measuring (finding the baseline) all of the other variables that can affect vibration.
These variables include all aspects of blast geometry; including face profiles, borehole location (burden and spacing), borehole deviation, and borehole depths. Blast design and layout may be a significant contributor to unwanted vibration. Precision detonators can never compensate for poor designs or lack of control in shot layouts or drilling. A heavily burdened face, for example, is one blast geometry that would certainly result in high peak particle velocities irrespective of what timing precision was available (Figure 2).

Figure 2: All aspects of blast geometry, including face profiles, should be measured to account for as many blast-design variables as possible.

Measurements play a critical role in the process of loading explosives, and improperly mixed or loaded explosives can have a direct effect on vibration levels. Proper column height, explosive density, stemming, and inert deck height can all play a direct role in reducing vibration levels. Too little stemming or inert decking material in a borehole can sometimes have a significant detrimental effect on vibration (see “The Origins and Effects of Inter-deck Pressure in Decked Blasts” Lee, Rodgers, Whitaker; ISEE 2000 Proceedings).
Velocity of detonation (VOD) traces shown in Figure 3 (below) depict the pressure wave from a bottom charge traveling through a crushed stone deck into the top explosive charge resulting in a “shoot through.” Once again, precision timing would not correct this obvious design or measurement error.

Figure 3: VOD traces depicting “clean” deck separation vs “shoot throughs.”

VOD measurements can be a valuable tool in analyzing and controlling your test program. Knowing that all of the explosives in your blast are performing as designed is critical to ensuring the value analysis of electronic detonators is not compromised.
Don’t forget to measure timing. Measuring individual boreholes and deck charges for timing can be time-consuming and, therefore, left out of the data collection process. It is sometimes incorrectly assumed that electronics are all the same and have “perfect” timing. Don’t assume anything with your test program. Even electronic detonators have some level of “cap scatter.” It may be measured in microseconds or milliseconds rather than multiple-milliseconds or fractions-of-seconds.
Find the baseline for both your standard and electronic shots for timing. This provides the necessary data to ensure that vibration results can be interpreted properly and that information is available to analyze and correlate signature waveform data, if available.
Once you’ve measured all of the possible blast-vibration variables and have them under control, it’s time to look at the seismic traces. You’re also now in a position to fine tune the timing using the precision of electronics. So whether your goal is improving seismic results or increasing fragmentation, don’t simply substitute a hi-tech product for good blasting practices. Measuring and controlling all of the variables is the only way to ensure success in meeting your goals.

New Safety Challenges
Now that you are ready to begin testing and measuring the effectiveness of electronic detonators, it’s important to re-emphasize that any of these new technologies will bring new challenges. Safe introduction of these products requires that users fully understand the individual design differences, capabilities, and complexities of the system being used in order to avoid mishap. In uneducated or untrained hands, these products may only provide a higher level of frustration.
As discussed earlier, the construction of electronic detonators differs from standard pyrotechnic devices and may have very different operational limits or specifications. In addition to the construction of the products, in some cases the system-level procedures, applications, and communication protocol varies greatly.
It is because of these differences that the Institute of Makers of Explosives (IME) established an Electronic Detonator Subcommittee to develop a thorough understanding of the electronic detonator systems under development and in use today to provide technically accurate information and recommendations concerning their proper use. A new set of “ALWAYS and NEVERS” has been developed for inclusion in the Safety Library Publication No.4 — “Warnings and Instructions for Consumers in Transporting, Storing, Handling, and using Explosive Materials.”
Additionally, the sub-committee has developed information on electronic detonators for use in Safety Library Publication No.17 — “Safety in the Transportation, Storage, Handling, and Use of Explosive Materials.” This publication was revised in March 2002.

		Blasting using electronic detonators at the John S. Lane & Son, Inc., quarry in Westfield, Mass.

ISEE Blasting Conference Set for Nashville The International Society of Explosives Engineers’ (ISEE) 29th Annual Conference on Explosives and Blasting Technique is scheduled for Feb. 2-5, 2003, at the Opryland Hotel in Nashville, Tenn. As many as 1,600 blasters, manufacturers, government officials, and suppliers from all over the world typically gather for this conference. The 2003 program includes exhibits, technical sessions, panel discussions, and educational workshops covering drilling and blasting in mining, construction and demolition. A Blasters Weekend package, beginning on Saturday, Feb. 1, includes a blasters training seminar and the popular Blasters R Us Video Roundup. For more information on the 2003 conference, contact the ISEE, 30325 Bainbridge Road, Cleveland, OH 44139; (440) 349-4400; fax: (440) 349-3788; web: www.isee.org

John Watson is manager of the Advanced Systems/Technical Services Groups for The Ensign-Bickford Company (EBCo) in Simsbury, Conn. He has been employed by EBCo for more than 17 years and most recently served as product team leader for the electronic detonator development program. He is an active member of ISEE, represents EBCo on the IME Technical Committee, and is chairman of the Electronic Detonator Sub-Committee. This article first appeared in the May/June 2002 issue of The Journal of Explosives Engineering. It is reprinted with permission from ISEE.