Exothermic Welding Problems Compared to Clamped Ground Connections White Paper

Contents

Background Safety at work Quality earthing systems

www.dehn-usa.com Exothermic Welding Problems Compared to Clamped Ground Connections White Paper

This article discusses the advantages of DEHN clamping con- Safety nection grounding systems over exothermic weld connected As for the advantages of using clamping over exothermic weld, systems. safety has to be at the top of the list. The issues start with In order to describe the overwhelming advantages of using personal safety but quickly broaden into more complex job site clamping methods over exothermic weld methods, this article and materials handling difficulties as well. compares and contrasts the following key areas: The assembly process for a StSt clamping system consists of ¨¨Safety mechanical fitting, alignment and then bolting connections. If the work pieces are misaligned, the fittings can be loosened, � Assembly process adjusted and tightened to the final torque specifications. The � Site and work preparation entire process of making the joint takes about the same time � Job site safety analysis as replacing a bicycle tire. The assembly process is intrinsically � Safety data sheet (SDS) repairable. The site work preparation includes all of the layout, � Materials transportation measuring and trenching to place the metal grounding materials into the soil, but that’s where the similarities between ¨¨Quality welding and clamping end. � Training Figure 1 depicts the typical layout for a bolted and clamped � Inspection earth system before it is covered over with soil. � Rework By contrast the assembly process for making exothermic weld connections includes the same material placement efforts, but ¨¨Longevity needs more physical trench room to get the molds and joint � Theft resistance in position. Then it gets even more elaborate to prepare the � Corrosion weld mold, chemicals and wire end alignments. Even slight misalignments will cause the work to be aborted and repo- ¨¨Cost sitioned. And then if the chemical thermite is ignited and pro- � Material duces a poor joint, the entire section must be redone. Even an � Labor time experienced and highly trained craftsman will need 10 or more � Tools and Personal Protective Equipment (PPE) minutes to prepare a good weld joint. After the weld is com- pleted, all the molds and equipment must be carefully cleaned � Installation Time or those parts will go to waste. � Insurance premiums Figure 2 illustrates some of the aspects seen with welded ¨¨Legal Ramifications joint grounding systems. � Worker injury � Environmental impact

Background DEHN has over 100 years’ industry experience providing lightning protection, grounding and surge protection solutions. The company has introduced many innovations through the years, including the implementation of Stainless Steel (StSt) clamp earthing and grounding products. These products meet or ex- ceed the IEC62305 [1] and NFPA 780 [2] requirements for the bonding of lightning protection systems and electrical earthing electrodes. The widely accepted exothermic welding of buried copper cable grounding systems is based upon joining copper materials through the application of the chemical process defined here [3]:

¨¨3 Cu2O + 2 Al � 6 Cu + Al2O3 + Heat That is to say, the combustion of copper thermite using copper oxide and aluminum powder creates a welded joint plus lots of heat and smoke. Figure 1 Bolted and clamped earth system

These symbols draw attention to the following hazards: H 302: Harmful if swallowed H 316: Causes mild skin irritation H 320: Causes eye irritation H 335: May cause respiratory irritation Figure 2 Welded joint grounding system H 411: Toxic to aquatic life and may cause long lasting harmful effects. Many construction sites require detailed Job Hazard Assess- Such hazards necessitate extensive precautionary ment (JHA) procedures to be created, approved, trained and measures: implemented everyday on a work site. This sensible effort P 261: Avoid breathing dust / fume / gas / mist / vapors / creates a safe environment for everyone and is part of our spray eco-friendly workplace. The JHA for a clamp system is straight- P 264: Wash hands thoroughly after handling forward with practically no steps, activities or chemicals that can cause injury. P 270: Do not eat, drink or smoke when using this By contrast the JHA for an exothermic weld is a safety man- product ager’s nightmare. Serious consideration must be given to the P 271: Use only outdoors or in a well-ventilated area 2500 °F molten material, off gas fumes and hot work permits P 280: Wear protective gloves / clothing needed to be in place to maintain a safety program for the worker who touches the copper thermite material and his Figure 3 Hazards and precautionary measures in case of exother- spotter for every shift. mic welding The danger symbols [4] can be found on a typical copper thermite weld kit data sheet: (Figure 3) As for transportation of comparable materials, StSt and copper bolt and clamp systems can be air shipped if needed, to any job site in the country without even needing a Safety Data Sheet. By contrast, that danger classification system puts the copper thermite weld materials in a hazardous class leaving only special handling and ground transportation options [5]. Job site safety officers will need advance notice to even allow the material on site, let alone grant the permits for the use and storage of several hundred shots that may be needed for a large industrial plant. A guideline for the reduction of job site hazards is to seek alternative processes or materials that remove risk before it enters the design altogether. Thus, it is best to design away the Figure 4 Parallel connector for different cable diameters more hazardous materials and processes.

Quality fasteners and connections are visually inspected and checked The contrast between the quality systems required to produce with appropriate sized hand or motorized torque wrenches. suitable bonds is also profound. Figure 4 illustrates a copper to copper bolt together bonding As mentioned previously, the procedures for bolting a clamp clamp suitable for above or below grade service. This can be system together are easy to understand, train and inspect. The used to join Copper to StSt materials with no problems.

Cost The contrast between the installed cost of a bolted compared to an exothermic weld system is also noteworthy. Of course each clamp will have a fixed cost to purchase the goods and transport the material to a job site. But the clamp is re-usable if the joint is flawed, and the materials do not have any shelf life limitations. Nor do they suffer or degrade if the materials get wet. The same cannot be said for copper thermite materials and mold fixtures. If anything goes wrong during the meticulous preparation of a weld, the kit is lost, the wire is lost and the mold is degraded. Even the best craftsman can only reuse a mold a limited number of times. Inclement weather raises hav- oc on the weld preparation and can spoil even the most careful efforts. If the kits are dropped into a mud puddle, they cannot Figure 5 Questionable weld connection be simply washed off and be ready for service. The difference in labor time required between bolting and welding cannot be ignored either. Nor can the differences The inspection of a welded joint is inherently subjective. The needed to get permits, paperwork approvals, transportation, interior of the weld cannot be confirmed and the inspector can inspection and purchasing. These efforts all require more up only go by the surface appearance of the joint to assume an front and back end investments when using copper thermite acceptable bond was achieved. Both the craftsman and the products. inspector require a great deal of hands-on experience. An un- For comparison, a properly sized StSt clamp will cost on the acceptable weld requires the entire segment to be cut away order of magnitude 1/5 than an exothermic weld. If you take and the process started all over again. into account the installation, the cost advantage of clamping As illustrated in Figure 5, a good joint is almost entirely sub- can be as high as 15 clamps for igniting a single exothermic jective with wide variations depending on the level of crafts- weld joint.” manship, manufacture, weather conditions and job site con- A questionable weld is depicted in Figure 6, and the possible ditions. rework will require painstaking effort to cut away and reposi- tion additional costly weld joints. Longevity The tools and PPE needed to install a bolt on connection are Stainless steel clamping systems are extremely robust with safety glasses, work gloves, appropriate sized wrenches and a long installation life expectancy. Exothermic weld systems torque wrenches commonly used by almost every auto me- also have a tremendous deployment track record. But there are chanic. some stark differences between the two. The tool kit and preparation needed for a craftsman involved Clamp systems using StSt materials are completely theft resis- with exothermic welding is more complex and costly. Depend- tant. They are nearly impossible for a thief to cut through and the StSt materials have practically no recycle market value to a would-be thief. The V4A StSt materials are corrosion resistant and provide long term, low impedance ground field service in most soil environments. As for copper thermic weld systems, who in the industry has not suffered from “over night” corrosion and job site theft from one day to the next? Copper still commands an attractive recycle value and a grounding system provides no electrical performance when it’s been ripped out of the soil. Copper materials are inherently prone to sacrificial anode reduction in almost all soil environments. Prior research from Chadwick [6] provides ample evidence of the problems at telecommunication sites where up to 27lbs of the copper ground field can be corroded away per year due to N-G current flow through SPD bolted-fault failures. Figure 6 Questionable weld connection

ing on the job site, they will include additional welding gloves, once the intense chemical reaction commences. By the time a face masks, fire retardant clothing, breathing aparatus and worker ever realizes he is in jeopardy, the flare of molten metal even arc flash rated PPE [7]. is already in his face and the fumes in his lungs, resulting in Mold sizes vary for each conductor size, so several types may metal fume fever [8]. be needed and stored and cleaned. Solvents are required to The risk of back injury from prolonged leaning over during clean the molds, so these additional SDS sheets must be ac- preparation is also comparably higher for welding. counted for in the project JHA and safety plans. The graphite The SDS sheet for a typical copper thermic weld product in- molds are fragile and degrade, and so that cost is recurring cludes these mandatory warnings for legitimate legal reasons: throughout the project as well. The molds and welding mate- “Improper use of the product or inadequate preparation of rial only work for a specific application e.g. ( rebar to copper, the conductors, molds or surroundings can result in aggres- copper to copper ), therefore a variety of molds and welding sive reactions. Self-propagating high temperature reaction will material may be necessary for a project. occur if heated above ignition temperature. Generates molten Woe to the contractor who must maintain workers’ compensa- metal in excess of 2500 °F (1370 °C), slag and dense, dusty tion insurance for projects that incur exothermic weld require- smoke. The molten product can cause serious burns. Inhalation ments. Many insurance carriers will outright drop the policy of powder or fumes may cause metal fume fever. Exposure to when they discover the holder is performing these weld oper- reaction: seek medical attention.” ations. These costs for special insurance conditions are either The copper oxide compounds in the thermite weld kits are absorbed by the contractor, ignored altogether or passed onto known to be very toxic to aquatic life [9]. This is stated on the the customer in the labor bid. SDS sheets as previously mentioned in this article. The environmental impact of these materials is severe and in unambigu- Legal Ramifications ous contrast to StSt and copper clamp components. Additional The manufacture, project site owner and installation contrac- measures must be taken when handling the weld kits to assure tor are all on the hook for any worker injury at a job site. The environmental contamination is avoided. For customers with contrast between the potential risk of worker injury incurred high visibility environmental policies, these measures must be by clamp methods as opposed to weld methods is extreme. followed rigorously and included in the Health, Safety and En- The injury that could result from clamping a system together is vironmental policies and procedures (Figure 8). pinched fingers, and the assembly process is almost certainly discontinued when a worker realizes his finger is pinched. Summary A bolt and clamp system for above grade connections is shown Properly executed exothermic welds do create a quality bond in Figure 7. The application of connection force can be safely that provides safe electrical operation and contribute to a and reasonably applied with little risk to the worker. highly effective protection system. The industry acceptance of But the injuries that can occur from weld operations if the this process cannot be disputed. But the contrast to simple bolt worker is improperly positioned are almost impossible to avoid and clamp systems is also clear. Designers, engineers and property owners have safety, quality, longevity, cost and legal consequences to observe when spec- ifying the materials and processes to employ when building their grounding system. DEHN protects. For the past 100 years we’ve led the way in lightning and surge protection solutions that guard people, industry and electrical/electronic systems against the effects of lightning and surges.

Figure 7 Bolt and clamp system for above grade connections – easy to install correctly Figure 8 The universal environmental hazard symbol

About the author Acknowledgements Mark Hendricks – Mark has contributed to various IEC and [1] IEC62305:2010 IEEE standards groups and has served the power quality in- [2] NFPA 780:2014 dustry for over 20 years. [3] M. Suban, et al, “Crack analysis in thermite welding of cathodic protection”, 2011 [4] United States Department of Labor OSHA.gov [5] 49 CFR Parts 101, 106, and 107 [6] R. Chadwick, “RRH Protection Considerations, PEG 2015, ATIS Proceedings [7] NFPA 70E, 2015 Edition [8] A.I. Swiller et al., American Journal of Medicine, January 1957, Volume 22, Issue 1, pages 173-174. [9] EPA Fact Sheet: 822-F-16-004, July 2016

Exothermic Welding Problems Compared to Clamped Ground Connections White Paper

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