ote Wen oes Coe to Ce on Connetons€¦ · per thermite weld materials in a hazardous class leaving only special handling and ground transportation options [5]. Job site safety officers

Exothermic Welding Problems Compared to Clamped Ground ConnectionsWhite Paper

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Contents

Background

Safety at work

Quality earthing systems

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WP303/USA/0317 © Copyright 2017 DEHN, Inc.

This article discusses the advantages of DEHN clamping con-nection grounding systems over exothermic weld connected systems.In order to describe the overwhelming advantages of using clamping methods over exothermic weld methods, this article compares and contrasts the following key areas:

¨ Safety¨ Assembly process¨ Site and work preparation¨ Job site safety analysis¨ Safety data sheet (SDS)¨ Materials transportation

¨ Quality¨ Training¨ Inspection¨ Rework

¨ Longevity¨ Theft resistance¨ Corrosion

¨ Cost¨ Material¨ Labor time¨ Tools and Personal Protective Equipment (PPE)¨ Installation Time¨ Insurance premiums

¨ Legal Ramifications¨ Worker injury¨ Environmental impact

BackgroundDEHN has over 100 years’ industry experience providing light-ning 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 mate-rials 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.

SafetyAs for the advantages of using clamping over exothermic weld, safety has to be at the top of the list. The issues start with personal safety but quickly broaden into more complex job site and materials handling difficulties as well.The assembly process for a StSt clamping system consists of mechanical fitting, alignment and then bolting connections. If the work pieces are misaligned, the fittings can be loosened, adjusted and tightened to the final torque specifications. The entire process of making the joint takes about the same time as replacing a bicycle tire. The assembly process is intrinsically repairable. The site work preparation includes all of the layout, measuring and trenching to place the metal grounding ma-terials into the soil, but that’s where the similarities between welding and clamping end.Figure 1 depicts the typical layout for a bolted and clamped earth system before it is covered over with soil. By contrast the assembly process for making exothermic weld connections includes the same material placement efforts, but needs more physical trench room to get the molds and joint in position. Then it gets even more elaborate to prepare the weld mold, chemicals and wire end alignments. Even slight misalignments will cause the work to be aborted and repo-sitioned. And then if the chemical thermite is ignited and pro-duces a poor joint, the entire section must be redone. Even an experienced and highly trained craftsman will need 10 or more minutes to prepare a good weld joint. After the weld is com-pleted, all the molds and equipment must be carefully cleaned or those parts will go to waste.Figure 2 illustrates some of the aspects seen with welded joint grounding systems.

Figure 1 Bolted and clamped earth system

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fasteners and connections are visually inspected and checked with appropriate sized hand or motorized torque wrenches. Figure 4 illustrates a copper to copper bolt together bonding clamp suitable for above or below grade service. This can be used to join Copper to StSt materials with no problems.

Many construction sites require detailed Job Hazard Assess-ment (JHA) procedures to be created, approved, trained and implemented everyday on a work site. This sensible effort creates a safe environment for everyone and is part of our eco-friendly workplace. The JHA for a clamp system is straight-forward with practically no steps, activities or chemicals that can cause injury.By contrast the JHA for an exothermic weld is a safety man-ager’s nightmare. Serious consideration must be given to the 2500 °F molten material, off gas fumes and hot work permits needed to be in place to maintain a safety program for the worker who touches the copper thermite material and his spotter for every shift.The danger symbols [4] can be found on a typical copper ther-mite 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 cop-per 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 more hazardous materials and processes.

QualityThe contrast between the quality systems required to produce suitable bonds is also profound.As mentioned previously, the procedures for bolting a clamp system together are easy to understand, train and inspect. The

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

H 411: Toxic to aquatic life and may cause long lasting harmful effects.

Such hazards necessitate extensive precautionary measures:

P 261: Avoid breathing dust / fume / gas / mist / vapors / spray

P 264: Wash hands thoroughly after handling

P 270: Do not eat, drink or smoke when using this product

P 271: Use only outdoors or in a well-ventilated area

P 280: Wear protective gloves / clothing

Figure 2 Welded joint grounding system

Figure 4 Parallel connector for different cable diameters

Figure 3 Hazards and precautionary measures in case of exother-mic welding

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The inspection of a welded joint is inherently subjective. The interior of the weld cannot be confirmed and the inspector can only go by the surface appearance of the joint to assume an acceptable bond was achieved. Both the craftsman and the inspector require a great deal of hands-on experience. An un-acceptable weld requires the entire segment to be cut away and the process started all over again.As illustrated in Figure 5, a good joint is almost entirely sub-jective with wide variations depending on the level of crafts-manship, manufacture, weather conditions and job site con-ditions.

LongevityStainless steel clamping systems are extremely robust with a long installation life expectancy. Exothermic weld systems also have a tremendous deployment track record. But there are some stark differences between the two.Clamp systems using StSt materials are completely theft resis-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 ma-terials 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.

CostThe 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 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 needed to get permits, paperwork approvals, transportation, inspection and purchasing. These efforts all require more up front and back end investments when using copper thermite products. For comparison, a properly sized StSt clamp will cost on the order of magnitude 1/5 than an exothermic weld. If you take into account the installation, the cost advantage of clamping can be as high as 15 clamps for igniting a single exothermic weld joint.”A questionable weld is depicted in Figure 6, and the possible rework will require painstaking effort to cut away and reposi-tion additional costly weld joints.The tools and PPE needed to install a bolt on connection are safety glasses, work gloves, appropriate sized wrenches and torque wrenches commonly used by almost every auto me-chanic.The tool kit and preparation needed for a craftsman involved with exothermic welding is more complex and costly. Depend-

Figure 5 Questionable weld connection

Figure 6 Questionable weld connection

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once the intense chemical reaction commences. By the time a worker ever realizes he is in jeopardy, the flare of molten metal is already in his face and the fumes in his lungs, resulting in metal fume fever [8].The risk of back injury from prolonged leaning over during preparation is also comparably higher for welding.The SDS sheet for a typical copper thermic weld product in-cludes these mandatory warnings for legitimate legal reasons:“Improper use of the product or inadequate preparation of the conductors, molds or surroundings can result in aggres-sive reactions. Self-propagating high temperature reaction will occur if heated above ignition temperature. Generates molten metal in excess of 2500 °F (1370 °C), slag and dense, dusty smoke. The molten product can cause serious burns. Inhalation of powder or fumes may cause metal fume fever. Exposure to reaction: seek medical attention.”The copper oxide compounds in the thermite weld kits are known to be very toxic to aquatic life [9]. This is stated on the SDS sheets as previously mentioned in this article. The environ-mental impact of these materials is severe and in unambigu-ous contrast to StSt and copper clamp components. Additional measures must be taken when handling the weld kits to assure environmental contamination is avoided. For customers with high visibility environmental policies, these measures must be followed rigorously and included in the Health, Safety and En-vironmental policies and procedures (Figure 8).

SummaryProperly executed exothermic welds do create a quality bond that provides safe electrical operation and contribute to a highly effective protection system. The industry acceptance of this process cannot be disputed. But the contrast to simple bolt 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, in-dustry and electrical/electronic systems against the effects of lightning and surges.

ing on the job site, they will include additional welding gloves, face masks, fire retardant clothing, breathing aparatus and even arc flash rated PPE [7].Mold sizes vary for each conductor size, so several types may be needed and stored and cleaned. Solvents are required to clean the molds, so these additional SDS sheets must be ac-counted for in the project JHA and safety plans. The graphite molds are fragile and degrade, and so that cost is recurring throughout the project as well. The molds and welding mate-rial only work for a specific application e.g. ( rebar to copper, copper to copper ), therefore a variety of molds and welding material may be necessary for a project.Woe to the contractor who must maintain workers’ compensa-tion insurance for projects that incur exothermic weld require-ments. Many insurance carriers will outright drop the policy when they discover the holder is performing these weld oper-ations. These costs for special insurance conditions are either absorbed by the contractor, ignored altogether or passed onto the customer in the labor bid.

Legal RamificationsThe manufacture, project site owner and installation contrac-tor are all on the hook for any worker injury at a job site. The contrast between the potential risk of worker injury incurred by clamp methods as opposed to weld methods is extreme.The injury that could result from clamping a system together is pinched fingers, and the assembly process is almost certainly discontinued when a worker realizes his finger is pinched.A bolt and clamp system for above grade connections is shown in Figure 7. The application of connection force can be safely and reasonably applied with little risk to the worker.But the injuries that can occur from weld operations if the worker is improperly positioned are almost impossible to avoid

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

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About the authorMark Hendricks – Mark has contributed to various IEC and IEEE standards groups and has served the power quality in-dustry for over 20 years.

Acknowledgements

[1] IEC62305:2010

[2] NFPA 780:2014

[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


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ote Wen oes Coe to Ce on Connetons€¦ · per thermite weld materials in a hazardous class leaving only special handling and ground transportation options [5]. Job site safety officers