Exothermic Welding Problems Compared to Clamped Ground Connections White Paper

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 2 WP303/USA/0317 © Copyright 2017 DEHN, Inc. Exothermic Welding Problems Compared to Clamped Ground Connections White Paper 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. WP303/USA/0317 © Copyright 2017 DEHN, Inc. 3 Exothermic Welding Problems Compared to Clamped Ground Connections White Paper 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.

Load more