Water cooled cables are subject to fatigue and thermal failure. Cables face the most vigorous collisions and movement within a furnace’s power system. Proper construction and management can reduce cable repair and replacement costs.
Understanding Your Cables
Cable Purpose: EAF and LMF cables are the only flexible parts of the power distribution system between the furnace vault and the electrode. Cables or “flexible buss” extend from the electrical conductors from the transformer bus to the rear bus tube terminal.
In general, all water cooled furnace cables a have similar construction. However, the protective features of these components should be adapted to the specific configuration and problems associated with your own furnace environment. Reading and understanding this module will aid in lengthening your cables’ lifespan.
External Cable Inspection
Routine visual inspection of your cables helps increase your cables’ lifespan. Externally, the most important observations to make for cable performance are listed below.
A) Contact Surface
The contact surface on a cable’s lugs should be smooth and clean. Dust and grime left on the contact surface creates an insulative barrier that may result in excess heat and arcing. Be sure surfaces are cleaned during installation. Avoid removing and installing cables with items such as crowbars and hammers. Indentations on the contact surface of terminals reduces surface smoothness, resulting in an uneven connection pressure which can lead to arcing. Difficulties during cable removal should be well communicated and discussed with your cable supplier to create solutions. We actively work with our customers to simplify their cable installation/removal process.
Contact surfaces should also have protection against oxidation. Moisture, air, and other elements can create a nonconductive layer on the surface of your terminal. Copper grease can be used on cable terminals as a lubricant and to prevent against corrosion. We silver plate all contact areas to protect our customers’ cables against the harsh elements and to create higher surface conductivity. Check your cables for silver color on the terminals to determine if they have this conductive protective layer. Also be aware your cables’ nonferric (commonly 304 or 316 stainless steel) bolts should be tightened to your OEM’s specifications and routinely checked. A magnet will have a very weak pull towards stainless in comparison to steel.
B) Solid Lug Construction
One piece lug/terminal construction is stronger and more conductive than two-piece terminal construction. We’ve received competitors’ cables after customers have experienced broken two-piece lugs; the terminals were sheared in half! Check to make sure your lugs are made from a durable one-piece construction. The seem between a lug’s head and base should be uniform without a bonding agent. Two-piece construction requires an additive such as silvering, welding, or brazing that’s possible to see with careful inspection. Avoid obtaining these weaker connections!
Your cables should be supplied with specialized banding for power transmission applications. Stainless steel banding secures the hose to the lug and keeps water from leaving cable’s interior. Banding should be tight and secure. Visually inspect your cables’ banding during routine maintenance.
D) Hosing & Coverings
Cables are typically constructed with multiple layers. Choosing the correct layer type is dependent on a cable’s application and location in respect to the furnace. We offer many cable protective features such as those listed on Image 2 & 3. Inspect cable hosing surfaces for burns, tears, deformation, and abrasions. If cables are receiving significant damage during furnace operation it may be time to look into covering options.
Note: Adding coverings such as a doubled hose may considerably increase your cables’ weight. You should verify your bus and terminal connections can handle the max load of extra added weight.
Internal Cable Inspection
Conductors (copper ropes) are designed to be highly conductive, flexible, and allow for excellent heat dissipation. Cyclic loading eventually leads to work hardening of the conductors’ copper strands, and fatigue eventually causes wire fraying over long periods of time. While fatigue isn’t 100% avoidable, preventions are possible. Cables should be stored and installed with a large arching radius. Tight bends should always be avoided. Cables should never be powered without waterflow.
Lack of power to a furnace could indicate conductor failure within cables. A microohm test can help determine if a cable’s conductors have failed. Click here for tips and info on performing a microohm test on your cables. An internal inspection is required to be certain that a cable’s conductors are intact.
F) Core Hose
A core hose is buried within the center of a cable and must be checked by internal inspection. Its purpose is to force fluid flow through a cable’s conductors and add strength to resist harsh bending. We check all customers’ core hoses in house. Core hoses that are too abrasive and/or too weak are replaced with our specialized polyester rubber cores.
Buildup is caused by impurities and is the biproduct of corrosion in your water system. Heavy debris are removed during hose replacement and cable inspection. Avoidance of buildup is achieved by having pure water and performing system flushes without cables in the loop (cables may act as a filter and harmfully store particles during flushing if left in the loop).
What to Avoid When Handling Your Cables
Avoid using chains or cable slings around the hose of your cables. Concentrated load may cause internal damage to the copper conductors or core hose thus causing an impediment to proper water flow. It may also damage the cover hose, scuff gear, and exterior cloth coverings. Ask us about cable lifting brackets for ease of installation and keeping your cables in good condition.
Avoid lifting cables around cover hoses during installation. Cover hoses aren’t meant to endure the load of an entire cable. Furthermore, installing the cables by lifting from the cover hose may damage the terminal blades, core hose, and copper conductors. Lifting lugs are a cost effective and efficient alternative method to support your cables during installation. Lifting brackets can be designed and supplied for all cable types.
Avoid placing cables within a tight radius when storing or transporting. Shipping your cables on pallets can add to deformation of the copper conductors. Deformation can lead to preliminary fatigue and cable failure.
Avoid bumping or hitting cable terminal blades during installation or removal of cables. Hammer/ding marks are one of the most common costly types of damage Erie Copper Works sees during repairs. Keeping a clean terminal blade reduces welding and machining costs on cables.
Avoid dragging your water-cooled cables. Dragging a cable will likely cause damage to the scuff gear, terminal lugs, water connections, etc. Pulling the cable across a surface can also remove banding and result in water leakage after installation.
Avoid twisting your cables after unloading or during installation. We’ve supplied customers with a simple solution, a terminal-to-terminal like, to visibly see that a cable remains straight. Longer cables have an increased probability of twisting without being recognized. Avoid tight storage spaces and keep track of your cable ends to prevent cable twisting.
The most optimal form of cable shipment is by flat bed trucks. Bed-space should allow for cables lay parallel, without bend, along the length of the truck. An alternative suggestion is to ship cables in large 7’x7′ boxes to allow for large diameter coiling of your cables. The boxes should be designed for tow motor movement. Again, we also provide customization and fabrication of cable racks that provide a safe way to transport and store customers’ cables.
Storing Your Water-Cooled Cables
Vertical Storage is the best option to store cables. Hang the cable from a terminal lug bracket and allow it to extend to just above the ground. Vertical hanging positions simplify visual inspection and require very little space for storage.
Horizontal Storage is also an acceptable method. But experience has shown caution must be taken to store horizontally-laid cables away from tow motors and areas of collision.
Coiled Storage is the least accepted method of cable storage. Coiled cables should have a diameter of no less than 6′. Keep in mind that caution must be taken to ensure cables do not become twisted when storing in coiled-form.
Other: Note that cables must be stored without being twisted. Keep terminal blades covered with the supplied protective boards. If used cables are being stored, drain interior water. Avoid storing cables in extreme temperatures.
•Cables should be properly designed. All controls, stops, and regulators should function properly. Information from the metering equipment should be carefully catalogued and monitored.
•Cables should be cooled with a dedicated system of cooled filtered water. Rocks, shells, and other debris might flow through electrode holders, bus tubes, or settle in the mast arms. Flushing of equipment should be done without cables in the loop. Buildup from unfiltered water may result in poor fluid flow and cable failure.
•Cables must be completely filled with flowing water before transferring power.