A Study of Boom Luffing – Part 1

     

Boom rope failures are historical. In 2020 we talked a lot about rope failures, but the message was not received. Some become philosophical and thoughtful upon aging, revisiting memorable events. I care because of my experience with accidents. We do not have a choice about aging. Caring is an option.

Fig. 1 Dropping Booms in the work area is an ole story!

     My first boom “falling” was at Cape Canaveral, FL in 1963 (22-B) boom rope broke. Philosophy, a study of how we think through problems and develop theories using research to solve difficulties in a specific area. I selected why boom ropes fail. A major cause is inadequate or no maintenance.

     Standards stress a “complete” annual inspection is necessary to solve the problem of taking worn ropes out of service. In this 1947 photo, we see, not too clearly, but visible in Fig. 1, boom failures are catastrophic. When a hoist rope breaks, the load drops straight to the ground (although load “splatter” is known to reach people 20’ away), fewer people are exposed to being hit. Drop a boom, and the entire worksite is exposed. You’re either in the right spot or the wrong one, no ducking it!

     Some maintenance people consider boom ropes of equal importance to any other ropes, unmindful of their particular needs. All wire ropes wear out quickly. In a crane’s life, ropes can be replaced as much as seventy-two times more often than the engine’s piston rings or rod bearing. Yet, these critical servants do not have “gages” to let us know when they are low on oil, knocking sounds when wearing, or reservoirs religiously kept full by mechanics. An engine blowing a rod has never killed but a failed rope has. Are we missing something?

Fig. 2 Dry lubricant must be removed from valleys before a new application.

     Severe wear locations (equalizer sheaves) must be viewed close-up each year. Requires taking the crane out-of-service for as long as needed. Some people do not correctly service the rope on their crane! Lubrication must penetrate the rope to the core allowing the wire to slide easily along each other, reducing friction and wire breaks at the “strand to strand” contact area. Fig. 2 shows valleys clogged with dried-hard lubricant how can a light spray of oil penetrate to the core, it cannot and is best applied when bent over sheaves. This dry lubricant must be removed before applying a penetration oil. How often? As often as it takes to prevent reoccurrence. When was the last time you saw a crew removing dry lubricant from a rope? There are rope cleaning devices available. Check ads in this magazine.

     A heavier lubricant for external corrosion is needed. Some say their lubricant can protect for a year; time intervals depend on the environment. The extra time spent on these critical ropes is worth the effort. To protect the rope, extending its life, use a heavier lubricant that sticks to the rope. Here is the dilemma. To lubricate the rope’s wires to the core requires a light viscosity lubricant. Learn how to penetrate the inside of the rope and also protect the outside of a rope.

Fig. 3 Outside wire wear shown here; then wires start breaking.

    If not failing at the equalizer sheave (some reeving systems do not have equalizers) or from rusty ropes. Another causation is broken wires due to fatigue. Not all the rope’s length is subject to outer wire wear; find their location and mark. The wires are scrubbed on the drum then bent around sheaves under tremendous pressure, ouch! Fig. 3. When the wires wear thin and flat, they break when bent; that simple, 1/3 diameter wearing is allowed. Proper outer lubrication reduces wear.

     A “test”, do you know the rope construction shown in Figs. 2 & 3? An inspector should, yet I have met some that did not but were inspecting rope. OSHA (1926.1412) says a competent person demonstrating the skill shall make an annual rope inspection. It matters that inspectors know what they are looking at to be called an “informed judgment.”

     If you have a good rope lubrication crew, you can have a good inspection crew. With proper training, eliminating these enduring catastrophe boom rope failures is possible!

As printed in the Wire Rope News and Sling Technology.

Dennis can be emailed at dennis@natlcrane.com.

Dangers in Crane Testing: Expect the Unexpected

Recent crane accidents prompted this article. I have certified cranes for various agencies and companies since the 1960s and know the requirements of the work. I find these accidents have peculiar circumstances in both causes and the number of injured and deaths (33.) Couldn’t this have been prevented? Who dropped the ball?

Fig. 1 Inspecting for deficiencies and correct assembly.

     There but for the grace of God, go I.” When John Bradford first uttered these words, he was reacting to prisoners marching to 16th-century gallows. Perhaps a bit too dramatic a statement for some, but to the people involved, they may think appropriate. In the vernacular of the street, “they were just in the wrong place at the wrong time.” Both viewpoints have merit. If it were a friend of yours that was killed, you would seek solace. But, if these accidents just cost you money, you may ask, why were they there in the first place, and who screw up? 

     Myself being a mercenary, asks, supposed these flawed cranes with their underlying defects, pass these tests that are performed cautiously under perfect conditions and certified? Then, one month later, working at job speeds, hectic conditions, and usual inertial load moments failed, the person who signed that certificate would have problems.

     Two accidents occurred during their initial testing and certifications “commissioning” the cranes. In the U.S. OSHA Maritime, it is Inspection and Load Testing for Initial Certification, and this inspection and testing is required every four years, after that, an inspection each year between the testing cycles unless modified.

THE TRAP

     The U.S. Navy places “load-bearing components” in two categories – load-bearing and primary load-bearing. The latter are components that the stress-induced in them is in direct proportion to the load on the hook and require in-depth documentation.

     It’s funny; the psychology (behavior) of overload testing of a crane is taken casually by some people very familiar with cranes. Why? Simple: Most incidents with cranes are caused by weather, operator error, or rigging breakage. I heard it said, “we over-load the cranes anyways, go for it!” 

     Before the test, the crane undergoes an intense visual and dimensional calculation of its structure, followed by mechanical/electrical performance and operating evaluations with no loads. The testing is performed; under good weather, known loads, measured radius, professional rigging, and smooth, controlled movements. What could go wrong?

     If the crane is new, to be honest, it is taken for granted that it was built correctly and the manufacturer’s engineers are always confident with this fact. The inspection is more straightforward, with no dirt, no wear, or repairs/modifications to evaluate. The effort is to determine that the configuration of the crane conforms with the manufacturer’s documents. The essentials are how much counterweight, type of wire rope/reeving, length of booms/jibs, accessories equipped, and capacity charts/manuals. These form a “benchmark” of documentation, referred to during future crane surveys allowing surveyors to recognize alterations that may affect the capacity or operating control of the crane.

     In these accidents, the structural failure of the mechanical/structural component occurred far below the crane’s capacity. Getting warming-up and building confidence that the cranes could lift their capacity loads. Then testing, we perform the maximum radius first, followed by mid-radius, and then minimum radius, which is the maximum load. The new 5000-ton ship crane was lifting 2,600-ton when it failed. The new port crane had handled 50% of its capacity for two days before and then collapsed during the test. Who would have thought?

WHAT COULD WE DO?

At the time of the initial certification inspection, the surveyor is not evaluating the material selected to construct the crane or the method of assembly. There is no “checking off” of sub-components, the design, or the material selected for the final product. What they are doing is verifying that the final product before them agrees with the manuals and drawings provided by the manufacture. A 40-ton Hydraulic R.T. crane – easy. A 5000-ton newly designed floating crane – not so easy.

     The crane certifier is responsible for determining that the crane is correctly assembled, no physical deficiencies, and is functioning correctly during the overload test, not to check Engineering. All areas of the crane are not accessible for inspection. John W. Davis, PE president of the Cranes Certification Association of America (CCAA), states, “the certificate can clearly define the scope of the inspection/testing and state the limitations involved, thereby specifying the limits of responsibility of the Surveyor, in our business called “failure to warn.” (See Fig. 1)

     These accidents are concerning because none of the on-site efforts could have prevented their occurrence. Then, how could they have been prevented? Could something be done at the time of these final acceptance tests? Are somethings just unforeseen? Some say that everything can be prevented, in theory, but at what cost. Maybe two unusual crane accidents a year aren’t too big a price to pay – in not trying to eliminate all accidents!

     Some refer to the crane companies as fabricators and designers. They depend on critical sub-assemblies from suppliers. So, vendor-source inspection is vital to the overall performance of their product. For example, no crane company makes its turntable slewing ring bearing or the bolts that hold it together and securing it to the crane. None make the hook in their load blocks.

     Identifying primary load-bearing problems can only be achieved at the sub-assembly or material selection levels, which means the necessary amount of quality control in the manufacturing process. Monitoring of the vendor to determine assemblies’ function, dimensions are essential. And, followed with visits checking material specifications and the vendor’s process. They depend on quality products from their suppliers. I would ask, who’s foundry poured the billet alloy for the hooks? Where are the turntable bearing races produced? Cast alloy steel or forged steel?

THE MAKERS

I observe the effects on material handling equipment in the workplace from the side of the application, maintenance, and operations. Witnessing the improvements in capacities, reach, and height increases as well as “cost per ton” reductions in bulk material handling. These devices are subject to market acceptance for survival; if they don’t sell – they won’t survive – competition.

     Some cranes can produce a return on investment performing a few lifts a month, while other duty-cycle “dirt machines” must labor years to profit. The new crane owner must choose wisely to prevent unnecessary problems in the future. It has been shown that the wrong machine on the job was the primary cause of an accident.

     How is it that giant new cranes, like these, get developed for humanity? Greed for market domination and profits? Is there a fantastic “panel” in the sky thinking up new ideas – no. They come from a practical solution to a real-world problem through the trial and error process. Nowadays, with computers, the adaptation of information (honorably or otherwise) automation of processes, etc. there is less “trial” but still – error. Bluntly put, with detailed computer designs, there is less “fat.” Fat is too costly in competitive international markets.

     China owns the Orion 5500-ton ship’s crane involved in the accident. It was built to install 103 wind-generating jackets in the North Sea. China controls 55% of the wind generation installation market world-wide in 2019, according to news releases. By following an old philosophy of “cheaper-by-the-dozen” and mass production techniques, the large scale installation of these jackets attached to the ocean floor is unmatched. The new way is to think big!

Fig. 2 1909 steam-powered crawler crane, wire rope luffing boom.

EVERYTHING OLD IS NEW AGAIN

Older crane designs are manufactured today with improvements. Why? Because they still meet the requirements of the job. A perfect example of this staying-power is the lattice boom, wire rope luffing crane mounted on locomotives, trucks, and crawlers. These machines have been transmuted over the last 110 years, but essentials do the same work (Fig. 2).

Fig. 3 The level-luffer design feature increases the crane’s CG height.

     Another older design still being built in some parts of the world is the “level-luffing” port crane. The India “new” port crane involved in this accident is of an older design from the 1920s - a mechanical Level-Luffing duty cycle port loader/unloader. An example, located at a port in Trinidad (circa 1942), is shown in Fig. 3. The turntable is located lower to the portal and is supporting the revolving upper works. Modern designs are improving on the two aspects of level-luffing and over-all lowering of the crane’s center-of-gravity and high maintenance costs – a lot of moving parts.

INDIA PORT ACCIDENT, 2020

This crane was delivered to this site two years ago for commissioning. At that time, it failed, and various deficiencies were issued, but the manufacturer, Anupam Crane of Mumbai, did not repair the problem. Anupam joint ventured with a Japanese firm to build the crane. Two years lapse without any repairs, and the owner contracted Greenfield Corp. to clear the deficiencies and commission the crane.

     The operating advantage of “level-luffing” is to increase productivity when loading/unloading of bulk material at ports. Handle bulk-cargo calls for continuous 180-degrees rotation, increase/decrease of boom angle/radius, and the hoisting/lowering of a load, then opening/closing a clam bucket to deposit the material. The result is that when the boom went up, the rocker-beam hoist end lowers. The result is that the hoist load remained level with the earth. Synchronizing the boom and hoist drive motors for new cranes has eliminated the need for this rocker beam design with all its negatives and produces the same results. Is that what it was going to do at the Navy shipyard?

Fig. 4 Turntable bearing, the bottom (basement) of “cone.”

     The turntable bearing support area failed, as evidence by the videos available on YouTube. All the mass of the load, crane upper works structure, and inertial moments concentrated at this rotating bearing located at the bottom of the gantry and overwhelmed its structure (Fig. 4).

     What could have been different if we were the test directors? Oh yes, the inspector/surveyor has had a change in his job description, responsibilities, and title. Test directors know their primary duty at this point is to signal the movement of the crane, when overloaded, away from other equipment, and limit personal to those required for the testing within the area. Then this crane’s failure; there were twelve people on the crane. Why?

ORION SHIP CRANE ACCIDENT, 2020

     This beautiful new Chinese 5,500-ton super heavy-lift offshore work ship is the Orion. Sort of a modern miracle of engineering, so though! The reported cause of this accident (I would think) sent the crane builder Liebherr’s management and engineers into shock. I would have to invent a whole new word to describe what they must have felt! Classic failure – load drops off-hook, boom recoils back over the crane (but rarely does the hook break, twice in my sixty years, and that was long ago.) This dramatic accident, caused by the lower “keeper” failure of a vendor’s hook. Was the hook tested before assembly? How would you build an 8,250-ton (150% of capacity) test fixture? Expensively.

Fig. 5 A forged bowl hook.

     Most crane hooks are basically in two parts. The hook with its shank is one piece and the other a “keeper” of some design to secure the hook to the hoist block. Industries forge most hooks, but some are cast alloy steel, Fig. 5. The hook that failed was of a newer design made from four parts, due to its massive size and capacity. It is an assembly of; a shank (stem), top keeper, which appears to be a pin connection, a four-prong hook that slid on the shank, and a bottom keeper to hold the hook on the shank. It was this bottom keeper that failed, allowing the hook to slip off the shank, dropping the load. No inspector could have determined this manufacturing defect.

SHIPS CRANE FAILURE

Fig. 6

     A 100-ton pedestal crane was due for its quadrennial inspection and load testing for maritime certification. When these cranes lift loads from the ship’s deck, then rotates to the dock and unload the cargo, the ship must remain level. This Indonesia flagship leveling is accomplished by high-speed jet pumps that transfer ballast water from one side of the ship to the other to maintain a minimum “list.”

    When picking up the test load, the jet pumps malfunctioned, causing the ship to list approximately 12 degrees sideloading the crane and triggering the pedestal failure. The test load swing starboards twenty-eight feet and hit the dock, no injures (Fig. 6). In this case, outside occurrence beyond the control of the test director caused the crane to fail. Properly controlling the test area avoided personal injury.

RAIL FAILURE

     Here the crane surveyor performed (before being elevated to test director, no extra pay) his duty during the quadrennial inspection. He had visually located deformed rails. Some deforming was first noted and monitored during monthly inspections by the owner.

Fig. 7

  The rails are fabricated. A rectangular-shaped railhead welded to a top flange that is welded on a vertical web, which in turn is welded to the deck base plate and gusset supports welded. This deficiency was on a four-year-old Turkish crane. Cause – residual welding stress (per manufacture.) Fortunately, the rail was good enough to last as long as it did under the light service at this U.S. shipyard (Fig. 7).

CONCLUSIONS

     The question first asked, how can accidents like these be prevented? Well, there is an interesting connection in all these accidents. The joint ventures between companies and nations to build or test the crane. The large hook that separated (China/Germany/Dutch), the crane turntable/bolts disconnection (India/Greenfield/Japan.) Then the ship’s pedestal collapse (Netherlands/Indonesia/USA), and the improper rail fabrication (Turkey/France/USA) during load testing. These types of collaborations are a trend in our industry.

    The decisions made by managers of the joint ventures control the success or failure of these activities. They can be separated, 1. The defects were preventable only at the subassembly level, requires adequate quality control, 2. Standard commissioning procedures need to be followed, no shorts-cuts during inspections, and control personal access to the test area 3. Accidents like these start the blaming, and the hiding of the facts – sealed agreements – prevents informing the industry.

    As these cranes become so gigantic and complex, I am concerned about Certifying Concealed defects, which will, from “time to time, rear their ugly heads.” Creating safety is done every day by how people work and communicate with each other – distance impedes. Everyone involved takes responsibility.

By: Dennis O'Rourke

Dennis can be contacted at dennis@natlcrane.com.

As printed in the Wire Rope News & Sling Technology October 2020

Train Your Kids in Proper Rigging - Not Like This!

     Pictured here is a load attaching method of hoisting an I-Beam some 250 feet in the air via a Tower Crane on a large industrial job site. The crane operator, about 275 feet away from where the beam is to be landed. He has little input as to  how the load is connected to “his Crane.” Yet, he and his Employer will feel the harmful effects of a dropped load, if someone should get hurt – it will be costly.

     The operations are 100% depending upon this rigger’s decisions; that will be made in a matter of seconds – based on his training and experience! He’s performed this “choker hitch,” a hundred times before (let’s assume) with no failures. The hitch may be the same – but are the working conditions that affect the outcome all the identical?

     What’s so wrong here that I am taking your time to “rail” about anyway? If I were testing someone in an entry-level Rigging 101 course, he would fail. Aside from the obvious of not running the eye through the yellow oblong link that re-duces wire wear and D/d ratio stress on the body of the sling, as the sling Manufacture intended. There is no kinking protection (softeners) between the beam/sling contact points. However, there is a much more important error.

     These experienced Ironworkers know that this thirty-foot, W 14 x 82 beam weighs about 2,460 pounds, (1,230 each end) is not going to break the 3/4" diameter wire rope sling they are using. So, they feel justified in abusing their employer’s equipment; after all, men will be men! So, bothersome soften-ers and sling body wear/stress is “kids stuff” not to slow down production and make this work harder than it is. There is some logic here, and I had witnessed an overuse of personal protection equipment (PPE), making things harder for the workers when no hazards existed, frustrating the people.

     The real “violation” here is the lack of control that could cause the beam to slip and fall from the choker hitch on its 250-foot journey over the heads of numerous workers - not the breaking of the sling. All manners of forces can occur to dislodge the beam along its route. To name a few; excessive swing speed, sudden starts/stops, beam caught on the obstacle, weather conditions, or setting one end down and releasing the “bite” allowing the beam to slip and fall. A bundle of metal studs from a single wrap choker hitch like this, occurred at a hotel under construction at Disney, killing one.

Corrected: Double Wrap, Softeners, and a Shackle in the “bite.”

     Simply a “double” wrap choker hitch would have provided all the necessary control, yes, a little more annoying for the riggers – but so much safer. A bad meth-od is a bad method no matter how many times you get away with it! And, it’s a terrible OJT example for the kids. These experienced riggers may have “fallen prey” to complacency.

     The camera is everywhere nowadays, catching us in the “act” as it were. Companies slogans like “Safety First, If you can’t do it right, don’t do it,” etc. will not stop an unsafe act, skills training helps. We ask ourselves why people take “short-cuts” why don’t people do it right all the time – oh yes, people were never made perfect!

As printed in the August 2018 issue of Wire Rope News and Sling Technology.

Dennis can be emailed at dennis@natlcrane.com.

Synthetic Ropes, "to be or not to be " on Mobile Cranes - that is the question

     There is a long-established belief that “if it ain't broke, don’t fix it.” Steel wire rope has been used successfully on cranes since the 1800s. Now some are replacing steel ropes with synthetic ropes. At the last two conferences that I attended, held by the Crane Certification Association of America (CCAA), synthetic rope manufacturers (Samson and Yale respectively) gave presentations as to why replacing steel ropes with synthetic ropes on cranes makes sense.

     What the crane industry has experienced in the past is fiber roped being easily cut when they are used as slings, blocks, and tag lines. Fig. 1 There is an established “belief” this material is too soft to be used on multipart reeving. It’s said that facts and words do little to alter a belief, experiences are what one trusts. Crane owners have required the installed synthetic rope be removed from their crane based on this weakness belief. Yet, no evidence of damage was evident.

Fig. 1

     The popularity of synthetic ropes on cranes is growing just by the number of companies offering the product. They call it in sales terms, “market push” The Heavy Lift off-shore Oil industry is a major user of these products due to their reduced weight.

     The benefits of synthetic rope over steel are lighter weight, more flexibility, anti-spin, and no need for lubrication to prevent corrosion. Some synthetic rope manufacturers claim a fourfold increase in rope life, thereby reducing operating costs – a true advantage if proven. The benefit of reduced weight has caught the attention of the crane industry.

     Let’s do a little arithmetic. Let’s assume the weight of eight parts of 7/8” steel wire rope at 1.42 pounds per foot at a 100’ hook height (1.42 x 8 x 100 = 1,136 pounds) add a 3,800 pounds load block. Now have 4,936 pounds suspended over the crane’s boom point. Replace the steel rope with synthetic rope, as pictured in Fig. 2, will see a reduction of the weight of the rope by 80%. The weight of the block will also be further reduced because the overhaul weight requirement will be approximately 65% of its original weight. The new total weight in the hypothetical situation is approximately 1,352 pounds, a 3,584 pound reduction. This weight decrease really gets crane manufacturers excited, especially the ability to reduce weight at the boom point. Also, note the nylon point sheaves a further weight reduction over steel.

Fig. 2

     Synthetic ropes have been installed on utility truck winches used in the power industry for decades. Synthetic ropes are less conductive than steel wire ropes, an advantage when working around powerlines. For most operations, the synthetic rope on utility truck winches is used in a one-part configuration. Now we are looking at synthetic ropes being used as multi-part configuration on a mobile crane, greater wear.

     At various locations the Navy, Grove, and others have conducted trial tests of synthetic ropes on cranes, and the performance of the rope was reported satisfactory. I question how safe it is to trust a synthetic rope that can be cut with a knife, to lift 80-ton loads? Especially since I have witnessed synthetic ropes damaged when used for rigging slings and tag lines. How will the rope last in “real” job activities?

     When a crane is operated and used conservatively, the synthetic rope should be as reliable as steel ropes. That is the rub. When we factor humans into the equation, things get complicated, job pressures increase. What “predictable misuse” should be expected. I think of the ABBA song “Take a Chance on Me.” Do I take a change when not knowing if the crane will be properly operated and maintained some months down the line? I believe that synthetic rope needs the “test of time” to show the crane community how it survives in the real-world struggles of a modern job site.

As printed in the December 2019 issue of Wire Rope News and Sling Technology.

Dennis can be emailed at dennis@natlcrane.com.

“Additive Manufacturing” of Hooks – Good Idea?

By: Dennis O'Rourke



Fascinated, when in 1984 I learned from a science magazine that a photo of a Statue Bust of Benjamin Franklin was taken in Cambridge, England and faxed to a laboratory in Massachusetts. Then, it was turned into a 3D CAD digital file which was loaded into a “molding printer” where it started to duplicate the bust of “Ben” - as a plastic replica, amazing.

Now in 2018, I learn of a comparable process of producing a crane hook, that caught my interest. This process forms an object layer on layer.  I thought it was a neat idea for ole Ben’s head but, for a crane’s load hook I have questions. As one who for about 45 years inspected and tested port cranes, I know that the hook supports all that is below it, no doubt critical to safety.

                                                               

History of 3D Technology

Well, why is it called 3D printing anyway? If you were to look at letters being typed on a page with a microscope you would see that the letters sit “on top” of the page, not stained into it. If you were to print over the same spot with different letters the area would build-up to form a three-dimensional object of a complex shape by the addition of each printed letter, letter by letter.

The “3D Printing” process technology started about 1981 and still is being performed using these basic steps.

1.  SCANNING - with 3D capabilities of making a virtual digital document of a drawing or object by locating digital points along it’s X, Y and Z axis, thus creating the digital copy of a solid object in a document file that can be distributed. A CAD file using a 3D-modeling program will create this file.

2. DIGITAL SLICING - this digital file is loaded into a computer having programs that turns the data into what could be thousands of thin cross-section digital layers. When the layers are stacked upon each other they will form the 3D replica. Then this digital message is loaded in an external “printer”.

3. PRINTING - Processes vary, a computer file then guides the printer’s robotic arm that lays on a liquid material in the prescribed pattern on a “product bed”, from the bottom-up, that instantly hardens the material forming a solid layer. The next layer is placed on top, layer on layer, till the object is duplicated per the digital instructions.

The 3-D printing started out in a laboratory using poly-based plastics that used very complex and expensive machinery at a university. Thus, ideas about how and where to use the new technology spread slowly throughout industry due to cost. The process, not only expensive but, the materials used were not strong and limited to “gadgets”.

                                    

These steps were at first three separate functions on different machines or even countries. Currently, all these functions are available in one low-cost unit suitable for the private-public to experiment.

Three major machine improvements took place through the years allowing many people to research with uses of the 3D printing process. Therefore, new ideas and products arose.

Now, products from plastics, cement, to the hardest steels are being used to manufacture structural components or gadgets at or below, current prices.

Current Process 3D “Additive Manufacturing”

Processes in printing of objects today to produce the 3D image and duplicate an object are evolving. The term Additive Manufacturing (AM) starts with a flat surface and builds up the object layer on layer. Developers feel this process of “adding” material more accurately defines the difference between taking a picture and producing an object (Ben’s head) vs. adding material to build-up an object (a hook). Additive manufacturing is only using the material you need, as opposed to Subtractive manufacturing, which involves cutting away what is not needed from a large casting.

In 2010 ASMT defined seven categories of Additive Manufacturing. Spray methods of building up material into objects are still used. To form plastic parts and decorative items. Structural concrete components for the construction industry use these spray methods.

Another method starts by spreading a thin layer of powered metal on a bed. Then using a laser, it welds the power into a solid layer of material on the bed, and then another layer is applied over that layer. The process is repeated until completing the object. There is a possible risk of the material not being fully fused during this “power” process.

Fusion welding which deposits metal to form 3D shapes by aiming a Plasma beam or Laser to achieve desired fusing results. Also, Wire & Arc using a GTAW or TIG power source are methods employed. This latest technique has replaced some casting/machining products manufacturing, ships propellers (wheel). At times in cast objects, 70% of the material is removed to form the item, a huge material cost. This savings is one major reason driving this method as well as the stronger objects (hooks) being made.

                                                

 The fusion zone and surface are subject to oxidation with some alloys and demand additional inert gas protection. Portal seals can be placed over the work area and filled with inert gas for protection against contamination.

Some draw-backs remain with “printing”. The process is not cost effective for some items; it cannot compete cost-wise with mass-produced items on the production line, yet.  Also, the smooth finishes necessary for some products are not achieved. Likewise, the variations in material types necessary are not available. Still, they are working on it, and the process is sprouting.

Steel Duplex hooks have been made by a Cast/machined process. A two-prong duplex hook cannot be forged as a Bowl hook is, they are cast and machined.

Cast Steel Hook

Forged Steel Hook 

A word about PLASMA, it is one of the four fundamental states of matter (plasma, gas, liquid, and solid). But plasma does not occur naturally on earth. It takes an electrical current or a strong magnetic field in a vacuum to strip or add electrons from an inert gas to place the molecules in the “Ionized” state, charged particular = plasma.  When these forces are removed the “freed” electrons emit light returning, and the molecule reclaims its normal state. However, plasma is familiar to us as in neon light tubes, the Northern lights in the sky, plasma TV or the “free” nitrogen released during a lightning strike.

When welding with a plasma beam (which is like a little rocket engine), the chamber inside the torch forms a vacuum heating the inert plasma gas that expands. The hot plasma ions gas rushes out the nozzle and can be precisely aimed. Because all this takes place inside the nozzle, there is no need for a vacuum chamber to produce the plasma state of the inert gas.

The process of building up steel by welding has been around for a while, in 1926, Baker-patented the use of depositing molten metal in superimposed layers to build-up objects. We all have seen multi passes welds on weldment to achieve the necessary strength in the structure.

World’s First 88-ton AM Duplex Hook

The Huisman Company, Netherlands accomplished the manufacturing and load testing of an 88-ton

WAAM Hook

Duplex Port Crane hook using a 3D printing technique. Termed “Wire & Arc Additive Manufacturing” (WAAM) process which utilizing a wire feed and plasma Arc to produce the midsize hook. WAAM process of Manufacturing is in some sense – special. The directions to the robot wheeling the Arc welder are the same as those in numbers 1 and 2 above. In step 3, the layering of the hook utilizes the Arc and Wire feed welding process which is hotter (10,000 to 20,000 degrees c) than carbon arc or laser to build-up the hook. This allows stronger materials to be used.

What’s next?

The Caterpillar Tractor Corp. is currently producing aftermarket parts using the AM method which are more cost-effective than starting up old production lines that no longer produced the part. One component which is manufactured new parts is a complex gas turbine nozzle which is used in their production equipment.

It is becoming cheap and easier to 3D manufacture metal parts, if widely adopted, it could change the way we mass-produce many products. Livermore National Laboratory announced they have 3D printing method for stainless-steel parts twice as strong as traditionally made one.

Markforged, a small startup, outside Boston, released the first 3D metal printer for under $100,000. Desktop Metal also in Boston, began to ship its first metal prototyping machines in December 2017 that are claimed to be 100 times faster than elder metal printing machines.

GE, which has long been a user of 3D metal Additive Manufacturing has a test version of its new metal printer fast enough to make large parts and plans to start selling them in 2018!

Even outer space is an option, NASA has challenged with a $250,000 prize to a company who can adapt 3D additive manufacturing technique for robots on Mars to build habitat designs to eventually house humans’ explorers on the planet! On the material side, they say the problem is solved. All we need now is a nozzle that is a little more “forgiving” to spray the material (may already have it). I guess, “the sky is the limit”.

3D HOOK MANUFACTURING CONCERNS

1.     The process of layering, how is 100% adhesion between layers assured?

2.     In use when loading/unloading flexes hooks, will layers delaminate?

3.     What type of NDE method would be appropriate?

4.     What visual inspection dimensions are assigned?

5.     Are the Hook Manufacturer’s data sheets available?