Saturday, May 19, 2018

“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?


Saturday, September 27, 2014

OSHA extends operator's certification requirement for 3 years.



OSHA extends compliance date for crane operator certification requirements

 
WASHINGTON – The Occupational Safety and Health Administration today issued a final rule extending the deadline for crane operator certification requirements in the Cranes and Derricks in Construction final rule* published Aug. 9, 2010 by three years to Nov. 10, 2017. The rule also extends by three years the employer's responsibility to ensure that crane operators are competent to operate a crane safely. The final rule becomes effective Nov. 9, 2014.

During the three-year period, OSHA will address operator qualification requirements for the cranes standards including the role of operator certification. The final cranes and derricks rule required crane operators on construction sites to meet one of four qualification/certification options by Nov. 10, 2014. After publishing the final rule, a number of parties raised concerns about the Standard's requirement to certify operators by type and capacity of crane and questioned whether crane operator certification was sufficient for determining whether an operator could operate their equipment safely on a construction site.

The agency published a Notice of Proposed Rulemaking on Feb. 12, 2014, proposing to extend both the deadline for operator certification and the employer duty to ensure competent crane operation for three years. After publishing the proposed rule, a hearing was requested and held in Washington, D.C. Comments from the hearing are available at http://www.regulations.gov/#!docketDetail;D=OSHA-2007-0066. OSHA analyzed the comments to the NPRM and the hearing testimony and decided to extend both the crane operator certification deadline and the existing employer duty for three years. OSHA has already begun the process of developing a standard to ensure crane operator qualifications.

Under the Occupational Safety and Health Act of 1970, employers are responsible for providing safe and healthful workplaces for their employees. OSHA's role is to ensure these conditions for America's working men and women by setting and enforcing standards, and providing training, education and assistance. For more information, visit www.osha.gov.

Read More

Sunday, October 6, 2013

Inspection of Boom Ropes

     In a recent fatal crane accident in New York the crane inspector is being investigated for performing an improper and/or an “casual” inspection of the crane by authorities base on testimony  by the operator and other witnesses.


     The boom running rope on the Crawler Crane failed and dropped the boom. I don’t have any more info at this time, but the “experts” are investigating.
 
 
 
 
 

 
     From our experience in the certification business we know that boom ropes are;  

1.     Hard to inspect and a precise method is necessary to inspect them properly.

2.     Failure mode is usually “Crushing” on the Drum WHICH CAN BE SEEN and “Embrittlement” of the wires in the rope causing fatigue failures of the wires WHICH ARE HARD TO SEE.

  
 
 
 
     One reliable way of knowing your wire ropes are in good working condition is to keep track of the time the wire rope has been on the crane and the condition and maintenance of the wire rope. Gottwald Harbor Cranes have an hour meter on their hoist which shows the actual time the ropes have been spooled in and out on the drum which causes the damaging fatigue. Presently, they say to change the wire rope at 8,000 hours of operations. No other manufactures to my knowledge has given an hourly replacement criterion. 

ACTION

     The method we follow when making an inspection on the critical Boom Luffing Ropes is;
 

 
 
 
 
 
 
  1. Get the date the rope was installed, they don’t know, deficient.
  2. Get the Wire Rope certificates, must have.
  3. Check to see it’s the correct rope, if wrong, deficient.
  4. Boom must be put on the ground and ropes slack for inspection, if you can’t, deficient.
  5. Inspect per my presentation, which I will go over at out next newsletter.
 
      The “attentive” crane owner is well aware of the importance of inspecting the wire rope on his crane, but the problem is that some are becoming accustomed to having third party inspection companies perform their annual inspections, This is the only time the wire rope is thoroughly inspected. However, the new OSHA construction standard 1926.1413 requires written monthly wire rope reports completed by a “competent person” to be performed and documented. What does it mean to be competent?
     The definition of “competent person” in OSHA is thirty five words long! But what says is, someone who knows what there are looking for, and has a good track record of finding it!
     However, this written report is most often missing from the crane file when we (as required) review the files during our annual inspection. Let’s all try harder to improve ourselves in these inspections of this critical component, Boom Luffing Ropes.

Sunday, May 12, 2013

IS HOW THE OPERATOR OPERATES THE CRANE CAUSING DAMAGE TO THE CRANE?

  Here is a 4600 Manitowoc Vicon (Variable Independent Converter), used in lift crane service. With a different type boom and without the torque converter, they are a preferred “dirt machine” because of their rugged machinery and single line drum hoisting capacity. Also, they have large disc swing frictions well suited for the wear and heat of “duty cycle” work as in clamshell operations requiring constant rotating of the crane between the pick-up and depositing of the material.


  The typical clamshell bucket below shows the three lines that control the movement of the load from one location to another. The tag line is under tension at all times from its take-up reel. It keeps the bucket in line with the crane and reduces swinging somewhat.


  The holding line does just that, and is attached to the top of the bucket. Holding the bucket at a given elevation, then lowering the closing line the jaws open and unloads the material. After dumping the load the closing line is hoisted to produce some slack in the holding line and shutting the clamshell to swing back to the digging pile.

  Then, the closing line is lowered opening the jaws of the bucket which are counterweight to open automatically. Next, both lines are lowered onto the material pile. Now the closing line is hoisted and the jaws “close” picking up the material. The closing line picks up the full bucket load keeping some slack in the holding line and both are raised in unison to the necessary height and held there until it is swung over the deposit area there again; the closing line is lowered opening the jaws of the bucket allowing the material to dropping out.


  Okay then, from all that you can see that a lot of skill is necessary on the part of the operator. Also, there are a lot of variables that affect the actual force on the crane. First, there are static weight and then dynamic (motion) force. How quickly you start and stop influence these forces. One other element to clamshell work is the sudden release of the load causing impact loading.

  Now, is the operator smooth or jerky? Does he work within the rated capacity of the crane? Taking into account the shock loading of bucket work, manufactures down grade their ratings by a minimum of 20%. What about the size (in cubic yards) of the bucket on the crane, correct or larger? Is he beyond the maximum radius causing the crane become unstable? These cranes are tough, but they have their limits. Here we see obvious signs of severe shock loading indicated by the pulling out of the rope from the wedge sockets!


  These cranes have their limits! After repeated mishandling the upper works broke away from the lower pedestal. We rarely see this severe damage on a turntable with minimum wear. Let’s review how it was being worked. You heard the old saying “being road hard and put away wet”, well that applies here. The operator was jerky on the controls that shock load the crane. This was done on a regular basic and over some time. There were indicators to the operator and the crane owner that problems with the crane operations were damaging the crane.

 



  And “the rest of the story” as Paul Harvey would say, is this. The bolts pointed two in the photo to the right were replaced many times with harder bolts should have been a tip off that something was wrong. This is the connection between the crane’s upper works and the pedestal mounted on a dock, so the crane is firmly held in place. This installation gives the operator a false feeling of confidence then he would otherwise get from an overloading a crane. Results of this “cowboy” operation is crane damage and the potential loss of load which could lead to death or injury of workers.





  Did they learn from this or are they living in denial? What do you think?


Saturday, March 2, 2013

FRICTION CRANES SHOES


Just in! Cranes that have internal expanding friction clutches and Lattice Booms were commonly referred to as “Friction cranes” by the Standard writers and the Manufacture themselves. Nowadays, the Clutch type drums on the new lattice boom cranes are being replaced with Hydraulic Winches. So, these crane types are currently being named “Conventional cranes” (I wonder what an un-conventional crane is).

A hydraulic winch on lattice boom crane is nothing new; I worked on one in 1962 at Cape Canaveral, a 100 ton Bucyrus Erie with a hydraulic winch and a Triangular boom. But, with the demands of modern cranes the hydraulic winch has advantages, one thing, less moving parts subject to fatigue.

The photos following show a broken friction shoe on the main hoist of a Link Belt crane. This is the “power down side”, and if you think about it is actually being “pulled” when working due to its job of slowly lowering a weight against gravity.

When it failed the load was still controlled because the other side was engaged but, the operator recognized something went wrong by the vibration he felt in the crane. He set the load on the ground and went back to look and this is what he found!
Inspection of the Frictions clutches is as follows;
  1. Lining thickness
  2. Contamination from oil or water
  3. Evenness of drum surface and contamination
  4. Proper adjustment
  5. Observe operation for smooth engagement
  6. Visible damage or cracking of shoes
  7. All pins, springs and keepers in place
  8. Evidence of overheating of any component
  9. Other noticed problem observed during operating under functional load test

Well this one got away, but now I look closer at this area of the shoe for “hammering” and cracking, so should you?

Monday, February 25, 2013

FOUR CRANE LIFT AT BATH IRON WORKS SHIPYARD

A 1000 Ton Deck House for the Destroyer DDG-1000 was lifted in place at Bath Iron Works Ship Yard in Maine this Dec. 2012. This was the first four crane pick at the yard. All four cranes were inspected, tested and certified to OSHA's maritime regulations done by National Crane Services. Also the US Navy certified these cranes per their regulations.
National Cranes Services has tested and certified the cranes at Bath Iron Works since the 1980’s. Two of the cranes used were portal cranes, which are permanently located at Bath Iron Works.  One of them is an American 300/25 ton capacity portal and the other portal is a Chinese 300/125/25 ton capacity and positioned on opposing runways.  These shipyard cranes are continually serviced, inspected and tested in accordance with Maintenance Program established by Bath Iron Works many years ago.  Greg Bridgman, Maintenance Engineering Manager, who is responsible for all of the crane documentation. These cranes operating capabilities’ were familiar to Bath Iron Works. 
However, the crawler cranes, two 16000 Manitowoc crane which are owned by Reed & Reed of Woolwich, ME, were not familiar to Bath Iron Works and needed to be evaluated by Bath Iron Works, US Navy and National Crane Services during the entire lift planning and set-up process. The cranes were set up and rigged with their “Max-er” lift attachments, which were a 157’ heavy boom, wheel counterweight @ 50’ and a 97’ fixed lattice mast that gave the cranes a 609,000 LB capacity at a 50’ radius. The calculated load for each crane was approximately 460,000 LB.  
There was over a month of preparation by all parties involved before the configuration; condition and testing of the cranes were agreed upon. The owner of the cranes decided to hire two Manitowoc technicians to aid in setting up the new Max-er heavy lift attachments.  
The completed Deck House, which was manufactured from a new type material, was built in Mississippi at Ingles Ship yard then transported by barge to Bath Iron Works in Bath Maine. The barge was placed in the dry dock. The dry dock was then moored to the dock of Bath Iron Works. Then the barge and Deck House was then driven off the dry dock and into position.. The Deck House was centered between the four cranes. The cranes were facing each other, two on each side of the ship way. The Deck House was then raised approximately 80’ in one piece to be set on a new class of Cruiser being built at Bath Iron Works for the US Navy. The lift went off without a hitch on Dec. 12-14, 2012.
To watch a time lapse video of the Deck House move click the link below.