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.

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?

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?

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.

Deck House Move