Note to Self: "It's the Runway Stupid"

40 Tons of Scary Crane Noise Overhead

I recently spent a week at a naval shipyard on a consulting contract. The client had three, 40 ton overhead cranes, span of approximately 125 feet, all on a single runway of 1000 feet. The end crane kept making a loud "snapping" sound when run on the eastern third of the runway. The noise was so loud that the client was afraid the wheels were climbing the ASCE rail and could possibly "jump the track."

After inspecting the crane, it was obvious that the crane had incurred one or more collisions  with either the other cranes or end stops and as a result, the end-truck diaphragm was visibly bent. Out of habit, part of my inspection process included checking the runway rail for signs of unusual wear. It was no surprise to find random accumulations of shavings along the runway rail indicating severe wear due to runway misalignment. In this case it was both bad runway alignment as well as a permanently skewed crane due to the bent end-truck diaphragm plates. Because the cranes were over a decade old, I couldn't tell if the shavings were recent or the result of a decade of wear. 

Buildings Near Water are Always Moving

This runway wear was not a big surprise, after all it was a shipyard and located on the shores of a waterway. Buildings along waterways almost always experience moving footings and therefore constantly moving runways. This footing movement is often so severe that it doesn't take the use of some fancy laser measuring device to detect. Frequently concrete floors are cracked or the top of footing elevations significantly differs from floor level.

At the completion of my inspection, I asked the crane tech assigned to me to take a can of spray paint and mark each of the locations where the pile of shavings had accumulated and then to clean off the shavings. If, in a month, we saw a new pile of shavings we could gage the severity of the problem. I then wrapped up my inspection and promised to have a report the following week.

A Simple Analysis of the Problem

The essence of the report was pretty simple. First to get the runways aligned and second to replace the bent diaphragm and bogey connector channel.

About three months later, I got an email saying that the replacement components had arrived and asked if I would supervise the crane repairs. We agreed upon a date and I submitted some names of runway alignment firms for the owners consideration. I suggested that the runways should be aligned prior to the structural repairs of the crane.

No Time to Align the Runways

Upon arriving at the job site, I asked who they got to do the runway alignment? I was told that because of time and scheduling issues, they were forced to do the structural repairs first and the alignment later. I was concerned that the runways had not been addressed, but still felt confident that the skewed shape of the crane parallelogram was the root cause of the crane noise.

After three days of working around the needs of production, my crane techs and I finished our repairs. We pushed the bridge travel button and the snapping sound had not changed! The three of us were baffled and exhausted.

We decided to ride the crane and watch the "wheel to rail engagement" again, to see what we missed. We rode the crane for half an hour, took pictures and even recorded a video with my iPhone. Refocusing my attention from the structural repairs to the runways, I noticed there was a new accumulation of metal shavings at each of the locations the crane tech had marked three months earlier. We then headed back down for a skull session.

It was late Sunday afternoon and the three of us sat at a lunch table in an empty break room. The building was empty and the three of us were both mentally and physically running on empty too. After tossing around a number of ideas, I mentioned the piles of metal shavings along the runway rails. I said I wish they had the runways fixed prior to these repairs because it would have removed a number of variables from our equation. 

"Half-Assed” Alignment is Better Than None

The junior crane tech said he knew most of the runway J-bolts were loose and a few were even missing. The lead tech suggested we do a "half ass" alignment and tighten the J-bolts for just one bay to see if that had any effect. We couldn't think of a better idea, so we went back up in the lifts and did a  rough alignment, tightening all the J-bolts of the bay where the loudest noises occurred.

Upon completion of the single bay, we went back to the floor and started up the crane. I pushed the bridge travel button and we were shocked by what we didn't hear. Our "half assed" alignment reduced the snapping noises by at least 80%!!! Yes, there was still some snapping noise, but our alignment and tightening was crudely executed at best. 

We didn't have the time or the equipment to perform a full runway alignment, but we had reliable evidence that we had discovered the "root cause" of the noise as well and the abnormal rail wear.

Summary: It’s the Runway Stupid!

As a lifelong crane man, it serves my ego well to utilize my collection of engineering and manufacturing crane knowledge to focus on just the crane itself. After all, crane runways are just simple, dumb structures with no mechanical or electrical controls; no moving parts! But, more often than not, most crane problems can be traced back to a runway problem. 

In the 1992 presidential election, political pundits attribute Bill Clinton’s elections to his strategist reducing the election to one simple phrase, "it's the economy stupid."  

I need to remember this when diagnosing ailing overhead cranes, as my first line of investigation.

Larry… it's the runway stupid
Larry… it's the runway stupid
Larry… it's the runway stupid

Larry Dunville