When Does a Ton Not Equal a Tonne?

Getting Everyone on the Same Page

This probably looks like an obvious statement, but a couple times a year I hear of a project where, for example, a lift of 50 tons was required and a crane with a capacity of 50,000 lbs. was supplied.

Every time this happens, the cost in worker safety and dollars expended is just astounding. Just last week I came across a project for a Fortune 500 manufacturing company where they had to make a 43-ton lift. A third-party rigging company was engaged to make two lifts, one lift to remove the 43-ton gear box from service and a second pick to put it in place after the repair work was completed.

Luckily the Lift Manager asked to see the crane’s paperwork during the JHA (Job Hazard Analysis Meeting) prior to the lift. Much to his surprise, the Liebherr mobile crane had a 50,000# capacity, or about half of what was needed. The rigging company had shown up with a 50,000# crane rather than a 50 Ton crane. After Tom called me and told me of his “close call,” I said he’d be surprised how frequently I hear stories just like his.

An All Too Common Communications Breakdown

About 10 years ago I was called in on a project by a major state university. Their engineering department was doing magnetic research and was putting up a new building specifically for magnetic research. First of all, I was surprised that there was actually university level research being done on magnets. I really didn’t think magnets were that high-tech, but evidently, they were. I was asked to bid and subsequently received an order for an overhead bridge crane capable of lifting 20,000 lb. magnets.

The fabrication and installation of the bridge crane went smoothly and the project was invoiced and paid for without incident. Almost a year later I got a call from a somewhat indignant project engineer. The engineer was upset because they were trying to make their first full capacity lift and he said the overhead crane could not pick up the 20-ton magnet! This is the kind of news that makes a crane builder’s heart come to a complete stop, as I envision tons (no pun intended) of dollars being flushed down the drain.

After I calmed him down, I asked him to give me 30 minutes to find the project folder. I would do a quick review of the data and call him right back. I assured him, one way or another, we would make it right.

I hung up the phone (back when a phone sat on a desk and was wired to the wall) and pulled the project file. I started leafing through the quote document as well as the crane and runways engineering materials and it dawned on me that all our materials, as well as the RFQ, it said 20,000 lb. capacity, and I could swear during our phone conversation, the project engineer said he was lifting a 20-ton magnet.

I called back and asked, did you say you were lifting a 20-ton magnet or a 20,000 lb. magnet? He answered… “is there a difference?” I told him that the RFQ, my Proposal and the Purchase Order all specifically call out a 20,000 lb. capacity crane, which is just 10-ton capacity.

I silently exhaled a gigantic sigh of relief. Simultaneously, I’m sure his heart had just sunk to his stomach. In total panic he told me that the whole funding for the building was based on research for 20-ton magnets and that the building, building support columns and column footing were based on the overhead crane loading I had submitted and they were apparently all for 20,000 lb. capacity.

The good news is that, after considerable head scratching, we came up with an idea for using a 20 ft load bar and a second 10-ton crane. This allowed us to distributed the load over two bays, thereby limiting the building loading to safe 20,000 lbs. The bad news for the buyer is that he had to go back to his boss to get funding for a second 10-ton crane and a load bar, but at least the building didn’t have to be altered and with the arrival of the second 10 ton crane the 20-ton magnets could be safely lifted.

Overhead Crane People Arn’t the Only Ones

Looking back on this event, I strongly suspect that the project manager was a scientist/researcher and lived in the metric world where 1,000 kg equals a ton and forgot, that for the building and crane, he was working in the world of pounds and not kilograms. In other words, he had to change his mindset from 1,000 kg to the ton to 2000 lbs. to the ton.

This Metric/Imperial snafu was not the first time this type of error has been made. Remember the colossal NASA mistake of the Mars Orbiter when it burned and exploded due to a metric conversion issue. See,

www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric/

The Moral to Our Near Death Experience

Bottom line here is that a US ton equals 2000 lbs. and to make things confusing, there are US (short) tons and Imperial (long) tons. The Imperial (long) ton equals 2240 lbs. The Imperial ton is used everywhere the metric system is used, which is pretty much everywhere outside of the US. Also, 1,000 kg is one (long) ton or 2240 lbs.

1 US (short) ton = 2,000 lbs. = 907 kg

1 Imperial (long) ton* = 2,240 lbs. = 1,000 kg

*long tons are sometimes spelled tonne

Lastly, discussing overhead bridge crane capacities, listen carefully and explicitly repeat the capacity requirements so that everyone in the conversation is hearing the correct unit of measure! Whenever possible list the capacity requirements as follows, “12.5 tons/25,000 lbs.” This may seem like overkill, but it may just save your bacon someday!