Some Examples of Crane Jobs by Philip Dybel

1) W.M.

It was my first day working with Crane 1 Services;  I was to go with our division’s senior crane tech to a plant, and install a “radio controller” on an existing crane.  At the time, the crane had only a “pendant” control station;  they wanted a “radio control” to make the crane’s operation more reliable.

The night before, I did an internet search on “crane radio controls” and looked at several different web sites:  most of them recommended a “Transfer Switch” – to allow crane control to be switched between the radio controller and the original controls [i.e., usually a “pendant” (“drop cord” with push-button control station), or “cab” (“operator enclosure”) drum controls].  (diagram attached)  This made sense to me:  if a fault happened with the radio control, the operator could simply “flip the switch” and go back to the old controls.  In other words, if they had a problem with the radio, they wouldn’t have to shut down production until they were able to get a crane tech on site to repair.

During the two-hour drive to the plant, I discussed this with the senior crane tech;  he said he thought this all made sense.  I asked him if he had a selector switch with him;  he said the office gave him an unopened cardboard box (delivered by U.P.S.) – apparently containing the radio controller, and “everything else we need should be in the box”.  He never opened the box;  he didn’t know if any installation manuals were inside.

At the plant, we opened the box and found a radio transmitter and receiver, and an installation / operation manual (however, no selector switch).  On my request, he got the crane manufacturer’s manual (including its wiring diagram) from plant management, and I spent an hour or two comparing this with the radio manual, and sketching out on paper how to connect them together (while the senior tech did other things).

Eventually, the senior tech and I went together on the lift and I installed the new controller (following what I had drawn out), while he watched me.  I checked that it was all properly connected;  we powered it up & checked operation – no problems.  The crane radio control worked great;  we demonstrated to the client (plant operations manager);  he was happy.

However, with no “selector switch”, I thought there was a huge safety issue:  while one person was operating the crane with the radio, another could press buttons on the pendant and cause the crane to move.  At my request, the senior tech discussed this with the plant operations manager, who said that this condition would be O.K. for the short term, and he will make all plant operators aware of this – but go ahead and get a selector switch, and install it as soon as possible.  With the plant operations manager’s permission, I left with a copy of his crane manufacturer’s manual and the new radio manuals, promising to return them to him when we returned.

At the end of the day, I went home and made copies of the diagrams from the manuals, and drew on them in red pen how I would redo the wiring and install a selector switch.  I also wrote up a description of what I thought needed to be done.  (diagrams & document attached

My next day at Crane 1, I made the extra effort (it was, after all, my first job with them):  I gave hard-copies of the above to my manager and briefly discussed them with him.  Finally, I asked him if an experienced crane tech / electrical tech from any one of the other nine Crane 1 divisions might look it over, and tell me if this is how they usually do this / if this is a good way to do this, any suggestions, etc.;  I gave him a “cover letter” to please send with my request.  (letter attached)

Next, I asked our senior tech where we stocked our selector switches;  he said we had none at the shop, and directed me to our local electrical supplier.  I also asked him if we had any “MTW” wire;  he said all we had was 12 or 14-gauge “THHN” wire, and just use that.  After that, I went to the supplier and looked through their catalogs and computer listings, to find a selector switch that would work (it needed to have 2-“N.O.” and 1-“N.C.” contacts).  We found several different types in stock;  I got written price quotes on them and also the other parts I’d need, and gave this to my manager. 

Over the weekend, I decided that 12 or 14-gauge “THHN” would be totally unsatisfactory for this application.  So I went to my own electrical supplier and bought myself a roll of 16-gauge “MTW”.

I never got a reply from anyone at Crane 1 about my “request for oversight” (above letters & diagrams).  Nevertheless, the following week, I was assigned to go to the plant and install a selector switch.  I went to our local electrical supplier and got the least costly items they had in stock (as directed) – I got a 20-mm operator and contact blocks, “Sta-Kon” crimp connectors, wire labels, and everything else I thought I’d need to complete the job.  Then I drove out there by myself and installed it.  (“as-built” photos attached)  When I was done, I made sure to demonstrate to the client (plant operations manager) how it worked, and give him his crane manual and the new radio manuals, with my modifications written in.

Also, the operations manager discussed with me the problems they were originally having with the pendant:  the wires inside the pendant’s cord would suddenly fail on a frequent basis, which forced them to shut down production and have the plant’s maintenance personnel repair it a.s.a.p.  While thinking about this later, I figured out why this was happening so often:  the tight bends in the cord, and the continuous stress and movement were causing the wires inside the cord to fail.  I wrote up several recommendations to alleviate this, gave a hard-copy to my Crane 1 manager and discussed it with him, and asked if he might want to email this to the client.  (document attached)

2) S.I.

During my first week with Crane 1, the senior tech and I went to a different job, where Crane 1 had installed 150 feet of new bridge girders & rail – 20 feet above the floor – and on it, two new cranes:  each crane has two trolleys, with each trolley having one hoist.  The mechanical was finished;  the only item left was all the electrical on the bridge (disconnect, controllers, power and control wiring).

The senior tech told me to mount (on the bridge girder) the crane electrical disconnect, the supplied control box, and the radio controller;  then, run conduit to the bridge motors and wire them;  and connect to the control box the cables to the power supply, trolleys, hoists, and pendant.

I opened up and looked inside the supplied Crane Control Box, looked at the Trolley / Hoist Assemblies;  and noticed a “big problem” – there were several sources of “control power” for each crane, and they couldn’t all simply be connected together.  So I “deferred” (I didn’t do what he told me right away).

First, I went through all our parts boxes (which were scattered throughout every square foot of the floor area of the job site), consolidated & organized them in an appropriate location, and found all the installation manuals (and also many other parts I’d need).  I looked through all the manuals for an hour or two, and learned that each crane had a total of five control transformers:  one for the bridge, and one for each trolley and hoist.  At the same time, the pendant and radio control needed to be supplied with only one single control power voltage (i.e. one transformer secondary).  On the spot, I thought the easiest way to make this work, was to install a set of “intermediate relays” to allow the pendant and radio controls to switch the control inputs for each trolley and hoist (and in that way, have only one control voltage run through the controls).

At first, I thought we would maybe need six of these relays in a separate enclosure.  I first located and paid cash for a 6 × 18 × 6" box, brought to the job site, and tried to lay out how I would install it on the bridge girder – together with the disconnect, the supplied controller box, and the radio controller.  But no matter how I arranged them, I couldn’t find enough room for them all to fit:  there was the trolley end stop just to the left, the ceiling six inches above the girder, the rail girder and the building wall to the right, and the power conductor rails eight inches below.  Due to clearance requirements, there was no way it would all fit.

I finalized & drew up diagrams of how everything would have to connect.  (diagrams attached)  There was no alternative – on my own best judgment, I went and bought an 18 × 18 × 6" “Nema 1” enclosure (box) from one of my own electrical suppliers (out-of-pocket cash);  went alone to the site & removed the existing components from the factory-supplied control box;  and mounted them together with the new relays in the new box.  Then I installed that on the crane, mounted and piped in the remaining electrical equipment, and did all the wiring.

It took about 4 days to get this all finished and operational.  Next, I did the exact same setup on the second crane.  (“as-built” photos attached)  When I finished, my Crane 1 manager sent me the text message:  “This took extremely longer than I thought.....”

3) VFD’s

Many crane’s motors are controlled by a “Variable Frequency Drive”, in order to allow smooth starting, acceleration, braking, and stopping.  Typically, these are supplied with 480-volt 3-phase power;  have a number of 120-volt control inputs;  and have dozens of user-adjustable “Parameters” to allow its operation to be customized perfectly for the installation.

a) H.A.

After I had been with Crane 1 for almost a month, I was assigned a service call at the “H.A.” plant – the trolley VFD on one of their cranes was “cutting out” (it suddenly stopped working, so they had to open the crane’s main power disconnect, wait a minute or two, then restore power – and hopefully then it might operate) – it clearly needed to be repaired.  I checked all the power, motor, and control wiring – no obvious problems.  I told them I’d have to get a manual for the VFD, and return to start checking that.

Next, I called the manufacturer and tried to get the VFD manual – I failed, because they told me it was “proprietary” (because I wasn’t the owner of the crane).  I asked our “senior tech”:  he directed me to the plant’s office / maintenance shop, which supplied me with it (“Smartorque bulletin 424V”).  I used this to retrieve the VFD’s “Stored Fault Codes”:  they were all “Short Circuit (on Load)”.  With this information, I checked every inch of the “Load” wiring between the VFD and the motor, and found the problem:  several wires were shorted in the middle of a 10-foot run of conduit.  (email attached)

[I later went back to fix a fault on the hoist VFD: “PG Open 2”...]

b) C.S.

Also in January I was assigned a service call at the “C.S.” plant – the hoist VFD on one of their cranes was “cutting out”, and needed to be repaired.  I did a quick check and found no problems.  I got the VFD manual from the plant’s office (“Ace-Tronics HVG+”) and retrieved the VFD’s “Stored Fault Codes”:  they were all “Pulse Generator Open” and “Speed Deviation”.  As the manual specified, I checked the wiring between the VFD and the “Pulse Generator” (the “Encoder”, which reads the motor shaft’s position and sends it to the VFD) – no obvious problems.  So I arranged with the operations manager to do a thorough check the following Sunday, when production would be shut down and I would have the crane to myself.

That Sunday, I started to looking at the “parameter” settings on the VFD;  a quick comparison of the basic settings with the motor’s nameplate data (HP, FLA, etc.) looked fine.  The VFD manual listed about 350 parameters, 9 pages total (listing attached).  Next, I looked at each one of these parameters – and for each one, I checked the corresponding page in the manual, compared with my own calcs if need be (Inductance, PF, etc.), and figured what each one “should” be and whether it was set right.  After examining them all, there were about six parameters that looked incorrect;  I set these to what I thought they “should” be, and tested the crane – smooth operation, no problems.

I was later told why many of these parameters were “incorrect”:  on three previous occasions, another crane tech had been assigned service calls for the same problem.  He clearly wasn’t able to fix it permanently – apparently he had tried to change some of the parameters to “see if that would work”.  I wrote up a document, suggesting that only qualified persons be allowed to change any settings on a VFD, and sent it to my manager and the plant’s operations manager.  (document attached)

c) M.S.

In June, I was assigned a service call at the “M.S.” plant:  the trolley on one of their cranes was “drifting” – whenever they moved the trolley, after they released the control button it kept on rolling for several seconds.  They wanted this fixed:  this was unsafe and needed to be repaired for safety reasons. 

On site, I did a quick check:  the trolley brakes were damaged;  the key was missing on one of the trolley wheel shafts;  and the VFD wasn’t decelerating the motors when the control button was released.  The operations manager didn’t have a manual for the VFD (“Magnetek Impulse P3”), so I didn’t want to “try” to do anything with it that day. 

But I did get the brakes to tighten up, so that they “dragged” enough for the trolley slow down much more quickly when the control button was released.  I made a list of the repair parts needed for the brakes;  the plant operations manager agreed to have us order them;  and when they came in, I’d make sure to bring a VFD manual and get everything fixed at that time.

The next day (and on many other days), I tried my best to have Crane 1 get these brake parts (gave copies of my parts list to our division manager & office manager, sent emails to our corporate parts manager & verified the correct parts numbers needed, frequent discussions & reminders, etc.).  At home I emailed Magnetek, and they promptly sent me their “P3” manual by email;  later, I went to Office Depot and paid (out-of-pocket) to have them print this out for me as a “hard copy”.

The next week, another Crane 1 tech called me from “M.S.” – he couldn’t get the same crane’s trolley to move at all.  (I was out of town for a different Crane 1 job, and couldn’t get there until the next day.)  He said he didn’t have an electrical “multimeter”;  also, he did not bring our “scissors lift”, so he was trying to use an extension ladder to get to the crane control panel – twenty feet off the ground, where the trolley was stuck, above a bunch of the client’s material.  I told him there was nothing he could do today:  please pull off the job, and tell the plant manager that I’ll be there the next morning to fix it.

The following morning, we didn’t have those brake repair parts at our shop (our office was still working on quoting repair cost to the client, and they hadn’t yet ordered from the mfr.).  I hitched up our scissor lift and went to the plant (alone).  Inside the VFD, I found a blown control fuse – based on my training & experience, I could find no reason why it had failed, other than the fact that it had been in service for thirty years (i.e. due to age).  The plant supervisor ran to get me a replacement fuse from our local supplier (on our account), while I installed the missing shaft key and backed off the brakes.

After installing the new fuse & powering up the VFD, I started checking parameters.  I did some serious programming on that VFD, in spite of the defective trolley brakes:  1) changed the stopping method to “Decel To Stop”;  2) extended the “Decel Time” to two seconds;  and  3) got the “Decel Rate” set so well, so that the trolley came to a full stop within 1 second, whenever the control button was released (no matter what speed it was going).  When I was done, the operations manager thought it worked so well, that “maybe we don’t need to repair the trolley brakes after all”.  (I told my Crane 1 manager to make sure to quote them on this anyway – “safety issue”).

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authored:  20 August 2012

last revised:  17 September 2012