CASEBOOK=

Stopping Construction SitesFrom Becoming Killing Fields

While some safety devices arenot 100 percent fail safe,it does not mean that theyshould not be used.

ThLS column. focuses on ,he eleetru:ul,-:fS~m.s dGSigner as a (orensu:zr.t'€Stzgator.

..3..pproximately nve hundred workers

.) "i?ar are ~ither killed or permanent·h: m:llmeO when a boom or hoistlinei~advertentlv contacts a bare, unin·sul:ued h:gh.voltage powerline Re·cent!y we completed In assignment inwhich we represented the estate of a'.'ouna man who lost his life.. Du;ing the course of our analysis"liedesigned a safety engineering ma-t,IX of the v:uious factors related tohiS dea~h. At the outset we reosearched, to enhance our empiricalprofessional expertise, devices and/ortecflniques that were available to re-duce the accident potential. These in-cluded a review oi various IEEE,A:\Si, ASE and ASM£ codes andst:lnciards, the principles of ground·i:-:g, a test of the dielectric efficacy ofinsulateo huoks and a study into thecuntroversy of opinion resulting fromthe evail.:ation of proximity warningce'Jlces for cranes. I am not unfamil·iar with the so-called "DependencyHypothesesft that suggests a personwho relies on a safety appurtenancethat is less than 100 pe;cent etTectiveat all times place ther.lselves in afalse sense of security.

The owner of a small meat process-ing facility contracted a local engi-neering firm to ~rform general con-tracting. The engin~ring firm, inturn, subcontracted with an ornamen-tal Iron works corporation to furnishand erect the steel structure. Theprincil'als of both the general and thesutH:ontractor firms met at the site toschedule the steel construction. Noone had alerted the local electric util-ity of the intent to bring in a flatbed

I truck of steel and a r.'lobi!c crane that

would operate in close proximity to a5-kV power line.

At 4:00 p.m. on a mid-Novemberafternoon, a 26-year old man, em-ployed by the steel erection subcon-tractor, drove a flatbed truck to theconstruction site with a load of steel.While standing on the flatbed truckdirecting the operator of the cranewith hand signals, he kept signalingfor the crane operator to "come down,"with the boom and cable. 'At one pointhe reached up to grab the hook. As hetouched it he fell to the ground. Aphysician who was driving by jumpedfrom his cor in :I vain attempt to savehis life. He ob~erved that the victimdied instantly.

The mobile crane's outrigger sup-ports were resting on thick woodenplanks. There was no grounding strapfrom the crane. The steel cable fromthe crane's extended boom contacteda high tension line. The current'spath to ground went through the con-structIOn worker.

Safety ProceduresIn our analysis we expressed a

strong conviction that the local cranedealer that serviced the site knewabout various devices that could havebeen utilized to reduce the risk ofdeath by electrocution from people inproximity to cranes on· constructionsites. It is, of course, possible to fore-see that mobile .:rane booms, as theyare extended and move, do come closeto power lines.

The local crane servicing agencysells insulator links tested for 50-kVprotection (these links are capable ofprotecting against ten times theshock potential that was lethal to thedeceased). Insulated safety links arerated to support 5 to 50 tons with a 4to 1 safety factor. Our client was at-tempting to lift a mere two tons. Giv-en the dynamics of this particular sce·nario (crane Clble touching powerline), the use of an insulated safetylink would have kept the man alive.

We stated in our testimony that ad·ditional devices were available that

the crane manufacturer/dealer knewabout. One -crevice is a dielectricshield that can be adjusted to fit alltypes of hydraulic cranes. Another isa proximity warning device - a solid-state electronic safety system used fordetecting the electric field of any acpower line. Proximity warning de·vices <PWD) provide an audio and v1-sual warning signal to alert the oper-ator and attendant ground personnelwhen the boom comes within the vi-cinity of an energized power line.

During my de~osilion, the attor-neys for the crane industry aggres-sively questioned me about the inci-dent. They asked if I was aware of thetests that were conducted on proxim-ity warning devices that concludedthey were not fail safe? Ironically, sixmonths previou:;!] I ~,~tended a foren-sic engineering seminar in which apaper titled Euaiuation o{ ProIimityWarning Devices {or Cranes was pre-sented by a Dean of an engineeringschool.

While I did not agree with all of hisconclusions it was obvious to me thatthe use of a proximity warning deviceon a mobile crane would have been alife-safety enhancement. In my com·prehensive research on the topic I in-terviewed the chief civilian engineerof a U.S. Navy Missile Base. Everycrane moved onto the base must beequipped with proximity devices.

Further research documented .thatone particular manufacturer has soldover 2600 proximity systems duringthe last 24 years. There has neverbeen a reported accident involvingpower line contact on equipment withtheir system installed.

As an electrical engineer, I empha-sized that proximity warning deviceswere not the only safety mechanisms.The insulator 50-kY link protectionwould have been a fail-safe device inthis situation. Decals stating "DangerElectrocution Hazard" on variousareas of the crane prov1de reinforce- .ment to crane operators and to peoplewho are in proximity to cranes. Rec-ognizing that STOP signs do notchange lluTnan facWr~. dangtr signs

will not, per $e. translate into opti-mum safety on t;,e job site. This doesnot mean" that when we cannotachieve 100 percent of a goal, the op-tion of doing nothing is acceptable.

Personal ReflectionsRecently I purch:lsed a 23-ft cabin

cruiser with a fly bridge. The boat is

docked on tht: c:lnal outside my win-ter home on the West CO:lst of Flor-ida. The boat is used to cruise thewaters of the Peace River and theGulf of Mexico from Tampa to KeyWest. Assuming I u~d the logic of thecrane industry I would have infonnedthe Commandnnt of the United StatesCoast Guard that. although my boatsleeps six I don't think it is prudent to

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provide any PFO (Personal Floata-tion Devices) for each person onboard. Tests have shown that they arenot 100 percent safe.

Do you think the Coast Guardwould accept the premise advanced bythe crane industry that ·those notaware of the performance deficienciesof the device can be lulled into a de;pendency and false sense of security. ~I would be crazy to use that logic tllavoid the small cost of safety devices.

In my car I have an airbag and seatbelts. On my boat I have a plethora ofsafety devices from PFO to Halon fireprotection. The fact that I have dualprotection on the highway and theocea n does not mea n tha t I takechances.

Just days before trial, one weekafter my extended deposition t~stimo-ny, the parties settled filvorably withthe est:Jte of the deceased.

EpilogueQuite recently [ read a iend article

in a Florida newspaper relating to ayoung man who was critlcJlly injuredwhen a crane struck a power line. Thestory W:lS disconcerti ng. The reportconcluded "no one was to blame -this type of accident can not be pre·vented." [ took umbrage with thosestatements. I wrote a letter to the edi·tor (that was published) stating. inpart, "that OSHA and those in thecrane and construction industries areaware of strict training proceduresand havt: tried, over the years. to edu-cate and warn those who come inproximity to danger. The electric util-ities are vigilant in their warnings.There is no excuse to sit on our handsand continue to let this type of acci-dent claim more victims. We worry.as we should. about the carnage onour highway during this time o( yeJr(New Year). Perhaps we should ex·tend that same concern to reduce fore-seeable electrocutions by paying at·tention to existing safety procedures.The force of more than 7600 volts isunforgiving." The man in Florida hadan ann and leg amputated in an at·tempt to save his life. He too died.

Those of us in the electrical indus-try should be in the vanguard forsafety!

The AuthorPauL E. Pritzku. P .E., is chairman

o(George Slack & Pritzku./nc., Wes-ton, MA. a consulting engintuingfirm.