Categories: Engineering

Lessons Learned, Again – Death on an Electric Arc Furnace

TASA ID: 1006

Maintenance work was being done on a three phase AC electric arc furnace that was about 30 feet in diameter.  It was on a prolonged shut-down for some extensive repairs.  There were many different crafts and contractors working on different aspects of the repairs, and many of them were out of sight of the others.  Work was being done on the furnace, its transformer, the control system, and the main power system.

The deceased was welding on the support section of one of the three electrode arms.  These arms hold and carry current to the main electrodes that do the melting in the furnace.  He was an employee of a sub-contractor to the mechanical contractor.  The clamping section (the part that holds the electrode) had been removed so that he could get access to the damaged area that was to be repaired.  The clamping section was being held up about 10 feet above him by an overhead crane, by means of a chain assembly on the main crane hook.  The removed clamping section was an assembly of aluminum and copper that weighed over two tons.  The repair being made was to weld shut a crack in the aluminum portion of the support arm.

By means of an electrical signal, the control circuit for the furnace sent a signal to raise all three electrode arms.  The stored energy in the hydraulic accumulators did just that: all three electrode support posts rose up to their full height.  In doing so, one of the other arms hit the suspended clamping section and dislodged it from the overhead crane.  It fell and killed the welder below.

The design for the furnace required that there be a large hydraulic accumulator for the electrode arms in order to be the source of a large volume of oil. This moved the electrodes faster than the hydraulic pumps could supply the oil.  These were piped to the electrode cylinders through three 4-inch diameter pipes, one for each phase electrode.  One of the times that this source of stored energy was needed was if the power were to fail.  At that time, it would be necessary to lift the electrodes so that they would not get frozen into the molten steel in the furnace.  Therefore, the circuit breaker that fed the high voltage to the furnace transformer had a contact on it such that if the circuit breaker were to open, the hydraulic system would operate to lift the electrodes.  There was an electrical contractor doing repair work on the circuit breaker.  In their work they needed to open and close the circuit breaker.  When they opened it, the signal was sent and the electrodes moved as described above.

All of the motors and electrical power to the furnace drive and hydraulic equipment had been opened, locked out, and tagged out as safety rules require.  The control power was not off because work was being done on the computer system.  Note that OSHA rules in 29 CFR-1910-147 (the rules for Lockout and Tagout) require that sources of energy be opened or disconnected and locked out or tagged out.  The lockout of control circuits is not proper, nor necessary, to do a complete lockout job.  The three, large, 4-inch diameter pipes each had a one-quarter-turn shut-off cock in the line at the main hydraulic panel.  Each one had locking hasps on them so that locks could be affixed to lock them shut.  All three of the valves were open at the time of the accident.  None of the three had been shut nor locked out as was required.

No records of training that were required to ensure a safe working environment were found after the accident.  Note that OSHA rule section 29 CFR 1910.147(b), entitled "definitions" states:

1.  "Energy isolating device. A mechanical device that physically prevents the transmission or release of energy, including but not limited to the following: A manually operated electrical circuit breaker; a disconnect switch; a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors, and, in addition, no pole can be operated independently; a line valve; a block; and any similar device used to block or isolate energy. Push buttons, selector switches and other control circuit type devices are not energy isolating devices." (The emphasis is added)

2.  "Energy source. Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy."

A number of factors set the stage for this accident:

1.   The deceased welder was a good worker, but he had never worked in a steel mill - nor any kind of factory - before this accident.  He had always worked on heavy over-the-road machinery.  Thus he knew nothing about the dangers of a steel mill.

2.  OSHA 29 CFR 1910.147(c)(1) states:  "Energy control program. The employer shall establish a program consisting of energy control procedures, employee training and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, startup or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source and rendered inoperative."  There was no evidence that this had been done for this maintenance operation.

3.  OSHA 29 CFR 1910.147(d)(5)(i) states: "Following the application of lockout or tagout devices to energy isolating devices, all potentially hazardous stored or residual energy shall be relieved, disconnected, restrained, and otherwise rendered safe."  This relieving of the stored hydraulic energy was never done.

4.  The OSHA rule section 29 CFR 1910.147 (c) (7) (iv) states: "The employer shall certify that employee training has been accomplished and is being kept up to date.  The certification shall contain each employee's name and dates of training."  There were no such records of ANY training having been given to this man.

5.  A portion of the specifications for the job stated: "Supplier will supply the following items:" and continues with "Training Courses for operation and maintenance personnel."  These were never supplied.

6.  An employee of the owner later described the proper method of locking out the hydraulic system.  He had been working alongside the deceased immediately before the accident.  If the lockout of the hydraulic valves had been done, as he described should have been done, the accident would never have happened.

7.  The detached electrode arm should not have been suspended above the worker.

This accident was preventable.  All that was necessary was to follow the various steps and intents of OSHA 29 CFR 1910.147.

Remote and non-obvious sources of energy are not recognized or remembered.  Hydraulic accumulators are devices that are too often forgotten, not understood, or not thought of in the normal course of events.

Planning, training, communication, and education of all employees are essential for a safe workplace.

This article discusses issues of general interest and does not give any specific legal or business advice pertaining to any specific circumstances.  Before acting upon any of its information, you should obtain appropriate advice from a lawyer or other qualified professional.  

 This article may not be duplicated, altered, distributed, saved, incorporated into another document or website, or otherwise modified without the permission of TASA.

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