Hotworks Safety

John Newquist

Draft 11 29 2011

Eight Killed in Blast at Colombian Power Station

• CHEC’s director, Bruno Seidel, told the media Thursday that the blast occurred during routine maintenance on a pipe carrying water to the plant.

The work consisted of applying rust-coating and other protective treatments to the inside of the pipe, he said. Just as the crew was completing the job, a spark ignited the fumes and triggered an explosion.

CSB

• The CSB has identified over 60 fatalities since 1990 due to explosions and fires from hot work activities on tanks.

VPP

• Hot Work Program• The company’s hot work program consists of an evaluation of

whether the work will be open or non-open flame along with the type of location in which the work will be performed, either a hazardous area or a non-hazardous area.  After determining those variables, they refer to requirements for issuing the hot work permit in their “Hot Work Permits Requirements Matrix.” For example, the most stringent permit requirements apply in the case of open flame work being performed in a hazardous area, necessitating measures such as a written Risk Assessment Pre-Plan, two management levels of approval, a standby fire watch with fire extinguisher, constant monitoring of the Lower Explosive Limit and/or Oxygen levels, and other appropriate safety measures.

"Hot work" means work involving electric or gas welding, cutting, brazing, or similar flame or spark-producing operations.

What is Hot Works?

Seven Hot Works Keys from CSB

1. Use Alternatives

2. Analyze the Hazards

3. Monitor the Atmosphere

4. Test the Area

5. Use Written Permits

6. Train Thoroughly

7. Supervise Contractors

Alternatives

• Weld in area with no flammable vapors or tanks present.

• Control sparks• Consider cold

cutting (see photo).

Use a Job Hazard Analysis

• Prior to the initiation of hot work, perform a hazard assessment that identifies the scope of the work, potential hazards, and methods of hazard control.

• Identify each major step of the job task

• List the hazard(s) to each major step

• Determine the control(s) that would prevent an accident for each hazard identified

Job Safety Analysis - Blank form - Copy for use at the workplace

Item Work activity Hazard Risk control Persons responsible Completion

Number Break the job down into steps What could harm someone? What can be done to make Who will make sure it Date and signoff

the job sale? happens?

Analyze for Sources of Ignition

• Vent pipes• Where do the sparks go?• “Hot work was allowed

near tanks that contained flammables including those that had known holes due to corrosion “

Monitoring

• Monitor for YOUR hazards

• Gas monitoring needs to be conducted immediately prior to and during hot work activities to ensure that workers are constantly aware of the potential development of an explosive atmosphere

• Monitor continually, record every hour.

Monitoring

• Calibrate your monitor – ensure the validity of your sensors

• Calibration must occur in clean air

NOTES: Fill out permits! Data must be reentered (minimum) each hour hot

work is in progress.

Is H2S, CO, or other toxics anticipated?

Test the Area

RECORD TESTS!

Minimum atmospheric entry conditions are: Oxygen - Between 19.5% - 23.0% Combustible - Less than 10% LEL

Sample Permits Part 1• PERMIT APPLIES TO AREA LISTED BELOW:

• Permit Requested By • Date • Start Time Stop Time ____________ • Permit Expires ____________ • Location • Description of Work Being Performed

• Before approving any welding and cutting, the Supervisor shall inspect the work area and confirm that the below precautions have been taken to prevent fire. (in accordance with NFPA, No.51B)

– ( ) Sprinklers are in service. – ( ) Cutting and welding equipment is in good repair. – Within 35 Feet of Work – ( ) Floors swept clean of combustibles. – ( ) Combustible floors wet down, covered with damp sand or fire resistive sheets. – ( ) Flammable liquids removed; other combustibles, if not removed, protected with fire resistant tarpaulins or metal shields. – ( ) Explosive atmosphere in area eliminated. – ( ) All wall and floor openings covered. – ( ) Fire resistive tarpaulins suspended beneath work. – ( ) Vent openings for flammable liquid tanks are identified . – ( ) Sources of Combustible dust .

– Work on Walls or Ceilings – ( ) Construction is noncombustible and without combustible covering or insulation. – ( ) Combustibles moved away from other side of wall. – Work on Enclosed Equipment – ( ) Enclosed equipment clean of all combustibles. – ( ) Containers purged of flammable liquids. – ( ) Organic material in vessels analyzed for potential of generating flammable gas.

– Fire Watch – ( ) Will be provided during and 60 minutes after operation. – ( ) Supplied with extinguisher and small hose. – ( ) Trained in use of equipment and activating fire alarm.

Sample Permits part 2

• The location where this work is to be done has been examined, above necessary precautions taken, and permission is granted for this work.

– Signature ____________ Date ____________ Time ____________

– Supervisor ____________ – Permit Approval ____________ – Final Inspection ____________

• After work has been completed, work area and adjacent areas where sparks and heat might have spread were inspected for at least 60 minutes, and no signs of fire were found.

– Signature ____________ – Time ____________ – Supervisor ____________

• This Permit should be completely filled out before any welding, cutting or brazing can be performed.

• Permit must be returned to Supervisor/Manager when work is completed

Training

• Train personnel on hot work policies/procedures, proper use and calibration of combustible gas detectors, safety equipment, fire watch responsibility, and job specific hazards and controls in a language understood by the workforce.

• Cutters or welders and their supervisors must be suitably trained in the safe operation of their equipment and the safe use of the process.

Supervise Contractors

• Provide safety supervision for outside contractors conducting hot work.

• Inform contractors about site-specific hazards including the presence of flammable materials.

What is the organic material?

• “Examination of a sample of the liquid indicated that bacterial decomposition of the organic matter likely produced flammable gas, which was then ignited by the welding activity”.

One Accident and Hot Works Citations

Photo from www.CSB.gov

Initial Response

• Welders with the specialty contractor, were attaching a bracket onto a 10,000-gallon, metal storage tank on the grounds of the plant, officials from the two companies said.

• The tank previously held a slurry form - a solid-liquid mixture - of the chemical polyvinyl fluoride, or PVF, which is used a protective coating for solar panels.

• The tank had been cleaned, inspected and taken out of use, a plant spokesman said, though it's not clear whether some chemical residue remained in the tank.

• "As far as I know right at this point, all safety precautions took place and everything was done to the letter of the law, and that's why we're all kind of mystified [at] what took place" the spokesman said.

1910.252(a)(2)(xiii)(D)

• Advise all contractors about flammable materials or hazardous conditions of which they may not be aware.

• The employer did not inform the contractor regarding any potential hazards related to hot works on the slurry tank.

1910.252(a)(2)(xiv)(B)

• The supervisor shall determine the combustible materials and hazardous areas present or likely to be present in the work location.

• The Supervisor made no determination regarding the presence of, or potential presence of, vinyl fluoride in the slurry tank prior to hot work.

1910.252(a)(2)(xiv)(C)(3)

• The supervisor shall see that cutting and welding are so scheduled that plant operations that might expose combustibles to ignition are not started during cutting or welding.

• Electric Arc Welding was permitted on slurry tank while the tank was interconnected to the polyvinyl fluoride process which was in normal production operation.

1910.252(a)(3)(i)

• Used containers. No welding, cutting, or other hot work shall be performed on used drums, barrels, tanks or other containers until they have been cleaned so thoroughly as to make absolutely certain that there are no flammable materials present or any substances such as greases, tars, acids, or other materials which when subjected to heat, might produce flammable or toxic vapors.

• Any pipe lines or connections to the drum or vessel shall be disconnected or blanked.

• After the slurry tank was cleaning during shutdown, the tank was reconnected to the polymer process through the common overflow line allowing an explosive concentration of vinyl fluoride to accumulate in the tank prior to welding on the tank.

• The Slurry tank was interconnected to other slurry tanks by the common slurry tank overflow lines.

1910.252(a)(2)(vi)(B)

• In the presence of explosive atmospheres (mixtures of flammable gases, vapors, liquids, or dusts with air), or explosive atmospheres that may develop inside uncleaned or improperly prepared tanks or equipment which have previously contained such materials, or that may develop in areas with an accumulation of combustible dusts

• The slurry tank had developed an atmosphere of vinyl fluoride vapor via piping, that was interconnected to the ongoing polymer process. The tank was improperly prepared.

1910.252(a)(3)(ii)

• Venting and purging. All hollow spaces, cavities or containers shall be vented to permit the escape of air or gases before preheating, cutting or welding. Purging with inert gas is recommended.

• Flammable vapors were not vented from the slurry tank prior to welding.

Aftermath

• "This death and injury graphically underscore how vitally important it is that employers anticipate the hazards associated with welding in potentially explosive atmospheres and institute all protective measures before allowing such work to begin," said OSHA

• Case is in contest

Resources

• NFPA 51B Standard for Fire Prevention During Welding, Cutting, and Other Hot Work 2009 Edition

• FM Global, Property Loss Prevention Data Sheet 10-3, Hot Work Management, 2006

• U.S. Chemical Safety and Hazard Investigation Board, Safety Bulletin, Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks, February 2010

• American Petroleum Institute (API). Safe Welding, Cutting and Hot Work Practices in the Petroleum and Petrochemical Industries, Recommended Practice (RP) 2009, Washington, DC, 2002.

• Kletz, Trevor. What Went Wrong? Case Histories of Process Plant Disasters, 4th Ed., Woburn, MA, 1999.

Further• This was prepared as a collaborative effort with several friends as a

preliminary aid for anyone involved in hot works. • These are just some the issues. A comprehensive job hazard analysis

should be conducted for any task where someone can get hurt.• This is not an official OSHA publication. Those will be on the

OSHA.gov website.• If you see any errors my email is Newquist.john@dol.gov or

johnanewquist@gmail.com• 312-353-5977• I want to thank Janet S. and Mark K. for her assistance in reviewing

the hazards in this sector.