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Other Hazards on the Drilling Site (Continued)

Confined Spaces

confined space

Many workplaces contain spaces that are considered "confined" because their configurations hinder the activities of employees who must enter, work in, and exit them.

A confined space means a space that:

  1. is large enough and so configured that an employee can bodily enter and perform assigned work; and
  2. has limited or restricted means for entry or exit; and
  3. is not designed for continuous employee occupancy.

Confined spaces include, but are not limited to underground vaults, tanks, storage bins, manholes, pits, silos, process vessels, and pipelines.

OSHA uses the term "permit-required confined space" (permit space) to describe a confined space that has one or more of the following characteristics:

  1. contains or has the potential to contain a hazardous atmosphere
  2. contains a material that has the potential to engulf an entrant
  3. has walls that converge inward or floors that slope downward and taper into a smaller area which could trap or asphyxiate an entrant
  4. contains any other recognized safety or health hazard, such as unguarded machinery, exposed live wires, or heat stress

Confined space hazards are addressed in specific standards for the general industry and shipyard employment. Also, see OSHAcademy Course 713 for more information.

Real-World Accident

Confined Space Rescue and Recovery: Oil Field Worker Dies on the Job in California

According to KBAK-KBFX TV station in Bakersfield, California, a supervisor and a welder were in a 15-foot tall tank. They apparently were testing for leaks by adding air pressure inside the tank. This process required having a “false bottom” in the tank. It wasn’t clear if the air pressure had built up under the false bottom. Investigators at the scene said there weren’t any harmful fumes inside the tank at the time of the accident. Eyewitnesses told reporters they heard a “loud sound, like an explosion.”

Crews at the scene used a tripod with a rope, and sent a firefighter into the tank. However, the rescue team found the deceased worker inside the tank. He died from a severe head injury. The other worker at the site suffered a broken ankle.

Source: KBAK-KBFX TV-Eyewitness News- October 3, 2012

Pressure Vessels

pressure vessel

Generally, a pressure vessel is a storage tank or vessel that has been designed to operate at pressures above 15 p.s.i.g. Recent inspections of pressure vessels have shown that there are a considerable number of cracked and damaged vessels in workplaces. Cracked and damaged vessels can result in leakage or rupture failures.

Potential health and safety hazards of leaking vessels include poisonings,suffocations, fires, and explosion hazards. Rupture failures can be much more catastrophic and can cause considerable damage to life and property. The safe design, installation, operation, and maintenance of pressure vessels in accordance with the appropriate codes and standards are essential to worker safety and health.

Pressure vessel hazards are addressed in specific standards for the general industry, shipyard employment, and the construction industry.

Compressed Gas and Equipment

Compressed Gas Cylinder Safety - Matheson

Hazards associated with compressed gases include oxygen displacement, fires, explosions, and toxic gas exposures, as well as the physical hazards associated with high pressure systems.

Special storage, use, and handling precautions are necessary in order to control these hazards. Gas cylinders should be stored in upright positions and immobilized by chains or other means to prevent them from being knocked over. If the cylinders fall over and are damaged the can be turned into rocket! Other important precautions to take include:

  • Store cylinders away from highly flammable substances such as oil, gasoline, or waste.
  • Store cylinders away from electrical connections, gas flames or other sources of ignition, and substances such as flammable solvents and combustible waste material.
  • Keep all flammable gases separated from oxidizing gases in storage areas. Acetylene and propane cylinders should be separated from oxygen cylinders when not in use.
  • Separate oxygen and fuel gas cylinders by a minimum of 20 feet when in storage. A fire-resistant partition between the cylinders can also be used.
  • Keep storage rooms for cylinders dry, cool, and well- ventilated. The storage rooms should be fire resistant and the storage should not be in subsurface locations. Cylinders should be stored in secure areas at temperatures below 125 deg. F, away from radiators or other sources of heat.
  • Store cylinders away from incompatibles, excessive heat, continuous dampness, salt or other corrosive chemicals, and any areas that may subject them to damage?
  • Permanently post the names of the gases stored in the cylinders in storage areas.
  • Make sure all compressed gas cylinders have safety pressure relief valves.
  • Maintain cylinders at temperatures below 125 deg. F.
  • Ensure flames never come in contact with any part of a compressed gas cylinder.
  • Store and label charged or full cylinders away from empty cylinders.
  • Protect the bottom of the cylinder from the ground to prevent rusting.
  • Regularly inspect compressed gas cylinders for corrosion, pitting, cuts, gouges, digs, bulges, neck defects and general distortion.
  • Ensure cylinder valves are closed at all times, except when the valve is in use.
  • Move compressed gas cylinders, even short distances, using a suitable hand truck. They must never be dragged across the floor. Serious accidents have occurred when a cylinder with a regulator in place was improperly moved. The cylinder fell, causing the regulator to shear off, and the cylinder rocketed through several brick walls.
  • Never use wrenches or other tools for opening and closing valves.
  • Never hammer on valve wheels to open them should be strictly prohibited. For valves that are hard to open, contact the supplier for instruction.
  • Always use suitable pressure regulating devices whenever the gas is emitted to systems with pressure-rated limitations lower than the cylinder pressure.

Hazards Associated With Other Drilling Techniques

Compressed Air - Compressed air may be used instead of drilling mud when there is no risk of encountering high-pressure, permeable formations or formations containing water. It has the advantages of faster drilling and of not having to recondition the circulating mud. The drilling dust is discharged from the "blooey line" and may be blown across the working area to cause a respiratory hazard; dust particles may cause eye injuries.

Directional Drilling - Drilling HSE

Directional Drilling - Directional drilling occurs when a contractor intentionally drills a well that is out of plumb. Surface conditions may dictate that a drilling rig cannot be erected over the formation to be explored or, as in offshore operations, the rig may be costly enough that multiple formations should be explored from a central drilling position. Directional drilling is achieved by a number of different methods. Directional tools include downhole hydraulic turbine motors, jet deflector bits, bent subs, flexible joints, or, most common in past years, whipstocks.

Redrilling - The redrilling of a well takes place when well depth must be extended. (The existing formation may not be productive and the well may be extended to tap a lower formation.) In some instances, the prior drilling operation may have stopped for reasons associated with annulus collapse, damaged casing, lost drilling string, or blowout.

Control of Hazardous Energy (Lockout/Tagout)


Workers servicing or maintaining machines or equipment may be seriously injured or killed if hazardous energy is not properly controlled. Injuries resulting from the failure to control hazardous energy during maintenance activities can be serious or fatal!

Failure to control hazardous energy may result in electrocution, burns, crushing, cutting, lacerating, amputating, or fracturing body parts, and others. For example, an effective Lockout/Tagout Program would have prevented the following accidents:

  • A steam valve is automatically turned on, burning workers who are repairing a downstream connection in the piping.
  • A jammed conveyor system suddenly releases, crushing a worker who is trying to clear the jam.
  • Internal wiring on a piece of factory equipment electrically shorts, shocking an employee who is repairing the equipment.



Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. OSHA defines a confined space as a space that includes all of the following criteria, except _____.

2. Generally, a _____ is a storage tank or vessel that has been designed to operate at pressures above 15 p.s.i.g.

3. An effective Lockout/Tagout Program on a rig could have prevented all of the following accidents, except _____.

4. Usually, failure to control hazardous energy may result in all of the following injuries, except _____.

5. OSHA defines a permit-required confined space as a space that includes any of the following characteristics, except _____.

Have a great day!

Important! You will receive an "error" message unless all questions are answered.