Stored energy is accumulated energy that can release suddenly, potentially causing serious injury or death.
Stored energy can have many forms, including gravitational potential energy, pressurised gases and liquids, stored mechanical energy, and stored electrical energy. It is particularly dangerous because the hazard still remains, even though the original source of the energy may have been removed. Some examples of stored energy in the working environment at a wellsite include cables or wireline reels under tension; drill string under torque; compressed springs; wellheads, tanks or pipelines under pressure; or objects that have been carried, lifted or elevated above the ground that could collapse or fall on a person, etc.
It is essential that all potential sources of stored energy are identified, and that suitable controls are implemented to prevent the unintentional release of that energy in a way that could cause harm. Additional controls might also be considered to limit the extent of any damage if the initial controls are not effective.
When Stored Energy is Unintentionally Released
Mines Safety Significant Incident Report No. 3 – Compressed Air Hose Connection – Fatal Accident
An exploration driller’s assistant was struck on the head by a large-diameter compressed air hose that blew off its fitting on a cyclone sampler. He received serious head injuries, which proved fatal. The air hose was clamped to the fitting but there was no restraining chain or sling.
IADC Alert 98 – 16 Stored Energy Hazards
A rig worker was seriously injured when the cap at the end of a top drive accumulator blew off and struck him. He had been helping another employee remove the cap, unaware that the nitrogen pre-charge in the tube was still active. Because it had not been bled off, the pressure was sufficient to violently blow off the end cap.
Controls
Stored energy must be managed carefully or serious injury or death can occur. Many of the accidents we investigate involve some sort of potential energy. There is always a way to safely control stored energy. In general, there are four basic steps to control these risks:
- Isolation of the energy source
- Maintaining the method of isolation
- Releasing or containing the stored energy
- Verifying that the isolation has been effective and that any stored energy has been dissipated or fully controlled.
The WPTW System provides a structured process for the identification of all stored energy hazards and for managing the risks associated with equipment that may contain stored energy. The requirement for verification of all Work Precautions prior to the issuing of a Permit means that stored energy hazards must be controlled before the Work Party starts work.
Sources of stored energy that are introduced during the work will be managed by Ongoing Controls listed in Section C of the Permit Form.
More information
For information about the identification, assessment, isolation, and verification of risk controls for stored energy, contact our support centre on 1800 078 939, or email [email protected].