Falling or dropped objects represents a safety hazard to all work sites where work is performed on different elevations.
On an offshore rig dropped objects is identified as one of the key areas to focus on to prevent injuries (or in a worst-case scenario fatalities) to personnel, and damages to equipment and facilities.
In this blog article we will discuss the consequences of different dropped objects scenarios and how to reduce the risk for this happening on an offshore rig.
Plausible reasons for dropped objects scenarios
Dropped objects may result from a variety of unintended events including:
- equipment failure
- equipment and structure exposed to excessive forces
- design failures
- weather conditions/inadequate sea fastening
- equipment/structural fatigue and/or corrosion
- loss of tools and equipment from an elevated position
- not properly tightened or secured bolts/nuts
- human error
Dropped objects on an offshore rig may vary from a small bolt weighing a few grams up to equipment/equipment parts or structural components weighing several tons. Needless to say, a dropped object weighing tons will have significant destructive impact force and must be avoided.
However, the same applies for e.g., a small sized bolt dropped from an elevated height, which impact force on a human may be fatal.
No wonder that oil companies, drilling contractors and the like, have implemented comprehensive and strict HSE procedures for safe zones, restricted access areas, working at elevated heights and work under hanging loads, etc.
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Obviously, such procedures are necessary and required, but can only reduce the probability of an unintended and potentially catastrophic consequence (e.g., loss of control of operations, injury or fatal accident) if a dropped object event occurs.
At the seabed, under an offshore drilling platform, safety and/or control equipment (Christmas trees (XMT’s), BOP’s, etc.) will typically be installed on the wellhead being a single well or a larger template consisting of several wellheads with flow lines. These components are critical equipment controlling well flow and preventing blowouts and pollution to the sea.
If an object from the drilling rig, e.g., drill pipe or drill collar is dropped into the sea and impacts the subsea equipment/installation, it may have disastrous consequences.
In an absolute worst-case scenario, it may result in a blowout, significant pollution, loss of the well and loss of lives. However, such a scenario is unlikely. A more likely consequence of such a dropped object scenario is significant cost and loss of time.
Reducing the probability for dropped objects ever to occur, on the rig itself or into the sea, is a key priority within the offshore industry.
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Measures to reduce risk
The offshore industry spends significant effort and investments to reduce risk and to reduce the consequence for an unwanted event. Measures implemented, in addition to strict and comprehensive work procedures, typically include:
Layout design requirements
Design requirements can involve a variety of elements to reduce the risk for dropped objects hazards such as layout arrangements, weather protected areas, safe enclosed areas, etc.
Equipment design requirements
Equipment must be designed to include a number of features to reduce the risk for dropped objects, including minimizing exposed components/hoses/tubing/piping, robust design, impact resistance, fail safe product designs, toe boards, redundancy, sewing safety wires / secondary retention and similar features for securing of bolts, large hoses, equipment, etc.
Illustrative example: One access basket with hose bundle loops on each side which typically can interfere with other equipment or structure and cause dropped objects. The alternative “slick design” eliminates this risk.
To avoid equipment failure and as a potential consequence of potential dropped objects, equipment must be designed and operated within its operating criteria.
Mechanization/automation/avoid manual work
Mechanization/automation is a means not only to improve efficiency and consistency, but also to move people out of areas especially exposed to dropped objects, e.g.: “red zone” on drill floor and certain areas underneath drill floor in the moonpool area.
Installation of special protective equipment, e.g. to protect structures at the seabed from dropped objects from well center(s), will prevent objects from falling into the sea.
Protective equipment such as a King Size Rathole can prevent dropped tubular down into the sea.
Seafastening and guiding of equipment during operations
In particular on floating structures, rig movements pose a challenge and risk to safe and efficient operations. It also reduces the rig’s operating window. Proper design and equipment for seafastening of critical equipment and components during adverse weather will reduce risk for dropped objects.
Properly designed equipment for lateral guiding of heavy equipment, such as BOP, XMT`s etc. will reduce the risk of dropped objects, protect equipment, enable safe operations, improve efficiency and increase the operational weather window.
Inspection and maintenance
The importance of regular inspection and maintenance of equipment and structure cannot be underestimated. A well-maintained rig and properly maintained equipment is a prerequisite for minimizing the risk for dropped objects.
Over time minor leaks, corrosion, fatigue, wear and tear of valves, bearings and other components, may result in weakened structures, unintended pressure buildups/loss, reduced system robustness, etc. and as a consequence potentially catastrophic equipment/structural failures may occur.
Access Platforms, as seen here with a BOP, makes manual work more secure.
The human factor
Adequate training, operational qualifications and adherence to safety procedures are a must to minimize risk exposure to dropped objects.
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Dropped objects is a major risk hazard on offshore installations. Dropped objects may be the result of external factors (e.g. weather conditions), human error, equipment failure, lack of maintenance, poor design or inadequate equipment.
The risk of dropped objects and their consequences cannot be fully eliminated. However, a number of risk reducing measures are available to reduce the risk of dropped objects to a minimum.