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STATIC DROPPED OBJECT

A static dropped object is a solid object, initially at rest, that falls from its original position

under its own weight. Examples of static dropped objects include nut dislodged in rig derrick,

fallen cable tray due to failed (corroded) fastenings.

 

DYNAMIC DROPPED OBJECT

A dynamic dropped object is a solid object that breaks free from its fastenings due to the

applied force from the impact of some other equipment or a moving object. Examples of

dynamic dropped objects include the top drive hitting the rig floor, a stand of drill pipe

falling across the derrick and hitting and breaking a light resulting in the light falling to the

rig floor.

 

 

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Replies to This Discussion

I do not understand the calculator-can you explain please?

Drops Calculator has been developed on the basis of kinetic energy calculations and is to be used as a guide to assess the impact of a dropped object . The calculator does not take account of the shape of dropped object,e.g sharp objects which can potentially increase the consequances should the object strike a person .

The attached figures can explain the consequances should the object strike a person e.g mass with 5kg dropped from height 10 m will lead to fatality . Same mass dropped from height 1 m will lead to first aid case

 

 

Droped Object Consequence Calculator"Microsoft Office Excel 97-2003 Worksheet"

This program is based on physical laws of how mass of an object dropped from a height from and the relationship to the energy/force affecting the human body.

Assumptions for use:
1.  All potential energy from a object initially at rest is transferred to kinetic energy when dropped.
2.  The only acceleration is due to the force of gravity, which is assumed to be constant and essentially at sea level.
3.  All energy is assumed to be absorbed by the individual and the PPE.
4.  A fatality is the result of the total force required to break both the hard hat as well as the cranium.
5.  A DAFWC is the energy required to break a bone in the shoulder or top of the foot.
6.  A medical treatment case is the energy necessary to cause a laceration requiring sutures.
7.  The energy levels less than that requiring medical treatment are assumed to fall into the first aid category at worst.
8.  The dropped object is assumed to be blunt edged, and whereas shape might be assumed to be spherical, it really only makes a significant difference if the object has a thin flat edge or is shaped like a javelin.
9.  The worker with a potential to be struck is 25 - 40 years of age, is a male and weighs approximately 80 kilograms.

Attachments:

Example of dynamic dropped Objects . while using the rig Kelly to work the stuck  (when jarring on string), the drillstring parted in the well .This caused the Kelly jump.During this process,the swivel bail came out of the hook of the travelling block ,allowing the drillstring to drop and the Kelly to fall in an uncontrolled manner. The system came to rest with Kelly bent over from the rotary table to the outside of the rig floor. No Persons were injured .It is standard practice that no persons are allowed on the rig floor when jarring operations are in process.Hence no injuries during this event .This situation will lead us to what is known as No - Go & Red zones !!

 

 

 

Example of Static Dropped Object Incident

While the mechanic servicing the wheel of rig rolling gear the inner sleeve of wheel rim sliding into outer sleeve , the mechanic trapped fingers of his both hands between two sleeves.

IP (Mechanic) sustained multiple injuries and dislocations to fingers of his both hands (2 fingers in his left hand and 3 fingers in his right hand).

 

 

 

 

 

 

  

Example 1 Standard Bolt (¾ x 3½)

Weight 220 grams
Dropped Distance 11M (3 floors) 23M (6 floors)
Impact Velocity 31mph (50kph) 50mph (80kph)
Impact Force 23.7kgs 49.5kgs
Resulting Injury Hospitalised (Recordable) Fatality


A bolt dropped from 23 metres is equivalent of being dropped from the 6th floor of a building. The velocity attained is 50mph / 80kph on impact. The bolt achieves a mass impact weight of 49.5kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.

Example 2 Screw Driver

Weight 500 grams
Dropped Distance 10M (3 floors) 14M (4 floors)
Impact Velocity 31mph (50kph) 38mph (61kph)
Impact Force 49kgs 73.5kgs
Resulting Injury Hospitalised (Recordable) Fatality


A screw driver dropped from 14 metres is equivalent of being dropped from the 4th floor of a building. The velocity attained is 38mph / 61kph on impact. The screw driver achieves a mass impact weight of 73.5kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.

Example 3 Claw Hammer

Weight 2 Kgs
Dropped Distance 4M (1 floors) 6M (2 floors)
Impact Velocity 20mph (31kph) 24mph (39kph)
Impact Force 78kgs 117kgs
Resulting Injury Hospitalised (Recordable) Fatality


A claw hammer dropped from 6 metres is equivalent of being dropped from the 2nd floor of a building. The velocity attained is 24mph / 39kph on impact. The claw hammer achieves a mass impact weight of 117kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.

Example 4 Sledge Hammer

Weight 5 Kgs
Dropped Distance 1M (1 floors) 3M (1 floors)
Impact Velocity 10mph (16kph) 17mph (27kph)
Impact Force 49kgs 147kgs
Resulting Injury Hospitalised (Recordable) Fatality

A sledge hammer dropped from 3 metres is equivalent of being dropped from the 1st floor of a building. The velocity attained is 17mph / 27kph on impact. The sledge hammer achieves a mass impact weight of 147kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.





All the above graphs show the likely-hood of injury or death from falling objects, relative to the mass and height from which a fall takes place This is a guide only, as in some circumstances even a light-weight object dropped from height may be fatal.

 

Preventive controls for Static dropped tools and objects include:

Tools and Equipment maintenance and periodic inspections Check tools are in good condition, not loose, corroded, or damaged e.g. check hammer heads are secure, tool lanyards, tethers, connectors and anchorage points meet manufacture's inspection instructions and or training. This inspection regime should include keeping an equipment inspection book. This is one of the tools that will be used as a preventive control for periodic inspections It should provide:

  • A header noting the inspection frequency
  • A picture of the equipment that requires inspecting
  • A reference number of the equipment
  • A description and location of the equipment
  • The fastening / tethering method and inspection procedure
  • Pass / Fail and comments section
  • Inspectors signature

If the equipment inspected does not meet the inspection procedure then it will be marked as a "Fail" and the failure detail noted in the comments section. Create a tool / equipment storage log book to be used to issue tools and equipment. Tools must be logged back in at the end of work to ensure none are left behind to become a hazard.



Electronic excel based calculator for determining potential consequence of a dropped object 2011.

A simple rule of thumb for potential dropped objects "The heavier the object , the more severe the consequances , the futhur it falls , the more severe the consequances"

 

Attachments:

Other example of dynamic dropped objects , Fatality on landing rig

18/01/2012,

At the time of incident, one casing joint was positioned in the v-door (with pin end rest to v-door’s bottom stop) and the single joint elevator (attached to the travelling block) was installed on the casing joint resting on the v-door. The floorman who was working on air winch start to lift the joints of casing from catwalk to v-door when he mistakenly colloid the casing joint that was being hoisted from catwalk with joint that was being positioned in the v-door . As a result of this collision the joint that was being positioned in the v-door fell down the v-door and continued off the v-door resulted in sudden release of tension to the single joint elevator wire which strike the floorman , the floorman was knocked face first into v-door post and fell down toward rig floor . He was severely injured and passed away shortly after

The standard oilfield rig – up and operational procedures were used to pickup and run in hole joints of 9 5/8” casing.

1- To hoist the casing joint from the catwalk to the v door a single joint elevator in combination with a drill – floor winch is used. The winch was being operated by a floorman from a position behind the winch with good visibility to the catwalk / pipe rack area

2-  After the casing joint is hoisted up the v – door ramp (casing box connection some 1 m above drill floor) the joint is positioned to rest against the v – door ramp with the pin – end being rest by the v door’s bottom stop

3- The single joint elevator is released

4- The second joint elevator hanging off from travelling block are used to lift the casing joint to the floor to enable to make it up to the casing string landed off in the slips

 

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