Dropped Object Study 4

[swtmoon]

Hi there,

Are there any one to help me about dropped object study?
Currently I should present about the Dropped Object Study
and I have few material.
It's not clear to me about followings;
1. Purpose of Dropped Object Study
2. Step by step method of Dropped Object Study
(I have one example, but I'm not sure this is all about)
3. What should we do with the result of dropped object study.

Please give me any informations or any text about the dropped object study.

Regards,

swtmoon

 

[Guidoo]

A dropped objects study is a study to identify hazards related to lifting of objects, to assess risk related to these activities and to take measures to reduce this risk to a tolerable and as low as reasonably possbible (ALARP) level. It can be part of a Quantitative Risk Assessment (QRA) that can be part of a Safety Case that may have to be provided to authorities (depending on which country the facilities are in).

The specific objectives of a dropped objects study study for an offshore production platform are:

To identify the number and magnitude of loads which are lifted to / from the supply vessel, and also lifts across the platform,

To identify the hazardous lifting operations and subsequently the areas at risk from dropped and swinging loads,

To review the potential consequences of the identified dropped object scenarios such that due attention is paid to the routing of the process equipment, pipework and subsea pipelines,

To assess the risk of dropped objects damaging topsides and subsea equipment.

To identify mitigation and control factors to reduce the risk from dropped objects. Examples of such measures are: layout changes, limitation of load weight, providing matresses around pipelines etc.

To provide input of dropped object risks to the QRA.

Hope this helps...

 

[swtmoon]

Thank you Guido,

Your brief introduction is great help to figure out the scheme of dropped object risk assessment.
Additionally is there any examples on the web? or books?
can help me to understand which kind of specific actions have been implemented by the result of dropped object risk assessment?

 

[Guidoo]

I don't think their are websites or books with examples of dropped object studies. These are usually done by consulting firms, and companies pay them quite some money to do the job. However, it's not rocket science: you just have to estimate the likelihood that a load is dropped on a piece of equipment and combine that with an estimation of the consequences (e.g. pipeline rupture) to get the risk...

What I did find was a website that shows some solutions (e.g. concrete mattresses) for pipeline protection against dropped loads:

http://www.sealmarksystems.com

and then select "protection".

 

[MetalMickey]

The dropped object study is an all too real design case that needs to be considered in subsea structures and pipelines. It highlights the probable impact loads that will be applied as a result of the dropped object.
If the water is deep enough object will reach terminal velocity.

Examples of impact energies are :

- Drill collar - 1050KJ
- BOP - 1290KJ
- Drill Casing - 164KJ

Hence they are substancial and need to be considered.

The main loads therefore are a result of :

- Kinetic Energy
- Momentum
- Mass and Velocity


The effect on the item can be calculated by a number of denting models for pipelines for example, i.e. based on the proportion of impact energy absorbed by local deformation of the pipe wall. General guidelines for UK sector can be found in HSE OTH561.

Hope this helps.

(Also posted on Offshore structures thread)

 

[texag75]

Try this website:

http://www.safetec.no/drop/