Blow Out Preventers: Addressing Design Shortfalls and Improving Safety

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In summary, the conversation discusses the design of blowout preventers (BOPs) and the potential for failure in the event of an explosion. The question is raised as to why BOPs are not designed to default to an open position, rather than a closed one, in order to prevent a loss of power in case of an emergency. The practicality of a high-pressure spring mechanism is also discussed, with concerns about the size and potential hidden failure mode. The conversation ultimately concludes that BOP design must comply with legislation and be redundant, but it is impossible to make anything completely fail-proof. The Deepwater Horizon disaster is compared to an aircraft accident, highlighting the need for thorough investigation and understanding of a sequence of events rather than focusing
  • #1
talk2glenn
This may be a silly question, but...

I recall one of the points of failure in the Deepwater Horizon's BOP was the loss of power when an explosion severed the hydraulic and electric cables.

Why don't they design these things to default to on, so that a flow of hydraulic fluid is needed to keep the valve open during normal operation, rather than to close it when there's a problem? Is there some practical reason inherent to BOP design generally, or was it a design shortfall of this particular model?

I'm envisaging some kind of high-pressure spring mechanism kept primed by hydraulic or mechanical pressure. If pressure is lost, intentionally or otherwise, the spring releases, forcing the valve closed.

Practical?
 
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  • #2
It may just be that the force required makes a "normally closed" type difficult to do. It could also be that the damage caused by an accidental closing makes you want to try to avoid that.
 
  • #3
russ_watters is right. The BOP knives must have the force to cut through the drilling column.

Any accidental closing is always undesirable, because going back to drilling means running lengthy systems and equipments checkups and also one would have to face the problem of trying to fish the drilling column out of the well, which causes further delays.

Any subsea equipment design is based at least on legislation, working depth and probability of failure. Let's say you got a powerfull normally closed BOP, will it be approved ? Probably. What is the probability of failure ? The same as a conventional BOP, because you will be required to make it redundant, as redundant as the system is today. Will this redundancy be enough ? No, you cannot make anything perfectly fail proof, only fail-safe enough to mitigate the probability of catastrophic failure.

You should treat Deepwater Horizon disaster as an aircraft accident, where it usually takes one or more years to gather enough information and build the whole picture, which is commonly related to a sequence of mistakes spaced in time and low probability events that when combined resulted in a tragedy, rather than the failure of a single component.
 
  • #4
talk2glenn said:
This may be a silly question, but...

I recall one of the points of failure in the Deepwater Horizon's BOP was the loss of power when an explosion severed the hydraulic and electric cables.

Why don't they design these things to default to on, so that a flow of hydraulic fluid is needed to keep the valve open during normal operation, rather than to close it when there's a problem? Is there some practical reason inherent to BOP design generally, or was it a design shortfall of this particular model?

I'm envisaging some kind of high-pressure spring mechanism kept primed by hydraulic or mechanical pressure. If pressure is lost, intentionally or otherwise, the spring releases, forcing the valve closed.

Practical?

The size of the spring would be unpractical for starters. The shearing force required is in the 1 to 2 million pound range (typically) depending on the tubular that is being sheared.

Plus spring breaks would be a hidden failure mode since the only way to detect it would be to function the BOP. Granted this would be discovered during routine testing, but the period between such testing would be a problem.

CS
 
  • #5


Thank you for bringing up this important topic. I believe it is crucial to constantly evaluate and improve upon designs to ensure safety and prevent disasters like the Deepwater Horizon incident.

In regards to your question about why BOPs are not designed to default to an open position, there are a few factors to consider. First, BOPs are designed to be a last line of defense in case of a blowout. They are meant to be activated in emergency situations to quickly shut off the flow of oil. Therefore, it is not practical to have them in an open position by default as it could potentially lead to unintended releases of oil.

Additionally, BOPs are complex pieces of equipment that require a significant amount of power and hydraulic pressure to operate. Designing them to default to an open position would require even more power and pressure, which could be difficult to maintain in emergency situations. This could also increase the risk of malfunctions and failures.

However, as you mentioned, there are ways to improve the safety and reliability of BOPs. One approach is to incorporate redundant systems and fail-safe mechanisms, such as the high-pressure spring mechanism you described. This could provide an extra layer of protection in case of power loss or other failures.

Overall, it is important for the industry to continually evaluate and improve BOP designs to address any potential shortcomings and ensure the safety of workers and the environment. This can be achieved through collaboration between scientists, engineers, and regulators to incorporate the latest technology and best practices.
 

1. What is a Blow Out Preventer (BOP)?

A Blow Out Preventer (BOP) is a large, specialized valve used in the oil and gas industry to control the flow of oil or gas from a well. It is designed to seal the wellhead and prevent the uncontrolled release of hydrocarbons during drilling, completion, or production operations.

2. Why are Blow Out Preventers important?

Blow Out Preventers are crucial for maintaining safety and preventing environmental disasters in the oil and gas industry. They act as the last line of defense in case of a well blowout, which can potentially lead to a catastrophic oil spill. BOPs also help to regulate well pressure during drilling and completion, ensuring the safety of workers and equipment.

3. What are some design shortfalls of Blow Out Preventers?

Some common design shortfalls of Blow Out Preventers include inadequate shear rams, lack of backup systems, and poor maintenance and testing protocols. These design flaws can lead to BOP failure and increase the risk of a well blowout, resulting in significant safety and environmental consequences.

4. How can the safety and effectiveness of Blow Out Preventers be improved?

To improve the safety and effectiveness of Blow Out Preventers, it is essential to address design shortfalls and implement strict maintenance and testing procedures. This can include regular inspections and upgrades of BOP components, as well as implementing redundant systems and backup controls to increase reliability.

5. What regulations are in place to ensure the proper design and maintenance of Blow Out Preventers?

In the United States, the Bureau of Safety and Environmental Enforcement (BSEE) is responsible for regulating the design, maintenance, and testing of Blow Out Preventers on offshore drilling rigs. The BSEE has strict requirements for BOP design and performance, as well as regular on-site inspections and audits to ensure compliance. Additionally, industry organizations such as the American Petroleum Institute (API) have established standards for BOP design and testing to further improve safety and reliability.

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