Delta P

Summary

The video script discusses 'Delta P', a lethal hazard in commercial diving caused by differential pressure between bodies of water. It explains how this invisible force can trap or pull divers with immense strength, often leading to fatalities. The script recounts several tragic incidents, emphasizing the importance of pre-job meetings, understanding site layouts, lockout/tagout procedures, and using proper equipment to mitigate risks. It also offers practical tips on recognizing and preparing for Delta P situations to prevent such accidents.

Takeaways

• 💡 Differential Pressure (Delta P) is a common cause of commercial diving fatalities, often due to the sudden and invisible nature of its dangers.
• ⚠️ Delta P occurs when there is a significant pressure difference between two bodies of water, which can lead to dangerous water flow and force.
• 🔍 The force exerted by water can be calculated using the formula involving the area of the hole, water depth difference, and PSI per foot of water depth.
• 📚 It's crucial for divers to understand the site layout, piping, and valve systems to anticipate and prepare for Delta P situations.
• 🔄 Bodies of water naturally seek to equalize their pressures, which can result in strong water currents and suction forces.
• 🚫 Divers should never venture into Delta P situations without thorough preparation and understanding of the risks involved.
• 🔗 The use of lockout tagout procedures can help prevent machinery and valve accidents, which are part of the Delta P hazard mitigation.
• 🤝 Communication between divers and surface personnel is vital for safety, especially in the event of a Delta P incident.
• 🛡️ Divers should use equipment that doesn't interfere or become fouled, ensuring they can be quickly assisted if trapped.
• 🛠️ Techniques such as cutting slots instead of holes can help reduce the risk of getting stuck due to Delta P forces.
• ❗️ Awareness and preparedness are key to avoiding becoming a victim of Delta P; divers must recognize potential hazards and act accordingly.

Q & A

What does 'Delta P' stand for in the context of commercial diving?

Delta P stands for 'differential pressure' and refers to situations where the pressures between two bodies of water are dramatically different, leading to a force that can be dangerous for divers.

Why are Delta P situations particularly dangerous for divers?

Delta P situations are dangerous because they are invisible and can strike suddenly without warning. Once caught in a Delta P situation, it is almost impossible to escape until the pressure between the two bodies of water is equalized.

What is the formula for calculating the force of water through a hole at a particular depth?

The formula for calculating the force of water through a hole is the area of the hole multiplied by the difference in water depth multiplied by the PSI per foot of water depth.

How does the force of water exerted on a valve differ between freshwater and saltwater?

The force of water exerted on a valve differs due to the specific gravity of the water. Freshwater has a PSI per foot of water depth of 0.432, while saltwater has a higher value of 0.445 PSI per foot.

What is the significance of the incident where divers were cleaning a dam's drain?

The incident highlights the extreme danger of Delta P situations. When the drain was cleared, the force of rushing water trapped the divers, leading to their deaths, emphasizing the importance of being aware of and prepared for such hazards.

What happened in the case of the scuba diver repairing a pool bottom?

The scuba diver was drawn against an open pool drain, creating a perfect seal. Since he was diving alone without a tender at the surface, no one knew he was trapped, and he eventually drowned due to running out of air.

Why were the two scuba divers in the water tower unable to prevent the tragedy?

The sudden opening of the drain created a great suction that pulled one diver into it. The other diver, unaware of the situation due to zero visibility, surfaced thinking the first had already come up, and was unable to locate the trapped diver, who ran out of air and died.

What mistake did the plant personnel make regarding the gate valve in the hydroelectric generation plant incident?

The plant personnel assured the dive team that the gate valve was closed, but it was actually open. When the winch was started to close the valve, the sudden force of the water trapped the diver, leading to his death.

What are some safety measures that can be taken to prevent Delta P incidents?

Safety measures include participating in pre-job meetings, understanding the site layout and piping systems, practicing lockout/tagout procedures, using a site-specific schematic and diving checklist, and ensuring clear communication and visibility with the surface and other divers.

What are some techniques to reduce or eliminate Delta P hazards?

Techniques include recognizing potential forces in the environment, calculating the force of water at the working depth, cutting slots instead of holes for draining or relieving pressure, and fabricating covers with screens or multiple holes to prevent getting stuck.

What is the main message of the video regarding Delta P situations?

The main message is to make divers aware of the potential for differential pressure situations and to emphasize the importance of recognizing them beforehand and being prepared to deal with them to avoid adding one's name to the list of fatalities.