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.

Outlines

00:00

💧 The Dangers of Delta P in Commercial Diving

The first paragraph introduces the concept of 'Delta P' or differential pressure, which is a significant hazard in commercial diving. It explains that Delta P is the pressure difference between two bodies of water and can cause sudden, powerful forces that are nearly impossible to escape once trapped. The paragraph details how this force can be calculated and provides a tragic example of divers being fatally sucked into a dam's drain due to the pressure difference. It emphasizes the importance of understanding and being prepared for Delta P situations to avoid such accidents.

05:03

🚨 Safety Precautions and Awareness in Diving Operations

The second paragraph delves into safety measures and the importance of pre-job meetings to understand the site layout and piping systems. It highlights the necessity of lockout/tagout procedures to prevent accidents and stresses the need for clear communication between divers and surface personnel. The paragraph recounts several incidents where lack of awareness and preparation led to diver fatalities, such as a diver being trapped by a well casing cap and another being pulled into a gate valve. It concludes with advice on equipment selection and techniques to mitigate Delta P hazards, like using covers with screens or multiple holes to prevent body seals.

10:03

🛡️ Recognizing and Preparing for Differential Pressure Hazards

The final paragraph reinforces the message of the video, which is to raise awareness about differential pressure situations. It advises viewers to recognize these hazards in advance and to be prepared to handle them. The paragraph suggests learning the layout of the site and understanding how the system functions to calculate potential forces. It also recommends techniques such as cutting slots instead of holes for draining water and using covers with screens to prevent getting trapped by Delta P forces. The goal is to avoid becoming another statistic in the list of commercial diving fatalities caused by differential pressure.

Keywords

💡Commercial Diving

Commercial diving refers to diving activities performed as a profession rather than for leisure or sport. It often involves underwater construction, maintenance, or salvage operations. In the video, commercial diving fatalities are discussed, highlighting the inherent risks and the importance of safety measures in this field.

💡Delta P

Delta P, or differential pressure, is the difference in pressure between two bodies of water or areas. It is a central theme in the video as it is identified as the common cause of many commercial diving fatalities. The script emphasizes the dangers of Delta P, which can be invisible and strike without warning, leading to tragic accidents.

💡Equalization

Equalization in the context of the video refers to the natural process where two bodies of water seek to balance their pressures. This can create dangerous conditions for divers, as the force of water trying to equalize can be immense, as illustrated in the script with the example of a valve being opened and the resulting force on it.

💡Force of Water

The force of water is a critical concept in the video, describing the pressure exerted by water due to differences in depth or other factors. The script provides a formula to calculate this force, which is crucial for understanding the potential hazards divers face, especially when near openings or valves where Delta P can occur.

💡Lockout Tagout Procedures

Lockout tagout procedures are safety measures used to ensure that machinery or valves are not accidentally or unintentionally started during maintenance or repair. The video script underscores the importance of these procedures in preventing accidents related to Delta P, by ensuring that no unexpected movements or releases of pressure can occur.

💡Pre-job Meeting

A pre-job meeting is a preparatory session conducted before starting a job, especially in high-risk professions like commercial diving. The video emphasizes the importance of these meetings for understanding the site layout, piping and valve systems, and recognizing potential Delta P hazards to ensure the safety of the divers.

💡Diver Fatalities

Diver fatalities, as mentioned in the script, are tragic outcomes that occur due to various hazards in commercial diving, primarily Delta P. The video uses real-life incidents to illustrate the severity of these accidents and the need for proper safety precautions to prevent them.

💡Schematic

A schematic in the context of the video refers to a simplified diagram or representation of a site's layout, including the piping and valve systems. The script suggests that diving supervisors should have a site-specific schematic to help identify potential Delta P hazards and plan safe diving operations.

💡Diver Equipment

Diver equipment in the video includes the gear and tools used by divers during their operations. The script advises on choosing equipment that won't interfere or become fouled in Delta P situations, ensuring that divers can work safely and be easily retrieved if needed.

💡Communication

Communication is highlighted in the video as a vital aspect of safety in commercial diving. Divers must be able to communicate with those on the surface at all times to alert them of any issues or to request assistance, which is crucial in the event of a Delta P incident.

💡Awareness

Awareness, in the context of the video, refers to the recognition and understanding of potential hazards, particularly Delta P situations. The video's goal is to raise awareness among divers and those in the diving industry about the dangers of Delta P and the importance of being prepared to deal with it.

Highlights

Delta P, or differential pressure, is a leading cause of commercial diving fatalities, accounting for two out of three deaths.

Delta P is invisible and strikes suddenly without warning, making escape nearly impossible once it traps a diver.

The pressure exerted on a valve can be enormous, depending on the difference in water depths and the diameter of the pipe.

A formula is provided to calculate the force of water through a hole at a particular depth, which is crucial for understanding Delta P hazards.

Diver safety can be compromised when working near dams, pool drains, and water towers due to the risk of Delta P.

Incidents are recounted where divers were trapped and drowned due to the force of rushing water through drains and valves.

Divers must be aware of their surroundings and the potential for Delta P when working in or near bodies of water with different pressures.

Pre-job meetings are essential for understanding site layouts and the operation of piping and valve systems to mitigate Delta P risks.

Lockout tagout procedures are emphasized as a method to eliminate machinery and valve accidents, thus preventing Delta P incidents.

Divers are advised to choose equipment that allows for clear communication and visibility, reducing the risk of getting trapped by Delta P.

Techniques such as recognizing potential forces, calculating water force at depth, and using covers with screens can help reduce Delta P hazards.

The importance of having a site-specific schematic and diving checklist is highlighted for pre-job preparation.

Divers should ensure their equipment will not interfere or foul when working in environments with potential Delta P situations.

The video emphasizes the importance of being prepared to deal with differential pressure situations to avoid becoming a statistic.

A call to action is made for divers to avoid adding their names to the list of Delta P fatalities by being vigilant and prepared.

Transcripts

[Music]

this is a partial list of the commercial

diving fatalities over the past 15 years

all have one common cause Delta

P two out of three commercial diving

fatalities involve Delta P it is

invisible to a diver and it strikes

suddenly without warning There is almost

no way to escape once it grabs you

knowing what it is where it lurks and

how to avoid its grasp is the subject of

this

[Music]

video Delta P stands for differential

pressure our discussion refers to

situations where the pressures between

two bodies of water are dramatic

different in a situation like this the

bodies of water continuously seek to

equalize themselves in this example the

body of water on the right wants to rush

to the body of water on the left by

means of the pipe between them the

pressure exerted on the valve stopping

this water transfer can be enormous

depending on the difference in the

depths of the water and the diameter of

the pipe if the difference between the

depth of water is 50 ft and the diameter

of the pipe is 10 in the force of water

exerted on the valve is nearly 1,700

lb if the valve was suddenly opened and

your arm was near it would be sucked

into the hole

instantly trying to remove your arm

would be like trying to lift a car

completely off the ground with one hand

you could only remove your arm if the

pressures between the two bodies became

nearly equalized but at the pressure in

this example your body makes a perfect

seal stopping the bodies of water from

equalizing the formula for calculating

the force of water through a hole at a

particular depth

is the area of the

hole multiplied by the difference in

water depth multiplied by the PSI per

foot of water depth or in the situation

just described the 10-in hole equals 78

square in time 50 ft of water depth time

0.432 PSI per foot of freshwater depth

equals

1,685 lb of water pressure if you are

diving in saltwater be sure to use

0.445 PSI in your formula

instead you can't see or feel a Delta P

situation as you dive near it it grabs

you suddenly and it doesn't let go until

the pressure is equalized when it's got

you it's

gotcha as you watch the following

Recreations of actual Delta P incidents

ask yourself if you have on occasion

ventured into situations without being

thoroughly

prepared diver 1 enters theall Water

behind the dam structure in order to

clean the strainer of the Dam's drain

when the drain is cleared the tremendous

force of Rushing Water through the drain

grabs hold of diver 1 sucks him

partially inside and traps him diver 2

enters the water to help diver 1 and

becomes trapped

also diver 3 enters the water to rescue

divers 1 and two and after 40 minutes

returns to the surface with both divers

they are

dead diver 3 was hospitalized for

injuries suffered in the rescue

[Music]

attempts a scuba diver was repairing a

pool bottom at a depth of 10 ft he came

close to the open pool drain and was

drawn against it his body made a perfect

seal against the drain he was diving

alone and had no tender at the surface

no one knew he was trapped he ran out of

air and

[Music]

drowned two scuba divers entered a water

tower to unclog a drain using a fire

hose to blast away the silt and mud that

was clogging the drain the drain

suddenly opened a great suction

immediately occurred diver 1 was pulled

into the drain visibility was Zero diver

2 did not know that this had occurred

diver 2 surfaced Thinking diver 1 had

already come up diver 2 made repeated

but unsuccessful attempts to find him

diver one ran out of air and died

neither diver was Tethered to the

surface had communication with the

surface or with each other

[Music]

a surface Supply diver was working

offshore in 86 ft of water on a well

re-entry project he was using a drill

string to hook a trash cap inside a

13-in well casing the first attempt

failed to catch the cap the diver was

asked to stand by the hole to make sure

the string caught the cap he reported

when he saw the cap was hooked and began

to leave the drill string was pulled to

the surface rapidly because the cap was

nearly the size of the casing a great

suction developed as the cap came free

the Rushing Water grabbed the diver and

forced one leg into the hole up to the

pelvis the diver was

[Music]

killed diver one enters the water at a

hydroelectric generation plant his

assignment is to seal off leaks in a

large gate valve the three-person dive

team is assured by the plant's operating

Personnel that the gate valve is closed

diver one surfaces and reports that he

thinks the valves are

open the winch is started and closes the

valve a 30-in SLO gate is manually crank

shut the dive team questions the plant

personnel the valve indicator shows the

valve not fully closed plant Personnel

reply that the indicator is never

correct and typically the valve is

cranked until tight diver 1 re-enters

the water convinced that everything is

okay in a few moments he begins to

scream the dive supervisor tries to

contact diver one on the intercom the

tender and supervisor pulled the

lifeline and umbilical both have broken

from their attach match points the gates

are cycled open while waiting for the

rescue divers two attempts by the

company diver failed to locate diver 1

12 hours later diver 1's body is

[Music]

recovered when you accept a new job make

sure you take part in a pre-job meeting

again how are you right good be sure

that you understand the layout of the

site and how the piping and valve

systems work

together the diving supervisor should

have a simplified but site specific

schematic of the site and a diving

checklist to make sure nothing is on or

open that shouldn't

be your client also needs to know about

delap P if they take your concerns

lightly make sure they understand the

life-threatening hazard

always practice lockout tagout

procedures these are tried and true

methods that can eliminate machinery and

valve accidents if practice

religiously make sure to consider the

potential Delta P hazards of your new

assignment when choosing your

equipment make sure others in the water

and on the surface can tell exactly

where you are they should be able to

communicate with you at all times and be

able to get you out if you're

stuck make sure your equipment won't

interfere or become fouled if you must

be near a Delta P

situation there are certain techniques

that you can use to help reduce and even

eliminate delt P hazards the first step

is to recognize the potential forces

working on each other in your

environment learn the layout of the site

and how the system

functions calculate the force of water

at the depth you're working based on the

size of the openings at that

depth instead of cutting holes to drain

water or relieve pressure cut slots if

your body or equipment can't make a good

seal against the flow of water you can't

get

stuck fabricate a cover for the drain

that has a screen or make a cover that

has more than one hole a good distance

away from the other the idea is the

water can still get through even if your

body gets in the

way the goal of this video is to make

you aware of the potential for

differential pressure situations the key

is to recognize them beforehand and make

sure you are prepared to deal with them

because when it's gotcha it's

gotcha don't add your name to this list

[Music]

[Music]