Delta P
Summary
TLDRThe 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
💧 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.
🚨 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.
🛡️ 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.
Mindmap
Keywords
💡Commercial Diving
💡Delta P
💡Equalization
💡Force of Water
💡Lockout Tagout Procedures
💡Pre-job Meeting
💡Diver Fatalities
💡Schematic
💡Diver Equipment
💡Communication
💡Awareness
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]
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