Delta P

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 video Delta P stands for differential pressure our discussion refers to situations where the pressures between two bodies of water are dramatically 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 feet and the diameter of the pipe is 10 inches the force of water exerted on the valve is nearly 1,700 pounds 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 four-foot of water depth or in the situation just described the 10 inch hole equals 78 square inches times 50 feet of water depth times zero point 4 3 2 psi per foot of fresh water depth equals 1685 pounds of water pressure if you are diving in salt water be sure to use zero point 4 45 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 got you 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 divert one enters the water behind the dam structure in order to clean the strainer of the dams drain when the drain is cleared the tremendous force of rushing water through the drain grabs hold of diver one sucks him partially inside and traps him diver two enters the water to help divert one and becomes trapped also diver three enters the water to rescue divers one and two and after 40 minutes returns to the surface with both divers they are dead diver three was hospitalized for injuries suffered in the rescue attempts a scuba diver was repairing a pool bottom at a depth of 10 feet and 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 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 one was pulled into the drain visibility was zero diver two did not know that this had occurred diver two surfaced thinking diver one had already come up diver two 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 a surface supplied diver was working offshore in 86 feet of water on a well reentry project he was using a drill string to hook a trash cap inside of 13 inch 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 camp 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 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 plants 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 inch sluice gate is manually crank shut the dive team questions the plant personnel the valve indicator shows the valve and not fully closed plant personnel replied that the indicator is never correct and typically the valve is cranked until tight diver one 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 and both have broken from there attached points the gates are cycled open while waiting for the rescue divers to attempts by the company diver failed to locate diver one 12 hours later divert one's body is recovered when you accept a new job make sure you take part in a free job meeting 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 Delta P if they take your concerns lightly make sure they understand the life-threatening hazards 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 delta 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're prepared to deal with them because when it's gotcha its gotcha don't add your name to this list

Channel: Sean Roos

Views: 3,363,717

Rating: 4.9447894 out of 5

Keywords: Commercial Diving, Hazards, Pressure, Underwater

Id: AEtbFm_CjE0

Length: 11min 28sec (688 seconds)

Published: Mon Oct 18 2010

Reddit Comments

[u/KeavesSharpi]

Now, imagine being the commercial diver going into the water after having watched this video as part of his OSHA mandated safety training.... NOPE. I QUIT.

[u/Beharkei]

Whoa. Thats a new way to crack open a crab.

[u/ripples2288]

Of all the gnarly shit I have seen on this sub, this is the most disturbing; even cracks are fatal (also they don't have eyes to poke out).

Whelp, time to design a rapidly expanding foam to fill in Delta P holes that can cleared by slowly introducing acetone through a hose NO ONE STEAL MY IDEA!!

[u/torankusu]

I saw this in a thread about the crab gif last year (there was a thread on the front page earlier; I'm guessing that's what inspired you to post this). One of the men was killed by being sucked through a 24 inch opening, similar to the crab being sucked through a crack in the pipe.

https://en.wikipedia.org/wiki/Byford_Dolphin#Diving_bell_accident

Subsequent investigation by forensic pathologists determined Hellevik, being exposed to the highest pressure gradient and in the process of moving to secure the inner door, was forced through the 60 centimetres (24 in) in diameter opening created by the jammed interior trunk door by escaping air and violently dismembered, including bisection of the thoracoabdominal cavity which further resulted in expulsion of all internal organs of the chest and abdomen except the trachea and a section of small intestine and of the thoracic spine and projecting them some distance, one section later being found 10 metres (30 ft) vertically above the exterior pressure door.

[u/bountyhunterdjango]

When it's gotcha, IT'S GOTCHA

[u/FluffyxBlanket]

This is actually so disturbing to know that people have actually died like this. I'll bet it's beyond gruesome...ugh...

[u/DucketShackleton]

Man, that really sucks.