A BIG lesson learned--accidentally put a LP hose into a HP port

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CoopAir

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Last summer while about to do a solo shore dive in the Bahamas, I made a VERY dumb mistake that could have resulted in being killed or seriously injured. Luckily, I ended up with minor injuries and a $30 bill from the local clinic.

I must say that I was very hesitant to post this, but I feel obligated to do so, as I want others to learn from my bad mistake.

I consider it fair game to be taken to the cleaners by the members of this forum over the mistake I made, but I hope at the same time other will learn from this.

It all started when I arrived in Crooked Island with all of my equipment, except tanks and weights, as well as a 13 ft pony bottle that I would sling (which had its own 1st and 2nd stage of course).

As I am laying all my equip on the beach, the assembly of my tank and 1st and 2nd stage is straightforward.

Not long after, I screw on my 1st stage to my pony bottle and turn on the air.

I quickly realize that one of the holes is not ported as air is leaking out. I turn it off right away and look for one of the screws that ports it.

Unfortunately I am unable to find one, so I drive a few miles into town to see if Robbie (the main dive guy on the island) has something I can use instead.

Unfortunately he does not have a plug that fits the port, so he is able to give be a BC hose that will do the job. Before leaving his shop, I check the BC hose on his tank, and it works fine, so I take it back to the lodge and get ready to set it up on the spare port for my 1st stage pony bottle.

As I screw in the BC hose, it fits perfectly and I make sure it is tight, but not overly tight and turn on the air.

Almost instantly, the next thing I remember, was for about 1/10th of a second hearing a big rush of air, and then a VERY LOUD POP!!

I'm as shaken up as can be and instantly know that something burst, and run away from the tank and let it drain.

Due to the loud pop, it seems I have some pretty bad ringing in my ears as well.

Still in shock, I look and see that the inside of my forearm, about 4 inches past my elbow is really swelling up, and bleeding slightly.

I then run over back to the tank and see that the hose burst about 4'' downstream from the 1st stage.

Still shaken up, I run inside to the check-in area of the lodge and ask someone to take me to the medical clinic at Landrail Point.

10 min later, the nurse gives me a block of ice to apply pressure to the swelling, and luckily 15-20 minutes later, the swelling is on the decline.

About another 30 min later, she takes me into her office and the swelling is still decreasing steadily. I mention to her the ringing in my ear so she has a look inside both of my ears, but luckily, nothing looks out of the ordinary.

Meanwhile she is talking to the doctor in Nassau, and asks him if there is anything else that should be done.

I ask the doc if it OK to fly (I'm a private pilot) tomorrow to Rum Cay, and he tells me that is OK, as long as I minimize my altitude to 1000' or less, just to be totally safe.

It was not until I returned home that I realized that it was a mistake that I had made that caused the hose to burst as I had believed that it was a bad hose that I was given.

Not so!!

Talking with my NAUI instructor made it clear that it the bursting was clearly caused by attaching a LP hose into a HP port.

To complicate matters even more, the 1st stage that I had on my pony was of an earlier era, when the threads of the HP port and the LP hose could screw onto each other. If that had been a newer 1st stage, there is no way I could have made this blunder since they are now different sizes.

The biggest lesson learned was to MAKE SURE YOU KNOW what hose should go into what port, not just that it can screw on.

I made a HUGE mistake by ASSuming that I could just put in any hose that could screw into the unoccupied port, and it could have resulted in me being killed or seriously injured.

THANK GOD I only received minor injuries and I hope that by posting this, that others (especially new divers) can learn from this blunder I made.
 
it shouldn't have been possible to even get it in the port. The fitting sizes are different.

Was it a really old reg or something?

R..
 
I'll have to have a look at my regulators but I am pretty sure (at least on mine) the diameter of the LP ports are different from the HP ports specifically to prevent what happened to you.
 
And, to make it even more fun, it may be a larger diameter hole size rather than the pin hole found on more modern regulators.

Thanks for the warning.
 
HP ports changed to 9/16" from the same 3/8" ports used today for LP in the early 1980s, or maybe the late 1970s, to prevent the possibility of this kind of error. Of course SPG hoses changed at the same time.

Modern HP ports are actually 7/16" threads.

In the 60's and 70's both the HP and LP ports in US built regulators were commonly 3/8" threads. The LP ports kept the 3/8" thread size (for a little while some went to 1/2" thread, but I think that was short lived), but they changed the HP ports. I don't know the details of the HP port switch. It would be interesting to look at the catalogs from the 80's to see if any manufacturer mentions the switch.

I have plenty of vintage first stages and HP hoses with 3/8" threads.

In the old days we were very aware of it and were always very careful about it. As far as I remember the HP ports were always marked, but I still looked inside to port to double check. If you look carefully, it is normally easy to see the difference from the inside of an HP port and an LP port.

I still have the habit of looking inside the port (any size port). HP ports normally have a very small hole inside, while LP ports are designed for high flow with a noticeably large orifice. I am not suggesting to use this as an absolute rule, but it is one more piece of information to try to avoid a similar incident.

After more than 40 years servicing regulators, I still have a lot of respect for compressed air... maybe more... than I did in the 70's


I am glad to hear the injury was minor.
 
1977 or so.
Been there.
Done that.
By the grace of God above, did not get hurt.

Chug
Still making up new mistakes.
 
Poseidon used to use metric threaded ports and there might have been other Europeans, but they never became standards.

Once the 3/8” became popular with US manufacturers, it just spread.

I don’t know if the 7/19” was a coordinated effort from several manufacturers (or involving DEMA) or if it was adopted by some manufacturers and others followed, but in either case it made sense to stay with the same standard.


BTW, the ports standard is more than just the threads. The ports loosely follow the MS16142 (Mil standard) and SAE J514 (Society of Automotive Engineer standards). Those are O-ring seal pneumatic/ hydraulic ports standards that specify all the interface dimensions, including O-rings groove and threads dimensions.

I say it loosely follows that standard because most manufactures design their own O-ring groove/ cavity slightly different than the standard, but they are compatible.

---------- Post added January 3rd, 2015 at 08:54 AM ----------

I meant to post this in the other thread that spun-off from this one... Oh well, it is loosely related to this thread. Sorry about the confusion.
 
I have a Sherwood I bought new in '80 or '81 that has 3/8 thread on both HP and LP ports. Like Lewis H, I always double check to make sure I know what port I'm dealing with. This has been second nature to me, since I dove when this configuration was common, and I better not get complacent because I still have a number of vintage regs I use and work on. I have an old Poseidon 300 and it has the same issue in metric.

Glad your lesson was not too bad and a good reminder to all to be careful.


Bob
 

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