Surprise! A HP 100 <> HP 100

[rx7diver]

One of my big regrets is selling my HP 100's (Sherwood Genesis 3,500 psig, manufactured by PST). They were amazing tanks when worn as singles when I was diving dry. However, as they were too short (for me) to wear comfortably as back-mount doubles--too difficult to reach the valves--I sold them and purchased HP 120's (also PST HP 3,500 psig), whose 28" length is perfect (for me) for doubles when diving dry. Paradoxically, this same 28" length leaves them too long for me to dive comfortably as singles!

I haven't needed big doubles for almost 15 years!

I decided that this year I would purchase, finally, a new pair of HP 100's (to dive as singles with drysuit), but was surprised to discover that a Worthington HP 100 (a) has a nominal capacity of *only* 95 cu ft (versus the 102 cu ft of my old PST HP 100), and (b) has length of *only* 22 inches (versus the 24 inches of my old PST HP 100)!

Can any of you who are approx 6'2" comment on your own experience diving dry with the Worthington HP 100? I own a pair of PST HP 80's (purchased new in 1988!) which I absolutely love as singles (diving dry)--except that their 20" length leaves them *much* too short for me to reach the tank valve. I suspect that the 22" Worthington HP 100 will be, like the PST HP 80, much too short for a drysuit diver who is approx 6'2".

Also, to anyone who has dove *both* the 102 cu ft PST HP 100 and the 95 cu ft Worthington HP 100: Did you miss the additional 7 cu ft of gas?

Thanks in advance for your replies.

Safe Diving

rx7diver

 

[tbone1004]

thought the worthingtons held 99.5cf when full? They are completely different animals since they use a different grade steel, they are heavier for the same volume. Almost a full 5lbs more steel required, most of it in the crowns, especially since the walls are 2 inches shorter, it's a very different beast indeed. They are also almost a full 1lb more negative than the old PST's, so while you can dive PST 100's, and 120's all using the same ballast because they have identical buoyancy specs, the worthingtons add more factors. The HP8's are actually 3.3 negative, so they are the oddballs.

You are better off hunting for a set of the old HP100's which do come up fairly regularly. The older OMS112's/Faber 108's might be a good option as well, they are 8" tanks so require cam adjustments, but they are a nice happy medium in tank height sitting right between the HP120's and the HP100's, and have similar buoyancy characteristics being 1lb negative when empty. PST HP100's and 120's are 1.3lbs negative

Also, just a nitpicky grammar exercise. The only true HP100's, are the old PST 3500 PSI tanks with the 7/8 necks. PST also made E7 series which were the first of the 3442 tanks, and predecessors to the Worthington X series with the 3/4 valves. These are not true "HP" tanks according to the DOT which is why they are allowed to have 200bar valves and yoke inserts. Unfortunately nothing like the old PST's are getting made anymore which is why I'm holding onto as many as I can. Trying to find a set of PST 45's, 100's and 104's right now actually.

 

[rx7diver]

thought the worthingtons held 99.5cf when full? They are completely different animals since they use a different grade steel, they are heavier for the same volume. Almost a full 5lbs more steel required, most of it in the crowns, especially since the walls are 2 inches shorter, it's a very different beast indeed. They are also almost a full 1lb more negative than the old PST's, so while you can dive PST 100's, and 120's all using the same ballast because they have identical buoyancy specs, the worthingtons add more factors. The HP8's are actually 3.3 negative, so they are the oddballs.

You are better off hunting for a set of the old HP100's which do come up fairly regularly. The older OMS112's/Faber 108's might be a good option as well, they are 8" tanks so require cam adjustments, but they are a nice happy medium in tank height sitting right between the HP120's and the HP100's, and have similar buoyancy characteristics being 1lb negative when empty. PST HP100's and 120's are 1.3lbs negative

Also, just a nitpicky grammar exercise. The only true HP100's, are the old PST 3500 PSI tanks with the 7/8 necks. PST also made E7 series which were the first of the 3442 tanks, and predecessors to the Worthington X series with the 3/4 valves. These are not true "HP" tanks according to the DOT which is why they are allowed to have 200bar valves and yoke inserts. Unfortunately nothing like the old PST's are getting made anymore which is why I'm holding onto as many as I can. Trying to find a set of PST 45's, 100's and 104's right now actually.

tbone,

Thanks much. I just double-checked the Worthington tank specs. (I just looked on the XS Scuba Web site.) You're quite right: Nominal capacity is 99.5 cu ft. And length is 23 inches (22.7") rather than 22". My apologies. I should have double-checked before sending out the op.

EDIT. Yes, I've dove the OMS 108/112's as singles (with drysuit). And, yes, they were excellent. But, about the same length as Al 80's (~26"), and 8" diameter rather than 7.25." So, they won't do for what I'm looking for.

Alas, I think you're quite right: I should wait for some PST HP 100's (3,500 psig) tanks to show up on the used market. Thanks again.

Safe Diving,

rx7diver

 

[lemke]

I dive singles... 100's, 108's, 119's, and 120's. I have never had a reason to "quickly" reach a tank valve while diving singles. Plus, I always found it easier to unbuckle and swing my plate around due to my jacked-up shoulders from rugby, LOL.

 

[tbone1004]

no worries. What is the difference for you diving wet vs. dry with tank length? For me length is length if they're on my back, so it's I either turtle over backwards, or am pushed forwards. The tanks all sit the same height on the STA if I'm diving singles, same as always putting the tank bands right below the crowns on doubles, so tank height only effects my ability to sit.

 

[rx7diver]

LENGTH: I can reach my valve (with a bit of effort) when diving dry and a 24" PST HP 100 (3,500 psig) single. I cannot reach my valve in this situation if I switch out the 100 for a 20" PST HP 80 (3,500 psig).

WEIGHT/BUOYANCY: I use a 3/2 mm when diving wet, with ~6 lbs on my weight belt in freshwater when using an old-school steel 72 and plastic backpack or Scubapro Stab Jacket and no additional weight. So the HP 100 is too negatively buoyant (and the HP 80 even more so) to use.

---------- Post added September 22nd, 2014 at 04:04 PM ----------

I dive singles... 100's, 108's, 119's, and 120's. I have never had a reason to "quickly" reach a tank valve while diving singles. Plus, I always found it easier to unbuckle and swing my plate around due to my jacked-up shoulders from rugby, LOL.

lemke,

I described elsewhere on SB, a Great Lakes solo ascent where I did just as you describe, but from ~135 ffw and a bit off the anchor line. Too much drama! Much easier to reach over one's shoulder, shut down the valve, and go to bailout. Of course, I knew all this at the time, but I chose to dive the way I did anyway!

EDIT: I just looked. The post I was referring to is here: http://www.scubaboard.com/forums/ad...475964-free-flow-incidents-4.html#post7035602. However, the details are absent. Those I wrote on a Facebook post. Here they are:

"Another view of a free-flow. Taken from my air-integrated computer after an actual recreational dive in Lake Huron, June 28, 1996. First graph shows the depth (blue line, left axis) and *temperature* (green line, right axis). Run time is on horizontal axis. Max depth is ~130 ffw. Water was cold at the surface (~48 F) and colder at depth (colder than 39 F, as tank was still cooling when I began my expeditious ascent at run-time ~05:45 mm:ss).

"Second graph shows depth (blue line, left axis) and *tank pressure* (green-yellow line, right axis). Tank (HP 80) is full (82 cu ft) at 3,500 psig, so dive was begun with a partially used tank (~2,500 psig). Free-flow began at run-time ~05:45 when tank still contained ~1,800 psig. Although ascent was begun almost immediately, and despite some "creative" measures taken toward the end, I ended the dive at the surface with a virtually empty tank. I was using a single Poseidon Odin (1st stage) + Scubapro D400 (2nd stage) regulator. This illustrates just how fast a free-flow through a high-performance reg can empty a tank!

"[There] were three of us in single file going to inspect something that had blipped the fishfinder. Lead diver had tied his reel to the anchor line, and we were venturing away from the anchor. I was at the rear. I felt my reg getting a little wonky--often you'll get some small hint if you're paying attention--and then swam forward to signal the others what was up and that I was going to ascend. I had traveled back just a few yards as the other two continued on their way, when the reg cut loose completely. I still remember thinking: 'Don't screw this up, Ronald.'

"Okay. The rest of the story: As I was ascending among all the noise and vibration and bubbles and monitoring my remaining air supply, I saw that I might run empty before I reached the surface. Rather than increase my ascent rate, I pulled off my Scubapro BC, swung it around in front of me, and then eventually began alternately turning off the valve, and then turning it on again (when I needed to take a breath)--while continuing to ascend while venting air from my BC and drysuit. This explains the blips that can be seen toward the end of the pressure curve. No big deal given our ... training, though you should have seen the Captain's eyes when I surfaced cradling my gear! (People on board can very readily see evidence of a free-flow at depth. The surface virtually boils, since air released at depth increases volume tremendously as it rises.)

"[My] HP 80 is such a short tank (~20 inches) and sits so low on my back in my Scubapro BC that I cannot reach my tank valve when I'm wearing it (especially when I'm wearing my drysuit), which is why I doffed my BC during the above incident. If I had been wearing a longer tank (e.g., a 25" steel 72, or a 26" Al 80, or, especially, a 28" HP 120 or 29" LP 126), then I would have simply reached over my shoulder to turn the valve on and off as needed—the way we all did, ad infinitum, throughout [our] training. The upshot: (1) A freeflow at depth can leave you empty incredibly quickly, so it must be managed without hesitation, and (2) there are so many ways my dive could have been done so much better (beginning with a better gear choice) so that this type of not-improbable incident could have been handled so much easier and without so much drama."


Safe Diving,

rx7diver

 

[fire_diver]

no worries. What is the difference for you diving wet vs. dry with tank length?

For me it has to do with the amount and location of buoyancy. My Worthington "HP100" doubles were impossible to wear with my wetsuit, even a 7mil wetsuit. The shortness of the tanks made me stand on my head every time. I didn't want to add a ton of extra weight to my waist just to make them wearable. That set of doubles was the final push for me to get a drysuit.

 

[j2s]

Although most of my diving is CCR, I use to dive (both wet & dry ) w/bm double 7/8th HP100 PST's and Worthington Hp100's.....I'm 6' 4" and preferred the PST's.....Even when both sets were 'cave filled' to 3800-4000, the PST's had better trim/buoyancy characteristics.....Go to Cave Diver's Forum and read a recent thread on tanks.......A lot of what has been published ( even by the manufactures ) about HP tanks is inaccurate....The Cave Diver's post/thread clears up the misinformation.........I sold off the Worthingtons and when I dive bm/doubles, it's w/PST HP100's and HP120's......

 

[rx7diver]

For me it has to do with the amount and location of buoyancy. My Worthington "HP100" doubles...

Although most of my diving is CCR, I use to dive (both wet & dry ) w/bm double 7/8th HP100 PST's and Worthington Hp100's...

fire_diver and j2s,

My op pertains to *single-tank* diving (rather than double-tank diving). Specifically, I am asking ~6'2" dry-suit divers to describe their experience wearing a *single* Worthington "HP" 100 (vis-a-vis a *single* PST 3,500 psig HP 100, if possible).

Safe Diving,

rx7diver