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HP vs. LP / High Pressure versus Low Pressure steel tanks

Discussion in 'Tanks, Valves and Bands' started by bigcat, Apr 13, 2002.

  1. TX101

    TX101 Barracuda

    How many rods to the hogshead does your truck get again?
  2. rab

    rab Solo Diver

    # of Dives: 100 - 199
    Location: Cincinnati, OH
    My car gets about 489,888 rods/hogshead.

    It's easy

  3. Mo2vation

    Mo2vation Relocated to South Florida.... ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: 33472
    I checked here - no dice. Guess I'll wing it.

  4. MarcHall

    MarcHall Instructor, Scuba

    In theory yes, in practice maybe not.

    There is no longer any hydro facility in San Diego County that does the additional testing required for a + rating.

    I believe there was only one in Orange County, CA but they the last 4 tanks I sent in passed hydro but did not get the + rating. These were all Fabers on their second hydro.

    Marc Hall
  5. roakey

    roakey Old, not bold diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Colorado Springs, CO
    I think you have to look harder, I bet there's tons. All bulk bottles (like welding) that are steel are tested to the + and/or star rating; just about any decently-sized hydro shop should be able to do this.

    Colorado Springs, which is a pipsqueek town in the greater scheme of things has several facilities that can test for a + rating -- I just got my two PST 104s tested to the + rating about a week ago.

    It appears that there's 5 San Diego hydro facilities:


    Check with them.

  6. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    I dive the HP when I'm local (fills to 3500 aren't a problem) but travel with a LP to ensure I get a full fill.

    Dr. Bill
  7. murphdivers286

    murphdivers286 Public Safety Diver

    # of Dives: 200 - 499
    Location: Port St Lucie, Florida
    As a novice diver I would appreciate some advice on purchasing new tanks. My wife and I are presently used aluminum 80 cf tanks. My wife wants to have at least 800 psi on the boat after a dive without to much limitation on her bottom time. She knows that some people would say that is not necessary, but she would feel more comfortable. If my wife would feel more comfortable, than I personally say do it.

    We have been looking at the 100 cf neutrally buoyant steel tanks..??? I have been looking at posts, and been having trouble understanding some of the lingo. I'm assuming "HP" means High Pressure and "LP" means Low Pressure. I really don't know the difference between the two in relation to diving and equipment.

    Is the 100 cf steel tank too much or not enough? Does it matter if it is HP or LP? What is the difference? Any input would be greatly appreciated.
  8. Scubakevdm

    Scubakevdm ScubaBoard Sponsor ScubaBoard Sponsor

    Your question requires considerable dialog to answer. Some questions that come to mind are:
    1 What kind of diving will you be doing?
    2 How much sheddable weight do each of you have?
    3 Is there someone to fill HP where you dive?

    If you're ever gonna be down in Boynton, PM me and I can show you different tanks and talk to you about the pros and cons of each. I work for a dive op, but we don't sell tanks, so no-one's trying to pitch you anything. For what it's worth, I dive HP 100's.
  9. scubasean

    scubasean Loggerhead Turtle

    Hp = high pressure (usually a 3442 or so PSI fill pressure)
    lp = low pressure; generally 2650 psi fill pressure

    hp or lp, the tank is at capacity when filled to its rated pressure. Thus, a 100cf tank rated to 3442 psi has close to 100cf in it at 3442, at 70F (I think I have the temp correct, but may be wrong...). I say close because some tanks are slightly less than 100 cf but still called 100...go figure.

    A 100 cf lp steel tank will generally weigh slightly more out of the water than a HP steel 100 cf tank, and may be slightly larger. But, look at the buoyancy characteristics to see what you want.

    I have found that some dive shops have a tough time filling hp tanks, even though they rarely admit they are having a tough time...Their compressors are often rated for 3000 psi, and they have to use a booster to get to 3442...which means that after your tank cools, you have a short fill by 150 psi or so, since they couldn't get above the 3442 to compensate.

    I love the HP steel anyway, and have a few of them. I also have a neutral buoyant 80, and like it also..
  10. murphdivers286

    murphdivers286 Public Safety Diver

    # of Dives: 200 - 499
    Location: Port St Lucie, Florida
    we do recreational diving down to 120 at the most.
    I have about 18-20 lbs on my BC. But I do notice I have a problem keeping my face out of the water when I survice with an almost empty aluminum 80. It really gets aggravating at times. I feel like that glass bird fill with colored fluid that bobs back and forth.
    Yes, we have a shop that fills HP. They fill for the local Fire Department's scba which I believe requires above 4000 psi

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