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Why does Oklahoma Only fill to 3000 psi.?

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  • Why does Oklahoma Only fill to 3000 psi.?

    I have read in many of the posts that you guys get to fill up to 3600 psi. Here in OK I consider myself lucky to get any were close to 3000 if you hit it on the wrong day or something you might be looking for at the most 2000 psi. Any help in this area would be wonderful.

  • #2
    Re: Why does Oklahoma Only fill to 3000 psi.?

    Originally posted by BRodri View Post
    I have read in many of the posts that you guys get to fill up to 3600 psi. Here in OK I consider myself lucky to get any were close to 3000 if you hit it on the wrong day or something you might be looking for at the most 2000 psi. Any help in this area would be wonderful.
    Sounds like your station has marginal storage or high traffic. If it's an older dispenser it may only have a nozzle for 3000psi. If one or more cars fill up ahead of you, they may be drawing down the pressure so far that you are getting what little is left in the cylinders.

    Try talking to the station manager and see what there storage size is. and if he'd consider turning up the pressure some. If you are the first one to fill in the morning and you can't fill up, he should crank up his pressure about 500psi and see if that helps. You only have about 20% of usable pressure, meaning that you can only draw down 20% of your storage capacity and still have a 3000/3600psi fill. 50gge of storage only allows for 10 gallons drawn off before your fills begin to drop below the "full" filling pressure.

    A typical storage may have around 100gge of storage, so once a few cars have gone ahead of you, or a bus, you won't get a complete fill up. Inceased storage and a new dispenser should give better fills and allow for 3600psi vehicles. That should only cost about $50,000-$100,000 or more. Local AQMD (Air Quality Management District) or Clean Cities would probably provide grants to pay for the bulk of it. It just sounds like they have an old, outdated station that needs a complete rebuild.

    Virtually all vehicles marketed up until 2002 had 3000psi nozzles. After that the 3600psi standard was set. A new dispencer could pump both, or even a used one that's set up for 2 hose/dual pressure. That would be around the lower price figure I mentioned above. Good luck with that.
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    • #3
      Re: Why does Oklahoma Only fill to 3000 psi.?

      Most of the newer systems keep their storage tank between 4,500 and 5,000 psi. They also keep three sets of tanks. The first set has the most volume but it's only used for about the first 2,500 psi of the filling process. The second set is use for a bit more of the filling process and the third set tops off the tanks. This way the top off storage tanks don't drop in pressure as mush so you can get the complete and faster fill. Mike can pop in here and give us more information than I since he used to work on these systems.

      All of this gives the commercial filling stations the ability to refuel several cars before the pressure in the storage system get below 3,600.
      John

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      • #4
        Re: Why does Oklahoma Only fill to 3000 psi.?

        I would have to guess that ONG has refueling stations similar to most of the ones the Questar runs in Utah. The pump does not set the pressure delivered, but rather passes thru the pressure in the station storage tanks. So the storage is probably set at 3000 psi, and as Curt mentions as soon as someone draws it down the compressor has to kick in right away. So you always get less than 3000 psi.

        Someone should try to convince ONG to simply set their pressure in all station storage tanks to 3300 psi. This is not overly high for 3000 psi vehicles (well within tolerance), and generally ensures over 3000 psi fills at any given time.

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        • #5
          Re: Why does Oklahoma Only fill to 3000 psi.?

          Not quite right, the pump does set the max pressure delivered to the vehicle but if the pump is supplied with less pressure it can only fill up to what it's given.

          In newer stations the pumps my see 5,000 psi but will keep that down to about 3,000 or 3,600 for the vehicle.
          John

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          • #6
            Re: Why does Oklahoma Only fill to 3000 psi.?

            My guess would be storage. If this is an older system The storage is probably limited to 3650-4000 psi. If they are trying to fill to 3600 psi every vehicle after the first will get a short fill. For fast filling the gas is stored in 3 separated in to 3 banks. In a perfect world I will be divided so that 70% is the low bank. 20% is Mid And 10% is high. When The dispenser first starts to deliver fuel it is from the low bank. Once the flow of fuel reaches a given point it switches to the mid and finally the high bank. Most dispenser shut off on flow as well as pressure. In other words if you reach a given minimum flow before you reach the set pressure the dispenser will shut off. storage can be optimized through changing the set point. But once you reach A certain pressure thats all you are going to get.

            Lets look at the Long Beach fueling station, They have a total of 99,000 cubic feet of storage. It is in 9 cylinders 6 of which are 3500 psi.(low bank) and 3 at 4500 (2 mid, 1 high) Only 25% of that storage is usable so out of a possible 825 gge. only 206 GGE is usable. CE has installed a compressor package of 1000 cfpm. So it can replace the fuel taken out at a rate of 8.3 gallons a minute. lets say all 4 of the Los Alamitos school busses show up at one time The all take about 40 gallons at a time so there is 160 gge In the morning there are about 20 city of Long Beach vehicles that fill That is a conservative 100 gge plus privet cars Shuttles and you and me. The chances of running out of fuel are very slim (as long as the compressors are running)

            Now lets look at Garden Grove It has 33000 cf of 4000 psi storage in 3 equal banks. With 2-60 cfm compressors or 68 gge of usable storage and 1 gge per minute of compression 1 bus and 3 taxis would wipe it out. (my sizing of this station are from hearsay)

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            • #7
              Re: Why does Oklahoma Only fill to 3000 psi.?

              I don't know how old this system is i just know that the storage is just a group of class 1 tanks back in the back with a compressor that never seems to stop running here in claremore but even when the compressor isn't running (which i guess means it's back up to pressure) at the pump it never shows above 3000 psi. This is a real hassle in our summers because even at night the temperature doesn't get below low 90's upper 80's so we get horrible fill ups then but if the temperature is below 20 it doesn't read above 2300 so pretty much either way we get the same gas charge.

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              • #8
                Re: Why does Oklahoma Only fill to 3000 psi.?

                Let me clear this up real fast. In Oklahoma most of the station were built before 3600 PSI was the operating pressure. The storage pressure on most of the station is 3600 PSI max because of the DOT3AA cyclinders. With 3600 in the vessels and the way the control system is and the size of the compressor, 3000 is what you should get on a normal day. The biggest problem we have in Oklahoma is that the stations are running at 100% capcity. If you pull up and hear the compressors running you can assume that the storage has been pulled down and the compressor is working its tail off the put gas back in storage. These stations were all built and designed 10 to 15 years ago when there was not very many CNG vehicles on the road but ONG's own vehicles. I think ONG has done a great service by opening these stations to the public and every gallon of fuel I get from these stations is a blessing. Untill Private companies invest in CNG stations please dont hit our gift horse in the mouth to hard but thank the ONG folks any time you see them. The alternative is purchasing your own equipment then you can always fill to 3600 psi any time you want. We are in the process of turning our station public and we have spent almost $200K by the time we are done. This is not the most profitable business in the world and at .90 per gallon, I am sure that ONG is not making a ton of money. Please Be understanding

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                • #9
                  Re: Why does Oklahoma Only fill to 3000 psi.?

                  Tom is correct the cost of upgrade our storage to handle 3600 instead of 3000 was huge. The profit margin makes it hard to justify to the bean counters the investment. Just keeping the faith and making it avaible so maybe more will go CNG is our hope.

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                  • #10
                    Re: Why does Oklahoma Only fill to 3000 psi.?

                    I don't want to buck the system or in anyway be misconstrued as critcizing ONG, but what can be done about the pressure (or lack thereof) we are seeing here in Tulsa?

                    Short of somebody coughing up a few hundred G to put in a modern station... I don't think many of us have that much sitting around in our annual fuel fund.

                    I'm still the noob around here, with only 3 weeks of actual CNG ownership, but I love my truck, but honestly, it's not working out as well as I'd hoped. I commute 90 miles per day. I fill up in the evening on the way home, and as often as not, I find that I'm driving back to Tulsa at least 1/2 the trip on regular gasoline. 12 GGE tank, getting 3-4 GGE of gas isn't a great result.

                    I've tried morning fueling and have slightly better results there, but by the time I drive around Tulsa some during the day, no better results, and I end up buying 1/2 a GGE on the way home, just to get those last few PSI stuffed in the tank.

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                    • #11
                      Re: Why does Oklahoma Only fill to 3000 psi.?

                      I got 3100 psi on my first fill at the 50th and Sante Fe station. I didn't think that was bad considering all the use it gets.

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                      • #12
                        Re: Why does Oklahoma Only fill to 3000 psi.?

                        Since it's ONG maybe Pickens will pony up the dough for the upgrade.
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                        • #13
                          Re: Why does Oklahoma Only fill to 3000 psi.?

                          hey now i have to give credit where credit is due. and the pump in stillwater is the best by far that I have ever had the pleasure of using. i cam in with 100 psi left and it got me all the way to 2800. at 28 gge that was pretty impressive by anybodies standards. i don't know if this was a fluke or not but it made me very happy. so hey if ol' boone had anything to do with it. thank you for taking the money from California. LOL. not serious on that last statement

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