Filling tanks to different pressures… 2400, 3000, 3300, 3500?

[noj3333]

When having tanks filled is it a big inconvenience for shop workers to ensure tanks are filled to their proper pressure? The reason I ask is because I like to use 100 cu/ft AL tanks when traveling and I know it very rare to get a proper fill (3300psi). I know almost nothing about fill stations/ compressors so if it’s a PITA I’ll just continue to live with the 2700-2800psi fills. If it’s a simple issue to address I’d prefer to give the fill tech/ my DM a generous tip and hope he remembers to fill my tanks properly for the duration of my trip…

 

[CuzzA]

When having tanks filled is it a big inconvenience for shop workers to ensure tanks are filled to their proper pressure? The reason I ask is because I like to use 100 cu/ft AL tanks when traveling and I know it very rare to get a proper fill (3300psi). I know almost nothing about fill stations/ compressors so if it’s a PITA I’ll just continue to live with the 2700-2800psi fills. If it’s a simple issue to address I’d prefer to give the fill tech/ my DM a generous tip and hope he remembers to fill my tanks properly for the duration of my trip…

The tanks need time to cool so they can be topped off. If you're wanting to have them fill your tanks and go then you'll never get a full fill. If you can drop them off with instructions or are willing to wait, then I see no reason why they wouldn't fill your tanks to their rated pressure. unless their compressor simply can't do it.

Communication is key.

 

[noj3333]

The tanks need time to cool so they can be topped off. If you're wanting to have them fill your tanks and go then you'll never get a full fill. If you can drop them off with instructions or are willing to wait, then I see no reason why they wouldn't fill your tanks to their rated pressure. unless their compressor simply can't do it.

Communication is key.

So at a resort (or shore diving in Bonaire), if a shop has enough tanks, where they're sitting for a day or two on end it should not be any issue to get a proper fill? I'd imagine most modern/ large dive operators are able to make 3300-3500psi. Would that be a safe assumption?

 

[boulderjohn]

It is no harder to fill a tank to 3300 than it is to fill it to 3000. It just takes a little longer. Yes, a hot fill will cool below the level of its initial fill, but any seasoned tank filler will know that and will know how much to overfill. I was just diving for 6 days in Santa Rosa, NM, and all our tanks were filled by a wonderful lady in a little shack by the Blue Hole. We used a variety of tanks with a variety of fill pressures. We just pointed at each one, told her what we wanted in them, and correctly assumed that was what she was going to give us.

If your tank is supposed to be filled to 3300 and it is being filled to 2700, you certainly have a reason to complain--and look for a different shop if they don't respond.

 

[noj3333]

@boulderjohn, thank you. I'll have no issue making sure I get a proper fill now.

 

[claymore]

Many shops will over fill tanks by 200 to 300psi and let them cool to working pressure. Working pressure is not the maximum pressure a tank can be filled to it is the pressure the in the tank at room temperature, 70 - 80 degrees.
Taking the time to let tanks cool and top them off to working pressure takes more time than they may have. My shop may have 20 plus tanks to fill on Monday after an OW I class and 30 plus tanks on a Monday after an OWII and AOW plus specialties weekend plus rentals and personal tanks. The shop has no dedicated fill person just the sales person, service tech and maybe the owner if he is in.

 

[tursiops]

Many shops will over fill tanks by 200 to 300psi and let them cool to working pressure. Working pressure is not the maximum pressure a tank can be filled to it is the pressure the in the tank at room temperature, 70 - 80 degrees.
Taking the time to let tanks cool and top them off to working pressure takes more time than they may have. My shop may have 20 plus tanks to fill on Monday after an OW I class and 30 plus tanks on a Monday after an OWII and AOW plus specialties weekend plus rentals and personal tanks. The shop has no dedicated fill person just the sales person, service tech and maybe the owner if he is in.

But those tanks probably aren't going to be used again until the following weekend. So there is plenty of time to just let them sit, then top them off.

 

[CuzzA]

So at a resort (or shore diving in Bonaire), if a shop has enough tanks, where they're sitting for a day or two on end it should not be any issue to get a proper fill? I'd imagine most modern/ large dive operators are able to make 3300-3500psi. Would that be a safe assumption?

It should not be an issue. At your LDS you would expect consistent service. When I go to my shop, they know I'll hang and shoot the **** for a half hour talking shop while my tanks cool to get topped off, but anywhere else I'm going to communicate that I want them topped off so there's no misunderstanding.

 

[tbone1004]

the way the fill stations are supposed to work is one of two ways.
First way is the cheap and time consuming way which is babysitting the pressure gauges. If that is the case, then there is no reason other than laziness or low banks with the compressor turned off for a short fill. That is really not excusable. Most all compressors actually pump out at 4500+psi, so there is no reason for a short fill on anything if the station is set up like this.

type 2 is the fancy way and the way most big fill stations are set up. There is a regulator on the wall that restricts outlet pressure of the banks. That regulator will be set to some pressure. Typically around 3200-3300psi, or 3000psi if the shop is run by an idiot. The extra couple hundred PSI is for cooling off. In this case, the tank monkey has to adjust the regulator in order to get a higher fill pressure. They may not be allowed to touch it, may not know how to use it, or are just ignorant and assume that AL100's fill to 3000. Many shops will just fill everything to 3000psi regardless of what it is. That is ignorance and/or laziness.

Your tank has a working pressure of 3300psi, you expect it to be room temperature with 3300psi in it

 

[northernone]

Short fills I wouldn't be shy about mentioning to the owner and requesting another tank. Some shops will intentionally short fill to get more dives in per day with reduced bottom time. I hope that's rare but have encountered it a few times.

A less confrontational way if to find who actually fills the tanks at the end of the day. Talk to them along with a generous tip the first day. Make yourself memorable and let them know you appreciate the job they are doing.

Reminded of that a few weeks ago. I picked up a tank and while small chatting mentioned how good a fill he gave me last time and how I appreciated the safely margin little extra helped me out... he voluntarily went and topped the current fill off just because I was grateful for the last one.

It's another story how to get cave fills.... I'm still learning the secret hand shake.