Y-size bottle time calculations (as in how many hours of welding)

[julianf]

My Y-size is getting low. Ive done a bit with it, so i didnt really think anything of it, however, ive just done the numbers, and they dont seem to add up -

BOC says aprox fill - 5.02 cubic meters

So that's 5020 liters.

At 10lpm, that's then 502 min, or 8.36 hrs.

Now i really dont think ive had the trigger down for over 8 hrs...

I guess if i had it at 15lpm, then that would be 5.56 hrs, which is still a fair while - longer than it seems, for sure.




So, maybe i need a flow gauge. Ive got a pea shooter, but its not easy to use without a wire feed disable. Ive also got a dual gauge reg, but i know there not that accurate.

Also, when i start welding, and open the bottle valve, there's a bit of flow from the bottle. So the welder leaks a bit when not in use (and, therefore, i assume, when in use) but its not like the output gauge is at zero when i start, so it cant leak that much, surely?


I reckon stage one must be to get a flow meter, eg -

http://www.ebay.co.uk/itm/SWP-1242-ARGON-FLOWMETER-0-14-LPM-FOR-TIG-MIG-WELDING-x-1-/361083246697

?

 

[Swift&Bold]

You'll still get wire feed from setting up that flowmeter.
The pea shooter is more accurate, just release the wire from the feed rollers when you set up. I have similar to the ebay one and have to do the same with my R-Tech.

 

[julianf]

Yep, i know the one that fits on the reg does not affect the wire feed, but the ones that fit on the end of the shroud become unusable with the wire feed active.

I was thinking that, for the sake of a tenner, the one on the reg would offer a quick "at a glance" reading at any time, without having to mess about in the sideo the welder.

 

[Pete.]

If you have a pressure gauge at the flow meter it might explain why your calculations are not adding up. 10L/min at 2 bar is twice as much gas as 10L/min at 1 bar.

 

[Chris Stevens]

Using your pea shooter, notice the rush of high pressure gas every time you start welding? That increases the amount of gas used particularly if you are doing lots of stop start work, and makes it pretty much impossible to relate the gas you actually use directly to the amount in the bottle.

 

[julianf]

If you have a pressure gauge at the flow meter it might explain why your calculations are not adding up. 10L/min at 2 bar is twice as much gas as 10L/min at 1 bar.

This is the unit i have -

and then one of these -

So, the regulator shows bottle pressure, and then the 2nd gauge shows post-regulator flow - which should aways see the same pressure, right?

 

[Pete.]

This is the unit i have -

and then one of these -

So, the regulator shows bottle pressure, and then the 2nd gauge shows post-regulator flow - which should aways see the same pressure, right?

No, well yes but it might not be at 1 bar, which is how you have derived your consumption figures. The fill capacity is given in litres of gas at 1 bar, or one atmosphere. So theoretically if you have 100 litres and you use 10 litres/min then you have 10 minutes of gas flow, but that is only true if it's being measured at 1 bar. If there is a restriction down-stream of the flow meter then pressure will back up, the meter can still be registering 10l/min but at a higher pressure, which means a larger mass of gas is flowing through it.

Here's what you do to minimise your gas use - wind the regulator off, set the flow meter fully open and set the maximum flow by increasing the pressure at the regulator. This will not only reduce the total mass let out by the initial surge (because the pressure between the regulator and the gas solenoid is at it's lowest possible) but will give you the most economic use of gas whilst maintaining your required flow rate.

 

[MoreWellie]

10 litres/min then you have 10 minutes of gas flow, but that is only true if it's being measured at 1 bar

I don't understand this, I understand that the pressure generates flow but surely 10l/min is 10l/min regardless of the pressure in the cylinder. Otherwise how could we cope with cylinders filled to different pressures or even with the reducing pressure as the cylinder runs down?

For the original question. When you have finished a welding session do you always turn the tap off on the bottle? if you don't then gas could easily be leaking

When I finish I turn the bottle tap off and over the course of a few hours the remaining gas in the regulator and pipes bleeds out so that the gauges work down although if I turn the reg off as well then it takes ages for the pressure gauge to fully drop

If you can hear a continuous hissing when you turn the bottle on then you don't have things sealed properly. I had one cylinder that was really difficult to seal but generally find they are ok

 

[Pete.]

I don't understand this, I understand that the pressure generates flow but surely 10l/min is 10l/min regardless of the pressure in the cylinder. Otherwise how could we cope with cylinders filled to different pressures or even with the reducing pressure as the cylinder runs down?

Cylinder pressure is irrelevant, pressure at the flow meter is what matters. The most wastage is in the surge as Chris Stevens said.

 

[Chris Stevens]

I would guess for anyone using a small hobby bottle, that one of the surge reducing devices would pay for itself in lessening gas used quite quickly? Especially so in the case of lots of stop start welding, which means far more surges and much more wasted gas.

 

[jimcrow]

How about fitting a switch to the pinch rolller motor this will then allow peashooter flow tester to be used without any alterations to the wire feed, Try not ELECTROCUTE YOURSELF

 

[julianf]

Surely easier, and just as good to spend a tenner on one of those floating ball meters that goes on the bottle?

I understand about LPM at different bar. The LPM gauge on mine is pre solenoid, but post any flow control. So, you would thing that, with the solenoid open, the pressure would be fairly close to 1,bar, assuming no restriction.

Likewise, there is only the single pressure control on my reg, so everything post that point should be low ish pressure. But, sure, there will still be the surge, I guess, as it won't be atmospheric.

I looked at the bottle last night and its still got 40 bar in it, so 1/5 ish left. Maybe with too high a flow rate, and surge when starting, the numbers might seem to add up.

I should look into the surge devices.

 

[Swift&Bold]

Surely easier, and just as good to spend a tenner on one of those floating ball meters that goes on the bottle?

No need to, you already have a peashooter so you gain no more advantage with a static one.

I should look into the surge devices.

I guess if you're doing a lot of stop/start welding or tacking that would be a worthwhile consideration?

 

[Chris Stevens]

Surely easier, and just as good to nti spend a tenner on one of those floating ball meters that goes on the bottle?

I understand about LPM at different bar. The LPM gauge on mine is pre solenoid, but post any flow control. So, you would thing that, with the solenoid open, the pressure would be fairly close to 1,bar, assuming no restriction.

Likewise, there is only the single pressure control on my reg, so everything post that point should be low ish pressure. But, sure, there will still be the surge, I guess, as it won't be atmospheric.

I looked at the bottle last night and its still got 40 bar in it, so 1/5 ish left. Maybe with too high a flow rate, and surge when starting, the numbers might seem to add up.

I should look into the surge devices.

If you are welding inside try turning the gas flow down till there are obvious issues, then raise it until everything looks good. Will often be a lot less than settings that are often recommended. Anti surge device is good idea on hobby cylinders, but even better idea is to negotiate price on a W, which will very often work out cheaper than hobby size, if you are welding on a regular basis, and using more than 4 or 5 hobby cylinders a year.