Apeks flow rate

[herman]

A couple of thoughts on this.
First off, the MK-17 is more or less an Apex design so why would there be such a vast difference. My guess is the Apex numbers are wrong. In any case, as long as the flow is above what 2 divers can use and the IP remain stable the breathing resistance remains the same and that is all that matters, pretty much any low end reg can do that.

Sorry if Im not being clear. If a light is 5000lux and another light is 20000lux side by side the 20000lux light will be brighter. So can the same comparison be made when comparing SCFM or is it not as simple as that. Using my perhaps funny logic I would have thought based on the different SCFMs then a higher flow rate would equal better breathing?

This is not an a valid comparison. You use lights at "full flow" if you will, a reg will never see full flow except in a lab test. A better example would be to think of 2 identical faucets -both with a max flow rate of 10 gal/min connected to 2 different sources. One is connected to a fire truck capable of 500 gal/min with it's pressure set to 150 psi and another connected to a small electric pump capable of 50 gal/min and it's pressure set to 150 psi as well. If you open them both to a comfortable drinking amount, both will flow the same amount and you can tell no difference. Open both to full flow and again they will flow the same amount because the max flow of the valve is still 10 gpm and again you can not tell which is connnected to the fire truck and which one is connected to the small pump because both pumps are capable of more than the 10 gpm of the faucet. If you remove both vavles completely and the pipes behind both of them are capable of flowing 100 gpm now you will see a difference. The electric pump will be past it's max flow but the fire truck can keep up with flow to spare but why would you ever want to do that?
So what does all this mean? A good second stage can flow around 35 cfm or 70 for 2 at full freeflow (= valve fully opened) and even a low end reg can match that flow just as the electric pump can match the flow of a fully open valve. Any more available flow rate can not be used, it just will not fit through the hole. I doubt the Apex numbers, they are way off from what I would expect but even so, even at those numbers it can supply all the gas 2 freeflowing second stages can use. Unless you have some need to remove all the hoses from a first stage and get as much gas as you can, the max flow rate means nothing......except sales hype. Anything past what 2 working divers can use is just extra capacity and for all intends useless, just as the excess flow rate of the fire truck is to a faucet you drink out of.

 

[buddhasummer]

A couple of thoughts on this.
First off, the MK-17 is more or less an Apex design so why would there be such a vast difference. My guess is the Apex numbers are wrong. In any case, as long as the flow is above what 2 divers can use and the IP remain stable the breathing resistance remains the same and that is all that matters, pretty much any low end reg can do that.




This is not an a valid comparison. You use lights at "full flow" if you will, a reg will never see full flow except in a lab test. A better example would be to think of 2 identical faucets -both with a max flow rate of 10 gal/min connected to 2 different sources. One is connected to a fire truck capable of 500 gal/min with it's pressure set to 150 psi and another connected to a small electric pump capable of 50 gal/min and it's pressure set to 150 psi as well. If you open them both to a comfortable drinking amount, both will flow the same amount and you can tell no difference. Open both to full flow and again they will flow the same amount because the max flow of the valve is still 10 gpm and again you can not tell which is connnected to the fire truck and which one is connected to the small pump because both pumps are capable of more than the 10 gpm of the faucet. If you remove both vavles completely and the pipes behind both of them are capable of flowing 100 gpm now you will see a difference. The electric pump will be past it's max flow but the fire truck can keep up with flow to spare but why would you ever want to do that?
So what does all this mean? A good second stage can flow around 35 cfm or 70 for 2 at full freeflow (= valve fully opened) and even a low end reg can match that flow just as the electric pump can match the flow of a fully open valve. Any more available flow rate can not be used, it just will not fit through the hole. I doubt the Apex numbers, they are way off from what I would expect but even so, even at those numbers it can supply all the gas 2 freeflowing second stages can use. Unless you have some need to remove all the hoses from a first stage and get as much gas as you can, the max flow rate means nothing......except sales hype. Anything past what 2 working divers can use is just extra capacity and for all intends useless, just as the excess flow rate of the fire truck is to a faucet you drink out of.

Thank you for your very thorough explanation, I find it difficult to understand the math/physics side of it all and your analogy made it easier to understand.

This form Apeks:

Hi Simon,
After some digging around I have a figure of 2057 l/min

Regards

Mrs Gill Kaneen (formerly Hook)
Customer Service Manager
Apeks Marine Equipment Ltd
Website: Apeks Marine Equipment Ltd
Reception: +44 (0) 1254 692200
General Fax: +44 (0) 1254 692211

Aqualung: Aqua Lung - Recreational and Professional Diving Gear

For no other reason than curiosity I will ask the again.

 

[DA Aquamaster]

I suspect the 72 scfm reflects the max flow rate of the second stage not the first stage - or it is just a mis print. A really old flow by piston first stage can do 72 scfm and the FSR is going to do better than that.

As noted above 300 scfm is not practical in the real world. It's done by hooking the reg up to a constant supply pressure of 3000 psi with a much larger passage in the valve than you'd see on a scuba valve. Then the gas is released directly out the end port so no LP hose or second stage is involved. It's a meaningless number.

However it is not much less meaningful than total work of breathing numbers. The quickest way to great WOB is to put in a great big exhaust valve to reduce exhalation effort - it gives you the most bang for the buck, but usually leaves you with a wet breathing reg that can have good WOB but still have a high cracking effort and high inhalation effort needed to sustain gas flow.

The cheap and easy way to partially fix that is to install a flow vane system that creates a very strong venturi effect. That then leaves you with a wet breathing reg with a high cracking effort and an artificial feeling positive pressure phase in the breathing cycle - but great WOB numbers. So in other words it will breathe like crap from a subjective perspective but the test numbers will look GREAT.

Thus WOB numbers are basically useless in identifying regs that deliver performance defined as delivering plenty of gas while feeling natural/effortless in the water. That requires a reg that is not noticeably wet breathing, that has a low inhalation (cracking effort) and has only enough venturi effect to reduce the inhalation effort to a normal level rather than trying to inflate you. Sadly, the WOB numbers won't be phenomenal, but it will feel so much better and breathe much more naturally.

 

[knowone]

Breathe a reg, whilst
depressing the purge

 

[DA Aquamaster]

I don't normally see the need to disagree with Herman but the MK 17 isn't more or less than Apeks design. Both are diaphragm designs but that's about where it stops.

The MK 17 flows more than an Apeks diaphragm second stage for a couple reasons:

- Higher flow rates past the high pressure seat, due to the seat design and due to the orifice design, and
- higher flow rates due to a greater working range in the valve achieved with greater movement in the seat carrier, a thinner diaphragm and an extra washer over the diaphragm.

The devil is in the details. The flow rate for the MK 17 is listed as 225 scfm (again pretty meaningless as long as the number is greater than what you'd need to supply 2 second stages) and while the Apeks first stage won't do that they are still more than adequate. But they are not really the same design other than in general layout - like almost every other diaphragm first stage.

-----

More to the point 70-75 scfm is very good performance for a second stage and more than that is overkill so provided that the first stage can feed two of them without an excessive drop in IP, no more is really needed from a first stage.

 

[buddhasummer]

A couple of thoughts on this.
First off, the MK-17 is more or less an Apex design so why would there be such a vast difference. My guess is the Apex numbers are wrong. In any case, as long as the flow is above what 2 divers can use and the IP remain stable the breathing resistance remains the same and that is all that matters, pretty much any low end reg can do that.




This is not an a valid comparison. You use lights at "full flow" if you will, a reg will never see full flow except in a lab test. A better example would be to think of 2 identical faucets -both with a max flow rate of 10 gal/min connected to 2 different sources. One is connected to a fire truck capable of 500 gal/min with it's pressure set to 150 psi and another connected to a small electric pump capable of 50 gal/min and it's pressure set to 150 psi as well. If you open them both to a comfortable drinking amount, both will flow the same amount and you can tell no difference. Open both to full flow and again they will flow the same amount because the max flow of the valve is still 10 gpm and again you can not tell which is connnected to the fire truck and which one is connected to the small pump because both pumps are capable of more than the 10 gpm of the faucet. If you remove both vavles completely and the pipes behind both of them are capable of flowing 100 gpm now you will see a difference. The electric pump will be past it's max flow but the fire truck can keep up with flow to spare but why would you ever want to do that?
So what does all this mean? A good second stage can flow around 35 cfm or 70 for 2 at full freeflow (= valve fully opened) and even a low end reg can match that flow just as the electric pump can match the flow of a fully open valve. Any more available flow rate can not be used, it just will not fit through the hole. I doubt the Apex numbers, they are way off from what I would expect but even so, even at those numbers it can supply all the gas 2 freeflowing second stages can use. Unless you have some need to remove all the hoses from a first stage and get as much gas as you can, the max flow rate means nothing......except sales hype. Anything past what 2 working divers can use is just extra capacity and for all intends useless, just as the excess flow rate of the fire truck is to a faucet you drink out of.

A follow up:

I re asked the question to Apeks, this was their reply, I think they got a little grumpy, oops

Hi Simon,
It isn't up for discussion as it isn't a necessary detail for the performance of the regulator as I explained the flow rate is irrelevant and we do not use it for any marketing purpose I was given the figure from design dept, the figure somebody else has maybe incorrect.

Regards

Mrs Gill Kaneen (formerly Hook)
Customer Service Manager
Apeks Marine Equipment Ltd
Website: Apeks Marine Equipment Ltd
Reception: +44 (0) 1254 692200
General Fax: +44 (0) 1254 692211

Aqualung: Aqua Lung - Recreational and Professional Diving Gear

 

[buddhasummer]

I don't normally see the need to disagree with Herman but the MK 17 isn't more or less than Apeks design. Both are diaphragm designs but that's about where it stops.

The MK 17 flows more than an Apeks diaphragm second stage for a couple reasons:

- Higher flow rates past the high pressure seat, due to the seat design and due to the orifice design, and
- higher flow rates due to a greater working range in the valve achieved with greater movement in the seat carrier, a thinner diaphragm and an extra washer over the diaphragm.

The devil is in the details. The flow rate for the MK 17 is listed as 225 scfm (again pretty meaningless as long as the number is greater than what you'd need to supply 2 second stages) and while the Apeks first stage won't do that they are still more than adequate. But they are not really the same design other than in general layout - like almost every other diaphragm first stage.

-----

More to the point 70-75 scfm is very good performance for a second stage and more than that is overkill so provided that the first stage can feed two of them without an excessive drop in IP, no more is really needed from a first stage.

Thank you. I guess Ill be keeping my Apeks.