Rate of bladder inflation

[Michael.52]

Hey, question here;
what are the components that determine the rate of inflation of the bladder on my BCD? and assuming one would be interested in adjusting this rate, how would one do so?

LP port on first stage? inflation control (where the buttons are)? bungee around bladder?

 

[Tortuga68]

Not sure I understand your question...

It's determined by the low pressure (LP/IP) your first stage is providing

Why do you want to vary it?

 

[Michael.52]

This is mainly about curiosity on equipment, but I guess it can be applied if one would want to have finer control over tuning their buoyancy.

 

[Dsix36]

I always fine tuned my buoyancy with my lung volume. I type that in past tense since it does not work with my rebreather.

 

[Tortuga68]

From an equipment perspective it's pretty much fixed

Increasing the rate of inflation won't help with fine tuning of buoyancy

 

[DevonDiver]

I'm guessing that different low-pressure power inflator systems have different rates of inflation.

For instance:

Scubapro X-Tek "Scubapro's Balanced Power Inflator provides a High inflation speed.."

Tusa Active Purge Assist "Increased flow rates (inflate/deflate) for better performance over standard inflators.."

Plenty of manufacturers like to load their BCD descriptions with random three-letter abbreviations to give the illusion of technological advancement. The notion of 'high performance' low pressure inflators is a common theme.

Never quite worked out why a "high inflation speed" was a good thing for most divers though.....

 

[g1138]

Aside from the IP of your first stage, the inflator mechanism adds another factor. It depends how wide the inflator mechanism opens when you depress the button. Some inflators open wider than others.

With higher flow rate inflators, you're often able to depress the button slightly to get a slower inflate rate. Most inflators work this way.
With really really slow inflators, often times it's all or none. The inflator won't inflate until the button is fully depressed. In fact the movement of the button is only a very short distance, usually in these cases. The orfice for air input is also very narrow in these units.

Exceptions to this are Air 2's from various manufacturers and the Scubapro Inflator. They all inflate pretty fast, but the button only depresses a short distance. So in my experience I'm only able to inflate at the highest rate, so you have to have a pretty good trigger finger to fine tune.

 

[TSandM]

I know inflator valves vary in the rate of flow of air, because Halcyon inflators are much slower than the generic inflators I have on my wings.

But even the Halcyon inflator will allow pretty rapid filling if it is held wide open. Bouyancy control comes from finesse with the buttons, not trying to change the rate of flow.

 

[herman]

There are 2 components of flow rate- volume per time and time. If the volume per time is fixed then varying the time accomplishes the same thing. Most inflators inflate way too quickly to make fine adjustments with so instead of controlling flow, you control the time you hold the valve open. While you can throttle most inflators they do not throttle easily so the easier method of volume control is the vary the time you hold the button in. That said, BCs are for gross buoyancy adjustments, fine control is done with lung volume and cadence. If you are properly weighted and are not using thick wetsuits or very large tanks, your BC should remain unused during the dive. If you are touching it more than once or twice during a dive, you are overweighed and need to reevaluate your weights.

 

[clownfishsydney]

I really think that this is something that has never been really worked out. At the Gabe Watson murder trial questions were raised about how quick Tina Watson's BCD would have been able to inflate. It was never answered and I do not know how many seconds a BCD (of any brand or model) would be able to overcome xx pounds/kilograms of weight. I will have to time this with my BCD to actually work this out.