Tech gas blender

Trimix - Heliox - Nitrox

Gas Blender

 

 

In the first screen-shot you can see the basic assumptions, like the calculation algorithm and the isotherm temperature (you can set these options in Menu, Settings).

 

Tech Gas Blender relies on a clear process workflow, not showing too much at once; you will be asked for the needed info according to the principle "only show what you need, when you need it" (see also GUI -Graphical User Interface):

 

The basic settings

 

The filling method:

In Real Gas mode each gas sequence has a fully dedicated calculation routine.

 

In the final step, you will have the filling procedure with some information about the resulting mixture, including the depth where the mixture achieves the PO2 and the END values you set in Menu, Settings, "Set Warnings Limits".

 

From this screen-shot, press "Next" to see the filling cost,  for both the total gas and "added only".  At this point, you can change the cylinder (and single/twin mode) and refresh the cost at real time.  

Tech Mixtures Blender

In this section there are the functional features for filling calculations of all the technical mixtures: EANx, Heliox and Trimix.

It is a particular progressive "What if" feature: it allows to calculate the mixture results filling a starting mix with another gas/mix.

 

Enter the values for the starting composition and pressure mix, then the final pressure, the Top Off gas and the desired step in pressure.

 

Top Off gas can be any pure gas, air or mix.

 

The software will calculate the resulting mix composition for each step.

 

Compared to the "What if" (menu "Tools") the Top Off is a more practical feature, whereas the "What if" is useful to understand the gas behaviour and the origin of  blending mistakes.

Advanced  top-off

An improved cylinder equalizer: you can calculate the equalized pressure and the resulting mix in the target tank according to the Real Gas model.

 

Assumptions:

- One way direction flow: the gas moves only from the storage cylinder to the target tank, so the gas/mixture in the supply cylinder drops in pressure and maintains the same composition.

- The calculation does not take into account the loss of gas due to dead space in transfer system like whips, valves, pressure gauge etc.

 

Wait for the target cylinder gases to cool to analyze the mix; with Trimix you should use Oxygen AND Helium analyzers.

 

Be aware that not all mixtures homogenize instantly. How long these mixtures take to homogenize is still a controversial issue.

The molecular speed is highly dependent on their specific atom/molecular physical properties and characteristics, temperature, pressure, density, interactions between different gases, kind of cylinder (its geometry) etc.

 

Kinetic Molecular Theory is right for ideal gases. Unfortunately, Helium is in many respects far away from that.

 

Most Nitrox mix almost instantly, some may take a couple of hours. Unfortunately, it is not the case for Helium based mixtures: some Trimix can take more than 12 hours to achieve a homogenous state.

Equalization

In case you want to fill Trimix with the Blender option "Trimix Continuous Flow", you might need to know how to produce this mix in a "stick" without a Helium analyzer.

 

This can be done with 2 Oxygen analyzers in series: in the first stage,  introduce Helium to reduce the Nitrogen and Oxygen percentages, in the second inlet,  inject Oxygen to achieve the final mixture.

 

After each gas injection you need a mixing chamber with something to create turbulence and, at the end of the chamber, an Oxygen sensor.

 

In this section you can calculate the two Oxygen readings you must have for each stage, before the gas enters the booster/compressor:

 

Reading analyzer 1 - Oxygen % after injecting helium into the inlet gas mixture

 

Reading analyzer 2 - Oxygen % after injecting Oxygen into the helium enriched inlet gas mix

 

This is not the best way to blend Trimix: you are completely dependent on the sensor's accuracy (if you have residual mix, including its composition) and, if you don't have a Helium analyzer, Helium content is calculated by difference.

More on "Blending" - "Continuous Flow"

Trimix Continuous Flow Calculator

Standard partial pressure - the most common method, sequential single gas steps.

 

Continuous Flow (EANx only with target EANx and any mix in case of target Trimix). With this option the program calculates the needed gas fractions in order to avoid/reduce pure Oxygen handling. In case the Oxygen fraction in the calculated Continuous Flow is higher than the maximum safety fraction,   set in Preferences, then the program will ask for Oxygen filling.

 

Bank Mix (EANx only in case of target EANx, any mix in case of target Trimix)

The target Mixture (what you want)

 

The current Mixture (what you have)

 

In case you need to vent the current mix, the drain pressure will be shown. According to the settings in Menu, "Current Mix Management", other options will be presented if available.

In case of multiple gas sequence options, you will be asked for a choice.

In some cases there is no multiple sequence: for example in the standard EANx option, the only available gas sequence is Oxygen = > Air, and there will not be a proposal of any sequence choice. (Remember:  Air, when needed, is always the final gas of the sequence).

 

On the contrary, in case of a target Trimix 50/20 with initial empty bottle and with a source of BankMix EAN 33.3, the following six alternatives will be presented:

 
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