BetaCAP30 is a gas divider that uses 30 capillaries, to operate 31 dilution ratios (between 0 and 100% of the concentration to be diluted).
The choice of 30 capillaries is not aimed at carrying out tests on 30 steps, but to increase the diluter application flexibility reducing the number of required cylinder concentrations. With BetaCAP30 it is possible to perform linearity tests on 5 steps (0, 20%, 40%, 60%, 80%, 100% of the measurement range) using cylinders that contain up to 6 times the analyzer’s span concentration.
The mechanical stability of the capillaries, combined with the clean gases coming out from cylinders guarantees very low maintenance charge for a long time and a very low drift of the flows (gas to be diluted and diluting gas) that define the dilution factors. Each of the above flows is induced applying a differential pressure to the gas across the involved capillaries. In the diluter two electronic regulators with calculated set point, automatically provide balancing the pressures with a repeatability better than ± 1 hPa on 2000. Controlling automatically the differential pressures (input – output) the output pressure has not influence on dilution and also in the output diluted flow.
The possible difference in viscosity of the two incoming gases is automatically compensated by unbalancing the pressures applied to the capillaries according to the laws that govern the physical phenomena in laminar motion of fluids through small diameter tubes. Mixture viscosities calculation is suggested when differences in concentration of some component in span gas and in zero gas are higher of 1% : in this case you may find the self-calculation sheet at the link “Viscosities calculations”
The advantages of BetaCAP30
Extremely compact and robust, built to withstand transport shocks and to operate with maximum reliability in industrial environments. This feature is mainly due to the “manifold type” design and construction : a hundred or so fittings of various types and relative lengths of pipe are replaced by holes that intersect inside the solid body so as to build the desired functional design. Such joints will never cause leaks (due to loosening or breakage).
The use of “equal” capillaries: makes the selection process simple and very accurate in two phases (classification and final selection) and consequently allows obtaining low relative uncertainties even before the metrological calibration for all dilution ratios.
PID electronic control of the pressures, together with the quality of the sensors: it guarantees a high repeatability (± 1 hPa on 2000) of the pressures applied to the capillaries.
The possibility of assigning a calculated set point has allowed the implementation of accessory functions (compensations and modes of use) that add potential to the diluter without asking the user for a particular commitment.
The user is informed “in clear” by means of a 4 x 40 character display in five languages on everything it happens in the diluter that could interfere with the correctness of the results. When something is going wrong (with operational uncertainty worsened) a clear alarm appears to support the user decisions.
It seams too much ? Please ask for a demonstration
Functional diagram and operating description
Pneumatic diagram
Looking at the diagram we see how the different combinations of the EV1 … EV5 solenoid valves realize the 31 possible dilution ratios. The purpose of the solenoid valve EV6 is to provide a rest position (no flow) of the diluter. The electronic pressure regulation regulates the differential pressures between input and output: the pressures actually applied to the capillaries. The calibration of the sensors is done in the “static” way (without gas flow): the solenoid-valves are configured and the regulation valves are closed so that all the sensors receive the pressure applied to the output. The only purpose of the calibration is the balancing of the sensors (not the individual measurements): therefore the value of the reference pressure applied is not critical (no traceability is required).
Continuous dilution with capillaries ? Yes, we can and we do it
All capillary dilutors produce a discrete number of dilutions, and the number depends on the amount of the installed capillaries. The excellent performance of the pressure regulation system and the relative simplicity of the rules governing the physics of capillaries led us to equip BetaCAP30 with two operating modes:
- Selection of the dilution ratio at 31 discrete steps is the typical mode of systems using capillaries or orifices
Selection of the target concentration with continuous coverage of the dilution range between 0.5: 30 and 29.5: 30 is the typical mode of MFC continuous systems.
The graph shown above makes both operating modes quite clear: the series of steps corresponds to the number N of capillaries crossed by the gas to be diluted (it grows from 0 to 30 as the dilution ratio indicated on the x axis increases). At the central point of each step the P1 / P0 ratio (gas pressure to be diluted divided by diluent gas pressure) is unitary and the corresponding dilution ratio is equal to N / 30. to the right of these points the P1 / P0 ratio grows and the dilution ratio increases almost linearly, while on the left it decreases. The P1 / P0 ratio is reversed at each change in the number of capillaries affected by the gas to be diluted.
Versions and options
BetaCAP30 is available in two versions with reference to the type of case: “CP” stands for compact version and “RK” stands for Rack version 19 “. The cost does not change depending on the case.
Two alternatives are also available with reference to the materials in contact with the diluted or diluting gases: the standard version uses fluorinated plastics and perfluorinated elastomers, while on request (with surcharge) the version is available entirely in AISI316L steel (with a few exclusions): this version has the same degree of immunity to corrosion, but guarantees lower permeability to gases even when the external connections are made of steel and greater safety if toxic and / or flammable gases are handled.
The InfoCAP3000 software package is available as an option, developed to automate and document linearity tests. A detailed description of the functions is available on this site.