Gas Purity Analysers for Cylinder Filling

Quick answer

Online gas purity certification combines ACCURRA-S for O2, CO2, CO, CH4 and moisture impurities with ACCURRA-TCD for binary purity of hydrogen, helium, argon and nitrogen. Calibration history with deviation values gives an audit record for each filled batch.

Updated 2 November 2026 · Figures from Sarvesh datasheets

The measurement and why it matters

Purity grades are written as digits. 99.999 percent means 10 ppm total impurity. Certifying a gas to that grade means measuring each specified impurity, usually oxygen, moisture, carbon monoxide, carbon dioxide and hydrocarbons, against a limit. Grab samples sent to a lab give a result hours or days late; an online analyser moves that check to the plant floor and records the whole fill.

ACCURRA-S measures oxygen, carbon dioxide, carbon monoxide and methane with sensors chosen to the range, and moisture as dew point. The calibration history stores deviation values, which is a record that the instrument itself was in tolerance when the batch was certified. Optional cyclic and remote auto-calibration keeps it that way between audits.

For binary gases, helium, argon, nitrogen, hydrogen, nitrous oxide, neon and krypton, ACCURRA-TCD measures the main component by thermal conductivity with no reference gas.

Models and ranges

Model	Measures	Range	Sensor and notes
3015 / 3030 / 3130	Oxygen	ppm to 100 %	Electrochemical or paramagnetic
6015 / 6030	Carbon dioxide	0 to 5000 ppm; 0 to 20 or 100 %	NDIR
2015 / 2030	Carbon monoxide	0 to 1000 ppm; 0 to 100 %	Electrochemical; NDIR
4030	Methane	0 to 100 % (min 0 to 5 %)	NDIR
M015	Dew point	-80 to +20 C	Ceramic sensor
ACCURRA-TCD	H2, He, Ar, N2, N2O, Ne, Kr	Binary purity	Thermal conductivity

Process notes

Cylinder and tank filling

Cylinder filling stations take bulk gas, compress or pump it into cylinders and send them out under a purity grade. Industrial grades allow a few hundred ppm of impurity; high-purity and specialty grades allow only a few ppm or less. The filling manifold is the last place to confirm the grade before the cylinder leaves.

An online analyser on the manifold catches contamination from a bad purge, a leaking fitting or a wrong source gas. Because ACCURRA-S can hold calibration history with deviation values, you can show an auditor that the instrument itself was in tolerance when the batch was certified.

Gas purity certification

Purity grades are written as digits: 99.999 % means 10 ppm total impurity. Certifying a gas to such a grade means measuring each specified impurity, usually oxygen, moisture, carbon monoxide, carbon dioxide and hydrocarbons, against a stated limit. Grab samples sent to a lab give a result hours or days late.

Online analysis moves that check to the plant floor. ACCURRA-S measures trace oxygen with an electrochemical cell, carbon dioxide and methane by NDIR, and moisture as dew point, and it can report two gases from one sample. The output goes to your batch record through 4-20 mA or Modbus RTU over RS 485.

Sampling and installation

Internal fine filter and rotameter are standard. An optional internal sample pump and auto-calibration valves depend on the model.
Purge manifold and sample line between gases so that the previous gas does not bias the next reading.
Specify a dedicated analyser per gas family, or a short, well-purged switching arrangement designed with us.

ACCURRA-S sample specification: non-corrosive, non-toxic, non-flammable, non-condensing and dry, free from entrained oil; sample pressure 2 to 10 psig, regulated externally; flow about 1 LPM; dust below 3 micron. Where your sample differs, we design conditioning around it.

Send us your process data

Application data sheet

The same pre-order design inputs our engineers design from, online. Fill in what you know, leave the rest. Your draft saves as you go, and you can print or send it when ready.

Start the data sheet

What the data sheet asks for

Send what you have and we will ask for the rest.

The gases to measure, the range, and the accuracy you need
Background gases and their typical composition
Sample temperature, pressure and dew point at the tapping point
Dust level, and whether the gas carries tar, oil or condensable vapour
Process connection and, for ducts, the duct diameter
Where the sample vents to, and at what pressure
Area classification of the tapping point and of the analyser location, and the IP protection needed
Distance between the tapping point and the analyser
Outputs you need: 4-20 mA, dual range, relays, Modbus RTU
Calibration approach, calibration gas available, and whether blowback is required
Utilities at site: power supply, instrument air, nitrogen, steam and cooling water, and the ambient temperature range
The gases you fill and the impurity limits for each grade

Recommended Sarvesh products

ACCURRA-S

Impurity analysis in trace, percent and purity ranges.

View ACCURRA-S

ACCURRA-TCD

Binary purity of H2, He, Ar and N2.

View ACCURRA-TCD

ACCURRA-S 3090

Oxygen purity 95 to 100 %.

View ACCURRA-S 3090

Frequently asked questions

Which impurities can ACCURRA-S check?

Oxygen, carbon dioxide, carbon monoxide, methane and moisture or dew point, in ranges from ppm to percent.

Can I check helium or argon purity?

Yes, with ACCURRA-TCD, which measures the main component of a binary mixture by thermal conductivity.

Do your analysers keep an audit trail?

They store alarm, fault and calibration history with deviation values, protected by dual-level passwords.

Can I certify several gases on one analyser?

The sensor is matched to the gas, and the dual-channel version reads two gases from one sample. For several different gases, a dedicated analyser per gas is usual.

Gas purity analysers for certification and cylinder filling stations