GASTEC

Calibration gas generating equipment

The Permeater is a gas generator for calibration purposes that utilises permeation and diffusion tubes to generate the calibration gas. When the permeation and diffusion tubes are set at a constant temperature, the weight of both the permeating and the evaporating diffusion gas will be respectively set at constant levels. In this manner, calibration gas is continuously generated by setting both tubes at a constant temperature and providing a constant flow of dilution gas such as air or nitrogen. This method is highly reliable because gas concentration levels are determined based on the dynamic weight loss obtained from measurements such as rate of permeation diffusion or evaporation diffusion as well as the quantity of dilution gas calculated by weight.

Permeater

[PD-1B]

Even calibration gas of very low concentrations can be continuously generated

[PD-1B-2]

It is possible to have two ventilation systems and to generate two kinds of calibration gas simultaneously

Features

Highly reliable because concentration levels are determined by calculating weight loss based on
Measurements and dilution gas volume
Many types (both organic and inorganic) of low-concentration calibration gases) can be generated
Gas for calibration of all organic solvents (as long as they are stable in their liquid state or at normal temperatures) can be generated
Gas for calibration can be generated continuously for longer periods of time
Calibration gas can be easily generated in a wide range of concentrations

Generating calibration gas with a permeation tube

A permeation tube is a fluororesin tube that contains high-grade liquefied gas. When the tube is exposed to a certain temperature, liquefied gas penetrates the tube wall by osmosis in time-increments enabling a specific quantity of gas to be retained in the tube . Consequently, a carrier gas flowing at a constant speed (for calibration purposes) can be continuously generated by keeping the tube at a fixed temperature and infusing a constant quantity of dilution gas. This method is highly reliable because the concentration of the calibration gas is determined by calculating the decrease in weight of the permeation tube and the quantity of dilution gas. This dynamic method also enables highly reactive gases such as chlorine, hydrogen sulphide or ammonia to be generated. As shown in the table below, there are many different kinds of permeation tubes and they are widely used because they can provide a stable supply of calibration gas.

Permeation tubes

Calibration gas name	P-tube catalog No	Concentration range (ppm)
acetaldehyde	P-92-1	0.1-5.2
ammonia	P-3	0.2-17.9
ammonia	P-3-M	0.3-40.8
ethyl mercaptan	P-72-H	0.04-1.87
ethylene oxide	P-163-H	0.5-23
Formaldehyde	P-91-H-5	0.0049×0.24
vinyl chloride	P-130-H	0.3-13.8
vinyl chloride	P-131	0.05-3.7
vinyl chloride	P-131-H	0.8-58
methyl chloride	P-132-H	1.6-77
chlorine	P-8-1	0.03-3.3
	P-8-5	0.15-16.4
	P-8-M	0.5-53.1
methylene chloride	P-138-H	0.3-15.8
dimethylamine	P-181-H	0.2-10.3
methyl bromide	P-136-H	0.5-23
bromine	P-10-H	0.05-2.5
trimethylamine	P-180-H	0.06-3.1
Styrene	P-124-H	0.0045-0.22
sulphur dioxide	P-5-5	0.04-3.6
	P-5	0.1-7.2
	P-5-H	1.1-76.4
nitrogen dioxide	P-9-1	0.05-3.99
nitrogen dioxide	P-9-H	1.8-133
dimethyl sulphide	P-73-H	0.003-0.45
1, 3-butadiene	P-174-H	0.7-31
hydrogen fluoride	P-17	0.11-11.3
	P-17-5	0.3-29
	P-17-H	0.6-58
propane	P-100	0.03-1.9
propylene oxide	P-164-H	0.7-33
chlorofluocarbon 11	P-51-H	0.4-16.4
methylamine	P-182-H	0.5-25.6
methyl mercaptan	P-71-5	0.007-1.52
methyl mercaptan	P-71-H	0.16-11.4
dimethyl sulphide	P-74-H	0.04-6.3
hydrogen sulphide	P-4	0.1-13.6

Generating calibration gas with a diffusion tube

A diffusion tube is a glass tube that consists of a liquid containing portion and a diffusing portion with a uniform inner diameter. A pure target liquid is put into the liquid container using a glass syringe. The liquid must have a vapour pressure of 5 to 400 mm Hg at 25 to 50ºC (77 to 122ºF) and be highly stable. If this tube is kept at a constant temperature, the liquid evaporates and diffuses at a constant rate.

*1 Although not a common application, gases of substances that are solid at normal temperatures can be generated using gas diffusion tubes. Please contact your licensed GASTEC representative for information regarding specific substances.

*2 This method cannot be applied to substances with extremely high or low vapour pressure or substances with decomposability, corrosiveness, hygroscopicity or polymerizability due to their diffusion rate not being constant.

Diffusion tube

[No.3100]

Suitable for continuous generation of single component gases for calibration over sustained periods of time.

Diffusion tube for multiple components

[No.3200]

Solvents such as thinner contain multiple components. Previous models permit the generation of single component gases for calibration purposes. However, a multiple component type diffusion tube enables the simultaneous generation of 4 types of gases for calibration. Employing this tube enhances analytical testing.