Natural gas is a natural product with a wide variety of compositions. In addition to a large number of aliphatic and aromatic hydrocarbons, it also contains various sulfur compounds. Methane CH4 (main component of natural gas) is odorless, so natural gas is often odorless as well. If a smell is perceived, it is caused by natural sulfur compounds. Low hydrocarbons are odorless. Higher hydrocarbons and natural sulfur smell, sometimes extremely strong. The concentration of natural sulfur is constantly changing. The composition of the natural gas can fluctuate considerably within a very short time.
Gases that are supplied to household customers must be adequately odorized. This also applies to commercial customers, who are comparable to household customers in terms of security. The technology and the control of odorization are regulated in DVGW worksheet G 280-1.
The most common odorants are sulfur-containing organic compounds such as tetrahydrothiophene or mixtures of mercaptans. In order to achieve a warning effect even with gas technicians, they have to smell repulsive. However, a nauseating smell should be avoided. For ecological reasons in particular, the trend in recent years has been towards low-sulfur odorants.
When supplying the general public with gas according to DVGW worksheet G 260, gases must have a sufficient odor (warning odor). If they do not have this, they must be odorized. The odorization is primarily a safety measure for the public gas supply and thus for the gas technician. Odorized gas that escapes from leaky house installations or unintentionally from gas consumption facilities should be recognized by its characteristic odor. Odorisation can also contribute to the early detection of leaks in underground pipes. It is expressly pointed out here that odorization is not a reliable safety measure for gas distribution, as the ground can sorb odorants.
DVGW G280, paragraph 8.2.
Natural gases that are distributed by public gas suppliers with concentrations of 0.8 vol% natural gas in the air must have a sufficient odor (warning odor). If this is not available, the gases must be odorized. A six-monthly check of the odorant concentration is required. This is done by taking appropriate measurements at representative points in the network, which are as far away as possible from the odorization system, and is used to check the setting of a sufficient odorant / gas ratio in the odorization system.
DIN EN ISO 13734:2014
Odorants must be “an intensely smelling organic chemical or combination of chemicals, these are added to the natural gas in low concentrations and which give a characteristic, distinctive (usually unpleasant) warning odor, so that gas leaks below the lower ignition limit can be perceived. The odor character must be the same when the natural gas is diluted with air differently. ”Since natural gas naturally contains substances that can be smelled, only these can be used as odorants, as otherwise the odor characteristics would be different.
Control of the odorant concentration in the gas distribution network
In DVGW G280 paragraph 9.2, a check of the odorant concentration is required at least twice a year. The odorant concentration must then be checked at representative points as far away as possible from the odorization system.
We measure the THT, TBM, S-Free concentration with a gas chromatograph according to DIN 51855, parts 7 + 8, procedure according to DVGW worksheet G 280 paragraph 9.2, including control of the odor level according to G280 and VDI 3882 sheet 1 and documentation of the measurement results.
The deadlines for measuring the odorant concentration are agreed with the client. A time frame and a cycle for the control measurement to be carried out are agreed. For each measuring point we carry out a calibration measurement, a measurement of the odorant concentration and a qualitative odor control. If the odorant concentration falls below the specified value, a control measurement is carried out.
If the measurement result falls below the minimum concentration according to DVGW worksheet G 280-1 or if no or insufficient odor is detected during the qualitative odor control, the client will be informed immediately. The measurement results are documented and handed over to the client in a format agreed with him.
Only experienced employees are used for this highly demanding activity, any problems in the area of sampling can thus be solved quickly and competently and the reliability of the results is guaranteed.