Spigots for pollutant emission measurements

krocce
We have been carrying out measurements of pollutant emissions for years, we often encounter installations that are not properly prepared for measurements, which is why we decided to transfer our knowledge and experience to the design and construction of measuring stubs and measuring stations, giving you the confidence that the work will be done professionally and in accordance with the requirements legal. A properly designed measuring station is crucial for the reliability of the measurement results of pollutant emissions in waste gases.

General requirements for mounting the measuring section in accordance with the standard PN-Z 04030-7:1994

In accurate or technical measurements, the measurement cross-section should be located on a straight section of the channel, free from flow disturbances, with a constant hydraulic diameter and, if possible, on a vertical section with length l ≥ 5 DH in front of the measurement section and with length l ≥ 2 DH behind the measurement section. For chimney ducts with an outlet to the atmosphere, the required distance of the measurement cross-section to the chimney crown is l ≥ 5DH.
If it is impossible to meet the above requirements, the measurement cross-section should be selected in the place where the gas flow velocities are the highest, while increasing the number of measurement points where the gas velocity is measured to obtain the most accurate flow profiles along the measurement axes. Then, the minimum lengths of straight sections of the flow channel for accurate and technical measurements should be taken according to the table below

Number of measurement points for a circular measurement section
Cross-sectional area m2 Section diameter m The smallest number of measurement axes The smallest number of measurement points on an axis
Technical measurements Accurate measurements
<0,09 <0,338 1 11) 2
0,09÷0,37 0,338÷0,695 2 2 2
0,38÷0,78 0,696÷0,997 2 4 6
0,79÷3,13 0,998÷1,998 2 6 8
3,14÷9,00 1,999÷3,385 2 8 10
>9,00 >3,385 2 10 12
1)A point located in the center of the measurement cross-section

Number of measurement points for a rectangular measurement section
Cross-sectional area m2 Technical measurements Accurate measurements
The smallest number of measurement axes The smallest number of points on the axis The smallest number of measurement axes The smallest number of points on the axis
<0,09 1 11) 1 2
0,09÷0,37 2 2 2 2
0,38÷1,49 3 3 4 4
>1,5 4 4 5 5
1)A point located in the center of the measurement cross-section

Minimum lengths of the measurement section when general requirements are not met
Type of flow disturbance in front of the measuring section The shortest length of the straight sections of the channel
Before the measuring section Behind the measurement section
Arches, channel branches and more 1DH 0,5DH
Partially closed dampers or louvers 3DH
Centrifugal fan outlet 2DH