SOURCE TESTING ASSOCIATION I Annual Guide 2019
Each method or variants thereof are also contained in the EU/ UK requirements for sampling (Table 1) and are just as key to obtaining a valid sample. In my opinion the USA follows a highly logical approach: to conduct a particulate test you simply follow US EPA Methods 1,2,3,4 and then 5. The European way, although encompassing the same requirements, makes it more diffi cult to follow. Several Standards with varying numbers must be dipped into to fi nd the full requirements, a small but important point. However, do not be tempted if working in the UK or Europe to follow the requirements of the US EPA and assume they will be right for Europe- they won’t be! The simplest example of this was a company who bought a calculator to calculate the emissions. This seemed great, but the USA expresses data at 68o
F (20o C) and hence the calculations
of concentration were wrong. We have had to check with manufacturers and their agents over the years because US manufacturers and manufacturers in other countries that Standard Conditions for expressing data are appropriate for the UK. In addition, if working abroad it is always worth checking what Standard Conditions are being applied to the data for reporting.
It is often these “Peripheral Standards” where not enough care is taken, because they are sometimes seen as almost a chore to achieving the goal. However, if all their details are not adhered to carefully, then the main test will be fl awed and/or the correction to Standard Conditions can be incorrect. Either way the incorrect result is obtained.
When a sampling team arrives to conduct the sampling, they rarely have any say in the selection of the sampling location. However, they need to evaluate what to do at the location, how many sample points will be required, and will it infl uence the sampling uncertainty. Teams are sometimes asked to advise in new plants where to locate sampling ports, but often it is too late, and the platform has been designed and the number of clear straight lengths of duct work have already been pre-set.
It is the consulting engineers in this case who need to have recourse to the Particulate Sampling Standards so that the sample point on stack/duct work complies with the Standards thereby allowing a compliant test to be obtained.
According to the US EPA, for ideal sampling, the number of diameters of a circular duct prior to and after the sampling location should be 8 before the sample position and 2 after. In the EU it is 5 before and 2 afterwards where the upstream disturbance is not the exit point. If it is the exit point, then this becomes 5 before and 5 afterwards. Then the team should determine the total number of points per plane. The number per traverse using two traverses on a circular duct is half this. However, as the positions become less ideal (i.e. as the sample point becomes closer to a bend than the ideal) the number of points increases to take into account that the fl ow may not be laminar and improve the sampling integrity and accuracy.
Re-distribution of Different Particle Sizes by Bends Re-distribution of Different Particle Sizes by Bends
Re-distribution of Different Particle Sizes by Bends
The diagram shows that the bend has concentrated large particles (i.e. t greatest momentum) to one wall, whilst the lighter and smaller particles are h so once again size distributions are important.
The diagram shows that the bend has concentrated large particles (i.e. t greatest momentum) to one wall, whilst the lighter and smaller particles are h so once again size distributions are important.
The diagram shows that the bend has concentrated large particles (i.e. those with the greatest momentum) to one wall, whilst the lighter and smaller particles are hardly affected, so once again size distributions are important.
Each standard has a method of dealing with being too close to the wall of the duct. As the wall of the duct is approached, the aerodynamic effects increase, and friction of the wall slows the gases. Even in almost ideal stacks the fl ow decreases as we approach the walls. This can be seen below as a function of the wall roughness.
4
The US EPA gives the sampling positions that are correct for that US Stan inappropriate to copy these to the EU standards as these are different. Indeed in BS ISO 9096 and BS EN 13284-1 are different in that the number of poin the high-level dust sampling is greater than for the low level dust sampling refl that using fewer points has less effect on low level dust measurements as th are usually smaller and so will be mixed more evenly as they tend to approa sizes.
The US EPA gives the sampling positions that are correct for that US Stan inappropriate to copy these to the EU standards as these are different. Indeed in BS ISO 9096 and BS EN 13284-1 are different in that the number of poin the high-level dust sampling is greater than for the low level dust sampling refl that using fewer points has less effect on low level dust measurements as th are usually smaller and so will be mixed more evenly as they tend to approa sizes.
The US EPA gives the sampling positions that are correct for that US Standard, but it is inappropriate to copy these to the EU standards as these are different. Indeed, the positions in BS ISO 9096 and BS EN 13284-1 are different in that the number of points required for the high-level dust sampling is greater than for the low level dust sampling refl ecting the fact that using fewer points has less effect on low level dust measurements as the particulates are usually smaller and so will be mixed more evenly as they tend to approach sub-micron sizes.
There are typically two types of pitot tubes in use in the UK: Staushiebe (S-ty and Standard ellipsoidal pitot tubes (L-type).
There are typically two types of pitot tubes in use in the UK: Staushiebe (S-ty and Standard ellipsoidal pitot tubes (L-type).
There are typically two types of pitot tubes in use in the UK: Staushiebe (S-type) pitot tubes and Standard ellipsoidal pitot tubes (L-type).
The effect of Stack Wall Roughness on Velocity The effect of Stack Wall Roughness on Velocity
The effect of Stack Wall Roughness on Velocity
So, what happens with a bend in a duct? The effect of a bend is that it re- particulates and hence if enough points are not used this re-distribution wou incorrectly.
So, what happens with a bend in a duct? The effect of a bend is that it re-distributes the particulates and hence if enough points are not used this re-distribution would be sampled incorrectly.
So, what happens with a bend in a duct? The effect of a bend is that it re- particulates and hence if enough points are not used this re-distribution wou incorrectly.
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