Generally when flue gases pass through second pass of boiler, because of resistance offered by the tube bundles , the flow tends to take place through the gap between boiler casing and boiler coils. As the area of this region is very small compared to total flow area, velocity in this region increases. Due to combined effect of high velocity and impingement angle of ash particles the tubes in this region get eroded. To pin point such problem areas the second pass of boiler is divided in to number of planes, and velocity of cold air is measured on pre defined points on each of these planes. This data is used to design the erosion control devices which help to minimize the erosion of boiler tubes. Commonly, E.M.S. (expanded metal screens) are used as E.C.D.

With the help of carefully designed E.M.S., resistance is introduced in the gaps to reduce velocity in the problem area. The E.M.S. not only add resistance to flow through gap but also take the erosion and protect the boiler tubes from erosion. E.M.S.s are easily repairable and replaceable.

Gas Velocity test for Ducts :

To ensure equi distriburtion in various ducts, velocity and flow is measured in each duct. Diverter plates with designed shapes are provided in duct at corrected prices to ensure equi distributions.

Gas Distribution test for ESP :

Velocity measurement is carried out by animometer by forming the grid between first and second field of ESP. The distribution is made uniform across the cross section of ESP by