A sight glass allows the operator to look into the pipe. It is often placed in front of a meter or degassing device so that it is easy to see when the product reaches the meter, if there are air inclusions or what colour the product has. It can also be placed in a manifold to see where product is, or how full the manifold is.
This sight glass has an hole in it vertically, for to assemble an I-Led lightning of products in the pipe. This I-Led hole is M8x1mm and is 10mm/13mm deep.
When assembling the sight glass, the tightening torque is 35 Nm.