Many know that a sightglasses wear, but how much and when the glass should be replaced is less known? Here is the answer to this question.
Wenn we take the most applied hardened borosilicate glass. In the graph you see how many millimeters per month this glass erods at a certain temperature and pH. For example, a sightglass with borosilicate glass in an application where the medium is 170 °C and with a pH of 10, the glass rubs 0.2 mm per month. This does not seem to be much, but that is about 2.4 mm in a year. At 200 °C., this is 8.4 mm. And that is a lot.
In general it can be said that the glass of a sightglas erods faster at a pH higher than 7 (lye). Glass is well resistant to acids but less to alkalis.
Roughly speaking, we advise, in consultation with the manufacturer of the sightglasses, replace the sightglass that is used under extreme conditions every 6 months. In normal conditions, we recommend replacing the sightglass every two years.
Tip: Order your replacement glass with the purchase of the sightglass.
You will save order and shipping cost for a single replacement eyeglass when you order it with the sightgass. You can put the replacement eyeglass in the box on the shelf until you need it. This also prevents unforeseen delivery times and maintenance planning problems.
