I have a tank and need a sight glass. What are my options? Although this may seem like an innocuous question… many factors come into play. While the choice is clear for some customers, there are many more for whom this choice is anything but clear.
Sight glasses allow you to safely observe processes inside your tanks, vessels, pipes, and reactors. It is a window that allows operators to inspect the process media, observe reactions, observe the functioning of mixing equipment, verify the presence or absence of media, see liquid level, etc. It consists of metal, glass and gasket components. In order to ensure optimal performance a variety of factors need to be considered. Here are 5 critical things to consider when specifying a sight glass for your process.
Let’s get started.
The glass materials selected, the unsupported diameter, and the glass thickness all play a role in determining the pressure capabilities of a sight glass assembly.
There are two types of sight glasses: a conventional glass disc and a glass disc fused to a metal ring during manufacturing. The metal ring squeezes the glass and holds it in radial compression. Glass typically fails as a result of being subjected to significant tension. With fused sight glass windows, the compressive force of the metal ring exceeds the tensional force (i.e., pressure) and, as a result, the sight glass is extremely resistant to failure. Fused sight glass windows offer high pressure ratings and high safety margins.
The strongest fused sight glasses are made from duplex stainless steel and borosilicate glass; this combination creates the highest compression.
Temperature will determine glass type and more commonly the gasket material.
Carbon steel and stainless steel are the two most common metals used. Stainless steel offers better corrosion resistance and is standard in pharmaceutical applications.
There are three methods to connection:
Will the sight glass come into contact with corrosive process media? Will it be subject to sanitize in place/clean in place processes? Will it be exposed to thermal cycles or extreme heat? Your L.J. Star expert can guide to the specific glass, gaskets, linings and shields that you will need.
Now that we have walked through the process and took a deeper look at what needs to be considered in choosing your sight glass, if you still have questions our sales team is happy to assist you so you can begin to see more clearly.
For more information about sight glass applications, download the Sight Glass Handbook for Chemical and Pharmaceutical Applications