On the face, the sight glass seems very simple. They are just metal tubes that have glass on their front side. This allows the readers to easily observe the level of the liquid inside the chamber. There are different types of sight glass like borosilicate sight glass and soda-lime sight glass. However, they are not as simple as most people think them to be.
Anything in the industry can go wrong at any point. Due to this, it is a must that the industries get the right sight glass for their equipment. Choosing the wrong borosilicate sight glass will have drastic consequences. Stuff like overpressure, impact, and thermal shock can crack and break the glass.
The wrong glass type or damaged glass can have severe consequences. If the glass breaks when it is hot and pressurized then a jet of boiling liquid and glass shards is released. They can injure the operators and can cause fatalities as well. Additionally, there will be costly equipment damage and it will halt the entire industrial process.
Several reasons can lead to the failure of the sight glass. However, the major reason which contributes to it is the wrong selection. If you choose the wrong glass for a process then it is going to have drastic impacts.
Annealed soda-lime sight glass
Several sight glasses in the market are prepared by soda lime. They are referred to as soda-lime sight glass. They are made of the same material from which home windows, drinking glasses, and several other common appliances are made. This ensures that these glasses are very cheap. However, at the same time, they are very easy to break.
So, a soda-lime sight glass is very weak. Additionally, if a glass is repaired with soda lime then it results in a weak spot in the glass. They are highly susceptible to thermal shock. When it comes to chemical resistance they are very poor. Additionally, their operating temperature is also very limited. Due to this, it is suggested that you don’t use them in critical processes and applications.
Tempered soda lime sight glass
Most commonly the soda-lime sight glass is tempered. They are made of the same material from which baking dishes are made. They have undergone special treatment. Due to this, there is a pressure of around 10,000 psi on their surface.
This gives a lot of toughening to the glass. When compared to the annealed soda-lime glass their strength is almost double of them. Additionally, they are more resistant to thermal shock as compared to any other type of soda-lime sight glass.
The borosilicate sight glass is highly resistant to thermal shock as compared to all types of soda-lime glass. They have a very lower coefficient of thermal expansion that makes them so resistant to thermal shock. They are generally used in laboratory glassware. Additionally, they are used in kitchenware and in other types of equipment that have to undergo thermal shock or chemical attack.
Glass is a chemical compound. Due to this, there is always a chance that it might react with the chemical. This is the problem with all types of the soda lime sight glass. Due to this, their usage is very limited. For such liquids, the borosilicate sight glass is employed.
They match the parental standards i.e. USP type 1 standards. This shows that they are safe to be used as injectable drugs. in comparison when soda-lime glass is used in drugs, the glass has a greater tendency of leaching into the process media.
Why a Sight Glass is necessary?
Whenever an experiment is being done in a closed container, you cannot just open it, again and again, to make sure everything is going fine or to check on your experiment. It will disturb the whole process. That is why a sight glass is used to look inside the system without interrupting the process as a whole.
In today's world of technology, this type of borosilicate sight glass has an important role almost in almost every field, they are used in various critical operations such as steam pipelines, chemical processing, pharmaceutical processing, and food processing.
Major types of Sight Glass:
- Tubular Sight Glass: It is generally the transparent glass tube through which the liquid level contained in the system can be demonstrated.
- Circular Sight Glass: These are used to see inside a vessel.
- Sight Flow: In this, the flow of a fluid in the pipeline is observed.
Sight Glass Accessories.
Sight glasses have various shapes and sizes, now all you have to do is find the one that fits the system according to your need. For better performance and improved functionality, sight glass accessories can also help you to get the best results. The best and most effective sight glass accessories include the following.
- Wipers: It cleans the inside of the glass service which results in better visibility. Otherwise, it is quite difficult to clean the inside of the glass.
- Heating Jackets: It prevents cool spots in the process line while maintaining a clear view of the manufacturing process.
- Light timers: It switches the light on and off automatically and helps in reducing power consumption.
- Spray nozzles: It mainly helps in glass cleaning.