Sight glass – For inspection of industrial processes
Sight glass – also known as viewing glass, peep hole glass or inspection glass – are used to inspect or monitor a process. It could be a liquid in a container. With sight glass you can look in from the outside and ensure that gases, quantity, temperature, colour or process are acting as desired, while keeping the substance inside the container.
Mirit Glas is a supplier of custom-made glass throughout the Nordics. We can offer same-day delivery if it is very urgent.
Want to hear more about how Sight glas can be the right solution for you, please contact us.
Properties and function
Sight glass is typically used to keep instruments or measuring devices separate from industrial processes and to monitor:- As a level indicator in liquid substances as oil (controlled with an oil level glass), water (controlled with a water gauge), chemicals or liquid foods (flow gauge) . These can be checked with inspection glass, either as flat glass or sight glass in tubes.
- Solid masses and materials such as grain in a grain silo or cement in a tank.
- Combustion processes with high temperatures, where an inspection glass is needed
- Freezing processes
- As Food Contact Material (FCM). For example in a flow indicator or a level gauge
- Air, gases or heat – possibly under pressure / vacuum (eg a vacuum chamber)
- Many sectors use sight glass. For example the food industry, process industry, pharmaceutical, offshore, marine and transport (cars, boats, ships and aircraft). We supply sight glass to be used in ATEX areas (to monitor explosion safe facilities).
SPECIAL CUSTOMIZATION
Fabricating and special processing is possible at Mirit Glas. For example with an anti-dirt coating, preventing oil and other substances to stick to the glass keeping the process fully visible at all times.
We can also print on the glass if, for example, if an indication of measuring steps is desired. We can bend the glass making the sigth glass curved. The glass can also be processed and cut into shapes or provided with a special edge.
Complies with standards
Regardless of which substance is to be inspected via inspection glass, the sight glass is adapted to specific needs and requirements, and is of course manufactured in accordance with approved standards.
- Round sight glass: complies with DIN 8902 or DIN 7080
- Sigth glass with curves or rectangular sigth glass: complies with DIN 8903 or DIN 7081
- Sight glass with special processing: Eg special cut-outs or drilling
- Sight glass in other glass materials: Eg quartz glass, sapphire glass or ceramic glass such as Robax or Neoceram
Sight glass from Mirit Glas can be ordered with various certificates, eg Certificate EN 10204 Type 2.2 and Certificate EN 10204 Type 3.1 as well as certificate for food contact material (FCM) according to regulation (EC) No 1935/2004.
We can to produce gaskets in custom sizes and pack these together with the sight glass.
Important questions in choosing the right sight glass
1. Temperatures
DIN 8902 and DIN 8903 can be used at temperatures up to 150 °C and 100 °C. DIN 7080 and DIN 7081 can withstand higher temperatures – up to 280° C. High pressure affects the temperature maximum the glass can withstand
2. Pressure
Mirit Glas has many different glass thicknesses in stock. If we know the diameter and clearance of the glass (the part of the glass that is not covered by the flange), we can find the right thickness so that the glass can withstand the desired pressure.
3. The substance behind the glass
Are there chemicals, oils or anything else in the container? What process is done behind the glass? Glass is generally resistant to most chemicals, but for example steam under pressure is a very aggressive process to ordinary glass, so special precautions must be taken.
4. The application
Why a sight glass? Just to able to look in visually, or does the application require that electronic sensors are able to measure through the glass? In that case, we need to pay attention to the transmission at certain wavelengths.
WHAT IS A SIGHT GLASS?
A sight glass is a common term for a glass that is used to get an overview of a process. It can be a boiler glass where you can see into a boiler. It can also be a glass tube that gives an overview of oil flow or a glass that makes it possible to see into a grain drying plant. Sight glasses are available in many varieties. What they have in common is that they make it possible to see otherwise hidden parts of a production.
IS A PETROL PIPE A SIGHT GLASS?
Sight glass is a broad term for a tube or glass that is used to keep an eye on, among other things, a process, a liquid or a combustion.
IS A SIGHTGLASS ALWAYS MADE OF ORDINARY GLASS?
A sight glass is made from the type of glass that makes sense. Many spectacle glasses, for example, are made of borosilicate glass. Others are made as heated windows to prevent fogging. Some sight glasses are made of Robax, which is very heat resistant because the purpose is to monitor a burn.
ARE SIGHT GLASSES ALWAYS ROUND?
A sight glass can be square, round or a glass tube. Sight glasses are manufactured to suit the situation. Many of the spectacle glasses that Mirit Glas manufactures are not round, oblong, shaped or square.
A sight glass is a transparent glass component used to inspect or monitor a process in tanks, pipelines, vessels, and other equipment. It allows operators to observe the process without opening the system or affecting its contents.
Sight glasses are used to monitor liquids, gases, and materials in industrial processes. They provide visual control of factors such as level, flow, colour, and condition without interrupting operation.
Sight glasses are widely used in:
- Food and beverage industry
- Pharmaceutical industry
- Process industry
- Offshore and marine industry
- Energy and transportation sectors
The most common types include:
- Round sight glasses
- Rectangular sight glasses
- Tubular sight glasses
- Custom-manufactured solutions
Materials include borosilicate glass, tempered glass, ceramic glass, quartz glass, and sapphire glass.
Yes, sight glasses are designed for demanding operating conditions and can withstand both high temperatures and pressure. The exact limits depend on the material, design, and application.
Yes, sight glasses can be manufactured to specific requirements, including:
- Custom dimensions and shapes
- Coatings (e.g. anti-reflective or chemical-resistant)
- Printed markings or scales
- Curved or reinforced designs
Sight glasses are commonly manufactured according to standards such as:
- DIN 7080 / DIN 8902
- DIN 7081 / DIN 8903
Additional certifications may be available depending on the application and industry requirements.
Sight glasses provide direct visual inspection, high operational safety, and reduced maintenance requirements. This makes them ideal for monitoring closed industrial processes.
Yes, with the correct materials, design, and certifications, sight glasses can be used in ATEX-classified areas and other demanding environments.
The terms sight glass and inspection glass are often used interchangeably. However, a sight glass typically refers to a standardised solution for process monitoring, while inspection glass can be a broader term for glass used for visual inspection in various applications.
A sight glass is typically mounted in a flange, frame, or holder using gaskets to ensure a secure seal. Correct installation depends on pressure, temperature, and application requirements and should always follow the manufacturer’s recommendations.
Borosilicate glass and ceramic glass are often the preferred choices for high-temperature applications due to their excellent thermal resistance and low thermal expansion. For extreme conditions, quartz glass and sapphire glass may be suitable alternatives.
The price of a sight glass depends on factors such as quantity, size, material, thickness, and any customization requirements.
The correct choice depends on several factors, including:
- Operating temperature and pressure
- Chemical exposure
- Dimensions and mounting requirements
- Safety standards and regulations
Technical guidance is recommended to ensure the optimal solution for your application.
The service life of a sight glass depends on operating conditions, but correctly installed sight glasses can last for many years. Regular inspections are recommended to ensure safe and reliable operation.
Please note that pressurized steam is particularly aggressive towards glass. In steam applications, sight glasses should be inspected at least once per year in a dry condition. Contact us for further guidance.
Yes, particularly in environments containing abrasive particles or aggressive chemicals. Selecting the appropriate material and coating can help reduce wear and extend service life.
Yes, when correctly designed, specified, and installed. Sight glasses are engineered to withstand defined pressure and temperature conditions and improve operational safety by eliminating the need to open closed systems.
