• March 2022
/ What is the Purpose of Sight Glass?

What is the Purpose of Sight Glass?

  • sight glass
  • industrial glass
  • tubular glass
  • gauge glass
  • gauges
  • annular glass
  • manufacturing
  • industrial manufacturer

What is the Purpose of Sight Glass?

Defining Sight Glass

Sight glasses are transparent industrial glass that are used for observing levels of liquids or gases inside of a pipe, tank, or boiler. This is critical as it allows plant managers or engineers to look inside their systems without disrupting the flow of operations. From this they can observe critical changes in pressures or chemicals. Sight Glass have become valuable in many industries including steam pipelines, chemical processing, pharmaceutical processing, and food processing.

APG's  Quality Gauge Glass Sight Glass

Types of Sight Glass

Sight glasses can come in a variety of styles including:

  • Tubular Sight Glass – This sight glass acts as a transparent tube that allows the operator to observe the level of liquid contained inside a boiler, tank, or pipe.
  • Annular Sight Glass – This sight glass can be used to see through a vessel or tank to observe liquids or gases.
  • Flat Gauge Glass – This glass is designed to let a technician, operator or another employee to quickly view the pressure inside a boiler or high-pressure equipment. The rough sides allow now less reflection and refraction to quickly identify the level of pressure - usually shown with water.
APG Manufacturing

Sight Glass Applications

It is important for a sight glass to be able to withstand whatever material, fluid, or gas it encounters. Oil sight glasses are made to withstand petroleum, oil, and gas. It is important to ensure the glass is of grade and quality needed for a specific application, so it does not tarnish or degrade your ability to use it for system monitoring.

Applications such as steam boilers use sight gauges to ensure the water level is maintained to prevent system failure. If the pressure of both the water and steam are equal, the water level will stay put. If you notice on the sight glass level indicator that the water level is different you could have unequal pressure which could cause a system failure or a dangerous fire or explosion. Sight glasses and gauges are important tools to monitor vital equipment.

The Purpose of Sight Glass

Sight glass (Guage glass) is a helpful tool if you need to monitor levels inside a closed off piece of equipment. Oil and gas industries rely on these to monitor the flow of crude oil from the sea floor as well as storage tanks to monitor changes in the oil. Even in the food and beverage or pharmaceutical industries, there are plenty of fluids under high pressure and intense heat that need to be monitored. Sight glass is a vital tool to ensure the safety of the workers and products. The purpose of sight glasses goes beyond just monitoring liquids and gas. It is used to provide safety for the workers and keep the product line running smoothly.

Industrial Glass at APG

Sight glasses can be connected to crucial parts of your system, it’s necessary to ensure they fit the specific needs of the operation. APG is a trusted sight glass manufacturer and can custom cut your industrial sight glass to fit your specific application. Contact us today for your industrial glass needs!

Related Items


    APG Item Number: H70472 


    APG Item Number: H70129


    APG Item Number: H90230


    APG Item Number: S70273


    APG Item Number: V90230

Suggested Articles
Industrial Hose Catalog

Industrial Hose Catalog

This catalog includes anodizing, cam & groove couplings, gaskets, crimping, combination nipples and menders, universal crowfoot couplings, house couplings, valves, gauges, clamps, and more!

Get to know spiral wound gaskets

Get To Know: Spiral Wound Gaskets

Spiral wound gaskets were developed to meet the high demands of the oil refinery industry. This gasket is widely used in many industries such as oil, gas, and petrochemical industries. This metallic gasket...

Written By:

Written By 
Matthew Miller.
Digital Marketing Specialist

Stay Connected!

Get the latest updates on products, new knowledge base posts, and everything APG!