BCST Sight Glass Flow Indicator

BCST is the leading sight glass flow indicator manufacturer in China and has been working in the production industry since 2000. The sight glass flow indicator is used to check the liquids instantly in industrial processes.

You can find sight glass flow indicators in petroleum and pharmaceutical plants across the world. Most of the applications use sight glass flow indicators for verifying the fluid visually without any hurdle in the flow. The use of casting methods in sight glass flow indicator makes it unique while comparing with other competitors.

Double glass sight flow indicator

The double glass sight flow indicator is suitable for the vertical flow in the downward direction. It can help to handle the full flow without interruption in the distillation process.

flange sight glass flow indicator

The drilling of the holes is on the bolt of the flange sight glass flow indicator. You must supply the size and standard of the flange. There is an alignment in the holes of the bolts.

Float sight glass flow indicator

It is suitable for the chemical and petroleum industries. It helps in making the flowing fluid visible through the ball float and observing the fluid from the inner view of the pipe.

Double Window Paddle Wheel Sight Glass Flow Indicator

This type of flow indicator helps to check the flow, condition, and color of the liquid. The spinner is available for sizes of ¼ inches to 6 inches.

high pressure sight glass flow indicator

The design is for the critical points of flowing gases or fluids. Different variety of connections are available, so the sight glass flow indicator is in the lines of the processes.

PTFE liner sight glass flow indicator

PTFE is the spinner that helps in making the fluid highly visible in this sight glass flow indicator. Carbon steel helps construct the body of sight glass flow indicator.

sanitary sight glass flow indicator

Stainless steel is beneficial in the construction of this flow indicator. Its head is round in shape, and the working temperature is 150 degrees Celsius. You can easily view the fluid at a 360-degree angle.

stainless steel sight glass flow indicator

BCST stainless steel sight glass flow indicator is mainly for the food, pharmaceutical industry, or medium with sight corrosive. It can withstand high pressure and temperature application.

Thread Sight Glass flow indicator

It helps in revealing the working of the fluid. You can easily control the troubleshooting issues through a threaded sight glass flow indicator in a cost-efficient way. The thread standards are: NPT, BSPP(T).

WCB Sight glass flow indicator

It helps observe any material flowing the WCB sight glass flow indicator. It has double windows and is suitable for different environments.

Wheel sight glass flow indicator

You can observe the inner liquid state better by the wheel in the flow indicator. Power plants are usually using this glass flow indicator for pumping the liquids.

Sight Glass Flow Indicator-FAQ


Below are the answers to the queries which the users often ask about sight glass flow indicators.

Q1- What is a sight glass flow indicator?


The sight glass flow indicator is a straightforward method for determining the flow of the liquid. It helps in the processes of low pressure, sterile and hygienic applications. The installation is in a horizontal way through which the view of the tube is clear. There are fewer wetted parts that make the sight glass flow indicator less maintain.  After the installation of the sight glass indicator, there is no need to disassemble it. Even it doesn’t require cleaning and inspections. The fixing of safety bolts is with all the sight flow glass indicators. Also, the solidify seals are also present, which reduces the risk of any leakage.

double glass sight flow indicator

Q2 – Where is the sight glass flow indicator commonly used? 


  • In industries, sight glass flow indicator helps in controlling and inspecting the flow of the liquid. The water level in the boiler of the industries requires continuous monitoring, and here sight glass flow indicator is most commonly used.
  • The biological plants use sight glass flow indicators regularly to note down the critical points for analysis.
  • Most researchers use sight glass flow indicators to manage the level of temperature and pressure to high the significance of the experiments.
  • Sight glass flow indicator allows visualizing the level of the oil in the machines.

Q-3 What is the ball type of sight glass flow indicator? 


The flowing of the fluid moves the ball from the bottom of the sight glass flow indicator, whose position is at the top of the window. You can see the ball from the window, so it is easy to view the flow. The interruption with the ball indicates the existence of the fluid. Because of gravity, the ball is again in the rest position. The sight glass flow indicator gets fixed in the pipe in a vertical position through the upward flow. Mostly, it is suitable for fluids and gases flowing slowly. There is one more ball type of sight glass flow indicator in which the ball keeps oscillating as the fluid starts flowing.


Q4 – How is the working of sight glass flow indicator? 


The sight glass flow indicator is the flow indicator with the glass window. It is in the pipe to check the flow of the liquid. For visibility, the spinner is with the stream to connect and make the sight glass flow indicator turn. This spinner helps in detecting the low flow rates and makes a clear view from the distance. Additionally, the rotating speed is direct concerning the speed of the flow. The sight glass flow indicator is also available with one window exactly in front of the indicator. Double windows sight glass flow indicator is presently available for the clarity and other properties of the liquid.

Q5- How is the construction of a sight glass flow indicator? 

The construction of sight glass flow indicator is according to different types of configurations. Therefore, the specifiers are available for delivering the idea regarding the making of sight glass flow indicator. The three ways of constructing sight glass flow indicator are as follows:

  • Mounting: There are different types of mounting. The mounting in sight glass flow indicator is in the center of the processes.
  • Gaskets: The availability of gaskets is in different materials. It is suitable for the compatibility between temperature and chemicals.
  • Glass: The glass in sight glass flow is not applicable for corrosive fluids. In the viewing models, the glass is with the metal ring connected with the body of the sight glass flow indicator. 

Q -6 Who are the manufacturers of sight glass flow indicators? 

Few countries are leading in the manufacturing of sight glass flow indicators. It includes UK, China, Japan, Canada, and America.  Among many manufacturing companies in China, BCST is serving in this industry for 21 years. Our specialization is in development, research, and producing different instruments, including sight glass flow indicators. BCST is also a registered and recognized manufacturer in the international market. There are different types of sight glass flow indicators available, which you can select according to your application. You can even adjust the fluid flow position in the pipeline through a sight glass flow indicator. 

Q7 – Which materials are using in the making of sight glass flow indicators?

While making the sight glass flow indicator, consideration and compatibility are to be kept in mind. Carbon and stainless steel are most commonly used for making the body of the sight glass flow indicator. Stainless steel is a better choice due to its corrosion resistance and helps pharmaceutical applications.  The integrity of the gasket is essential for the indicator to perform successfully. It is also necessary to check the compatibility of the gasket’s material as it is in contact with the flowing medium. The typical gaskets help in industrial applications. It is made up of improved PF material or Teflon.

Q8- What are the applications of sight glass flow indicators?


Most chemical and pharmaceutical companies use sight glass flow indicators to monitor the chemical during the production process. The sight glass flow indicator also helps in wastewater and environment-related applications. While processing the solids in bulk quantity like plastic or any food product, sight flow glass indicator allows the operators to view the free-flowing of the fluid. The sight flow indicator also supports inspecting the pipelines. Many other industries are also using sight glass flow indicators which are:

  • Food and beverages
  • Industrial
  • Aerospace
  • Agricultural
  • Medical
  • Marine
  • Pharmaceutical
  • HVAC


Q9- What are the standard specifications of the sight glass flow indicator? 


Typeà glass window for indicating the flow of the liquid

Temperatureà 200-degree Celsius

Pressureà20 kg/cm square

Size of the lineà approximately to 8 inches


Glassà toughened borosilicate

Glass tubeà toughened borosilicate

The version usedà viewing of double or single window

Type of connectionà flange or threaded

Materials for constructionà PFA fluorocarbons, PFA ductile lined iron, carbon steel, PFA, PTFE, hard glass

Rating of the pressureà up to 275 pascals

Range of the temperatureà  from -20 Fahrenheit to 300 Fahrenheit

Range of the sizeà ½ inches to 6 inches

View of the fluidà From bottom or top

Windowsà are hardened with the glass

Q10- What are the features of the sight glass flow indicator? 

  • Different options are available such as single and double tubes in the full view and armored styles.
  • All the wetted parts are suitable for corrosive processes and high-temperature applications.
  • The seal is fitted on the outer side of the glass sight tube. Its primary purpose is to remove the stress due to the expansion between the housing and sight tubes. In addition, it helps in preventing leakages.
  • The flanged or sanitary ones are readily available in different models
  • Varieties of sizes are present with the diameter of 1-10 and length is up to 60
  • Every chamber from inside is tested for hydrostatic pressure

Q11 -How does a sight glass flow indicator work for gas? 


You can easily monitor the whole process through the glass window. The sight glass flow indicator for gases shows the flow with low speed and the less weight of the flapper. Use any wet or dry gases in the applications along with the air. It is equal to the effect of mass with the speed of 2ft/sec or can be more. It also indicates the leakage in the system, less velocity of the flow from the natural gas, and chemically reacting on pressures more than the atmospheric pressure. Most of the time, it is applicable in horizontal applications.

Q12-What is a full-view sight glass flow indicator? 


The full-view sight glass flow indicator gets assemble with the tubular shape of borosilicate glass. These types of indicators are straightforward and help in checking the flow from a single direction. Different valves or pumps are working according to the flow line—this kind of sight glass flow indicator where no automatic strain exists in the pipeline. Mostly the diameter of the glass tube is larger than the actual size internally. Mainly,  the designing process proceeds where there is neglect in the drop of pressure.  Typically, suitable for vertical applications so the fluid is visible at maximum level.

 full view sight glass flow indicator

Q13- What is the type of glass in sight glass flow indicator? 


During the manufacturing process, the attachment of the glass is with the metal ring.  The windows attached with the glass make it resistant and prevent any failure/crack. Mainly, it works in the food industry. There are various types of glass windows used insight glass flow indicator. Typical soda glass is used when the temperature is below 300-degree Fahrenheit, and there are no changes in the temperature.  Borosilicate glass is resistant to heat and in particular conditions where the hot equipment is a wash from the cold water.  As the suggestion, sapphire or quartz glass can tolerate the temperature above 500-degree Fahrenheit. Mostly, this type of glass is applicable in steam applications.

Q14 – What information is required while installing the sight glass flow indicator? 


  • Pressure: Check the sight glass flow indicator at normal and peak levels of pressure. It indicates the thicken of the glass in sight glass flow indicator. 
  • The fluid process doesn’t affect the wetted materials; it acts as an electrolyte. Therefore, the activities of the fluid are in direct relation to the temperature.
  • Tolerance towards the leakage: for some applications, high temperature and high pressure are important factors. Even the small leakage can cause the difference between the metal ring and glass.
  • Temperature: Glass is not capable enough to handle the maximum temperature. It depends on the pressure of the processes.

Q15 – What is the difference between the sight glass flow indicator and magnetic level indicator? 


There are three primary ways to differentiate sight glass flow indicator and magnetic flow indicator:

  • Enhancement in safety: The sight glass flow indicator has shot-comes related to security. There is a risk of glass breaking in specific conditions like high temperatures and corrosive materials. Whereas, magnetic flow indicator remains unaffected for an extended period in terms of pressure and temperature.
  • Reduction in maintenance: The sight glass flow indicator requires maintenance after every five years. There is a need for a proper plan related to inspection, repairing, and cleaning the glass. The warranty period of the magnetic flow indicator is mostly 10 years. In this duration, there is no need for repair and care.
  • Increase in visibility: Insight glass flow indicator, the glass might get cloudy, and operators face difficulty determining the fluid level. In some models of Magnetic flow indicators, fluid is visible from the angle of 200- degrees.

Q16 – How to prevent failures in sight glass flow indicators? 


The main reason for failure in the sight glass flow indicator is improper installation. For example, over-tightening causes the glass to bend and results in a crack. Sometimes changes in temperature from one side of the glass cause expansion or contraction from the other side and done during the process, or even the hot sight glass flow indicator cools down during the washing of any outdoor equipment. To reduce any failure in the sight glass flow indicators, specify the proper unit for handling the failures. Sometimes, the chemicals cause corrosion on the glass.  To avoid this, do check the charts of chemical resistance.

Q17 – What are the maintenance tips in the sight glass flow indicator? 


The sight glass flow indicator is a straightforward device that needs maintenance only if a suitable model is selected according to the application.  And it is installed correctly. If in case the glasses are dirty and getting disassemble, replace the disc at the exact moment. You can also replace the glass with a plain disc (not the fused or metallic frame). You can also replace the fuse-glass in sight-glasses. Use the commercial cleaners for cleaning the glasses. No need to use the brushes of wire and scarpers of metal. Never clean the glass when the sight glass flow indicator is working.

Q18 – How to install a sight glass flow indicator? 


  • For installing the sight glass flow indicator, choose from the 360-degree flow indicator and view-angle flow indicator.
  • You must know the purpose of using the indicator. There are different indicators for evaluating the speed of the flowing fluid, including a flapper flow indicator, visual flow meter, rotatory flow indicator, drip indicator, ball flow indicator, and flutter indicator.
  • Selecting the type of mounting (flanged, thread-on for small sizes and sanitary clamp in pharmaceutical industries)
  • While determining the materials to use in the sight glass flow indicator, don’t forget about the compatibility with the rest of the components.

Q19 – What are the components of the sight glass flow indicator?

  • Glass: It is an important component in every unit of sight glass flow indicator
  • Body of the unit: typically, it handles the glass where the medium is present. Most of the commercial sight glass flow indicators are different from one another. The body can also manage the level of stress on the surfaces of the glass in a proper way. Generally, various designs of the unit body are dependent on the rating of pressure.
  • Gaskets: or the packing material is always available. It is the requirement of the sealing, and extra features are also present according to the need.

Q20 – How is industrial sight glass flow indicator made?


The most expensive part is the unit body of sight glass flow indicator. Mostly, the use of casting methods is making the bodies at a low cost. The castings are especially effective and efficient for superalloys. It just needs the minimum amount in making the sight glass flow indicator with less wastage. Sometimes casting is not applicable as the transparent window is weak. Here, other methods of fabrication benefit in accelerating the time of output. All the machinery begins with the plate stock, bar, or tubes. After that, the stock is according to the operations of the machine. As the standard, flange type of sight glass flow indicator serves the purpose of stock bodies.

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