Glass tube flow meter is basically a type of variable area flow meter or rotameter where the way it works depends on the cross-sectional area of the tube, In its application the material of this type of flow meter is available several types from stainless steel, pvc, teflon to aluminum materials.
Glass tube flow meters are widely used for installation applications with vertical systems and the amount of flow rate can be read directly. Usually use a glass tube where the material of glass is quite good, namely pyrex glass. This type of glass tube flow meter is widely used when installing liquid pipes do not have a horizontal area that does not require a large area.
For its application, Glass tube flow meter is only maximal at a temperature of 120 degrees Celsius. While the maximum pressure in this type is not too high only in the range of 10 bars, this type of glass tube flow meter is only available for fluids in the form of liquid and gas types. When we want for higher pressure working, in the range of up to 60 bars can be used type of metal tube flow meter.
The accuracy of a glass tube flowmeter is usually not so precise and the maximum flow rate capacity is limited to the size of the DN100 tube. For the connection itself, there are usually 3 that use threads, flange and triclap.
Also Read: Coriolis Mass Flow Meter
Working Principles of Glass Tube Flow Meter
The basic variable area flow meter is an indication type of Glass Tube Flow Meter. The tubes are made with precision from borosilicate glass, and the buoys are made with precision from metal, glass or plastic. Metal buoys are usually made of stainless steel to provide corrosion resistance. Buoys have sharp meter edges where readings are observed using scales mounted next to tubes.
End fittings and joints of various materials and styles are available. Important elements are tubes and buoys, often called combination tubes and buoys, because it is this part of the meter that provides the measurement. In fact, similar combinations of glass tubes and stainless steel buoys are generally available, regardless of the type of casing or end fitting that the application can request, to best meet customer needs.
The meter scale may be calibrated for direct readings of air or water, or it may have a scale to read the percent range or arbitrary scale for use with equations or conversion charts. Safety-covered glass tube variable area flow meters are commonly used throughout the industry to measure liquids and gases. They provide a flow capacity of up to about 60 GPM, and are produced with metal or plastic end fittings to meet the chemical characteristics of the measured liquid.
The only liquid that this meter does not match is the one that attacks the glass measuring tube, such as water above 90 °C (194 °F), with a high pH that softens the glass; wet vapor, which has the same effect; caustic soda, which dissolves glass; and hydrofluoric acid, which detects glass. The main limitations of general purpose gauges are the pressure limit and temperature of the glass measuring tube. Small, 6 mm (1/4″) tubes are suitable for work pressures of up to 500 psig, but the operating pressure for large tubes of 51 mm (2″) may be as low as 100 psig. The practical temperature limit for a glass variable area flow gauge is 204°C (400 °F), although operation at such high temperatures substantially reduces the operating pressure of the meter. In general, there is a linear relationship between operating temperature and pressure.
Tri-flat Glass tube meter size 1/16″ – 1/4″
Used in the smallest size. The tube expands coneically in the direction of flow and contains three flats parallel to the central axis of the meter tube. The ball buoys are guided by these three flats over the entire flow range and the minimal space between the float and the flat in the meter tube ensures the readability of the floating position even in the murky liquid. The buoy is guided right in the middle of the tube meter.
Glass tube meter tube tyre Size 1/2” to
1/4″
It is also used with ball buoys to measure smaller discharges. Their accuracy is not as high as that of a tri-flat meter tube and is therefore only used for simple applications. The ball floating in the middle is inserted into a plain tyre meter tube by fluid flow.
Glass tube meter tyre size 1/2” to 2”
It is usually only used for extreme operating conditions (pressure shocks, vibrating pipes, etc.). In a size of 2″, a higher end value of the flow range is possible because the flow area is larger than in the beadguide metered tube. The buoy is guided by a pole guide in a regular tyre meter tube.
Beadguide tube meters size 1/2″ to 2″
Standard in this size range. This type of meter tube combines three ribs that are parallel to the middle axis of the meter tube and performs the same function as flat for a flat three meter tube. They drive buoys across the flow range. Here also the minimal space between the edge of the float reading and the beadguides ensures the reading of the float position even in the murky liquid. Used in conjunction with the shape of a buoy.
Glass Tube Flow Meter application
- Industrial processes
- Pharmaceutical production
- Oil and gas pumping and refining processes
- Fuel cell research
- Chemical manufacturing
- Analytical instrumentation
- Water treatment and distribution system
Also Read: Flow Meter Working Principles
Hopefully this article “Glass Tube Flow Meter” can answer the reader’s question about the definition, working principle, and application of this type of flow meter.