Introduction to Dall Tube

hello friends I hope you all are doing great. In this post, we will have a detailed look at the introduction to Dall Tube.

The Dall tube is a shorted type of venturi meter that comes with low press losses as compared to the orifice plate. As compared to these flow meters the tube flow rate is measured through pressure loss caused by hindrance of the conduit. So let’s get started with Introduction to Dall Tube.

Introduction to Dall tube

• The pressure differential is measured with the use of diaphragm pressure transducers having digital readings.
• These meters come with low permanent pressure losses as compared to orifice meters, all tubes are used for measuring the flow rate for larger pipes.
• Differential pressure is generated through all larger venturi tubes and nozzle but they come with the same throat diameters.

construction of Dall Tube

• The Dall flow tube comes with a high ratio of pressure generated to pressure lost as compared to the venturing flow tube. It is compact and used for larger flow applications.
• The tube comes with a short, straight inlet component with a sudden reduction in the inner diameter of the tube. That part is called the inlet shoulder and comes with a converging inlet cone and a diverging outer cone.
• The two cones are parted through a slot or gap in two cones.  The low pressure is measured for a slotted throat. The high pressure is measured at the upstream edge of the inner shoulder.
• There are medium to larger sizes exist for all flow tubes. For larger sizes, the cost is lower than a venturi flow tube. This flow tube comes with pressure losses of about five percent. Flow rate and pressure losses are shown in this equation

V = k√DP

• In this equation :
• V  tells about the volumetric rate of flow.
• K  is constant.
•  DP  is a pressure difference.

Advantages

• The fall flow tube comes with a high ratio of pressure generated with pressure loss of the venturi flow tube.
• It is a compact meter and is used for larger flow measurements.
• It has half a percentage of energy losses than the venturi meter for the same differential pressure losses.
• Its permanent pressure losses are low.
• It can easily connect and is shorter in length.
• It provides accurate results for clean glass, liquid, and steam
• It has very low erosion and wear so not need high inspection

Disadvantages

• its structure is complicated to make.
• It has a sensitive nature to turbulence.

Applications

• It used for flow measurement for gas transmission pipelines
• It is used to provide flow metering for lean gasses.
• It is used for hydrocarbon gas single-phase flow measurement.
• It provides flow measurement for circular pipes.