Rotameters for all applications

What are Variable Area Flow Meters and How Do They Work? 

Variable Area Flow Meters typically consist of a tapered tube through which fluid flows. Inside the tube is a float, buoyant in the fluid, and as the flow rate changes the float moves up or down. The position of the float within the tapered tube provides visual indication of the flow rate.

Here at Boiswood we are an approved supplier of Kobold flowmeters. These flowmeters are based on the principle of the well-known float-type flowmeters. These instruments are provided instead with a cylindrical flow tube with conical slots around the periphery. This eliminates the usual problems of guiding the cylindrical float within a tapering measuring glass.

The novel design including the provision of an appropriately dimensioned annular gap of constant width between the float and the flow tube has enabled the sensitivity to dirt to be considerably reduced. The float comprises permanent magnets actuating a bistable reed contact external to the flow circuit, that is, the flowing medium is hermetically separated from the electrical contact.

In addition it is embedded in a height-adjustable switch housing, thus ensuring that the contact cannot be damaged even by an aggressive atmosphere. As the medium enters the instrument the float rises. Once its magnetic field reaches the contact tips of the reed switch the contact closes. As the flow increases the float rises further until it reaches its stop. This prevents the float from going beyond the contact range of the magnetic operating tube, that is, the contact remains closed, thus ensuring bistable switching.

With the models SMV-2... and SMV-3... the magnetic field also activates an external, that is, hermetically separated indicator, as a result of which flows are measured accurately even at high operating pressures. The magnetic field and the indicator are designed so as to ensure that the pointer follows even abrupt changes in flow rate.

Types of Variable Area Flow Meters

Rotameters

Typically consist of a tapered tube with float inside. As fluid flows through the tube, the float rises and its position is indicates the flow rate. These are commonly used for measuring gases or liquid in various applications in diverse industries including:
 

• Chemical Processing
• Water Treatment
• Laboratory Settings
• Pharmaceuticals
• HVAC Systems
• Oil & Gas Productions
• Food & Beverage Industry

Rotameters are widely used as they are versatile, reliable and known for their simplicity.

Piston type meters

Often known as a positive displacement meter. It's a flow meter which measures fluid flow by counting the number of discrete volumes that pass through the meter (usually cubic units). It consists of a piston or rotating impeller that moves with the flow, dividing the fluid into known volumes. These meters are known for their accuracy and suitability to measure low to medium flow rate of liquid where precise volume measurement is essential. There are commonly used in the following industries:
 

• Oil & Gas Productions
• Water Utilities
• Chemical Processing
• Pharmaceuticals
• Food & Beverage Industry
• Aviation
• Automotive

Piston type meters are valued for their accuracy and reliability where exact volume measurements of fluid is critical.

Selection Criteria for VA Flowmeters

• Type of fluid - ensure the flow meter is suitable for the fluid you need to measure.

• Accuracy of measurement - understand the flow range/turndown you need to measure.

• Surrounding environment - ensure the flow meter can withstand environmental surroundings which can include the temperature exposure, pressure, density, flammable, corrosiveness, toxicity & viscosity.

• Materials of Construction - choose a flow meter based on the construction materials which can withhold temperatures and pressure of the atmospheric conditions.

• Hygiene Requirements - identify any hygiene requirements for the flow meter to ensure the flow meter adheres to strict processing standards.

Our knowledgeable technical support team at Boiswood can support you in selecting the correct flow meter to fulfil the needs of your application, ensuring efficiency & accuracy to support the high performance of your business.