Flow meters are more common than most people realize. Water meters—used by municipal water suppliers—are a type of flow meter that tracks how much water a household uses, allowing for accurate billing based on consumption.
Another common example of a flow meter in everyday use can be found in the pumps used to transfer gasoline and diesel fuel into vehicle fuel storage tanks. Customers are billed on the amount of fuel dispensed into their tank.
When it comes to industrial chemical applications, liquid flow meters are incredibly valuable for several reasons. Accuracy, safety, cost efficiency and process control all rely heavily on them.
What Is a Liquid Flow Meter?
Flow meters for chemical applications measure how much liquid volume moves through a pipe or hose in a given period of time—for example, gallons per minute (gpm)—or can be a totalizing style that measures the total volume dispensed (think gasoline pumps).
Common types of technology used in liquid flow meters:
- Paddle wheel/turbine: A rotating paddle assembly that contains a magnet is inserted into the liquid stream. As the magnet moves past a hall effect sensor, it creates a pulse that represents a discrete volume of liquid. Paddle wheel styles can be mounted inline or can be insertion style and mounted vertically in the pipe work.
- Ultrasonic: External, clamp-on ultrasonic flow meters allow for faster installation and have lower maintenance requirements because there are no rotating components. They track the amount of time it takes for an ultrasonic pulse to journey from a transmitting element to a receiving element. More advanced models utilize two signals.
- Magnetic: Electromagnetic flow meters use a transmitter and sensor that together measure flow. The magnetic flow meter’s sensor is placed inline and measures an induced voltage generated by the fluid as it flows through a pipe. The transmitter takes the voltage generated by the sensor, converts the voltage into a flow measurement and transmits that flow measurement to a control system.
- Variable area: These flow meters consist of a cone, float, scale and piping connections. Operating under the variable area flow principle, rotameters use a simple design in which a float rises inside a conically shaped glass tube as the flow increases and its position on the scale gives the flow rate. They are cost-effective, easy to install and maintain and require no external power source.
- Coriolis flow meter: This meter is considered one of the most accurate types of mass flow meters and is widely used in industrial applications for accurate measurement. The meters measure mass through inertia. Liquid flows through a tube that is being vibrated by a small actuator. This artificially introduces a Coriolis acceleration, which produces a measurable twisting force on the tube, resulting in a phase shift. This force is proportional to the mass, with the meter measuring flow by detecting the resulting angular momentum.
6 Reasons to Use a Liquid Flow Meter in a Chemical Application
In chemical applications, precision and safety are paramount, and that is where liquid flow meters come in. These devices ensure accurate measurement and control of fluid movement, helping to maintain product quality, optimize processes and prevent potentially hazardous errors.
1. Precise measurement = better chemistry
In chemical processes, exact proportions are everything. Whether it is a reaction, dilution or blending, knowing the exact flow rate of a liquid ensures:
- Desired chemical reactions occur properly
- Product quality stays consistent
- Overuse or waste of expensive reagents is avoided
2. Safety comes first
Many chemicals are toxic, corrosive or reactive. A liquid flow meter helps:
- Detect leaks or abnormal flow early
- Prevent overflows, pressure buildup or unintentional mixing
- Maintain safe operating conditions under regulatory standards from the Occupational Safety and Health Administration (OSHA), Environmental Protection Agency (EPA), etc.
3. Process automation and control
Most modern chemical plants rely on automated systems. A liquid flow meter can:
- Feed data into control systems such as programmable logic controllers (PLCs) and supervisory control and data acquisition (SCADA)
- Allow for real-time adjustments and feedback loops
- Support smart dosing, batching and continuous processes
4. Cost savings
Misuse of raw materials can get expensive quickly. Flow meters can:
- Track consumption in real time
- Help optimize usage and reduce waste
- Allow better forecasting and inventory control
5. Versatility across fluids
In chemical environments, it is common to deal with:
- Viscous, corrosive or volatile liquids
- Different flow conditions such as low/high pressure, single/multiphase, etc. Flow meters are available in many types (e.g., Coriolis, magnetic, ultrasonic, turbine) to handle this diversity reliably.
6. Compliance and documentation
A good flow meter system can automatically log and store required data for:
- Environmental reporting
- Quality assurance
- Audits or certifications
Component Compatibility
All the wetted components in a system pumping chemicals must be compatible with the liquid. This is a critical step that must not be overlooked. Refer to the chemicals’ safety data sheet (SDS, formerly MSDS) for the fluid.
Key elements include:
- Fluid name – This is required to use chemical resistance guides.
- Concentration – Some materials may be suitable with lower or higher concentrations but not others.
- Fluid temperature – This is required to use chemical resistance guides. Chemical resistance can vary by temperature (typically at higher than ambient temperatures).
- Specific gravity – This can affect certain types. For example, variable flow meters rely on moving a float inside a tapered tube, which is affected by the density of the fluid.
- Viscosity at the pumping temperature – This can affect certain flow meters like turbine or paddlewheel by slowing their rotation.
- Solids – These can potentially cause issues with some types of flow meters, as the solids can cause wear of moving parts, leading to increased maintenance. Identify the solids type, particle size, hardness and concentration.
- Flammable or combustible – If the fluid is flammable or combustible, the flow meter and associated system components must be of suitable construction to prevent an explosion or fire.
Selecting a Flow Meter
Huge volumes of liquid chemicals pass through flow meters every day worldwide. Many of the chemicals are highly corrosive.
For example, large quantities of sodium hypochlorite (bleach) are used to treat water so it is safe to drink. Sodium hypochlorite is incredibly corrosive, and in the United States alone, approximately 39 billion gallons of potable water are treated per day, resulting in enormous consumption of just this one chemical, which is one of many used to treat
potable water.
Larger chemical grade flow meters are used to track the volume of chemicals being loaded and unloaded into railcars, tanker trucks and large storage tanks.
Smaller flow meters are commonly used to fill drums and intermediate bulk containers (IBCs), providing an accurate and efficient way to measure the flow of liquids during the filling process. They can also be attached to portable drum/IBC pumps for dispensing liquids out of drums and IBCs.
Make sure to choose the correct style of flow meter for the application. For example, some flow meters do not handle solids well or may not be suitable for a hazardous location. Review the location where the meter will be installed to make sure the one being considered will fit. Utilize the knowledge and experience of the distributor or manufacturer.
For more on flow meters, visit pumpsandsystems.com/tags/flow-meters.
