Float Switches

A float switch (or a float sw) is a level sensor used to detect the level of liquid usually in a tank, container or well. The flotation part of the device sits on top of the liquid and will switch on the rise and fall of the liquid. Float switches are used for automatic level control of groundwater, wastewater, and sewage pumps, for raw water and liquid transfer pumps at waterworks, and for high water alarms.

How Does a Float Switch Work?

Float switches have a reed switch and a pivoted magnet, and they can be used for normally open (N/O) or normally closed (N/C) operation. The switch action can be reversed by rotating the switch through 180°.

Float switches function by floating on the surface of the liquid. As the liquid level changes, the float moves up or down, causing an internal reed switch to activate (either closing or opening) at a predetermined level.

The internal mechanical switch opens or closes the electrical circuit due to gravity, which enables it to turn the equipment on and off.

What Materials Are Float Switches Made of?

• Nylon: Used for oils, diesel and organic chemicals.
• **Polypropylene (PP): **Acids and alkali, detergents, oils, water and organic chemicals.
• Polyphenylene sulphide (PPS): Used for more aggressive chemicals, and applications that require higher temperatures of up to 120ºC.
• Stainless steel: Medical and food industries, hydraulic fluids and chemicals.

Types of Float Switches

Float switches are versatile level sensors used across numerous industries. From residential to industrial applications, these devices offer reliable solutions for managing liquid levels effectively and safely:

Vertical Float Switches

These common float switches are designed for vertical installation and trigger a switch as the float moves with the liquid level. Ideal for water storage tanks, sump pumps and sewage systems, vertical float switches come in a variety of specifications, including 240V options, to meet the needs of different setups.

Horizontal Float Switches

Horizontal float switches are installed horizontally, typically on the side of a tank or vessel. Much like vertical float switches, they utilise floats that rise and fall in response to liquid level changes, activating a switch mechanism. These switches are often used in applications where space constraints or specific mounting requirements necessitate a horizontal configuration.

Cable-suspended Float Switches

Cable-suspended float switches offer greater flexibility for installation, as they are suspended from a cable within the tank or vessel. This allows for precise positioning and level control, making them suitable for applications requiring accurate level monitoring, such as chemical processing or water treatment.

Magnetic Float Switches

Magnetic float switches utilise a magnetic field to activate the switch mechanism, eliminating the need for direct physical contact between the float and the switch. This design enhances reliability and longevity, particularly in harsh environments or applications involving corrosive or viscous liquids.

Stainless Steel Float Switches

Stainless steel float switches are known for their exceptional durability and corrosion resistance. They are ideal for use in demanding industrial environments, chemical processing plants and food and beverage applications where hygiene and cleanliness are paramount.

Pneumatic Float Switches

These float switches operate based on changes in air pressure within a tube or chamber as the liquid level rises or falls. They offer a reliable and intrinsically safe solution for hazardous environments or applications where electrical sparks could pose a risk.

Waterproof and IP-Rated Float Switches

Designed for use in wet or submerged environments, waterproof and IP-rated float switches provide reliable level control, ensuring protection against water ingress and damage. They are indispensable in applications like water storage tanks, wastewater treatment plants and marine environments.

Ultrasonic Float Switches

Utilising ultrasonic waves to measure the distance to the liquid surface, ultrasonic float switches provide non-contact level detection, making them ideal for applications prioritising cleanliness and hygiene, such as food and beverage processing or pharmaceutical manufacturing.

Dual-Point or Multi-Point Float Switches

Dual-point or multi-point float switches incorporate multiple floats or sensors to provide control or monitoring at two or more levels within a tank or vessel. This allows for greater control over liquid levels, and enables features such as high-level alarms, pump control, or automatic filling systems. They are essential in optimising efficiency and ensuring safety in various industrial and commercial applications.

Features and Benefits of Float Sensors

Float switches also offer a range of features that make them a reliable and effective solution for liquid level monitoring and control:

• Highly Flexible: They are available in various configurations, including vertical, horizontal and cable-suspended configurations. This adaptability makes them suitable for a wide range of applications and environments.
• High Mechanical Load Rating: These switches are robust and capable of withstanding significant mechanical stress, ensuring reliable operation even in demanding industrial environments.
• Insensitive to Turbulence: Float switches are designed to function accurately even in turbulent or agitated liquids, providing consistent level detection and control.
• Shock and Rupture Proof: Many float switches are built to withstand shocks and impacts, making them suitable for applications with potential mechanical disturbances.
• WRAS Approvals: Certain models comply with Water Regulations Advisory Scheme (WRAS) standards, ensuring suitability for use in potable water applications.

Applications of Float Switches

Float switches are adaptable tools used across various industries to effectively monitor and manage liquid levels. Their common applications span various fields, including:

• Sump Pits: To prevent flooding, float switches manage pumps to remove excess water from basements and other flood-prone areas.
• Fuel Tanks: Float switches help ensure safe operations by monitoring fuel levels. They can trigger alarms or halting pumps to avoid overfilling.
• Coolant Tanks: Optimal coolant levels in engines and machinery are upheld by float switches, preventing overheating and subsequent damage.
• Oil/Water Separators: Efficient operation and environmental compliance are ensured as float switches automatically drain accumulated water while preserving valuable oils.
• Wastewater and Sewage Treatment: Float switches — similar to flow meters — regulate wastewater flow and trigger alarms or pumps at critical levels to avert overflows and uphold treatment procedures.

Explore Temperature Controllers Today

RS NZ, a trusted source for industrial automation and control, offers a comprehensive range of float switches from top brands like Flowline and ATMI.

Whether you’re using a digital thermometer or other equipment to ensure accurate temperature management, shop RS NZ’s selection today and experience the difference precision makes to take your process control to the next level!

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