Case Study – Implementing Four-Point Liquid Level Control Using a Float Level Switch

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The float level switch is a common level measurement and control instrument in industrial production. It operates faster and has a longer service life than mechanical switches; it is more resistant to interference than electronic switches; and it can achieve multi-point control. It is widely used in shipbuilding, papermaking, printing, generator equipment, petrochemicals, food industry, water treatment, electrical engineering, dye industry, hydraulic machinery, and other industries.

Four-Point Liquid Level Control

Customized Case Sharing

A customer from the Philippines saw our product on our website and contacted us. The customer wanted to achieve four-point control of the diesel level in a storage tank. After multiple communications and drawing revisions, the final parameters are as follows:

  • Float Level Switch
  • Measuring Medium: Oil
  • Measuring Range: 643mm
  • 4 Control Points, from top to bottom:
  • 236mm (Normally Open)
  • 326mm (Normally Open)
  • 506mm (Normally Closed)
  • 596mm (Normally Closed)
  • Ambient Temperature and Pressure
  • ANSI 3-inch Class 150 Flange Connection
  • Material: 304 Stainless Steel
  • 220VAC

What Are The Components Of A Float Level Switch?

The liquid level measurement technology of a float-type level switch is based on the buoyancy of a float. Because of its low density and buoyancy, the float rises when the liquid level rises and falls when the liquid level falls. The liquid level is measured by utilizing the rise and fall of the float caused by changes in liquid level. Modern float switches are designed with high precision. The simplest single float switch consists of the following components: a hollow float with a built-in magnet, a guide tube for guiding the float, a reed contact inside the guide tube, and an adjusting ring to limit the movement of the float within the guide tube.

Working Principle

One or more reed switches are placed inside a sealed metal or plastic tube. One or more hollow floats containing ring magnets are then passed through the tube. A fixing ring controls the position of the float and the reed switch, allowing the float to float up and down within a certain range. When the liquid level rises to a set value, a set switching signal is emitted.

The reed switch consists of contact pieces located inside the sealed body. When a float switch is used in conjunction with a normally open reed switch, the contacts move closer together when a magnetic field is applied, allowing current to flow and completing the current loop. If a normally closed float switch is used, the contacts move further apart, breaking the current loop when a magnetic field is applied. This creates the opening and closing action, which can control the liquid level. The diagram below shows the positions of the float switch in normally closed (NC) and normally open (NO) states.

Float Level Switch structure
Float Level Switch working principle

Features

  • Multi-point control is possible.
  • Switch positions can be customized to user needs.
  • No power supply is required; using reed switches.
  • Contact life reaches 2 million cycles.
  • All switch wiring exits are in the same junction box, which requires external installation and reduces wiring costs.
  • Compared to other types of level switches, it offers high cost-effectiveness with multiple switch control points.
  • Junction boxes have an IP65 or higher protection rating.
  • Conduits are available in PVDF, PP, PVC plastic, and SUS304 and SUS316 metal. Therefore, suitable products are available for use with acids, alkalis, solvents, and various fuels.
  • The reed switch and wiring are completely isolated from the liquid, making it safe for use in high-temperature and high-pressure equipment.
Multi Level Float Switch-Controller
Multi Level Float Switch/Controller | 1~4 Points
Magnetostrictive Level Transmitters
Magnetostrictive Level Transmitter | High Accuracy 0.2m～23m
Rf admittance level switch
RF Admittance Level Switch
Electrostatic Capacitive Level Switches
Electrostatic Capacitive Level Switches

Installation Requirements

  • When the liquid fluctuates significantly, please install a wave deflector.
  • Keep away from water inlets during installation.
  • Clean regularly to prevent debris from clogging the float and causing malfunctions.
  • Always use within the contact capacity to prevent burnout.

Application Industries

Petrochemical Industry: Level control for chemical raw materials, intermediate products, and finished product storage tanks.

Power Industry (Generator Equipment): Monitoring of cooling water and lubricating oil levels in generator sets; boiler water level control.

Shipbuilding Industry: Monitoring of fuel tanks, freshwater tanks, and ballast tank levels.

Food Industry: Level control in food processing, beverage, and dairy production.

Water Treatment Industry: Monitoring water levels during wastewater treatment; controlling the rise and fall of raw water and purified water levels.

Float Level Switch thread installation

How To Find A Suitable Float Switch?

To find the right float switch for your application, you should determine the following parameters:

  • Measuring medium
  • Medium density
  • Process pressure
  • Process temperature
  • Number of switch contacts
  • Position and function of each switch output
  • Conduit length
  • Electrical connection
  • Process connection (threaded or flanged, and dimensions)
  • Material compatibility (stainless steel, plastic, etc.)

Most importantly, you can directly provide us with a drawing of the tank dimensions and the height of the level point you need to control. As a float level switch manufacturer, we will create custom drawings based on your requirements. This avoids incorrect production dimensions that could lead to installation problems.

FAQ

After installing the float level switch, add liquid. As the liquid level rises, the float will also rise. If used in conjunction with a normally open reed switch, the rising float will sense the magnet inside the conduit, causing the contacts to move closer together. Current will then flow through the contacts, completing the current loop and controlling the downstream valve.

A float level switch may malfunction due to a stuck float; weakened magnetism inside the guide tube; a detached float; poor wire contact caused by oxidation or corrosion; or water ingress into the terminals, leading to switch failure.

A level transmitter continuously monitors the liquid level and transmits the level signal to downstream equipment. It can also be configured with a display to show the current liquid level. Furthermore, it can be used in conjunction with secondary instruments to control the liquid level.

Level switches include RF admittance level switches, rotary paddle level switches, tuning fork level switches, capacitive level switches, and float level switches. While float level switches can only be used with liquids, the other types can be used with both solids and liquids.

Level meters are generally classified as non-contact level meters and contact level meters. Non-contact level meters include ultrasonic level meters and radar level meters. Contact level meters include capacitive level meters, submersible level meters, and float level meters. The biggest advantage of level meters is their ability to continuously measure liquid level and output analog signals or communication protocols to backend devices for level monitoring. Furthermore, level meters can be used in conjunction with secondary instruments to control liquid level.

Level switches, on the other hand, are all contact type, including capacitive level switches, tuning fork level switches, and float level switches. Level switches only output one or more relay signals when the liquid level reaches one or more set heights. Level switches can only provide simple level control and cannot continuously monitor the liquid level.

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Sino-Inst’s float level switch is a simple, easy-to-use, safe, reliable, and cost-effective level controller suitable for various level measurement applications. Customization is supported for conduit material and length, switch output position, process connections, and other specifications. If you have level control needs, please contact us.

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