Specialist Ultrasonic Level Technologies

Welcome to Coltraco Ultrasonics’ range of Ultrasonic Tank Liquid Level Indicators. 

We pride ourselves with the quality, reliability and accuracy of our instruments – all made in the UK. 

Our Ultrasonic Tank Liquid Level indicators are non-invasive and are designed to measure the liquid levels in your tank through the external side-walls, different to conventional ultrasonic tank level gauges which need to be inserted from the tank top and performs the level measurement top-down. 

Why choose Coltraco Ultrasonics’ range of Ultrasonic Tank Liquid Level Indicators

  • Portable and non-invasive to locate liquid levels through the side walls of tanks (no drilling or tank opening is required, thus no downtime) be 
  • Works on tanks as small as 0.5 metres to 15+ metres 
  • Works on tanks with different wall materials (metals, plastics, glass etc.) and wall thicknesses
  • Works on virtually all types liquids – it can be measured as long as it is in a liquid state!
  • Ideal instrument to locate liquid levels in tanks which do not have existing methods of locating the liquid level
  • A highly accurate replacement to traditional level gauges such as sight glasses or float level gauges without needing to make any changes to the tank
  • A complementary instrument to tanks with built-in fixed level indicators in order to periodically verify the accuracy of their measurements
  • Advanced diagnostics available through a supplementary handheld oscilloscope which is included with each instrument for calibrating the sensor to the tank being tested for maximum accuracy and assist in troubleshooting
  • The Portatank® is a portable instrument which allows one instrument to be used across multiple tanks on the same site and requires only a single operator and no installation costs 

The Portatank® is also a suitable “interim” instrument for detecting liquid level in tanks undergoing maintenance or re-fitting of their built-in level gauges 

How does Coltraco Ultrasonics’ range of Ultrasonic Tank Liquid level Indicators work? 

All of our ultrasonic tank liquid level indicators use ultrasonic sensors to identify the liquid levels in the tanks. Ultrasonic sensor technology or Ultrasonic Testing (UT) is a reliable, versatile and safe method for Non-Destructive-Testing (NDT). Ultrasonic waves are sound waves with frequencies above the upper limit of human hearing (above 20kHz, or 20,000 Hz). Sound waves are mechanical waves that travel in a straight line and require a medium through which to travel. The propagation and attenuation of sound waves depend on the structure of the medium down to an atomic level; therefore, ultrasound is a useful method of studying a material’s structure and the processes occurring within it. 

Whilst the highest frequency a human can hear is around 20,000 Hz, our range of ultrasonic tank liquid level indicators are high-frequency ultrasound transmitters that use sound at a frequency of 200,000 Hz (200 kHz) up to 2,000,000 Hz (2 MHz). To do this, the main unit sends a strong electrical signal to the sensor (a piezoelectric crystal), which then emits a high energy pulse of ultrasound into the tank wall through what is known as the reverse piezoelectric effect.  

The term ‘piezoelectricity’ has its roots in the Greek word ‘piezein’ (to press) and was discovered in 1880 by Pierre and Paul-Jacques Curie. Piezoelectricity is the appearance of an electrical potential across a crystal when it is subjected to mechanical stress and is a reversible effect. A crystal that exhibits this effect by becoming charged when it is compressed, or distorted is a piezoelectric crystal. Similarly, passing electricity through a piezoelectric crystal causes the crystal to vibrate back and forth (producing ultrasound); this is the reverse piezoelectric effect. 

The ultrasound is conducted through the solid walls of the tank and then interacts with the contents. After the sensor stops emitting ultrasound, it starts listening for the returning echoes of the signal. If liquid is present, the echoes will return to the instrument and the instrument will react accordingly through LED indication. If no liquid is present, the echoes will not be returned. This process allows the instrument to detect the presence or absence of liquid behind the area of the container wall where the sensor is placed. This method of ultrasound liquid level detection is commonly known as “pulse-echo”. 

ultrasonic sensor

Types of Application for Our Range of Ultrasonic Tank Liquid Level Indicators 

Transformer / Ring Main Unit (RMU) oil level indication  

The Portatank®, which is our handheld ultrasonic tank liquid level indicator has been successfully used to detect the oil levels in several transformers and ring main units (RMU). 

The ring main units (RMU) tested were part of the Yorkshire switchgear distribution box. The oil tanks contained in the switchgear distribution box were approximately 35cm – 40cm in length and width. We have successfully identified the correct oil level in these distribution boxes and compared the result against a built-in mechanical level indicator. During the test, the built-in mechanical level indicator indicated that the tank is full, while the result from the Portatank®, identified the oil level about 7cm below the tank level shown by the float gauge. 

The oil level found with the Portatank® was later verified using a dip stick. The dip stick measurement was exactly the same as the level accurately identified using the Portatank®. This was able to showcase the limitations of a built-in mechanical level indicator and how the Portatank® is an accurate and reliable instrument of non-invasively detecting the oil levels. 

Separately, the Portatank® is also currently in use with multiple Power Generation companies around the world. These are used to locate oil levels in Single-Phase and Three-Phase transformers and are applicable to multiple kVA ratings i.e. 19.9, 25, 50, 75, 100 kVA etc. Due to the non-invasive nature of the Portatank® measurement, these transformers can remain “live” during testing without having to risk opening the transformers. When a transformer is opened, there is a risk of introducing oxygen into the structure. If the oil levels are depleted, there is a potential for combustion to occur with the mixing of oxygen due to the excessive amount of heat generated by the transformers themselves in the absence of oil which cools and insulates the structure. 

Key Measurement Considerations – Ultrasound Couplant 

For the Portatank® to measure liquid levels reliably, it is important to ensure sufficient ultrasound couplant is used. Ultrasound couplant, in the form of ultrasound gel works by reducing the air pockets between the sensor and the tank wall, and allows for efficient ultrasound transmission. Our sensors for the range of ultrasonic tank liquid level indicators we manufacture, such as the Portatank®, works with almost any type of ultrasound gel. These usually can be purchased locally in your country, in a pharmacy for example. Medical ultrasound gel is cheap and widely available and will work well with our instruments. 

Key Measurement Considerations – Presence of Intrusive Structures 

As described in previous sections, the measurement principle of our range of ultrasonic tank liquid level indicator is based on a “pulse-echo” methodology. This relies on the transmitted ultrasound from the sensor through the liquid which is reflected off the opposite wall in your tank. 

If internal structures are present in your tanks, it is possible for our instruments such as the Portatank® to work as the ultrasound signal can still be reflected off your internal structures back to your sensor. Please get in touch with us to discuss your application if you feel you have a challenging application. 

More complicated structures such as transformers may be filled with internal structures, of various shapes and sizes which can cause the reflected sound waves to be inconsistent. In this instance, it is recommended to test on a section of your tank closer to the edges where you are able to obtain a clear pathway of ultrasound transmission through your tank. The Portatank® sensor is about 25mm / 1” wide and therefore you will only need a strip that is as wide as 25mm / 1” for the measurement to be done successfully. 

How to identify if you are performing a reliable measurement with only a single LED on the instrument? 

Our range of ultrasonic tank liquid level indicators, such as the Portatank® is supplied with a handheld oscilloscope. The handheld oscilloscope connects directly to the Portatank® and provides visibility to the ultrasound signal as it travels in your tank. It is not required during measurement, however, it can greatly aid troubleshooting purposes and help establish a reliable liquid level in your tanks. 

The reflected sound waves are clearly observed on the oscilloscope when the sensor is below the liquid level and the reflected sound waves are often not visible when the sensor is above the liquid level. Some examples of this can be seen in the screenshots below: 

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