Ultrasonic and Pressure sensor
telemetry solutions for tanks

tank telemetry: home tank connected

Ultrasonic and Pressure Sensors


The introduction of IoT allows a wider choice of technical solutions, but it increases the complexity of the installation options. SilentSoft Customer Service Specialists take care of the whole project management for the installation campaign, covering device availability for the installers, appointments with site managers and interfacing with customers on specific requests. With more than 20 years of experience in installing telemetry solutions on tanks, SilentSoft has built a European network of trained installers. We invite you to contact us to see how we can best help you manage your IoT project for bulk tanks.

From the very start of tank telemetry in 2000, two main sensor technologies have existed to monitor liquids in tanks: ultrasonic and pressure sensors. With 20 years’ experience in telemetry installations, SilentSoft is sharing practical use cases where the installer may select the best implementation.

How do the sensors work?

Pressure sensors are placed at the bottom of the tank, measuring absolute pressure and sometimes temperature. The pressure at the bottom of the tank is compared with another pressure sensor in the transmitting device (we call this solution differential) or with pressure information coming from weather monitoring sites. The pressure difference allows to calculate a product height taking into account the density of the product inside the tank. The product volume is calculated with the tank geometry and dimensions.

tank telemetry: pressure sensor with data logger

Ultrasonic sensors measure the absence of product in a closed environment (like a liquid in a tank). The product height calculation is made taking the tank height (up to the Safety Fill Level – SFL -) subtracting the absence of product. There is sometimes need for an offset if there is a difference between the bottom of the ultrasonic sensor and the Safety Fill Level.

tank telemetry: ultrasonic sensor with data logger tank telemetry: ultrasonic sensor (zoom) with data logger

What are the technical differences?

The pressure sensors used by SilentSoft have a precision of +/- 3mbar with a measure spread of 800 to 1400 mbar. There is need for a different type of sensor if the tank is at an altitude of more than 1500m or if the tank height is over 4m.

Ultrasonic sensors have a precision of +/- 2cm and do not need any outside pressure information. There may be slight differences due to temperature variations as the monitored product may expand.

Ultrasonic sensors need to be placed on a fitting that is in the center of the tank.

What are the installation constraints?

All telemetry solutions on tanks need to have access to a fitting. If it is available and that there are no network issues, the sensor installation can be done in 30mn.

In the absence of a fitting, and as long as safety regulations will allow it, there is the possibility to drill a hole on the top of the man hole, create a fitting, and insert a pressure sensor at the bottom of the tank. In case there is already a device using the only available fitting, the technician can install a “T” to allow a pressure sensor to be inserted.

tank telemetry: pressure sensor with data logger at fitting point

Ultrasonic sensors need to be placed on a fitting that is in the center of the tank.

tank telemetry: ultrasonic sensor with data logger

If it is too close to the edge (as shown below), or if the tank has a rectangular shape with internal metallic reinforcements, there is the possibility that the radar interprets that the tank is still full when in fact it is empty.

tank telemetry: ultrasonic sensor not properly installed tank telemetry: ultrasonic sensor not properly installed

Should these cases occur, there is the possibility to drive the radar signal through a PVC tube to avoid interferences. The solution works when there are no physical constraints inserting the PVC tube to the bottom of the tank. Some tanks in cellars or basements do not have sufficient height between the top of the tank and cellar / basement ceiling for installation of such a solution The installer will have to drill small holes (too large holes could have an impact on the ultrasonic readings) at the top of the PVC tube to allow the air to escape when there is a filling.

Current solutions used for ultrasonic sensors require a fitting of at least 2 inches. Anything smaller will need a pressure sensor solution that can adapt to a one inch fitting. PVC tubes also need to be placed away from the filling point. The force of the pressure can damage or misplace the PVC tube.

tank telemetry: ultrasonic sensor on the side with tube tank telemetry: ultrasonic sensor in the middle with tube
tank telemetry: ultrasonic sensor on the side with tube and discharge point

Installation optimizations

SilentSoft has introduced solutions that allow to manage 2 tanks with one transmitting device. This will reduce the cost of the telemetry solution when two tanks are physically side by side.

tank telemetry: pressure sensor 2 tanks with one data logger

How to manage an installation on site?

The ideal situation before performing any installation is to have a picture of the tank situation / location and a picture of the man hole to check if there are fittings available. In all cases the installer needs to have fitting adapters pending the tank configuration, “T” adapters, in case the fitting is already used. Placing a PVC tubes on ultrasonic sensors have transport and installation constraints.

SilentSoft installers will always seek to install the most cost effective solution by default. On top of adapting the sensor solution to the tank configuration, the technician has to select the best available network. There is the choice of Public Cellular Wide Area Networks (2G/3G/4G) vs. Low Power ones (LoRa, Sigfox, NB-IoT for example). Some transmitting devices give the option to add an external antenna. Pending the product measured there may be the need to have ATEX certified sensors and modems. This will also drive the choice of the device prior installation.

2G / 3G Sunset: Managing a real life case study

2G / 3G sunset

2G / 3G Sunset

As telecom operators are freeing up spectrum resources to introduce 5G, certain 2G or 3G networks are planned to be switched off. This is likely to have severe impacts on customers who wish to continue benefiting from existing M2M (Machine To Machine) services based on those technologies. This article shares some ideas to what service providers have to take into consideration when managing a 2G/3G Sunset situation and extending an Internet of Things service.

Interface regularly with telecom operators and start early

Every European country has its own migration strategy. There may also be different agendas within a same telecom operator. The telecom operator B2C and B2B/M2M/IoT business units have different priorities. There are several technical, business (and sometimes political) considerations before deciding to switch off a network. Some operators may favor a 3G Sunset to better guarantee voice services over a large territory (2G base stations can be installed further apart). Should a 2G network be planned for a shutdown, with devices communicating on 2G modems, there are no software upgrade options to manage the sunset. The M2M/IoT service provider has to finance the acquisition of new hardware and manage an important installation campaign. When there is a 3G Sunset, the situation can be easier, as recent 3G modems generally have 2G capacity.

Optimize the existing technology solutions

SilentSoft has been operating an M2M (Machine To Machine) service in Europe since 2000. SMS and GPRS services have been used very early with a satisfactory quality of service at reasonable prices. The introduction of dual mode modems allows to install 3G/2G solutions. In case of lack of network in a domestic market, SilentSoft uses Mobile Virtual Network Operators (MVNO) to allow national roaming. For non-Swiss territories, SilentSoft uses a Swiss telecom operator SIM card to allow roaming on the best available network.

Involving the customer

The SilentSoft Service License Agreement (SLA) focuses on delivering a daily service. Nevertheless, the M2M/IoT service provider cannot guarantee the continuous operation of the public network managed by a third party telecom operator. SilentSoft is managing a complex operational challenge since 2017. The joint announcements of Swiss telecom operators ceasing to guarantee quality of service on 2G networks beyond 2020, obliges SilentSoft to contact more than 800 customers and manage close to 15’000 2G subscriptions. SilentSoft has chosen to share the upfront cost burden with the customer in exchange of a promotional offer over the replacement subscriptions. The complete process to change the park will take 4 years.

Selecting the appropriate replacement technology

There are 3 considerations to take into account: (1) network coverage, (2) cost, and (3) quality of service.

1. SilentSoft operates an Internet Of Tanks service: StockView. The transmitting device is often in a “deep indoor” coverage situation. This means that the communicating device can be located underground or in a basement. SilentSoft has been measuring network coverage with different technologies upon every installation for the past two years. The first findings show that there is a difference to take into account between the signal strength indicated by the network detector and the signal strength received in the payload of the communicating device. Results differ between different technology providers. When performing coverage tests for Low Power Networks (like LoRa for example) in Switzerland, we have noticed that there is a better coverage in urban areas vs. rural ones. This can be due to the fact that telecom operators wish to maximize smart city use cases.

2. After receiving quotes from different telecom operators and modem/sensor providers for two years, it appears that there are greater gains in battery costs vs. telecommunication subscriptions costs. The Low Power technology allows to have smaller batteries with similar lifespans than existing M2M solutions (more than 5 years pending network and weather conditions).

3. For quality of service there are extra considerations to take into account: (i) is the sensor connected to a unit that records the readings – we call a Logger – or does it send the last reading pending the planned transmission schedule, (ii) is there a fall back strategy should there be a temporary lack of network – SilentSoft interprets SMS messages when there is no GPRS connection, and (iii) is there need to review network access strategies (signal strength output) when operating a service on license free networks (LoRa and Sigfox for example).

The technology selection process is dependent on 5G introduction strategies of each telecom operator (these may differ between different operators in a same European country). Low Power networks (NB-IoT, CAT M, LoRa, Sigfox) will gradually become the replacements for 2G and 3G beyond 2025. The variety of options and technology transition calendars per European country have led SilentSoft to integrate solutions from third party technology providers. This allows us to deliver several telecommunications access combinations in order to deliver the optimum quality of Service in any given European country. SilentSoft is currently integrating LoRa devices on top of the existing 3G/2G solutions. The integration of NB-IoT and Sigfox sensors will start in 2020.

Current understanding of the European landscape for 2G/3G Sunset

This is our current understanding of the 2G/3G Sunset timeline in Europe:

Country Operator 2G/3G sunset date*
Norway Telia Norge AS Final 3G shutdown 2021, phasing out starts in 2019
Norway Telenor Norge AS 2G shutdown 2025, 3G shutdown 2020
Sweden Three 3G shutdown 2020
Sweden Telenor Sverige AB 3G shutdown 2020
Sweden Tele2 AB 3G shutdown 2025
Sweden Telia Company AB 3G shutdown 2025
Denmark Three 3G shutdown 2020
Netherlands KPN B.V. 3G shutdown Jan 2022
Germany Vodafone GmbH 2G shutdown 2025, 3G shutdown 2020
Austria Three 3G shutdown 2020
Liechtenstein Telecom Liechtenstein AG 2G shutdown Jan 2021
Switzerland Swisscom Ltd 2G shutdown 31.12.2020
Switzerland Sunrise Communications AG 2G shutdown 31.12.2021
Switzerland Salt 2G shutdown 31.12.2020
United Kingdom EE Limited 3G shutdown 2022
United Kingdom Three 3G shutdown 2020
United Kingdom BT 3G shutdown 2021
Ireland Three 3G shutdown 2020
Italy Vodafone Italia S.p.A 2G shutdown 2025, 3G shutdown 2020
Italy Three 3G shutdown 2020

*The information is not always official and there may be some mistakes. We appreciate if the reader can correct us with any official links and statements to be sent at: info@silentsoft.com

From M2M to the Internet of Tanks

télémétrie citerne - connected tank telemetry

The Internet of Tanks

The tank telemetry customer value proposition exists since 2000. The main service is to prevent stock outs for property managers and distributors using Machine-to-Machine (M2M) type of connectivity. The latest Internet of Things technologies applied to tank telemetry (we call it “the Internet of Tanks”) allow to prepare new business models, reduce operational costs, build new sales and marketing propositions, digitalize and optimize processes with more efficiency than before.

For nearly two decades the cellular M2M solutions have allowed one machine to communicate to another one using the cellular networks. The installation, hardware, platforms and portals are generally all available from one same provider. The technology bricks (hardware, platforms, and applications) are generally proprietary and all coming from one same service provider.

This model has the advantage of dealing with one vendor and getting one invoice only. Installation campaigns are performed by the vendor from a list of tank locations shared by the oil and gas distributor or property manager. The service provider is the project manager. He captures the tank geometry and dimensions, the availability of a fitting (to place the gauge), makes the appointments for the technicians, configures the alerts and manages the park surveillance. He is also in charge of planning the intervention orders should there be a maintenance visit to perform. The technician has the responsibility of selecting the best suited hardware (ultrasonic vs. pressure sensor) on the best network (cellular vs. LoRa or Sigfox).

The Internet of Tanks (IoT) opens up this model. With IoT technologies, service providers like SilentSoft can extract every building block of the value chain. At SilentSoft, we have taken the strategic decision to make this shift, evolving from a closed model to an open approach. The service offerings are tailored from a MySilentSoft platform licence in case the distributor wishes to operate the service himself up to a complete end-to-end solution. This license only option is currently used by some of our customers (distributors).

Telemetry – What for?

The tank telemetry proposition is primarily used to prevent stock outs. This first (and essential) service can be completed by adding new sales and marketing value propositions.

  • « Push » sales : We see many distributors who negotiate annual contracts with their B2B customers. It may be for heat (heating oil and LPG), lubricants or collecting waste oil. Open purchase orders are linked with telemetry propositions allowing automated replenishments. This model helps to deliver on forecasted revenues and gives the end customer piece of mind.
  • « Pull » sales : We have distributors who decide to share an access to the My SilentSoft platform (telemetry dashboard) to the end customers. In this case, SilentSoft will white label its platform to the distributors brand. The end customer is within the distributor’s environment. The management of the orders (and the responsibility of stock outs) is transferred to the end customer. This service can be invoiced by the distributor. SilentSoft sees a great deal of garages and workshops who want to have their own view of lubricant and waste oil levels. It is important to note that the distributor still has access to the data. Sales teams and/or administrators connect daily to the My SilentSoft platform and encourage customers to place orders.
  • ERP Integration : We see distributors and hauliers who use their own ERP and give access to their customers. In this case the data collected by SilentSoft is retrieved via web services. The transmitted data gives the required information to give visibility on the stock status online.

Logistic Optimisation

Logistic optimisation for replenishments makes sense when a certain percentage of the tank park is monitored. The most common figures shared by telemetry service providers are 8 to 15% savings. We have seen distributors share the portal access with hauliers to renegotiate contract services. Certain lubricant distributors have optimized their deliveries by checking all lubricant tanks on site once a threshold is met. This allows to prepare all compartments when going on site. This is particularly appealing to lubricant distributors who promote several blends on a same site.

Operational Optimisation

SilentSoft has worked on a specific case with an LPG distributor in Northern Africa where the distributor decided to equip the whole park to not only avoid stock outs but also better predict the amount of product required before placing an order upstream. The gains covered the telemetry cost the first year. Every distributor has precise models for forecasting. Nevertheless, we can work on evaluating what is the gain in precision. Can the distributors place an order under better conditions should they have better visibility on what can be replenished at any given time?

Migrating to Low Power connectivity

New networks dedicated to the Internet of Things are being promoted throughout Europe. IoT-enabled devices can now operate either on public networks (subscription-based solutions) or on private networks (with services operated by the customer).

The private networks are used in two specific cases: B2C solutions for smart homes (via an xDSL gateway), and facilities (campuses / manufacturing or storage sites) with a wide variety of devices to monitor.

Most of the time, public/operated networks are the best option for tank telemetry. At this stage, SilentSoft is operating devices working on 2G cellular (GPRS) and 3G networks and now on Low Power Wide Area Networks based on the LoRa, NB-IoT and Sigfox technologies. We will also start integrating hardware from third parties. The new low power telemetry devices are more compact (smaller battery for the same life span) and the connectivity subscription rates are similar to low cost 2G.

In terms of sensors, SilentSoft is first integrating pressure and ultrasonic sensors on LoRa and NB-IoT, and in a second phase, on Sigfox. In certain cases, SilentSoft opens the possibility to distributors to contract directly with the installing company.

The MySilentSoft platform will collect and decode the payload (message structure sent from the device) to transform it in meaningful business data (liters). To date, SilentSoft has integrated messages from 5 different hardware providers covering several part numbers.

With more than 20 years of experience in telemetry solutions as an M2M service provider, SilentSoft is now embracing the new opportunities created by the IoT. Contact us to discuss how we can help you to manage efficiently your tanks of lubricants, diesel, heating oil, LPG or waste oil.