By Caleb Hansen
Picking the right remote tank level monitoring system can seem an overwhelming task. With so many options and technologies to choose from it’s perfectly normal to worry about picking the wrong one. The best way to avoid making a bad decision is to have a thorough, research-based understanding of your applications.
To reduce the chance of buyer’s remorse, an experience much to be avoided, ask the questions that follow.
Where are your tanks?
This question really has to do with the distribution of your tanks rather than the actual geographical location. What we mean is: Are all the tanks grouped together in one location? Or are they spread out across the country, miles apart from each other?
If the tanks are all in one location next to each other, you can have multiple sensors on one Internet connection. You will want to choose a sensor that takes advantage of this. A good example is a system that uses a communication protocol, known as Modbus RTU, which designates sensors as master and slave units.
In this scenario, one master sensor polls all of the slave sensors. Each slave reports back to the master with its reading. Then the master bundles all the readings and transmits the data through a single Internet connection. This saves money by reducing long-term data expenses.
On the other hand, if your tanks are spread out then each sensor must have its own connection. Besides paying more in data charges expect to pay extra for additional communication equipment needed at each tank site. If landline is readily available at some of these sites, take advantage of it. If this is not the case, consider sensors with wireless access to the Internet. These can be convenient, but come at a cost.
The important thing to remember here is to not make the mistake of installing a solution that is not really needed. It doesn’t make sense to place a wireless sensor, or a network connection on each tank at a tank farm.
What power supply options are available to you?
Evaluate what kind of power infrastructure is available for your tanks. Ensure that all equipment — including tank gauging, communications and other support equipment — will receive sufficient power to perform properly. Depending on what is available, the voltage requirement on the sensors may become a priority specification during the procurement process.
For locations where there is no electrical grid, consider using batteries or even solar panels to power sensors and communication equipment. Some batteries can last up to a year or more. Become familiar with your options to limit the number of replacement trips to tank sites.
Solar panels don’t need to be replaced nearly as often. However, before installing solar panels take note of how often the area sees sunny versus overcast days, and be aware of the trees or other features that may cast shadows throughout the day.
What are your communication options?
If your tanks are installed in a location where there is an existing infrastructure with Internet connectivity, think a little about your communication options before making a final decision.
If landlines are available, use them. If installing landlines is feasible, seriously consider doing just that. Landlines allow transmitting the maximum amount of data for the best price. You won’t be limited as much by data-size restrictions as with other communication technologies. But, if landlines are not available and it doesn’t make sense to install them, consider other technologies.
Over the past two decades, cellular coverage has grown so rapidly that even seemingly remote locations have service. If no landlines are nearby, the next logical choice is a cellular modem. Most level sensors don’t require a lot of bandwidth to transmit their readings. Quite often, just signing up for a three gigabyte per month data plan is all that is needed. This is more than enough space for a few dozen sensors logging once a day. So at an average of $30 a month, you are transmitting valuable data.
If your tanks lie outside of an area with cellular coverage, consider purchasing radios to extend connection range. Or use a mesh network — i.e., a web of radios — to transmit data over long distances until reaching cellular coverage or a landline.
If neither of the above options is available, look into paying for satellite equipment. This technology is expensive but may be the only option. Even then it still may be less expensive than routinely driving out to a tank.
How do you want to access data?
This question really boils down to how accessible you would like your information to be.
For maximum accessibility, look into an online solution hosted by a company that specializes in remote monitoring. Many sensor manufacturers offer solutions that allow users to log into a website and access the tank level there. The ability to access data from any device with Internet connectivity makes tank level monitoring convenient. Furthermore, these services are often inexpensive.
If you prefer not having data online and are more comfortable keeping it on the local network, be prepared to spend a little more. Keeping the data to yourself often requires investment in additional equipment and heavy involvement by IT personnel. There are a variety of software packages available for tank level monitoring.
Again, this can get expensive, especially if you are looking for a custom solution.
How tall are your tanks?
Finally, start thinking about what kind of sensor technology to use. We won’t go into much detail here since so many factors need be considered. But a good starting point for choosing a tank level sensor is to know the tank height.
This is for two reasons. First, it precludes certain technologies immediately. For example, stem float level sensors that are more than 20 feet long are expensive to transport. Not to mention the heavy machinery needed to install them.
Second, knowing the height helps determine the detection/sensing range of the sensors. Non-contact level sensors like ultrasonic and radar sensors come in various ranges. Buy something that is able to sense the full range.
It is also worth mentioning here that pressure sensors are often among the better technologies for tank level measurement. The easy installation, small price tag, extensive sensing range and immunity to most environmental issues, such as surface turbulence and foam, make pressure sensors a versatile option.
Additional factors must be considered when choosing a remote tank level monitoring system. So be sure to seek advice from tank level monitoring professionals and be confident in getting the right solution for your unique application.
Caleb Hansen is a technical support specialist with Automation Products Group, Inc., Logan, Utah. He is a graduate of Utah State University. He enjoys assisting professionals overcome their tank level control challenges and has built a reputation as the “go to guy.”
Automation Products Group, Inc. (APG) supplies flexible sensing solutions for measurement applications to many industries, including the water and wastewater, oil and gas and medical markets. APG specializes in level, pressure and remote sensing technologies and is known for sensors that perform well in harsh and hazardous conditions. APG has roots in the sensor business spanning more than 35 years.