Understanding the Complexities of Remote Monitoring and Control
Many people think that remote monitoring is as simple as placing a measuring stick into the top of the tank or reading gauges on the side of a tank, and that controlling equipment remotely is too expensive and not an option. In the last few years, most of the obstaclesthat prohibited these types of solutions in the past have been solved by technology. Tanks, for instance, come in all shapes and sizes and may contain many different substances, from water to grain and even harsh chemicals or explosive materials. In many of these instances, remote monitoring can become a critical requirement. Understanding the what it takes to implement a solution can seem like an overwhelming task. This white paper will help you understand many of the concepts that are important to helping you choose a solution that will not only provide you with the ability to remotely monitor your tanks and other equipment but can potentially save you thousands of dollars inlost revenues and fines. Depending on the chosen solution, you can implement features such as pump shut down or even criticalsecurity monitoring at a fraction of the cost you might expect.
To understand the process of remote monitoring, you need to understand the specific sensors required toprovide the data beingmonitored. In many cases, the sensor not only monitors the equipment—it also provides thecommunicationmechanism to transmit the information. These two features combined are what constitute a full remote solution. A common application that is often the first application for remote monitoring is tank level monitoring. This is important since both full and empty tanks require attention, and tank spills are costly because of product waste and cleanup costs. Becausetanks come in so many different shapes and sizes, the sensor that is used for monitoring the contents is the most critical part of the solution. Data is typically collected by a controller device which gathers the information from the sensor and then transmits the information to a person in alerts or text messages, or to a remote platform computer system. The platform can analyze the information and make critical time-sensitivedecisions. The collection of that information—and the ability to present and analyzethe information—is considered the monitoring piece of the solution. Some of these monitoring systems can also control the equipment used to fill or empty the tank (such as pumps or valves). This is known as a remote monitor and control solution. Having the ability to control equipment remotely (in either a manual or automated fashion) can provide businesses with the ability to better utilize personnel and other resources to maintain the site without fear of excessive downtime from equipment outages or costly spills.
Finally—andpossibly the most important part of having a complete monitoring and control solution— isthe alerts. Having the ability to receive alerts automatically when something goes out of control or reaches a critical reading provides you with a huge advantage in managing your site. Solutions that also provide you with the ability to manage the remote site from any PC orSmartphoneare even more beneficiary and will help to reduce costly trips to your operating sites.
KNOW YOUR TANKS
Tanks come in all shapes, capacities, construction materials, orientationsand access ports. When you add to this complexity of the type of material in the tank with pressure and temperature variations, it becomes difficult to accurately measure tank levels and amount of material in a tank.
When considering remote tank monitoring these are the variables that must be taken into consideration when planning a solution:
- Shape and orientation of the tank
- Height and capacity
- Tank contents
- Location: is it stationary or mobile?
- Sensor accuracy required and margin of error
- Temperature (of both the location and the tank contents)
- Size and location of the access port(s) and obstructions
- Power source: line power or solar
- Cellular coverage availability (and which carrier)
- Does the tank have an agitator inside?
- WiFi or Ethernet availability
- Is this a secure area where additional protection is required?
CHOOSING THE RIGHT TANK SENSOR
Choosing a sensor might seem overwhelming, but if you consider the questions that you answered above then the task will not seem so daunting. In this section, we will review the different sensor technologies available and discuss in what circumstances you might want to consider using each one.
Float Sensors:These are used to sense the level of liquid within a tank. They consist of one or more sensors that are buoyant in the liquid and float to the top of the liquid. There can be more than onefloat when used to detect both oil and water and the water floats on the interface layer between oil and water. These usually have magnets in the sensors and an array of reed switches in the pipe or “stick” running the length of the tank. The float closes the reed switch and the output resistance changes as each reed switch is closed.
- The readings from these sensors can be digital (off/on) or analog resistance which can be converted to voltage (1 to 5V) or current (4-20 mA) readings. Since the sensors provide either dry contact (open-closed) or resistive readings, they are ideal for low power applications.
- Since the readings depend on reed switches being closed, the size and spacing of the reed switches affects the accuracy. This are often accurate to only ½ to ¼ inch.
- Float level sensors can be affected by chemical compatibility, temperature, specific gravity (density), buoyancy, tank movement and viscosity of the liquid that can lead to reading accuracy errors.
- To use these types of sensors you must have a tank where there is no obstruction or agitator under the opening of the tank to appropriately install the sensor.
- Float sensors are commonly available with stainless steel poles or sticks. They are also available with flexible tubing which the floats can move up and down.
MagnetostrictiveLevel Sensors:These are like float type sensors in which a permanent magnet sealed inside a float travels up and down a stem in which a magnetostrictive wire is sealed.
- These sensors are ideal for high-accuracy, continuous level measurement of a wide variety of liquids in storage and shipping containers.
- Magnetostrictive sensors are usually available with analog 4-20mA or digital Modbus or other industrial protocols. They often offer direct digital display options for locally reading the tanks.
- They require the proper choice of float based on the specific gravity of the liquid.
- Magnetostrictive level and position devices charge the magnetostrictive wire with electrical current, when the field intersects the floats’ magnetic field a pulse is generated. The pulse travels back down the wire at the speed of sound. Just like ultrasound or radar, the distance is measured by time of travel from pulse to return.
- The more complicated electronics require more power than a traditional reed switch float sensor.
- Because of its accuracy, the magnetostrictive technique is popular for “custody‐transfer” applications (permitted by an agency of weights and measures for conducting commercial transactions).
- To use these types of sensors you must have a tank where there is no obstruction or agitator under the opening of the tank to appropriately install the sensor.
- They are also available in solid stainless steel or flexible sticks.
Ultrasonic Sensors:: These sensors are normally used for non-contact level sensing of highly viscous liquids, or bulk solids. These would also be a good choice for water treatment applications such as pump control or open channel flow measurement. The sensors work by emitting high frequency (20 kHz to 200 kHz) acoustic waves that are reflected back to the emitting transducer which detects the wave.
- These sensors are affected by the changing speed of sound due to moisture, temperature, and pressures of the air between the sensor and the material to be measured.
- These sensors can be configured to factor in these environmental parameters to provide more accurate readings, but if the environment is constantly changing it can lead to inconsistent level readings.
- Other conditions to be aware of which can cause inaccurate readings include; turbulence, foam, steam, chemical mists (vapors), and changes in the concentration of the process material. A common issue in oil and gas production is that blanket gases on the top of liquids can affect the readings.
- Harsh chemicals can negatively affect the transducer if not housed in the proper material. In oil and gas applications the H2S vapors can destroy the seals on the transducer, so make sure that the sensor is rated for this environment, such as constructed using Kynar® PVDF materials.
- Proper mounting of the transducer is critical to get the most accurate readings. If there is any obstruction under the transducer you can experience false returns.
- They need to emit a powerful ultrasonic wave which requires power. The typical maximum range for ultrasonic sensors is normally 30 to 50 feet.
- Ultrasonic sensors provide analog voltage, current (4-20mA) or digital protocol (I2C, Modbus) interfaces.
- Ultrasonic sensors are considered mid-range in pricing depending on the substance being monitored.
Radar Sensors:These sensors are designed for applications requiring non-contact liquid level measurement, in which a higher level of accuracy is required. These sensors can be adjusted for variables such as materials, tank configuration, and system interface. They are ideal when vapor, dust, foaming surface or blanket gases prevent ultrasonic‐wave measurements from providing consistent, accurate results. These sensors use microwave‐pulses to track any target material from the tip of the antenna to the bottom of the tank. The pulse widths and sensitivity depend on the distance of the target from the antenna and the dielectric constant of the reflecting material.
- This technology provides reliable, continuous pulses and are unaffected by environmental factors such as temperature, vacuums, methane, steam, pressure, carbon dioxide, vapors, and condensation.
- The tank must have a metal bottom to stop the microwave signal for accurate tank level measurements.
- Radar sensors can measure multiple interfaces, such as the level of both oil and water in a tank.
- Since there are complex electronics inside Radar sensors, they normally provide industrial digital protocol interfaces (Modbus, HART, Profibus, etc.) for setup and data access.
- Generating the radio energy requires power and the greater the distance, the greater the power required.
- These sensors are the most expensive choice of tank level sensors and can be double or triple the ultrasonic sensors in price.
Pneumatic Level Sensors:These are used in hazardous areas where there is no electricity and in applications involving heavy sludge. These work by having a compression of a column of air against a diaphragm which then actuates a switch.
- These sensors are suitable for use with highly viscous liquids such as grease, or water-based and corrosive liquids.
- They have the additional benefit of being a relatively low-cost sensor for point level monitoring. They are not suitable for analog measurements.
Capacitive Level Sensor:These sensors are exceptional in sensing the presence of a wide variety of solids and organic liquids. The technique used is frequently referred to as RF for the radio frequency signals applied to the capacitance circuit.
- Dual-probe capacitance level sensors can also be used to sense the interface between two immiscible liquids with substantially different constants, providing a solid-state alternative to “oil-water interface” applications.
- These sensors contain no moving parts, they are rugged, simple to use, and easy to clean, and can work in high temperature or pressure applications.
- A significant limitation for capacitance probes is in tall bins used for storing bulk solids. These applications require a conductive probe that extends to the bottom of the measured range. Long conductive cable probes (20 to 50 meters long), are suspended into the bin or silo, and are subject to tremendous mechanical tension due to the weight of the bulk powder in the silo and the friction applied to the cable. Installations such as these will frequently result in a cable breakage.
- A danger does exist from build-up and discharge of a high‐voltage static charge that result from the rubbing and movement of dielectric materials. This danger can be eliminated with proper design and grounding.
- The power levels are very low, and they are ideal for low power applications.
- They provide both analog (1-5V, 4-20mA) and digital industrial protocol interfaces.
Thermal Sensing: When accuracy is not required but you need immediate feedback of the current level within a tank, thermal sensing may be the best solution. Thermographic cameras detect radiation in the long-infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nanometers or 9–14 µm) and produce images of that radiation, called thermograms. Tank liquids are a slightly different temperature than the air above them, allowing the liquid body to be seen “through the tanks”.
The tanks shown are being monitored with a Thermal Imaging camera. The solution shown here to the left, provides an instant view of the current level of all the tanks in view showing the two tanks on the left are about quarter full, the tank on the far back right is nearly full, and the tank on the right is empty.
These cameras are a powerful tool in combination with video analytics to detect tank levels with an added benefit of being able to deter theft – notice the vehicle approaching the site in the picture to the right.
- These cameras work in sunlight or at night to give you up to date information on tank levels.
- Thermal cameras can be mounted on a Pan Tilt (PT) mount allow remote control of the camera to cover a wide area of tanks.
- Thermal cameras are more expensive than a single radar or magnetostrictive sensor, but a single camera can be used to monitor multiple tanks, lowering the overall cost of implementation.
- Thermal video images use far more bandwidth than sensor data. However, by intelligently setting motion zones and looking for “motion” as the liquid reaching a certain location, the camera can be used for monitoring events.
- Video cameras with constant monitoring consume far more power than other sensor technologies.
- Thermal cameras can be used for security and asset protection.
SHORT RANGE VS. LONG RANGE COMMUNICATIONS
You may have heard the term “Intelligence at the Edge” or “Edge Technology” and asked yourself what does that mean? These terms refer to those areas in which cellular connectivity may be sporadic and, in some cases, non-existent. When trying to introduce automated solutions in these areas it is critical for the equipment to be able to operate even when a clear connection back to a cloud-based server is not possible for a time. Think about what would happen if your tank were about to overflow but you could not get a cellular signal to receive a command from the server to shut down the pump. By having an intelligent controller on-site, it would be able to make the decision to shut-down the pump and carry out the action without ever having to talk with the server application. When communications are restored, the controller would be able to update the information on the server and get back into sync with current operations without ever missing a beat.
CENTRALIZED EDGE SOLUTION
When considering a centralized Edge Solution, it usually requires some type of short‐range sensor connectivity. Typically, these solutions use 900MHz, 2.4GHz, LORA or Bluetooth Low Energy (BLE) sensors. Solutions of this nature usually connect to a local controller and then the information is gathered, processed and transmitted to a remote server where the data is saved and potentially analyzed in real-time or by on-demand. This type of solution is known as a Centralized Edge Solution.
|Single point forlong-range communication reduces airtime||If the controller is down the site is down|
|Ability to make immediate decisions at the site||Short-range wireless sensors are more prone to interference|
|Short range sensors are more cost effective and easier to install||Short range sensors are usually battery operated which means that you must change the battery occasionally|
Items to consider when implementing a centralized edge solution with wireless communications between the sensors / actuators:
- Obstructions and other environmental factors can limit the maximum distance by which these sensors can communicate. Pay close attention to physical obstructions such as vegetation, hills, vehicles, doors, buildings, tanks and other equipment that may cause loss of signal due to reflections in the Fresnel zone.
- RF interferences (referred to as “noise”) in the same bandwidth which will also impact the range of the wireless sensor.
- The choice of the antenna can increase the distance of communications between your sensors and the central controller, through both using antennas with gain (boosting the signal) such as Yagi antennas and by increasing the height.
- Higher frequency signals (e.g. 2.4 GHz compared to 900 MHz) are greater impacted by materials (e.g. buildings). Lower frequencies have better in-building penetration.
- An advantage of the 900MHz frequency is that it is not nearly as crowded as higher frequency bands. Bluetooth devices, standard WiFi networks (802.11.x), Zigbee and other 802.15.4 devices all share the 2.4GHz frequency band and may contribute to radio interference depending on your location
All these should be taken into consideration when planning to use short-range sensors in your centralized solution, to obtain optimized performance from your solution
DECENTRALIZED EDGE SOLUTION
Decentralized Edge Solutions are just as they sound: each sensor will connect wirelessly with a remote server and they will serve up their own information. These sensors will use either Cellular (WWAN), Low Power LAN (LPWAN) or Satellite communications to send their payload back to the server. The decentralized solutions tend to be costly in both hardware and the cellular/satellite carrier charges. Each sensor requires a cellular or satellite radio as part of their package. They tend to optimize the amount of information sent to the server, so the payload is kept very small.
|Eliminates single point of failure access||Increased monthly wireless charges|
|Increased bandwidth for high bandwidth sensors (i.e. Video)||Increased device cost|
|Lower transportation cost (move between sites)||Increased maintenance cost more can go wrong|
|Better power management (sleep until needed)||Each antenna must be positioned to get the best coverage in remote areas|
|Faster path to intrinsically safe certifications and there are more sensors available||May require regulatory certifications|
|LPWAN technologies like SigFOX, NB-IoT are lower cost for both hardware and service fees|
CELLULAR VS. SATELLITE
When considering what sensors to use, location is the number one consideration. Cellular technology has improved greatly over the past 10 years; however, there are places where cellular will not work. In these situations, satelliteor implementing your own VHF/UHF network could be your only option. Satellite sensors are approximately double the cost of cellular sensors and the cost of transmitting data is higher. The sensors must be in full view of the sky to transmit the information to the orbiting satellites.
Cellular connectivity may be more ubiquitous for remote locations they pose challenges of their own. In the U.S. we must deal with several different carriers. When deploying remote solutions using cellular radios, you must be keenly aware of which carrier has unobstructed towers in the area. When choosing a location to deploy your solution you should pay close attention to obstructions in the area such as trees, buildings, tanks and even hills or mountains. Once you have chosen your location it is a good idea to locate a company that can install the antennas and verify that they are the correct size and positioned such that you can get the best connectivity possible with the cellular networks. This takes someone familiar with RF and that has the equipment to correctly place and position the antenna(s).
A good rule of thumb when choosing the correct type of communication is that the use of satellite would only be practical if you absolutely need to collect the information and there is no other way to transmit the information.
CHOOSING THE RIGHT SOLUTION
Understanding what features are most important to youwill go a long way in choosing the correct solution for your needs. If your goal is simply to monitor a few tanks on a site and let you know when they are about to spill, then a decentralized solution is probably your best option. There are numerous single wireless sensor solutions available to you depending on what is in your tank. However, if you have several items that you want to monitor, and you want your site to be able to operate even when you are not there, a centralized approach may be just what you need. When considering a centralized approach here are some additional things to consider:
- What method of communications is available to me?
- What sensors or equipment will I be connecting to and what protocol does the equipment use?
- Do I have power available at the site or will I need solar power? If solar, how long can I go without sunlight?
- What do I need to happen if my tanks are empty or full?
- What do I want to do with the data collected?
- What happens if I can’t get a communication or I lose power at the site?
- Is there a controller that does everything I need, or do I need a customized application developed?
- Are there any special requirements such as Intrinsic Safety (Class 1 Div 1)?
- Where will the controller be mounted?
Telematics have been around for many years. In the past these solutions have been very expensive and require extensive infrastructure build out to provide a full solution. Technology has reached the point where even the smallest of operations can afford a high-tech solution for remote monitoring and control of tanks and equipment.
The ReignRMC ReignCloud™ web application can monitor your remote site 24/7, process any information gathered from the various sensors located at the site and provide real-time information to any PC or smartphone, no software to download required. Contact ReignRMC at the number below for more information on our solutions.
When determining the right solution for remote monitoring and control solutions, knowing your site equipment, the location and the tanks you are monitoring is critical. It is often best to go with a flexible solution that allows you to handle any condition on the site and allows for integration with other equipment on site. Using remote monitoring solutions can free up your support resources to handle more critical situations and allow you to better manage your resources (i.e. preventative maintenance, new sites, etc.) rather than continually fight with problem areas. Your resource might have just visited a site and would normally not return for 24hours. If something goes wrong at the site right after they leave, the remote monitoring could potentially save you a spill, loss of equipment, or loss of production for several days. Even worse, you could incur a large fine from a costly spill. For 24/7 production sites remote monitoring and control is a must. When trying to make sense of tank monitoring or any remote monitoring and control applications you can count on ReignRMC to provide the right support in making the correct decision and in providing a full solution that meets your needs and your budget. Please use the contact information below if you need any help with deciding what to do.