Tony Tielen, global field sales director at Honeywell Enraf outlines the benefits of a new generation of radar tank gauging equipment.
Most process plants have tanks that hold feedstock or finished products. As an example, a 150 000 bbl/day refinery may have more than 50 tanks near the plant.
Each of these tanks could be 50 feet wide and 60 feet high, holding approximately 25 000 bbl of gasoline worth more than US$2 million. These tanks may be located anything from 500 feet to two miles from the process units.
Monitoring and controlling the volume of tank liquid is absolutely vital to operations, such as refinery planning and scheduling, but also to ensure the accuracy of data used for financial statements.
Inaccurate measurements may result in sub-optimal capacity usage, accounting errors and even environmental incidents through spills. The traditional work practice of monitoring tank inventory levels involves two operators, one in the field and one in the control room.
The field operator takes the reading from a tank level gauge and tells the control room operator to start/stop the pumps. This practice is expensive. Extrapolated that could represent a loss of hundreds of thousands of dollars every year. In addition, it exposes the field operator to hazards, including falls and noxious hydrocarbon vapours.
As soon as the oil is out of the ground, whether you are in an offshore or onshore environment, it gets stored. What we then need to do is measure volume very accurately in two different ways. We measure volume by means of the level in the tank, and by flow metering.
Sticking with level measurement, we can provide gauging which involves both level measuring, plus temperature measurement. The volume of the product will change quite significantly as temperature increases, so it is very important to cross-check these tank temperatures with correction tables, which will enable a more accurate volume measurement.
On a typical large oil tank, the accuracy of measuring 1 degree Celsius more or less could represent 80 metric tonnes of oil. With the current oil price it’s more important than ever to have that added degree of accuracy.
Common problems
A millimetre in difference across a tank can represent a lot of money, so accuracy is imperative. If you picture a tank from the outside it’s fairly clean. On the inside however, it’s a harsh environment. There are obstructions such as wires, heating coils, stilling wells, and ladders. Typically with so many objects alien to the product itself, these can cause interference with radar gauging.
Typically two technologies can be deployed for measurement. These are usually servo, which is an electromechanical device, which has a displacer that passes through the liquid. These can measure more than just level, and can differentiate between different fractures of product and water.
The other technology is radar. The big advantage with this is that it is non-contact and has no moving parts. Depending on the type of customer or the product involved, radar may not be suitable.
This is usually down to pure physics when we are talking about very light fuels such as gas or jet fuels. Gauging accurately with these liquids is made difficult because of the physical properties and gas layers present in the tank. For these very light goods customers would prefer a servo for measurement.
Breakthrough technology
The new lines of radar products actually have embedded algorithms which eliminate the mis-readings generated. The Honeywell Enraf 970 SmartRadar gauges offer an effective solution for effectively capturing precise data.
The SmartRadar features a number of innovative technological developments, resulting in genuinely state-of-the-art instrument. The radar is intended for level measurement of intermediate storage tanks with an accuracy complying and exceeding the API standards, Chapter 3.1B. It is a reliable and robust instrument that will continue to give consistent results for many years to come.
The SmartRadar has reaped the benefits of Enraf’s advanced digital processing, employing the new digital Advanced Radar Transceiver (ART) and the new Smart Echo Analysis (SEA) means highly reliable processing resulting in superb measuring results.
Of course, customers will find in the market existing products that can accurately read levels, and they do it well. But the migration towards using algorithms is the next stage for these types of applications.
Tank farm automation
Due to the costs and risks mentioned above, modern plants are choosing to automate the tank farm processes. They may need to integrate the tank level information and the tank farm pump data with a central control room.
The Honeywell Enraf SmartRadar series offers an ideal solution for measuring tank level, delivering contact free measurement without moving parts.
The accuracy of the SmartRadar gauge under reference conditions is 3 millimetres over the entire measuring range (around 30 metres). Overall, the device provides a wide operating range of -40oC to 80oC and is certified intrinsically safe for use in Class 1 Div 1 oil and refinery areas.
In a 50 tank example, the costs of wiring the radar level gauges and pumps could come in at over $5 million, including the cost of laying fibre optic cables, and the project could last more than three months to create 5000 feet of cable trenching.
By adopting a wireless network, provides a flexible and long-range network, while the transmitters provide reliable and predictable battery life up to 10 years.
Larger facilities shouldn’t be daunted by the scalability of the product either. The OneWireless systems from Honeywell have a theoretical ceiling of 30,000 nodes, and its capable of supporting multiple applications like wireless worker and location system applications.
