Are there any level gauges with accurate measurement?

Currently in China, the market for steel belt gauges seems to be shrinking gradually. The reasons for this are as follows: 1) The older generation of steel belt gauges indeed has many problems; they have a high failure rate, and their installation and maintenance are very complicated. 2) Consumer awareness in China is not yet mature – people always want to use the latest models of instruments, but they often don’t understand the actual performance of these instruments, whether they are suitable for use, whether replacement parts are easily available, or whether timely maintenance can be ensured. 3) In order to increase sales, instrument dealers exaggerate the actual range of use, functions, and accuracy of these instruments. Such dealers give the impression that their instruments can be used with any type of tank, that their accuracy can reach 1 mm, and that there’s no need to worry about quality (after all, they’re imported). 4) Users are very wealthy; their general mindset is that since they can afford tanks worth tens of millions, why should they care about spending 100,000 yuan on an instrument? Domestic instruments and steel-band level gauges (including imported ones) can go away. In fact, in the international market for level gauges, there is yet no instrument that can dominate the market; each type of gauge has its own niche, including differential pressure level gauges and steel-band level gauges. 　　 Since last year, I’ve heard that there have been various improvements in steel band watches (I’m not entirely sure exactly what those improvements are), but I think it’s normal for such improvements to occur – after all, technology is constantly evolving, and we’re in the 21st century now. If I get the chance, I’d like to find out more about them. 　　 　　

For accurate level gauges, it is necessary to choose one based on the properties of the material being measured. Optoelectronic level gauges are generally used for accuracy. Another alternative is the scale-type level gauge.

It depends on the structure of your storage tank and the type of fluid being stored, as these factors have a direct impact on the selection of the level gauge. For example, for gasoline, floating roof tanks with guide posts are generally used; we employ ENRAF servo level gauges, which provide very accurate measurements. For diesel, dome tanks are typically used, and in that case we use radar level gauges. Servo level gauges are not suitable for waxes, residue oils, and other substances with high viscosity.

Radar-based level gauges with a fixed roof work very well

Currently, most measurement systems rely on computer monitoring, and the accuracy of measurements is dependent on the software developed for this purpose. During construction, I used radar level gauges in tank areas; the computer system showed significant fluctuations in their readings, and their accuracy was not high. It was necessary to constantly pay attention to the errors and adjust the measurement results accordingly. Photoelectric level gauges offer higher accuracy. The choice of level gauge should take into account various factors such as the location where it will be used, the requirements for measurement, as well as economic considerations.

For atmospheric-pressure storage tanks equipped with single-flange differential pressure level gauges, it is easy to measure the liquid level as long as the density of the material remains constant. I’m not sure if there are any issues, and what is the accuracy like?

Depending on the type of medium stored, different types of level gauges are selected: radar for gasoline, diesel, and residue oil, and servo for liquefied gas.

I stand by my view: for common petrochemical products, Enraf’s servo level gauge combined with Saab’s radar level gauge is generally sufficient to meet the level measurement requirements for the vast majority of applications.

In fact, a measurement accuracy of 1 mm or higher is only achievable in a laboratory (or rather, where can you find a reference for higher accuracy?) What level of precision can be achieved with manual measurement? ), but in terms of the actual use of these level gauges, they are all very mature instruments worldwide; the actual performance they deliver depends heavily on the quality of installation and calibration, and this factor has a significant impact.

The discussion was very good. May I ask if a fiber optic level gauge is a type of photoelectric level gauge?

There are currently quite accurate level gauges, namely magnetostrictive level gauges, which can measure both the liquid level and the temperature of the interface, output digital signals, and display them directly on a computer. The magnetostrictive level gauge is developed based on the magnetostrictive principle; it features high measurement accuracy, stable digital signal output, and no need for regular recalibration. Magnetostrictive level gauges are installed at the top of oil tanks, connected via flanges. For ranges of up to 6 meters, stainless steel rigid rods are generally used, while for ranges exceeding 6 meters, stainless steel flexible hoses are preferred; these gauges have already been applied in various gas stations and storage areas. Signal acquisition software can be developed using configuration software; by entering the data from tank gauges into this software, the volume of the oil can be calculated. By entering the density as well, the weight can be determined. Generally, stainless steel is used for refined oil products, while corrosion protection is a consideration for crude oil. If there are multiple oil media, a magnetostrictive level gauge can simultaneously measure the interface between the liquid and the oils. Imported magnetostrictive level gauges are relatively expensive, while domestic ones are much cheaper. Moreover, the quality of domestic products is improving day by day, and more gas stations are considering using them. The factors that influence this decision include cost, after-sales service, and technical reliability of the products.

However, I don’t think magnetostrictive level gauges are suitable for large storage tanks, especially those with flexible hoses; the hoses may bend and deform inside the tank (the hoses are stretched when the tank is empty and relax when it is full due to the hydrostatic pressure acting on the tank). How can measurement accuracy be ensured in such cases? Based on the specifications of magnetostrictive level gauges, their measurement repeatability (or resolution) generally does not reach 0.1 mm levels (although mainstream servo level gauges and radar level gauges used abroad can achieve this). Additionally, according to API standards, magnetostrictive level gauges have a insufficient number of temperature measurement points (usually around 5). In short, it is recommended to use products that are widely recognized internationally; those with NMi certification are the best choice.

Fiber optic + servo = unbeatable; the results are excellent – a practical conclusion!

Each issue should be analyzed on a case-by-case basis; different types of level gauges are suitable for various applications. From a practical standpoint, the simpler the design, the more applicable it is

Neither of these is very accurate, right? There will always be errors; the most accurate methods are visual inspection or weighing.