Railway scales: features, placement and installation

For the proper operation of rolling stock, traffic management and for commercial calculations, it is of great importance to take account of the goods transported by rail. It is also important in metallurgy, where the weight of the raw materials delivered directly to blast furnaces and open-hearth furnaces in railway carriages plays an important role in the technological process and for intra-plant transport. To provide such an account, and we need a railway balance.

Classification of railway scales

With the help of railway scales empty and loaded wagons are weighed, and consequently, as the difference of these quantities, the mass of the cargo is determined.

The first scales for weighing cars were mechanical, including lever, based on the mechanism of balancing. Then there were electromechanical devices that converted the mechanical action of gravity into an electrical signal. To this variety of weights are also the strain gauges.

Today, with the help of railway scales, it is possible to weigh wagons separately standing in static and in motion without disengaging the composition, that is, in dynamics. Automation of modern weighing devices recognizes locomotives, identifies the type of car, determines the unevenness of its loading and the direction of motion.

Scales railway wagons are foundational and besfundamentnye, for weighing in static and dynamics.

Static weighing

With the static weighing, the railway scales began. The weighing of the train in static is very slow. The train disengages and the cars are fed to the balance one after another, weighed with a stop on the platform, their mass is fixed, then the train is formed and sent. The road and the cargo owners suffer enormous losses due to downtime.

This problem was particularly acute with the development of the rail network and the increase in freight traffic. It was tried to solve it with the help of the same static weights, according to which the train was moving very slowly, at a speed of 3 km / h. A special signal system was even developed that helped the driver to withstand this speed. Time of downtime was slightly reduced, but the weighing process was rather complicated, and the error was high, more than 1%.

Dynamic weighing

Automatic weighing scales are used for weighing moving parts. Weighing in dynamics, I must say, the direction of weight measurement is promising, and not only on the railroad.

The process consists in determining, in a fraction of a second, the mass of the wagon passing through the load-lifting platform, its registration and transfer to a control computer or an automated control system for transport.

In the process of weighing, the types of wagons are determined, since in axle weighing the mass of axles of each car is important, and the loading is correct, locomotives are recognized, since they are not weighed.

Recognition of the rolling stock is based on the determination of their inter-axle and inter-base distances.

The most vulnerable node in the weighing system is the track signaling devices that give out a signal when the wheel flange or the car axis passes over them. The reliability of these devices is very high, and they work in harsh conditions, both operational and climatic.

Loading platform

Railway scales for weighing cars are distinguished by a variety of constructive solutions, but common for them is the presence of one or several load-receiving platforms. On them passes the car during weighing, and the vertical forces that act on them are transferred to the converters.

When rolling the car, not only vertical forces but also longitudinal forces act on the platform, which create certain errors in the weighing. To reduce their impact, the load-carrying platform includes various mechanical and electronic devices. These can be restrictive stops, stretching strings, transitional bridges; Force-measuring converters, converting force into a certain electrical signal; Track control devices.

Electronic devices that control the weighing process process the signal from the converter and output the result to the computer and for visual reference on the scoreboard. The computer processes the weighing results with the help of special software and generates a report.

Types of load receptors

The scales of railway wagons also contain mechanical weighing devices. They come in two types:

- good old lever devices, in which through the summing levers the load is perceived by one force-measuring device;

- Mechanismless devices with four or more force meters on which the load platform is located.

Leverage - reliable, stable, simple enough to be regulated by the method for all types of lever weights. But large-sized levers, firstly, are manufactured using special technology only at enterprises with a high level of production. And secondly, for their work, an expensive special foundation is needed.

The hand-held devices in the design are simple. They can be made in small workshops, and the foundation can be much smaller.

Force meters of railway scales

Today railway wagon dynamic scales are manufactured with strain-gauge or vibration-frequency converters as force meters.

Vibration-frequency converters with the simplicity of communication lines and processing of output signals, noise immunity, absence of data loss, which eliminates additional errors, are preferable in scales with a lever device. The volume of secondary equipment is the same as when using strain gages. It increases significantly if these converters are used in scales with a beltless load receptor, since they need to be installed four or more and their signals pass autonomously through different channels, and separately obtained characteristics are summed up.

With strain gauges, load cells are connected in parallel or in series, and one common signal is processed.

All devices are mounted in the pit of the basement, on which the railway scales are located. On the concrete base, the rails of the feeding paths are also laid to reduce the vertical fluctuations of the composition in the weighing zone. In a special room near the load-receiving platform, secondary electronic equipment and a computer are installed.

Weighing accuracy

Scales railway for weighing freight cars must provide a weighing accuracy, corresponding to the established standards, which today there are four: 0.1; 0.2; 0.5 and 1% of the weight of the cargo.

With static weighing, only the last two accuracy standards are fulfilled on the scales. When weighing in the dynamics, the error of the device is influenced by the auto coupling, acceleration, weighing method.

Practice has shown that the accuracy rate of 1% is ensured for the weight of the load in each car of the train, 0.5% for the unloaded cars unloaded and the total weight of the train, and 0.1% if the convoy contains no more than 20 cars.

Weighing methods on railway scales

Wagon rail scales differ in the way of weighing. It is chosen on the basis of several conditions:

- the necessary accuracy of weighing and the maximum speed of the convoy associated with it;

- capital costs for the installation of a weighing system.

Wagon weighing is performed on a long platform, on which the entire car is placed. This method is convenient in those cases when the entire rolling stock consists of identical cars.

When weighed individually, each truck of the car is weighed individually, their masses are memorized and summed up by the measuring device, and the result is entered in the computer.

When weighing is weighed and summed the masses of all axes with the totalization on the scoreboard and transfer to the computer.

Advantages and disadvantages of methods

All weighing methods have their advantages and disadvantages. The wagon method is the most accurate, but the platform must be long, and only the composition, linked from cars of the same type, more precisely of the same length, can be weighed. Load with this method is measured in the range from 80 to 160 tons.

Weighed weighing on some scales is possible for most types of cars, but for this method a rather long platform is needed. The load on the railway scales varies from 40 tons, if a four-axle wagon weighs up to 80 tons, if the car is eight-axle.

A small platform is required for the weighing method. Because the distance between the axles of cars of different types is the same, then we can weigh the whole park on one balance. The maximum load in this case is 20 tons.

The downside of axle weighing is the high probability of a load redistribution on the axis. Reduce the effect of this factor on the reliability and accuracy of measurements can be by choosing more rigid paths and more carefully stacking them. In this case, weighed weights are most beneficial both for installation costs and for servicing different types of wagons.

Installation of railway scales

The method of installation of carload scales depends on their type. For example, there are portable railway scales (see photo below), which are installed from the inside between the rails and weighed each axis in series.

Scales can be installed on the foundation and without it. In different types of scales, strain gauges can be integrated into rails, sleepers or between them.

Selecting the type of scales, you need to determine the location of their installation. First, use the device should be convenient. Secondly, the slope can be no more than 1: 2000, and the straight section - no less than three lengths of the car (experts advise on 15 meters from both sides of the weighted car).

Before installation, you need to find out how close to the surface the groundwater suits and whether there are underground engineering networks in this zone, whether rainwater and meltwater are going in it.

The manufacturer's instructions contain sufficiently detailed instructions for installation, including a drawing of the concrete base and the necessary embedded elements for the foundation installation of the balance.

During installation, there should be gaps between the rails of the load receptacle and the main ones.

According to GOST R 53228-2008, the checking of the rail weights for determining the measurement error should be carried out annually.

Repair of railway scales

If the wagon scales are used for prolonged or incorrect use, mechanical breakage of the structural elements, malfunction in the electrical circuit or malfunction of the software may occur.

To eliminate these problems, different specialists are needed, therefore it is better to purchase measuring equipment in specialized companies that have a license to repair scales, which can later carry out repairs, replace failed parts and assemblies and verify.

Summarizing, we can say that you need to choose the railway scales, first, by the required accuracy; Secondly, in terms of operation; Thirdly, on financial opportunities. And it is equally picky to choose a company in which this equipment will be bought. A low starting cost can lead to serious problems in the operation and maintenance of scales, which ultimately entail additional costs.

The operating conditions are not only the quantity of goods transported per day. This is the presence of electricity, because it is not in all regions, and strain gauges without it can not work. In the low temperatures of the regions of the Far North, mechanical force-measuring sensors work better and more accurately.