The use of ACS in mining

    Judging by the growth rate of the complexity of the network, a huge amount of mining equipment is put into operation every day. The pace is high and companies operating mining equipment on an industrial scale do not have time to design full-fledged data centers with the proper level of security and automation.

    Successful launches and operational experience of equipment in the early days or even months gives rise to confidence in the reliability of the equipment. And the customers who place the equipment in mining hotels are sure that their hardware is in good hands. Let's look at what 21st century mining hotel is.

    ACS in Mining

    ACS means “Automated Control System”. Such a system can control production processes, and automatic parking, and a gas boiler, and will also be useful in mining.

    At the dawn of the development of industry, next to each equipment was a specialist who controlled it and monitored the health of his work. So, elevators controlled the elevator, porters opened the doors, and the aircraft were flight engineers.

    Today, the situation in mining is reminiscent of the last century. In mining hotels, electric machines are used for electrical protection and it is believed that this level of protection is quite enough. Turning on and off the miners is carried out by maintenance personnel, in a simple way - by pulling out the plug from the outlet. The ventilation system is often automated and stabilizes the temperature in the room, which is quite enough. The hardest things are with the fire extinguishing system. Most often, mining equipment is located in industrial premises of a large area and with high ceilings. With this approach, gas fire extinguishing systems are expensive to use, and powder systems are ineffective. For this reason, in most hotels mining fire extinguishing system is not provided.

    And now let's imagine what a modern mining hotel of the 21st century should look like. The first thing I would like to do to increase efficiency and safety is to eliminate the human factor and use ACS to control the entire system. ACS elements are an automation cabinet, actuators, sensors and a controller. In the cabinet itself there are many blocks: PLC (Programmable Logic Controller), expansion modules for various interfaces, automatic machines, power buses, signal converters from sensors, signal converters for actuators, frequency converters, etc. The front panel of the cabinet is usually equipped with controls - buttons, switches and indicators of operating modes.

    The logic controller is a very reliable device. In general, the word reliability is the middle name of ACS. Imagine what will happen if the elevator suddenly decides to open the doors while driving, and the plane pulls out the landing gear. That is why the safety and uninterrupted operation of ACS are always given maximum attention.

    From the ACS cabinet there are many wires to the sensors and actuators. For example, in ventilation systems you can find sensors of temperature, flow rate, pressure and actuators - actuators controlling the valves.

    An important element of ACS is the PLC program. It determines the behavior of the system in various situations, controls the actuators, processes data from external sensors.

    ACS or operator?

    Often, large and expensive installations are still monitored by a human operator. The operator sits at the remote control workstation (Workstation). On the monitors screen of such a remote control, the parameters of the entire system are visible. A clear mimic diagram reliably displays a lot of data, and one glance at the screen is enough to understand what is happening with the equipment. All data and controls are brought together in one place, a kind of original control panel of a small universe.

    If you compare the ACS system with an employee who could monitor the system and manage it manually, you can identify a number of obvious advantages. ACS works 24 hours a day, does not get tired, does not quit smoking, does not sit on social networks, is not distracted by phone calls and does not make mistakes. And the processes performed are predictable and repeatable. Also, do not forget that a person cannot react to a situation with the necessary speed. For example, it is difficult to imagine that it is possible to press a special button in the car to deploy airbags when necessary. Electronics, on the other hand, does this reliably, at a given speed, and only when it is really necessary; in that fraction of a second when it will be safe and effective.

    For industrial mining, the coordinated work of all systems is required: ventilation and electrical distribution systems, fire extinguishing systems, local networks, security systems, access control systems, plus reliable access to the Internet with a backup communication channel is necessary. All of these systems must be managed efficiently and in real time.

    Mining is a complicated process, cryptocurrency mining equipment is very expensive, and any downtime leads to significant financial losses. Maintenance and frequent repairs, again, cause a series of new downtimes and result in large losses. There are also known cases of fires at mining farms with losses of millions of dollars. All these factors indicate that the industrial operation of mining equipment is a responsible and complex process and it is impossible to leave it without automation!

    Objects for industrial mining

    There are two main types of objects for industrial mining: a mining hotel and a mobile container. In the first case, mining equipment is located on racks inside the building. As a rule, in such buildings there is a lot of free space, high ceilings, a lot of space for the placement of ventilation and distribution equipment. But, from our point of view, there is one significant minus - the stationarity of such objects. In the second case, the equipment is located inside the mobile container. Places here are much smaller, equipment is denser, ceilings are lower. The metal walls of the container have poor thermal insulation: in winter, during maintenance, the switched-off container freezes, in the summer it is very hot in the sun. In the building where the mining farms are located, usually a specialist sits, which is involved in setting parameters and monitoring the operation of equipment, maintenance and repair of the system. Such a specialist cannot be near the container, and, as a rule, he comes only when necessary for after-sales service, and in the main period of time is located at the AWP console.

    ACS for mining container

    Now on the market there are many solutions in the form of containers for industrial mining. They differ not only in the design and principle of operation of the cooling system, but also in ACS systems. Most often, inside such containers is an electrical distribution cabinet, consisting of an introductory machine and an electricity metering unit. From the cabinet, many power cables stretch to the outlets for miners located on the shelves. Many, but by no means all solutions, use separate machines for each outlet. From the point of view of the rules for operating electrical installations, separate machines for each miner are simply necessary, but manufacturers often neglect this simple rule. For example, the popular ASIC Antminer S9 consumes about 1300 W and the absence of a simple machine in the event of a power supply failure can cause a fire. Thus,

    Also in the container is a network switching equipment providing Internet access. As for the ventilation system, everything is much more interesting and complicated. Most often, free cooling is used for cooling. Inside the container, it is necessary to maintain a constant and comfortable temperature for mining equipment at 30-40 ° C, and this can be done by adjusting the engine speed of the supply unit. As a rule, specialized frequency converters for ventilation installations are used. And in general, the whole range of equipment looks logical and efficient. Manufacturers assure that the container is efficient, safe and fully operational.

    Our experience of force majeure in mining

    Let's consider the following situation. The container worked in the winter for several days, after which there was a technological power outage for 2 hours. And on the street there is a temperature of –30 ° C. The container freezes over these 2 hours, all the electronics, accordingly, cools down to the same –30 ° C and after two hours the power is supplied to the container ... By the way, this is a fairly typical situation in harsh winter conditions. In most containers offered on the market, there is no start-up schedule where the system with an automatic control system must ensure that the temperature inside the container does not correspond to the operating temperature of the electronics and start pre-heating. And only after reaching a positive temperature, start the launch of electronics. At high freezing temperatures, most consumer electronics such as motherboards, processors, and memory will not work.

    Another significant problem is the simultaneous connection of a large number of power supplies to the mains. For example, on power supplies without a soft starter, the starting current is about 100 amperes, and 10 power supplies will already give 1 kA! Imagine now that you have 10 containers, each containing 100 power supplies. With a simultaneous start, the starting current will have an unacceptable value and may damage the electrical distribution equipment. To avoid this, the ACS should make the inclusion of computing units sequentially, in accordance with the trigger sequence.

    Note. There are two types of power supplies: with soft start and without. In the first case, the capacitance of the rectifier is charged through a thermistor with a small current, which reduces the current pulse when connected to the mains, but it remains quite high. In the second case, at the moment of switching on, the capacitors are charged with the maximum current, which leads to the above problems even when several PSUs are connected. Most often, no one takes these factors into account.

    But what if we burn?

    Another situation. If a fire extinguishing system is installed in the container (and many manufacturers use it for some reason), then it can work only for two reasons: excessive temperature or smoke. There are solutions using thermal imagers, but they have a number of limitations. The supply unit delivers approximately 50,000 m3 of air per hour. With such a flow, the presence of even a strong source of ignition will not warm the air, and smoke will blow out even before it reaches the sensor located under the ceiling.

    It turns out that the definition of fire by standard methods in this case is impossible, and, therefore, timely suppression of the fire is not feasible. Also, before extinguishing a fire, it will be necessary to turn off the air supply unit completely, de-energize all current consumers and, in the case of using gas fire extinguishing systems, ensure the tightness of the container by lowering the shutters. Such an algorithm for working in containers without ACS is simply not possible. Also, if triggered, the use of powder fire extinguishing systems will cause enormous damage to the electronics, and the restoration of the operability of such an object will take a long time.

    Consider another example. Under certain climatic conditions, a dew point occurs in the room. Inside the container, even after a slight downtime associated with a technological shutdown or maintenance, moisture can accumulate, and when the temperature drops, it can manifest itself in the form of dew on the surface of miner boards. Starting in such a situation threatens to damage the electronics. The ACS system must monitor the start conditions of the electronics, and prevent start-up when critical humidity occurs in order to protect expensive equipment from damage.

    More frequent situations are equipment freezes. If this happens with a miner working on video cards, then the freeze will require a system restart. To solve this problem, simple watchdog timers are usually used, connected at one end to the USB connector on the motherboard and the other to the Reset button. However, if the cooler of the video card breaks down, it will be necessary to disconnect the miner as soon as possible. If a person sits nearby and controls the mining process, he will of course be able to do this using the power supply switch. But until this moment, the video card will work in overheating mode, which can damage the processor. Remote power management of each miner is absent in almost all containers on the market. At first glance, this is not essential,

    Basics of the effective work of ACS in mining

    For the correct and long-term operation of the object requires careful interaction of all systems. It is also necessary to establish a sufficient set of actuators so that the ACS can fully control the facility. It is difficult to predict all possible situations, as a rule they are completely not obvious, therefore sometimes they seem impossible and fantastic. However, statistics on equipment repair and fires at such facilities indicate the opposite.

    Correct operation of the equipment is possible only with well-designed cyclograms programmed in the PLC. These cyclograms should provide an automatic transition from one mode to another. For example, after applying power, it would be logical to check the voltage levels of the mains, check the temperature and humidity inside the container and, if necessary, turn on the heating of the air with heat guns. And until all the parameters come back to normal, it is unacceptable to supply power to the mining equipment.

    The inclusion of miners must be carried out in stages, alternately supplying power to each miner. At the same time, it is necessary to ensure the operation of the supply unit in the required mode. The fact is that in winter the air temperature sometimes drops to –40 ... –30 ° С. It is impossible to purge equipment that is just starting to mine with such cold air. It is necessary to maintain a balance between the heating of the air by the miners inside the container and the influx of cold air.

    The ACS system should also interact with the fire extinguishing system and, if necessary, immediately turn off the supply ventilation, removing power from all equipment and closing the dampers.

    For the accurate operation of all modes and error-free transitions from mode to mode at the request of the operator or when certain indications from the sensors occur, an appropriate sequence diagram should be drawn up. It is important to foresee all possible situations in which the container with equipment may be located and to ensure the correct transition from one state to another. Only when all situations are described, the logic of the container’s work is worked out and all the tests are carried out, can we say that the object will function properly in all possible situations and the human factor will not affect the timeliness of the actions. Since all systems regularly exchange data with each other, failure of any of them will be immediately detected. For example, if the air supply unit engine fails, you can find out about this even before

    As for the cost of such ACS systems, their price is relatively low - at least in comparison with the cost of all miners and their possible repairs. And with the right approach to the design of ACS, the control system will not only respond to events that have already occurred, but also predict possible equipment failures by comparing the readings of various sensors with information already accumulated. Thus, the cost of operating equipment will be significantly reduced, and the management of such an object will become truly remote and efficient.

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