- Warming of the internal space BSU, warming of the inclined gallery of the feeding conveyor or skip hoist, insulation (covering) of silos of inert materials.
- Warm up inert materials, preheating process water, heating the interior of the BSU, the operator's cab.
- Heating of unloading heat of ready concrete.
(Recommendations for preparing a concrete mixing plant for winter).
First, you need to determine at what minimum ambient air temperature it is worth producing concrete-mortar mixtures. If it is a question of the southern regions of Russia or Ukraine, then it is rational to expect a temperature of at least -5°C to -8°C, and it's better to sacrifice 15-20 winter days with a lower temperature. For the rest of the regions, one must decide - either the victim is two or three cold months, or serious capital costs. But in any case, in our opinion, work at a temperature below -15°C makes sense only when absolutely necessary.
So, the main stages of preparation of the summer concrete mixing plant (BSU) for winter:
1. Warming of the internal space of the BSU, warming of the inclined gallery of the feeding conveyor or skip hoist, warming (covering) of the hoppers of inert materials.
Practically any enterprise can insulate the BSU. The only question is, from what materials and with what accuracy this event will be produced. Well, if in the summer BSU there are factory frame structures that allow to easily produce the sheathing of the installation, but if they are not, and their creation will be entrusted to the unreasonable persons, then after such a covering the installation can become similar to an ugly monster. Skeletons should be made with allowance for water spills, withstanding the maximum wind and snow load inherent in the area. Usually, for the production of wireframe forms, metal rolling is used: along the perimeter of the channel No. 8÷10, bracing and jumper - an equal-angle corner 63÷75mm.
The choice of sheathing (wall) material depends on the location of the BSU and the temperature regime in which it is necessary to ensure the operability of the installation. In southern regions, for work at near-zero temperatures, the skin of a profiled sheet with a thickness of 0.8-1.2 mm can be sufficient, which will protect expensive equipment not so much from the cold as from precipitation. But if we talk about real insulation of the BSU, then it must be factory three-layer insulated sandwich panels with polyurethane foam or other filler with a thickness of at least 50 mm, preferably two types (wall and roof) and necessarily complete with racks and other sealing materials. In general, the ideal option would be to entrust this work to a specialized organization that is knowledgeable in this matter.
2.Heating of inert materials, heating of process water, heating of internal space of BSU, operator's cabins.
Sellers of concrete mixing plants, even the winter version of the equipment, do not often immediately supply all the necessary equipment for work in the cold season. First, the customer often at the time of purchase does not even know at what temperatures in winter the BSU will be used, what kind of fuel the heat unit will work on, what method of heating the inert is the most progressive and economical, and also other aspects of this issue. The answers usually come later as the BSU is used, studying the local coolant market and the experience of other enterprises.
The most energy-intensive process is the heating of inert materials. The inert material hopper should be (in addition to the insulation lining) appropriately refined: additionally equipped with insulated covers with opening and closing mechanisms; In the internal cavity of the hoppers, depending on the adopted method of heating, either tubular registers or nozzles for supplying hot steam are installed, or a special system of diffusers for supplying hot air under pressure. The choice of an acceptable option and, accordingly, the selection of the necessary heat equipment - at the discretion of the host BSU.
The most common, but also the most conservative system is the supply of hot water in a circular system from the traditional boiler house to the tubular registers (Ø108 - Ø159mm), mounted in a hopper inert. From the same boiler through the water heater-heat exchanger, the process water can be preheated to mix concrete and using traditional cast iron radiators - heating the entire interior space of the installation. Advantages - relatively inexpensive boiler and pipeline equipment, which does not require special knowledge from the personnel; Wide choice of boilers on gaseous, liquid or solid fuels; At near passage of a heating main - an opportunity of reception of the heat-carrier from the centralized boiler-house. The disadvantage is the low efficiency. System, and, consequently, a long time to the initial (for example, after the night) heating materials in the bunker. Experienced, according to surveys of enterprises using this heating system, it is determined that at an ambient temperature of -10÷15 °C, the amount of thermal energy necessary for heating the inert, water and premises of the SB-145-4 type SBU is 500÷600 Mcal/hour. For information - the installation of SB-145-4 (production of "Betonmash", Slavyansk, Donetsk region) has a capacity of up to 40 m³/h, a reserve of inert material bins of 120 t (4 compartments), a tank for process water 2000 l, Panel thickness of 50mm.
A more modern system of defrosting (warming up) of materials is the injection of hot steam through special nozzles directly into inert materials. This technology is successfully implemented by the Russian engineering company Interblok (interblock.ru) on the basis of the Canadian instantaneous steam generators ST. According to their information, the technology is highly economical, it ensures the supply of steam with a temperature of 110-160 °C as early as 15 seconds after the steam generator is switched on. In addition, the technology does not require the installation of chimneys (combustion products of fuel are not emitted into the atmosphere) and complex water treatment systems. The disadvantage is the saturation of inert materials with condensate, which requires its removal from under the bunkers, as well as the presence in the inert oil residues of the combustion products during operation of the steam generator on liquid fuel.
The most innovative and progressive way is warming up inert materials with hot air by means of SIMUN generators and heating water with Boiler type GEYSER boilers from IONE S.r.l or similar BOOSTER units from Sauter (Switzerland, sauterag.com). The air, heated to 200 - 260°C with a pressure of 0.2-0.4 bar, is fed through perforated diffusers to the lower part of the supply hoppers of inert materials, effectively heating them. When the heating starts, water can be injected into the hot air stream to increase heat transfer and more rapid thawing. Gases from the combustion of fuel into the stream of hot air do not enter, but give their heat in the heat exchanger to the heating of water, they are cooled to 40-60°C, and through the low-temperature pipe they are diverted beyond the circuit. Advantages of this system - along with heating simultaneous drying of inert materials, high efficiency, environmentally friendly technology. The disadvantage is the high cost of the equipment (to ensure the productivity of the BSU 40-60m³/h, the price of thermal equipment will be about 90 thousand euros, and with the installation of a generator, a boiler and fuel tanks in a special container - up to 110 thousand euros).
Of course, the best way to choose the type of heating would be the option of visiting the company where it is used, and preferably not in the first year. Only then from the source you can get objective data about the merits and demerits of each method, and, possibly, learn about others not mentioned above.
3.Heating heating discharge of ready-mixed concrete.
This is an important nuance of the work of the BSU in the winter. Here you can offer the following options for combating frost: creating a warmed tambour with a gate or blowing hot air with hot air.
We hope that the above information will help you to correctly choose the option of preparing your concrete plant for the autumn-winter season and become a quality concrete manufacturer in this difficult time of the year.