Explosion chamber for synthezis of detonating nanodimond
FIELD: blasting operations.
SUBSTANCE: explosion chamber contains cylindrical hull, plain bottom, cover and fastening tools for charge of explosive substance inside the chamber, installed in cooling casing. The vertical hull and the chamber bottom is faced by steel of reinforced concrete, and as cooling casing it is used the water, partly filling the internal chamber volume, on the chamber bottom it is fixed the perforated tubes, connected with gas system or with water pump, on the inside hull surface it is fixed the vertical splitter of the air-blast wave with rectangular section, connected by several steel rings, the hull is provided with hatch, which is opened inside the chamber, nipples for gas and water excluding from the chamber and nipples for gas feeding to perforated tubes, the hatch is steel hermetical cistern filled with the water, which has nipples for water and water feeding, and also nipples for water feeding from cistern to the chamber, which are made as curved tubes, that the curve is situated higher then the water level in the cistern.
EFFECT: it is exceeded the productivity of the chamber as well as the convenience of using without stuff entering inside.
4 cl, 2 dwg
The technical field
The invention relates to a pressure treatment of materials, namely the explosive chambers designed to contain explosions in the processing of explosive materials for the purpose of industrial production of detonation nanodiamonds.
There are various construction blasting chambers for the synthesis of superhard materials (see the book V.V. Danilenko, "Synthesis and sintering of diamond Bang, M.: Energoatomizdat, 2003, 272 C.). They represent a strong steel vessel, inside which is placed the explosive charge and the material being processed. When the explosion of the charge inside the cell load on the walls of the chamber are determined by the amplitude of the pressure pulse shock wave on the walls. To ensure the robustness of the walls when multiple explosions amplitude pressure should be 4 to 5 times smaller than the yield stress of steel used, and the pulse is offset by the weight of the chamber walls. Depending on the materials and construction of the camera for each kilogram of exploding charge 2 to 10 m3the internal volume of the chamber. The pressure of explosion products on the surface charge of about two orders of magnitude higher than the yield strength of the best grades of steel. Therefore, any part or parts of the camera located near the exploding charge will quickly deteriorate.
About is a rule for research and technological objectives are easier to manufacture cylindrical explosive chamber, which in the greatest explosion loads are on the Central section (which explodes the charge), the centers of the bottoms and joints bottoms with the walls of the chamber.
For the industrial production of detonation nanodiamonds need to blow up the camera charges of explosives large mass (20 kg or more). For reliable localization of multiple explosions such charges steel Luggage must have a large volume (>100 m3) and weight (over 100 tons), which increases the camera, and have a large volume (>100 m3) and weight (over 100 tons), which increases the camera and makes its transportation and installation.
For rapid cooling of nanodiamonds produced in the detonation wave at temperatures 3500-4000 K, the charges in the cell explode in the cooling shells from the water or ice with optimal mass equal to ten mass of the charge.
Known Luggage for explosive working of metals (see ed. mon. The USSR №875706, CL 21D 26/06, 1985), comprising a housing consisting of a Central part, made in the form of concentrically mounted with clearance in the cylinder and adjacent the bottom and top fixed by the lock, and the inner cylinder is installed freely and with a gap relative to the cover, and the ends of the outer cylinder is made covering the ends of the inner cylinder tabs, centering the latter along the axis. In the bottom of the strengthened specimen table on which I placed on it processed by the explosion of the product. This technical solution adopted for the analogue of the claimed invention. The disadvantages of analogue are limited operational capabilities, since cameras of this type it is necessary to open after each explosion to retrieve the processed material and cleaning its internal cavity.
Known Luggage for explosive treatment of materials by Russian Federation patent RU 2078661, CL 21D 26/06, 1997, selected as a prototype, since it is also suitable for the synthesis of detonation nanodiamonds.
Camera-prototype includes a housing, a cover and bottom with Central aligned holes. The charge in the ice shell is mounted in the open top of the cover, made in the form of thick-walled pipes, partially located in the Central part of the body. The bottom has a tapered divider of explosion products and sloping radial openings through which the products of an explosion into the collection containers are located next to the camera. Thus, the condensed products of the explosion (carbon charge) are removed from the chamber without breaking.
The disadvantages of the prototype:
required parts are manufactured from ice, destroying each explosion;
- exploding the charge through the ice closely adjacent to the cover, which leads to its rapid destruction;
- products of the explosion with nanodiamonds partly is released from the atmosphere, which leads to the loss of nanodiamonds;
- the camera is not designed for explosions charges a large mass that determines the performance of the production of nanodiamonds.
Disclosure of inventions
The technical result of the present invention is to provide a construction explosion chamber for the synthesis of detonation nanodiamonds with a wide operational capabilities, due to the enhanced camera performance, safety and convenience of its operation. We offer explosion chamber ensures the conduct of multiple explosions explosive substances a large mass (20 kg or more) without making massive cooling shells and without entry of personnel into the camera for setting charges in the chamber and discharging from the chamber received nanodiamonds, and reduced explosive loads on the chamber design.
This is due to the fact that in the blast chamber for the synthesis of detonation nanodiamonds containing cylindrical body, a flat bottom and a lid and means for mounting inside the chamber of an explosive charge placed in a cooling jacket, a vertical casing and the bottom of the camera is made of coated steel reinforced concrete, as the cooling shell use water, partially filling the internal volume of the chamber, on the bottom of the camera is fixed perforated the cuttings, United with gas or water pump, on the inner surface of the body has vertical dividers shock wave triangular cross-section, United several steel rings, the body is provided with a hatch opening into the chamber, connections for pumping gases and water from the chamber and pipes for gas supply in the perforated tube, the cover is a steel pressure tank with water having nozzles for supplying water and gas, and pipes for supplying water from the tank into the chamber, which is made in the form of a curved pipe, and the bending of the pipe is above the water level in the tank, in the center of the bottom under water is lined with steel reinforced concrete cone, and at the junction of the bottom and cover with the chassis between the dividers installed coated steel concrete reinforcing insert triangular cross-section, means mounting the explosive charge in the water made in the form of passing diametrically through the casing wall and the upper edge of the hatch steel cable mounted on two rollers mounted on the outer surface of the housing, and having the possibility of lateral movement and sagging during the rotation of the rollers.
Comparative analysis of the invention with the prototype shows that the stated camera has new features that enhance the product is italinate chamber for the production of detonation diamonds the safety and convenience of its operation.
The stated objectives of this invention are achieved as follows. Improving the performance of the synthesis of nanodiamonds in the chamber is ensured by using charges a large mass, with the exception separately manufactured solid water or ice shells exploding around charges, mechanization of technological operations, in particular transport charges in the camera and unloading of nanodiamonds from the camera.
The security and usability of the camera is provided by the mechanization of technological operations that do not require entry of personnel into the camera with a hazardous atmosphere, the use of devices that reduce explosive load on the camera.
To reduce the loads on the camera and hardening of the proposed design of the camera is used in the following ways: created in the water before the explosion many gas bubbles, falling stream of water in the chamber to neutralize the energy of the water flow and the gas generated by the explosion under water and rising from the surface of the water, the dividers of the shock wave on the camera body, their connection with steel rings, installation in the center of the bottom of the massive coated steel reinforced concrete cone installation between the dividers at the junction of the bottom and cover with massive walls lined with steel jelly is betonnyh inserts.
The duration of operation of the camera is also determined by the fact that the camera does not have parts close to the charge and therefore perishable.
The stated problem is solved. The camera can be used repeatedly for the industrial production of detonation nanodiamonds with the mechanization of the basic technological operations without logging personnel inside the camera.
Brief description of drawings
Figure 1 shows a longitudinal section of the explosion chamber, and figure 2 is a fragment of the cross-section.
Explosion chamber consists of a vertical cylindrical body 1 with a flat bottom 2, is made of coated steel reinforced concrete, and stainless steel flat cover 3. On the inner surface of the housing 1 along its height set to vertical dividers shock wave 4 triangular cross-section, made of coated steel reinforced concrete and United several steel rings 5. On the side surface of the housing 1 is Luke 6 opening inside the camera. Cover 3 is a sealed tank 7 for water with pipes for water supply 8 and the compressed gas 9 and the pipe 10 for supplying water from the tank 7 into the chamber in the form of a curved pipe, and the bending of the pipe is above the water level in the tank 7. At the level of the upper edge of the hatch in the diametrical cross section of the camera is set to the cable 11, eobny to move horizontally across the diameter of the camera or SAG during rotation of the two rollers 12, mounted on the outer surface of the housing 1 and having separate actuators (not shown). The cable 11 on the wire 13 is suspended from the explosive charge 14.
On the bottom of the camera it is lined with steel reinforced concrete cone 15. At the joints of the cover 3 and the bottom 2 from the housing 1 inside dividers 4 are lined with steel concrete reinforcing insert 16 of triangular cross-section.
On the bottom 2 installed perforated tube 17 connected via a manifold solenoid valves with compressed gas system and water pump pumping from the cell suspension with nanodiamonds (not shown). The housing 1 has an inlet 18 which is connected through the solenoid valve with the compressor pumping gas from the chamber (not shown), the pipe 19 which is connected through a solenoid valve with a pump for pumping water from the chamber into the tank 7 (not shown)and the pipe 20 for supplying gas to the perforated tube 17.
Explosion chamber works as follows.
The tank 7 is filled with water.
The chamber is partially filled with water to a level below the lower edge of the hatch 6.
Off camera about the hatch on the cable 11 through the wire 13 is suspended from the explosive charge 14. The hatch opens 6. The rotation of the rollers 12 of the cable 11 with the charge 14 is moved from the outer wall of the housing 1 is about the camera axis. Then the opposite rotation of the rollers 12 is created sagging of the cable 11 by an amount providing immersion charge 14 into the water at the desired depth. Luke 6 is closed.
Open the valves in the compressed gas which is fed into the tank 7 through the pipe 9. Compressed gas through the nozzles 10 displaces water from the tank 7 into the chamber, where a vertically falling stream of water. At the same time opens the valve connecting tube 17 through the pipe 20 with the receiver of compressed gas, and through the openings in the tubes 17 compressed gas released into the water, where there are a lot of bubbles rising to the surface of the water. When bubbles and falling from the nozzles 10 of the flow reaching the surface of the water in the chamber, is undermining the charge 14. Immediately after blowing close the valves in the compressed gas. Switch on the compressor, and gases from the chamber through pipe 18 is partially pumped into the receiver and partially extend into the atmosphere (gases do not contain nanodiamonds, which remain in the water in the chamber). Again, the hatch opens 6, and the working cycle is repeated.
After spending a few explosions (e.g., per day) blasting operations shall be terminated on the time required for settling to the bottom chamber of the suspension 21, containing nanodiamonds. Part of the water above the slurry pump is pumped from the chamber through pipe 19 back into the tank 7. Offe is by valve, connecting tube 17 with pump, includes pump, which pumps the slurry from the chamber, for example, a centrifuge or a vacuum filter, where she wrung out the water and get the carbon mixture containing nanodiamonds.
After swapping the suspension the camera is ready for blasting.
This invention will find application in the production of detonation nanodiamonds. For the production of up to 5 tons per year of detonation nanodiamonds the explosion of charges of alloy TNT - RDX TG/60 by weight 30 kg declare explosion chamber of coated steel reinforced concrete should have an internal diameter along the edges of the dividers - 10 m, the height of the section dividers - 1 m, the height between the bottom and lid inside the camera - 14 m, outer diameter camera - 13 m, the thickness of the steel sheet cladding concrete - 10 mm, the thickness of the steel cap in the form of a water tank -1 m, a base thickness of 1.5 m, the length of the leg inserts triangular section at the joints of the body with lid and bottom between dividers - 1 m, the height and base radius of the cone in the center of the bottom of a 1.5 m
1. Explosion chamber for the synthesis of detonation nanodiamonds containing cylindrical body, a flat bottom and a lid and means for mounting inside the chamber of an explosive charge placed in a cooling shell, characterized in that Thu is a vertical casing and the bottom of the camera is made of coated steel reinforced concrete, as the cooling shell use water, partially filling the internal volume of the chamber, on the bottom of the camera is fixed perforated tube connected to the gas system or water pump, on the inner surface of the body has vertical dividers shock wave triangular cross-section, United several steel rings, the body is provided with a hatch opening into the chamber, connections for pumping gases and water from the chamber and pipes for gas supply in the perforated tube, the cover is a steel pressure tank with water having nozzles for supplying water and gas, and pipes for supplying water from the tank into the chamber, which made in the form of a curved pipe, and the bending of the pipe is above the water level in the tank.
2. The camera according to claim 1, characterized in that the center of the bottom under the water is lined with steel reinforced concrete cone.
3. The camera according to claim 1, characterized in that at the junction of the bottom and cover with the chassis between the dividers installed coated steel concrete reinforcing insert triangular cross-section.
4. The camera according to claim 1, characterized in that the means of attachment of the explosive charge in the water made in the form of passing on the diameter of the chamber through the wall of the housing and the upper edge of the hatch steel cable mounted on two rollers, replenish on the outer surface of the housing, with the possibility of lateral movement and sagging during the rotation of the rollers.
FIELD: inorganic chemistry, possible use in bio-medical research and during manufacture of non-magnetic materials, sorbents.
SUBSTANCE: in accordance to the method, industrial mixture of diamond with graphite and metals is processed by mixture of acids and oxidizing compounds. The suspension is additionally processed by cleaned concentrated hydrochloric acid with concentration of nano-diamonds in the hydrochloric acid not exceeding two percents with simultaneous ultrasound processing. Temperature of suspension is measured. Then temperature increases by at least ten degrees, irradiation is stopped. Suspension is settled. Aforementioned operations are repeated at least three times. Then suspension is washed by cleaned concentrated hydrochloric acid until coloration disappears and thiocyanate sample reaction becomes positive. Final washing is performed by deionized water until suspension stops settling.
EFFECT: resulting nano-diamonds do not contain admixtures of iron.
FIELD: crystal growth.
SUBSTANCE: method comprises separating the inoculation from the source of carbon by a metal-dissolver made of an alloy of ferrous, aluminum, and carbon when a 20-30°C temperature gradient is produced between the carbon source and inoculation. The growth zone is heated up to a temperature higher than the melting temperature of the alloy by 10-20°C, and the melt is allowed to stand at this temperature for 20 hours. The temperature then suddenly increases above the initial temperature by 10-25°C and decreases down to the initial value with a rate of 0.2-3 degree per minute.
EFFECT: improved quality of crystal.
1 tbl, 2 ex
FIELD: inorganic chemistry; mining industry; electronics; other industries; methods of the synthesis of the needle-shaped and lengthened diamonds.
SUBSTANCE: the invention is pertaining to the field of the inorganic chemistry, in particular, to the method of production of the needle shape synthetic diamonds and may be used in the industrial production of the special-purpose diamonds, for example, for manufacture of the boring crown bits and the dressers, and also in the capacity of the blocks details of the audio-video playback equipment, for manufacture of the feeler probes, in the micro-mechanical devices etc. The method provides for commixing of the fusion charge composed of the alloy of Mn-Ni-Fe in the mass ratio of 60±5÷30±5÷10±5 and the powder of the carbon-containing substance and treatment of the mixture at the pressure exceeding 40 kbar and the temperature over 950°С at heating rate less than 100°C/minutes. In the capacity of the carbon-containing substance use the needle-shaped coke or graphite on the coke basis with the single-component anisotropic structure with the degree of graphitization of no less than 0.55 relative units. The invention allows to simplify the production process of the synthesis of the needle-shaped and lengthened diamonds and to increase the percentage of their output within one cycle of the production process.
EFFECT: the invention ensures simplification of the production process of the synthesis of the needle-shaped and lengthened diamonds, the increased percentage of their output within one cycle of the production process.
2 ex, 2 dwg
FIELD: chemical industry; methods of processing of the diamond-containing concentrates.
SUBSTANCE: the invention is pertaining to separation of the diamonds from the diamonds-containing rock and the marks of technological processes concentration and may be used in the production shops of the final treatment of the diamond- -containing concentrates in the mining-and-processing integrated works of the diamond-mining firms. For creation of the self-contained ecologically safe cycle of production of pure diamonds the processing of the diamond-containing concentrates is conducted in the autoclave at the temperatures of 200-400° С using the saturated solution of the sodium carbonate with addition of 3-5 % of the weight % of sodium hydroxide in the field of the ultrasonic radiation, then the autoclave is cooled and in the reaction mass, which contains the non-reacted water solution of the sodium carbonate, they route oppositely to the gravitational force the stream of the concentrated hydrochloric and nitrogen acids for formation of the conditions of the flotation-gravitational division and separation of the diamonds from the products of the production process. At that for creation of the closed cycle of the production process at flotation-gravitational separation of the diamonds from the products of the production process use the concentrated acids, which have remained after the final cleaning of the diamonds. The invention ensures the high quality of the cleaning of the diamonds at the minimal usage of the toxic mediums, which allows the considerable reduction of the cost of the production process.
EFFECT: the invention ensures the high quality of the diamonds cleaning, the minimal usage of the toxic mediums in the production process, the considerable reduction of its cost.
2 cl, 2 ex
FIELD: chemical industry; mining industry; other industries; methods of production of the heat-resistant composite diamond sintered articles.
SUBSTANCE: the invention is pertaining to the heat-resistant composite diamond sintered articles used in the capacity of the cutting tools, the tool used for the high-precision machining and to the jewelry branch. The diamond composite sintered article contains in the capacity of the article the diamond crystal and the very small amount of the non-diamond carbon and has the hardness according to Vickers of 85 GPa or more. The article is produced by the method providing for inclusion of the synthetic diamond powder having the average size of the grains of 200 nanometers or less, in the tantalum or molybdenum capsule, both heating and application of the pressure at usage of the apparatus for the synthesis under the super-high pressure in the thermodynamically stable conditions including the temperature of 2100°С or more and the pressure of 7.7 GPa or more. The technical result of the invention is production of the articles having the electric conductivity, the high thermal stability and having the brilliance and the glaze.
EFFECT: the invention ensures production of the articles having the electric conductivity, the high thermal stability and having the brilliance and the glaze.
6 cl, 4 ex, 3 dwg
FIELD: chemical industry; other industries; production of the superfine-grained diamond sintered articles of the high purity and high hardness.
SUBSTANCE: the invention is pertaining to the production of the superfine-grained diamond sintered articles of the high purity and high hardness, which is intended for usage in the capacity of the wear-resistant material capable to let the light go through it, and may be used in production of jewels. The article has the size of the grain equal to 100 nanometers or less. For its manufacture the superfine-grained natural diamond powder having the granulometric spread of values from null up to 0.1 microns is subjected to desiliconization, to sublimation drying in the solution, inclusion into the tantalum or molybdenum capsule without the sintering additive, heating and application of the excessive pressure to the capsule using the device for the synthesis at the super-high pressure at the temperature of 1700°С or more and under pressure of 8.5 GPa or more, which meet the conditions of the thermodynamic stability of the diamond. The technical result of the invention is realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method and without usage of any sintering additive. The article has hardness according to Vickers - 80 GPa and more and is excellent concerning resistance to the tear and wear and the thermal resistance.
EFFECT: the invention ensures realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method, and without usage of any sintering additive, ensures its hardness of 80 GPa and more according to Vickers and the excellent properties concerning resistance to the tear and wear and the thermal resistance.
4 cl, 5 ex, 3 dwg
FIELD: carbon materials.
SUBSTANCE: invention relates to inorganic chemistry of carbon and can be utilized when obtaining stable nano-diamond sols. According to an embodiment of invention, synthetic diamond-containing substance contains 82-91% carbon, 0.8-1.5% hydrogen, 1.1-2.2% oxygen, and 1.1-1.3% metallic impurities with content of non-diamond carbon 2-25% based on total weight of carbon. diamond-containing substance is characterized by ζ(zeta) potential from -40 to -85 mV. According to second embodiment, substance contains 97.5-98.5% carbon, 0.09-0.2% hydrogen, 0.3-0.5% oxygen, and 0.5-0.8% metallic impurities with content of non- diamond carbon 0.2-5% and zeta potential from 0 to -75 mV. Synthetic diamond-containing substance according to invention manifest high colloidal particle stability and are susceptible to be fractioned with narrow particle size distribution: 3 to 1700 nm and 3 to 8000 nm, respectively. Present substances are recovered by treating dry nano-diamond powder obtained from mixture of explosives (trinitrotoluene-hexogen or graphite-hexogen) in boiled organic solvents, succession of solvents going from hydrophobic solvents to hydrophilic ones so that each precedent solvent dissolves well in subsequent one.
EFFECT: increased economical efficiency and commodity of transportation of raw material and diamond-containing substances obtained thereof.
3 cl, 9 dwg, 4 ex
FIELD: carbon materials.
SUBSTANCE: invention relates to electrochemistry of carbon materials, namely to removing carbon-containing impurities from diamond powders. Method comprises electrochemical treatment of diamond powder in sulfuric acid electrolyte, more specifically in sulfuric acid solution of manganese sulfate while electrochemical treatment is effected at concentration of manganese in electrolyte 15-30 g/L, solids/liquids ratio 1:(3-5), anodic current density 0.10-0.20 A/cm2. and temperature 125 to 170°C for 2 to 7 h. Degree of purification reaches 99.8%.
EFFECT: increased degree of removing residual graphite under relatively low temperature preventing oxidation of diamond.
1 tbl, 7 ex
FIELD: production of nanodiamond suspensions in various media for conducting of plating processes.
SUBSTANCE: method involves providing thermal processing of nanodiamond powder in air at temperature of 440-600 C until powder weight losses reach 5-85%. Thermally processed powder forms stable suspensions in water, ethyl alcohol and other solvents upon common mixing. Sediment stability of nanodiamond suspensions thermally processed in accordance with invention and produced using supersonic treatment is at least 1.5 times as high as similar parameter of nanodiamond suspensions produced by prior art processes.
EFFECT: simplified method allowing stability of nanodiamond suspension in various media to be improved.
FIELD: chemical industry; cutting tool industry; mechanical engineering; methods of the production of the artificial highly rigid materials.
SUBSTANCE: the invention is pertaining to production of the artificial highly rigid materials, in particular, diamonds, and may be used in chemical industry; cutting tool industry; mechanical engineering, boring engineering. The method provides for compaction of the powdery carbon-containing materials in the field of the quasi-equilibrium state of the graphite-diamond system and the slow refrigeration in the zone of the thermodynamic stability of the diamond or other synthesized material. The heated capsule made out of tungsten with the pure carbon raw fill in with the liquid silicon at the temperature of 1750°K, hermetically plug up, then reduce the temperature to 1700°K during 30-40 minutes and cool to the room temperature within 5-6 hours in the process of the synthesis of the high-strength materials. The monocrystals of the boron carbide of the 400-450 microns fraction and the diamonds of the 40 microns fraction have been produced. The technical result of the invention consists in improvement of the quality, the increased sizes of the monocrystals, and also in the decreased labor input of the production process.
EFFECT: the invention ensures the improved quality and the increased sizes of the produced monocrystals, the decreased labor input of the production process.
2 cl, 2 ex
FIELD: plastic working of metals, namely pulse hydrodynamic formation.
SUBSTANCE: apparatus includes reservoir with liquid where tube, base and two valves are arranged. Plate with fitting is mounted on base in upper part of tube. Valves are mounted in upper part of tube. Valve designed for providing dynamic pressure of liquid has larger cross section and it is communicated with atmosphere. Other valve is communicated with compressor and it is used for completely discharging liquid out of tube. Blank is deformed by action of dynamic pressure of liquid. Natural water basins may be used as reservoirs with liquid.
EFFECT: simplified, lowered-cost process for forming parts due to using valves and compressor, increased power of apparatus.
2 cl, 1 dwg
FIELD: petroleum processing.
SUBSTANCE: group of inventions relates to processing of petroleum and liquid hydrocarbons and can be applied separately as rotary pump with mechanical cracking during pumping of crude oil in order to increase yield of low-molecular weight hydrocarbons and to lower viscosity. In a process of processing a mixture of liquid hydrocarbons, processing is accomplished via mechanical catalyst-free hydrodynamic cracking in at least one step in a single process space, which is centrifuge with cylindrical or conical rotor protected against external effects by a special system and having outlet pipes, wherein feedstock stream is continuously supplied to process space of rotating cylindrical or conical rotor; feedstock is stirred mechanically with the aid of rapidly rotating rotor provided with partitions and combs mounted thereon at the rotor rotation speed 8000-28000 rpm and pressure inside centrifuge up to 1.2 mPa; feedstock processing temperature is controlled by preheating it and also by heating or cooling front cover and space between rotor and centrifuge case, while processed feed is discharged over outlet pipes. An apparatus for implementation of above-described process is also provided.
EFFECT: enabled processing of crude oil at its production site, facilitated transportation thereof, and increased crude oil processing efficiency.
16 cl, 4 dwg