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Chemical enamel knowledge
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Date?2010/3/22 |
Borosilicate glass enamel is generally used, but the silica content higher than normal enamel. Sometimes the use of ceramic enamel to improve its mechanical and thermal properties.
Mainly used in chemical piping, pumps, valves, reaction vessels, autoclaves, mixers, distillation towers, filters, tanks.
Chemical equipment and have a metal enamel device's mechanical properties and corrosion resistance of enamel double advantage, in addition to hydrofluoric acid and fluoride ions as well as high-temperature phosphoric acid or alkali media, the ability of various concentrations of inorganic acids, organic acids, salts , organic solvents and alkali corrosion, chemical enamel surface is smooth easy to clean and to prevent interference with the chemical reaction of metal ions and the role of product contamination. Therefore widely used in petrochemical production, especially in medicine, pesticides, synthetic fiber production, is often used as a corrosion resistant non-metallic materials. Chemical enamel can be used instead of expensive alloys. Chemical Enamel is a high acid content of silicon in steel or enamel coated cast iron surfaces of equipment after 900 ℃ calcined to form a dense metal, corrosion of the glassy thin layer, which is a composite metal and enamel materials, such devices as chemical enamel equipment.
First, the basics of chemical enamel equipment
1, the chemical origin of the name enamel The use of enamel technology, will have close to the industrial nature of the acid-resistant glass, glass to metal matrix composite material, and get the glass / metal complexes, because of its cover glass, which preserves most of the acid nature, such as smooth, transparent, dense non- hole, high chemical stability, are less than for the general daily enamel, so called "glass-lined." Glass-lined production process is equivalent to enamel process, it is still the enamel. People often have a different routine in the call, such as acid-resistant enamel is termed its special acid-resistant and chemical enamel, its products are mainly used for chemical production equipment and call it. 2, the performance of enamel products
Enamel device is a high silicon content from the vitreous enamel coating on steel surface after 920 ℃ ~ 960 ℃ high temperature enamel fired several times, dense vitreous enamel surface is made of metal tires. Enamel performance are:
(1) Corrosion resistance: resistant to organic acids, inorganic acids and organic solvents PH value less than or equal to 12 alkaline solution, but the alkali, HF, and temperature greater than 180 ℃, 30% phosphoric acid concentrations greater than does not apply ; (2) non-stick: the face of the glass medium non-stick smooth and easy to clean;
(3) Insulation resistance: suitable for the process medium is easy to produce static electricity of the occasion;
(4) Isolation: glass layer medium with fetal isolated vessel steel , iron is not integrated into the media;
(5) preservation of: glass layer on the medium with good preservation properties.
3, enamel equipment conditions
Enamel level medium and so on ability majority inorganic acid, organic acid, organic solvent, especially in medium and so on hydrochloric acid, nitric acid, aqua regia have the fine anti-corrosive performance.But cannot use under the following condition:
(1) any density and any temperature HF all not ability corrosion;
(2) phosphoric acid: The density above 30%, the temperature are bigger than 180℃ when corrodes intensely;
(3) hydrochloric acid: Density 10--When 20%, the temperature is bigger than 150℃, corrodes intensely;
(4) sulfuric acid: Density 10--30%, the temperature is bigger than 200℃ when not ability corrosion;
(5) lye: PH is bigger than or was equal to when 12, the temperature are bigger than 100℃, not ability corrosion.
Second, the chemical enamel equipment manufacture
1. chemical industry enamel equipment parent metal characteristic
uses in making the glass lining product the substrate material mainly is massively the high quality low-carbon steel, the cast iron and the stainless steel, in which is most common by the low-carbon steel and the cast iron.The former took the glass lining the suitable steel, uses for to manufacture the equipment and the vessel massively: The latter, because can the casting formation complex part, also the cost is inexpensive, therefore is widely used to make the pump, the valve, the bantam and the spare parts.Carboniferouss, the sulfur low enamel is suitable the steel
Parent metal chemical composition mechanical property
C si Mn P S longitudinal strength MPa elongation ratio % yield point MPa resilient MPa
steel ≤0.14 ≤0.37 ≤0.65 ≤0.035 ≤0.45 >330 >310 200 - -
welding rod ≤0.1 ≤0.12 ≤0.45 ≤0.05 ≤0.03 >430 >180 - - 80
cast irons 3-0.35 2.0-2.6 0.4-0.6 0.1-0.5 < 0.1 - - - - - - - -
(graphite carbon 2.5) - - - - - - - - - - - - - - - - - -
Attached list 1: Chemical enamel equipment parent metal technical specification
3, bottom embryo's request the enamel equipment's quality, first decides in the iron-gray roughcast. The high grade iron-gray roughcast, has been impossible to have the high grade enamel equipment. Must guarantee the product quality, the iron-gray roughcast should satisfy the following six requests: the (1) bottom embryo surface should level, do not have the remarkable tool scar, the pit, the band and so on mechanical defect; the (2) bottom embryo surface's weld bead must be straight, be neat, the welded joint width do not surpass the steel plate, thickness 1.5 times. The welded joint attachment must transit smoothly, does not allow to have the entrapped slag, the blowhole, the undercut, not flaws and so on penetration; the (3) bottom embryo surface's welded joint must carry on the polish before the sand blasting; the (4) bottom embryo surface's butt welding seam inlaying quantity must being smaller than thickness 10%; the (5) flange undulation must be smaller than the diameter 0.15%; the (6) docking flange's compaction surface must guarantee under the design pressure the seal. [the result originates from: http://tran.httpcn.com/Fanyi/ After 4th, the surface treatment
bottom embryo processes, because the parent metal surface quality often could not achieve the enamel the technological requirement, like the metal surface still had the oxide layer, the surface clamped the skin (when rolling creates) the fat contamination which, in the welded joint flaw and the machining process stuck and so on, all had to affect keeps out burns the quality, therefore had to carry on the polish, fever surface treatments and so on oil decarbonization and sand blasting.
Grinds generally carries in the grinder or with the portable grinding wheel.The polish request is keeps out in the charring to weld slope smoothing by grinding, rubs the cuspidal edge angle the circle, and clamps the oxide skin the skin to rub off, appears the metal true colors.
Burns the oil decarbonization is the fat which, the organic matter sticks and so on under the high temperature the broadcast burn. When sometimes the steel plate carbon amount surpasses the standing operating procedure, also adopts the high temperature surface decarburization the means to make compensation processing. after enamel equipment trouble, carries on to the enamel factory duplicate keeps out, must carry on the heat treatment (dehydrogenation), eliminates explodes porcelain spot parent metal permeating the hydrogen. The sand blasting is hits roughly the bottom embryo surface, increases the superficial free energy and compared to the surface area, thus enhances the bottom embryo metal and the underglaze is being dense.
5, repair or recap tires after surface treatment iron-gray roughcast, before spurts officially keeps out the porcelain glaze, must inspect carefully, everything does not meet the enamel technological requirement “the problem” should the stitch in time, like burr, incisive angle, concave-convex pit, band, blister and so on. These “the problem” may use the manual polish, digs the shovel patching to regrind the equal work sharpening.
6, will keep out burns underglaze the iron-gray roughcast to resharpen good later then to carry on the spray coating and to keep out burns the underglaze. The spray coating may use spurts manually, may also use the mechanization (semiautomatic) the spray coating. Both's glaze thick liquid thickness control is dissimilar, this must experience itself according to the operators to grasp, because the spray gun caliber, the spray coating use the air pressure and glaze thick liquid thickness are the incident cross-correlation. Spurts keeps out the underglaze the main point is must make the underglaze thickness to be even, its thickness value control after incineration for 200±50 μm for appropriate. Underglaze spray coating after iron-gray roughcast must pass through dry, generally adopts the natural drying, may also put to the drying room in dry, before placing the stove, or nearby the drawing a charge workpiece carries on the slow roasting. Must pay attention prevents the fast roasting, bakes Yi Shifen fast the level dehiscence. After powder level dry, then enters in the firing furnace to carry on fires. The underglaze firing temperature is high. In order to enable the underglaze to be reliably dense with the hard surface, uses when the method of three-in-one underglaze the firing temperature cannot be lower than 880℃. But to cause between the iron-gray roughcast and the underglaze the temperature can meet the above requirements, the firing furnace temperature must control 920℃ above. In order to raise the efficiency, the best firing furnace temperature is 960~980℃. The underglaze fires must grasp the time carefully, namely cannot fire (popular name to burn insufficient lives), cannot burn (popular name fire in a big way). The former is dense is not being good, the latter meeting loss by burning underglaze. Fires the moderate underglaze to be the luster cancels, surface smooth luminous, does not have the air bubble. After a bottom bakes with glaze, if the quality qualified then carries on spurts keeps out the surface glaze; If is unqualified must carry on the sharpening, the loss by burning is serious when needs to spurt keeps out second the underglaze. When spurts keeps out the second underglaze, cannot spurt too thick, must make two underglaze the total thickness controls at 350μm below. Thick has wanted again the influence surface glaze level the effective thickness.
7, after keeping out charring glaze the underglaze keeps out burns, the quality meets the requirement then to carry on the surface glaze to keep out the fever. The enamel equipment's true anticorrosion protector is the surface glaze level. The surface glaze level's spray coating and keeps out burns is similar with the underglaze. Surface glaze level's thickness, requests about generally 1mm. Makes concrete decides according to the operation requirements, if the consideration heat transfer, should cause porcelain glaze level thin, cannot transfer heat the medium which uses to corrode when the domestic animal is serious, porcelain glaze level thick. Japan allows to reach 2.55mm thick, our country standard stipulated that do not surpass 2mm, thinnest 0.8mm. Must achieve the stipulation porcelain to be thick, on the product surface glaze must spurt keeps out many. Each thickness take thin somewhat as good. But consideration production efficiency, also cannot be too thin, generally take controls each thickness to increase 2mm as good. If the metal surface condition is good, the welded joint does not have problems, spurts keeps out in the process to resharpen carefully, then after spurting keeps out three to four surface glazes, may achieve the stipulation thickness. Keeps out for the guarantee burns the quality, spurts every time keeps out, must undergo the inspection, on the inspection porcelain surface whether to have soaks, the pinhole darkly and so on, As soon as passes through Zha Dao to polish advances a line of patching. Regarding goes nonstop to the metal surface the pinhole and soaks darkly must rub digs, even patching. Every sees the base metal patching place, must make up spurts the underglaze. The above patching procedure is each spurts keeps out the operator to grasp.
Third, chemical enamel equipment's use chemical industry enamel equipment's mechanical strength, although the glass, the ceramic equipment must be much better than, but the enamel is the complex which eventually forms together by the glass ceramic body and the metal, therefore still had the similar glass, the ceramics such not to be able to withstand the clash, to strike with impact weakness. Their difference, is only because the enamel equipment has the metal shell, when porcelain glaze level damage does not look like the glass, ceramic equipment such to lose the use value immediately, but is needs to have a section to reveal that the time which destroys (time length along with is located environmental condition to decide) only will then lose the use value. This characteristic, from the advantageous aspect looked that is for the user by the security sense, but looked from the disadvantageous aspect, then as a result of has the security sense to have the illusion easily for many inattentive users, down to neglects the safety handling condition. Regarding this must bring to the attention. The correct use enamel equipment, can enhance the enamel equipment's life greatly, uses the enamel equipment including already to correctly act according to the exploitation conditions choice quality to be good, specification being suitable and outside variety appropriate enamel product, but must observe each kind of safe operation stipulation strictly.
Fourth, before the chemical enamel equipment selects and purchases the 1, purchase enamel equipment, to understand in detail purchases in advance enamel situations and so on plant technology, production, creditworthiness, does not want as far as possible, because the price reason purchase product has problems frequently the Manufacturer enamel equipment; 2, must to the enamel Manufacturer explanation enamel cauldron's actual medium environment, if possible simulate the production environment to make the porcelain glaze the anti-corrosive experiment; 3, will purchase in advance enamel cauldron's each performance and the actual production environment contrast; 4, want the enamel equipment which purchases should after the assembly qualified settles above half a month (time to be longer well), eliminates the surviving stress; after 5, determination purchase equipment, (high frequency electric spark generator should better supply for oneself) according to the attached list test method examination.
Fifth, use operation matters needing attention (1) feeding: when feeding must be prudent. Should not have any hard object to fall to the enameled vessel, meanwhile should avoid the spatial pot heating material and the hot pot as far as possible adds the cold material, the use temperature difference should not surpass equipment's technical specification stipulation. The material joins the equipment planted agent to take strict precautions against smuggles the reguline metal or the sundry goods, regarding the bulk flinty material, should crush add-on enters. Reduces between the material and shell of tank's temperature difference as far as possible, avoids the cold pot heating material or the hot pot adds the cold material; (2) operation revolution: when the use has clamp cover's equipment, must pressurize slowly the elevation of temperature. Must pass over 0.1MP in advance the pressure, after maintaining the quarter, passes over the vapor to reach the service pressure slowly again, if the condition permitted, may act according to this unit's actual situation, discovers being suitable to rise the temperature decrease curve, generally control in 3℃/min below. In the equipment revolution, must pay attention to the flange, take over a business, the person hole and the stuffing box seal situation, if discovery divulging should take the measure immediately; the operation revolution when uses the clamp cover equipment, should slowly carry on the compression, the elevation of temperature, generally passes over 0.1MPa first (super atmospheric pressure) the pressure steam, maintains 15 minutes later, then slowly pressure-rise, the elevation of temperature (pressure-rise speed rises the 0.1MPa pressure take every 10 minutes as suitably), in until pot's service pressure, no matter heats up or cooling should carry on the permissible temperature scope, my factory equipment application temperature 0-200℃, temperature difference thermal shock 120℃, cold impact 110℃. (3) material: when leaves the material, in case the tank bottom jamming, does not hit using the hardware shovel, the available bamboo pole or the plastic stick, the wooden bat hold gently. The response ended when needed to cool, must treat in the pot the temperature dropped naturally after the certain extent again to the clamp cover in passes the cooling water, took strict precautions against the quenching. When acid, alkali replacement, must bears the alkali enamel equipment's service life big reduction, must therefore pay attention to the choice kali resistivity good enamel equipment. The acid-proof enamel should avoid using in the acid and alkali alternate situation. When leaves the material, if discovered that has the enamel detritus, should open the pot inspection immediately, after the patching porcelain surface, uses again.
Sixth, enamel equipment's maintenance (1) must inspect frequently, like the discovery crack or explodes damages and so on porcelain, must patch well promptly only then uses; (2) must clean frequently, prevents the contamination corrosion equipment surface, the protective paint to want regular coating; (3) cleans the clamp cover to refuse with the hydrochloric acid, in the clamp cover to enter the hydrochloric acid to be able to cause the pot endophragm “the scale to explode”, when eliminates on the porcelain surface the adherency, cannot use the metal to knock the shovel; (4) must take care of properly, every does not use the enamel component which or does not use temporarily, must pay attention protects and deposits, prevents the clash and the rain drenches, pays attention to the clamp cover, in the thermometer drive pipe not to enter the water, in the winter the water ices up the porcelain level expansion crack; in (5) clamp cover, regardless of being the media which the heating or cools uses, should assume the neutrality, do not smuggle any acid liquor, because otherwise “the hydrogen will bubble” causes the glass lining to have the scale to explode; in if (6) clamp cover the use cleaning media removes dirty stuff, should in such a short time complete, and flushes repeatedly along with it to the clamp cover, the examination residue should assume the neutrality; (7) inspects in the enamel village, the transmission part frequently. Seal situation and so on to be whether normal, if discovered that exceptionally should the stitch in time, not be possible to delay; in the (8) regular replacement transmission device and the mechanical sealed chamber's lubricant, guarantees each revolution spot the normal lubrication; (9) watches out the pressure gauge to be whether keen. If discovery pressure gauge system instruction losing accuracy, should the prompt replenishment transformer oil, the comparison standard pressure gauge readjust; (10) enamel equipment's under design pressure operating temperature scope for 0~200℃, if the equipment uses under the atmospheric pressure, may expand for - 20~200℃; Regarding the belt clamp cover's enamel equipment, its pot (cauldron) in permits the vacuum, but its inside and outside differential pressure should conform to the stipulation; (11) FK (FK) in the series response pot's winged thermometer wrap, may according to the craft need in 190 ℃. The scope internal assignment in the random angle, by is obtaining the different resistance. The adjustment angle should better carry on the stopped state, if must adjust in the reaction process, should inspect the stop ring beforehand whether to join reliably, in order to avoid has the accident; (12) configuration mechanical seal response pot, when the operating temperature surpasses 70℃, the disposition packing seal's response pot, surpasses in the operating temperature 100℃, should in the chiller, the stuffing box clamp cover pass over the cooling water separately, avoids the potted component damage; in the (13) mechanical sealed chamber's lubricant (sealing fluid) should guarantee purely, do not smuggle the solid particle. Has the sublimation phenomenon reaction process, is not suitable uses the mechanical seal which this equipment provides to install directly the (14) enamel level exterior metal surface to prevent strictly with the acid liquor and the acidic material contact, avoids the metal semblance and the acid reaction produces the hydrogen, causes the porcelain level “the scale to explode”. If has the acid liquor dripping to give to clean, the leak stoppage immediately. |
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