Kettle body
1. Replacement conditions
If the reaction kettle has been used for a certain period of time and one of the following situations occurs, it should be replaced:
a. The uniform corrosion of the wall thickness of the kettle exceeds the minimum value specified in the design;
b. The local corrosion of the wall thickness of the kettle exceeds the minimum value specified in the design, and the corrosion area is greater than 20% of the total area;
c. During the hydraulic test, there is obvious deformation or residual deformation of the equipment exceeding the specified value;
d. When cracks cannot be repaired due to alkali embrittlement or severe intergranular corrosion in the
Reactor body or weld seam;
e. When the damaged area of the porcelain surface exceeds 15% or the damaged part cannot be repaired;
f. Excessive defects (such as serious structural defects that endanger safe operation, unqualified welds, severe incomplete penetration, cracks, etc.) that cannot be repaired.
2. Steel kettle body
a. The partial corrosion of the shell is repaired using the arc surfacing method. If the corrosion area is large, the patching method is used for repair.
b. Unpenetrating cracks. If the depth of the crack is less than 10% of the wall thickness and not more than 1mm, the crack can be ground flat with a grinding wheel and smoothly transitioned to the metal surface. If the crack depth does not exceed 40% of the wall thickness, the groove can be excavated within the crack depth range,
Weld repair should be carried out, but small holes should be drilled at both ends of the crack to prevent it from extending. For long cracks, the step-by-step welding method is adopted (welding from both ends of the crack to the middle) to reduce welding stress and deformation. If the depth of the crack exceeds 40% of the wall thickness, it should be penetrated according to the
Narrow crack treatment.
c. A narrow crack that penetrates. Before welding repair, drill anti crack holes at both ends of the crack, with a hole diameter slightly larger than the crack width, and process the groove. When the wall thickness is less than 12mm, V-shaped grooves are used; When the wall thickness is greater than 12mm, an x-shaped groove is used. During welding, cracks with a length less than 100mm can be welded in one go; When the crack is long, it is advisable to weld from both ends of the crack to the middle, do not draw an arc, and use multi-layer welding. Except for areas with concentrated stress, welding repairs are allowed for cracks and penetrating narrow cracks in all parts of the kettle body.
d. A wide crack that penetrates. Wide cracks should be repaired using the patching method. The length of the excavation should be 50-100mm larger than the length of the crack, and the width should not be less than 250mm. The welded repair plate should be flush with the surface of the body, and the curvature radius should be the same as the body.
e. Stainless steel lined drum. When the lining undergoes extensive deformation and the ratio of the bulging height of the lining to the average diameter of the deformation area is less than 0.15, it is advisable to use the water filling and pressure boosting method to restore the deformed lining. For shells or linings with small deformation areas, machines can be used
The mechanical top pressing method is used for repair, but attention should be paid to preventing embrittlement during the correction process.
3. Cast iron kettle body
For common defects such as sand holes, cracks, pitting corrosion, or local corrosion in cast iron kettle bodies, arc cold welding is usually used for repair. During welding repair, one through hole for crack prevention should be drilled 3-5mm outside the crack endpoint.
4. Glass lined kettle body
Glass lining is brittle and prone to damage, and has poor thermal stability. During maintenance, attention should be paid to protecting the porcelain surface. Hanging or tying ropes should be used at designated locations for lifting, and necessary cooling measures must be taken during welding. According to different damage situations, the following repair methods can be used separately.
a. Corrosion resistant metal filling method. When micropores are found on the porcelain surface, corrosion-resistant metal materials can be used to make plugs and directly insert them into the micropores.
b. When the porcelain surface is slightly damaged, fasten it to the damaged porcelain surface with corrosion-resistant metal bolts and corrosion-resistant material pads.
c. Inorganic coating repair method. Clean the surface to be repaired, first remove rust with 15-20% dilute sulfuric acid, then neutralize with a 10% caustic soda solution, then rinse and wipe with water, blow dry with hot air, and finally apply the inorganic coating, slowly heat and cure. Coating weight
Quantity ratio, pyroxenite powder: 100, fineness 80-100 mesh; Sodium fluorosilicate: 5, purity>95%; Water glass: 95, specific gravity 1.48.
d. Organic coating repair method. The steps are the same as the inorganic coating repair method.
Organic coating weight ratio:
Epoxy resin: 100
Dibutyl phthalate: 15
M-phenylenediamine: 12-14
Graphite (or other filling materials): 50-100.
After coating, heat treatment at a temperature of 80-100 ℃. Slowly raise the temperature during heating, and use it after all have cured.
e. The number of fastening clips for the flange of the glass lined kettle body must maintain the specified standard and be evenly distributed. The fastening clip must be tightened symmetrically and evenly along the diagonal direction, without excessive force or one-time tightening.
5. Quality standards for kettle body repair
a. The weld seam should have a smooth transition with the base metal.
b. The local undercut depth of the weld seam shall not exceed 0.5mm, and the length of the undercut connection shall not exceed 100mm.
c. The weld seam should be free of defects such as cracks, incomplete penetration, incomplete fusion, slag inclusion, and porosity.
d. The slag and splashes on both sides of the weld seam should be removed thoroughly.
e. After repair, there should be no cross welds, and the longitudinal joints between adjacent cylinders and between the head and adjacent cylinder sections should be staggered. The distance between them should be greater than three times the thickness of the cylinder and not less than 100mm.
f. The repair of welds should not exceed two times.
g. The welding rod material should be selected correctly, and the welding rod and flux must be dried and taken as needed.
h. The welded kettle body must undergo a hydraulic strength test.
When conducting a hydraulic strength test, the air inside the kettle should be completely discharged. When the wall temperature of the kettle is close to the liquid temperature, slowly increase the pressure, maintain it at the test pressure for 10 to 30 minutes, and then lower it to the maximum working pressure for inspection to ensure there is no leakage or visible abnormal changes
It is qualified if there is no abnormal sound during the shape and test process. The kettle body with an external insulation layer or whose external condition cannot be observed shall be maintained at the highest working pressure for at least 2 hours, and it shall be deemed qualified if the pressure does not decrease and there is no abnormal sound.
i. The kettle body that requires air tightness testing should be tested after passing the hydraulic test, and the temperature of the gas used in the test should not be lower than 5 ℃.
Transmission device
V-belt drive
a. When installing and aligning the pulley, the parallelism of the axis of the two pulleys shall not exceed 0.01a, and the axial displacement of the width symmetry plane of the two pulleys shall not exceed 0.005a (a is the actual center distance between the two pulleys, unit: mm).
b. The fit between the pulley hole and the shaft is H7/k6, and the surface roughness is 1.6/0.8.
c. The tension of the V-belt should be uniform and moderate.
d. If there are cracks in the pulley hole, or if the groove gap or groove surface is severely worn, it should be replaced.
e. The triangular belt is severely worn; Contact with groove bottom; Belt aging; Cracks; Plastic distortion should be replaced.
f. The triangular belt on the same wheel should be replaced at the same time.
Mixing device
a. When the mixing shaft is bent, it can usually be straightened using mechanical pressure method. The straightness of the mixing shaft is 0.10mm/m, and the straightness of the shaft diameter position is 0.04mm/m.
b. When the mixing shaft and sealing filler are worn, micro machining and rounding are required. If the wear is greater than 0.5mm, welding should be carried out and machining should be carried out to restore the size of the drawing. The surface roughness is 0.8.
c. When the uniform corrosion of the mixer exceeds 30% of the original thickness, it should be replaced.
d. Local corrosion, cracks, and deformation of the mixer shall be repaired by welding, shaping, and correction methods. When there is corrosion, detachment, and other damage to the glass lined mixer, repair it according to the enamel repair method.
e. The axis of paddle, frame, and anchor mixers should be perpendicular to the blades, with a verticality of 4/1000 of the total length of the blades, and should not exceed 5mm.
f. For turbine type agitators with a speed higher than 100r/min, a static balance test should be conducted for the propulsion type agitator. Balance can be achieved by using either the weight removal method or the weighting method. The thickness of the cut or increase should not exceed 1/4 of the wall thickness, and the connection should have a smooth transition. When the speed is less than 500r/min, the unbalanced mass on the outer diameter of the impeller should not exceed 20g.
g. The impeller hole and mixing shaft neck of turbine and propulsion mixers are matched with H7/k6, and the surface roughness is selected as 1.6/0.8.
h. The rolling bearing is disassembled using special tools, and the oil temperature during hot installation is 140 ℃. It is strictly prohibited to directly heat it with flame.
i. When installing the rolling bearing at the lower end of the mixing shaft, the outer ring should not be pressed tightly and there should be an axial thermal expansion displacement of about 0.5-1.0mm left.
j. The rolling element and raceway surface of rolling bearings should be free of corrosion, pits, and spots, and the contact should be smooth and free of noise. The journal that fits with the inner hole of the rolling bearing is selected as k6, with a surface roughness of 0.8. The hole that fits with the outer ring of the rolling bearing is selected as K7, with a surface roughness of 1.6.
Axial sealing device
1. Packing seal
a. The fit between the packing gland and the packing box is H11/d11, and the gap between the gland hole and the shaft is 0.75-1.00mm (shaft diameter 50-110mm). The gap between the mixing shaft and the box is 0.60-1.00mm (shaft diameter 50-110mm).
b. The end clearance between the packing gland and the box should be equal, and the error should not exceed 0.3mm.
c. The material and specifications of the filler should be used correctly, with a moderate length. The laps of each layer of filler should be evenly spaced and staggered along the circumferential direction, with a 30 ° notch for the laps. The notch should be flat and aligned up and down.
d. The filling material must have appropriate compression allowance.
e. Ensure that the position of the oil ring is accurate and the oil circuit is unobstructed.
2. Mechanical seal
a. The verticality between the shaft and the sealing chamber is generally 0.05mm, the coaxiality with the sealing chamber is generally 0.5mm, the radial runout is 1mm, and the axial displacement is 1mm.
b. At the installation of mechanical seals, the surface roughness of the shaft should not be less than 1.6.
c. The sealing chamber should be kept clean, and the roughness of the sealing surfaces of the dynamic and static rings should not be less than 0.2, and the water should not leak.
d. The adjustment of the end pressure ratio should be appropriate, with good lubrication and minimal leakage. Place the sealing surface in a semi liquid friction state.
e. The rotation direction of the spring should be consistent with the working direction of the shaft.
f. The perpendicularity of the static ring end face to the axis should not exceed 0.05mm.
g. The installed mechanical seal should have a flexible and reliable opening of its moving ring.
h. Turn the car by hand, and the sealing area rotates easily without any abnormalities.
i. During the airtightness test, it is considered qualified if no continuous small bubbles are generated.
Safety accessories
Safety valves, rupture discs, and pressure gauges shall be executed in accordance with the relevant regulations of pressure vessels.
Liquid level gauge
Before installation and use, the liquid level gauge should undergo a water pressure test of 1.5 times the nominal pressure of the liquid level gauge.
When one of the following situations occurs, the liquid level gauge should be stopped for maintenance or replacement;
a. Exceeding the inspection cycle;
b. The glass plate (tube) has cracks or breakage;
c. Valve parts are fixed;
d. False liquid levels often occur.
Other instruments, signal interlocks, safety devices, etc. should comply with relevant regulations.
Installation
a. The allowable horizontal error for the installation of the kettle body is 1mm/m.
b. The allowable error in the installation elevation of the kettle body is ± 5mm, and the allowable error in the position of the warp and weft lines is:
± 5mm when the diameter is less than 1m;
± 8mm for diameters greater than 1m.
c. The distance between the pressure tube, thermometer sleeve, heating coil and the mixer shall not be less than 40mm.
d. The deviation value between two flanges should be less than 1mm, and the distance between flange faces should be less than 2mm. Only one cushion can be added between the two flanges, and it is not allowed to use additional cushions to eliminate the defect of excessive distance between flange faces.
e. The flange sealing surface should be smooth and clean. No mechanical damage, radial scratches, severe rust, welding scars, material residue, and other defects. The cover plate of the manhole and hand hole shall be free from obvious deformation, rust, cracks, and other defects.
f. The sealing gasket must be installed upright and coated with a thin layer of scaled graphite paint on both surfaces of the gasket.
g. The nut should rotate flexibly on the bolt, but not shake, and the thread should be clean. When tightening the flange, it is required to use a torque wrench to tighten it symmetrically and evenly in two to three times, and the tightening force should not be excessive, insufficient, or uneven.
h. It is not allowed to mix bolts of different materials and specifications on the same flange.
i. For bolts that require hot or cold tightening during the heating or cooling process, relevant regulations must be followed.
Source: Reprint
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