Some standard content:
National Standard of the People's Republic of China
Urea High Pressure Scrubber
Technical Conditions
Specifications for H - P urea scrubber1 Subject content and scope of application
UDC 66. 05:661| |tt||.717.5
GB 9843-88
This standard specifies the manufacturing inspection and acceptance regulations for urea high-pressure scrubbers (hereinafter referred to as scrubbers) in urea plants. This standard applies to scrubbers with ultra-low carbon austenitic stainless steel lining structures with a design pressure not greater than 16MPa and a design temperature not greater than 198C.
2 cited standards
GB2270 stainless steel seamless steel pipe
GB3323 steel fusion welded butt joint radiography and quality grading asbestos rubber sheet
GB3985
ZBG93001 urea High-pressure equipment manufacturing and inspection methods Preparation of samples for intergranular corrosion tendency of ultra-low carbon austenitic stainless steel Urea High-voltage equipment manufacturing and inspection methods Test for intergranular corrosion tendency of ultra-low carbon austenitic stainless steel ZB G 93002.
ZBG 930031
Urea high-pressure equipment manufacturing inspection method Selective corrosion inspection and metallographic inspection of ultra-low carbon austenitic stainless steel ZB G 93004
ZB G 93007
Urea high-pressure equipment manufacturing inspection method Automatic Ultrasonic inspection of surfacing layer Welding process assessment and welder skills assessment of corrosion-resistant stainless steel pipes and tube sheets of urea high-pressure equipment ZB G 93008
Surface welding process assessment and welder skills assessment of urea high-pressure equipment Lining plates and internal parts Welding procedure qualification and welder skill qualification ZB G 93009
JB 741
JB1147
JB1151
JB1152
JB3963
Steel welding pressure Technical conditions of vessels
Technical conditions of steel tube and tube heat exchangers
Ultrasonic flaw detection of high-pressure seamless steel pipes
Ultrasonic flaw detection of butt welds of boiler steel pressure vessels Ultrasonic flaw detection of pressure vessel forgings| |tt||JB3965
Magnetic particle inspection of steel pressure vessels
JB 1127
JB755
Technical conditions for steel welded spherical storage tanks
Pressure vessel forgings Technical Conditions
JB3964 Pressure Vessel Welding Process Assessment
JB2536 3 Basic Requirements for Pressure Vessel Painting, Packaging, and Transportation
The manufacturing, inspection and acceptance inspection of scrubbers shall not only comply with the provisions of this technical condition , and should also comply with the requirements of JB741, JB1147 and drawings.
4 Materials
Pressure component materials and materials in contact with corrosive media must have quality certificates, approved by the Ministry of Chemical Industry of the People's Republic of China on August 16, 1988 848
1989- 03-01 Implementation
4.1 Carbon Steel
GB 9843--88
4.1.1 For steel plates used for pressure components in high-pressure parts, the grain size grade should be no less than 6, with The yield strength of the material at the design temperature should be guaranteed.
4.1.2 The tensile strength of carbon steel materials of welded parts (including welds and heat-affected zones) at room temperature should not be greater than 720MPa, and the yield ratio should not be greater than -F0.8. The strength of any part of the material after welding The hardness shall not be greater than HB280. 4.2 Ultra-low carbon austenitic stainless steel
4.2.1 The lining layer, sealing ring, pipe, internal parts and other parts in the equipment that are in contact with corrosive media should be: 00Cr17Ni11Mo2 improved type or 00Cr25Ni22Mo2 type Ultra-low carbon austenitic stainless steel materials (hereinafter referred to as urea grade stainless steel), the chemical composition of this type of material should comply with the requirements in Table 1.
Table
Material
Material
00C:17Ni14M02
(Improved type)
00Ct25Ni22Mo2
4.2.2 gold phase organization.
Cr
Ni
1≥17.00≥13.00
0.030
≤0.020
24.50~
25.50|| tt||21.50~
22.50
Mo
Chemical composition
N
2.20~
3.00
1.90~
2.30
Including N pot
0.20
0.10~
0. 14
Mn
Si||tt ||S
P
%
≤2.00—1.00≤0.030—≤0.0351.50~
2.00
≤0.015—0.020||tt ||0.40
The urea grade stainless steel materials used (including deposited metal) should have a single-phase austenite structure after welding or final heat treatment, and there should be no continuous network carbides or phases. The ferrite content shall not be greater than 0.6%. 4.2.3 Intergranular corrosion tendency test.
The urea grade stainless steel materials (including deposited metal) used should be tested according to the regulations of ZBG93002. The average corrosion rate CR of five cycles must meet the following regulations:
00Cr17N114Mo2 improved stainless steel CR≤3.3um /48h00Cr25Ni22Mo2 type stainless steel CR≤1.5μm/48hb.
The sampling for intergranular corrosion tendency test should be carried out in accordance with the provisions of ZBG93001. 4.2.4 Selective corrosion inspection and metallographic inspection. The lining plates, heat exchange tubes and welded joint samples that have passed the intergranular corrosion tendency test must be subjected to selective corrosion inspection and metallographic inspection. For stainless steel parts such as internal parts that are in contact with corrosive media (including deposited metal), If the corrosion values ??of the fourth and fifth cycles in the intergranular corrosion tendency test exceed 50% of the corrosion values ??of the third and fourth cycles respectively, these samples must also undergo selective corrosion inspection. The inspection method shall be carried out according to ZBG93003, and the results shall be Comply with the following regulations. When the selective corrosion inspection results exceed the requirements of 4.2.4, the container manufacturer may report the actual inspection results to the user or its agent. After obtaining written approval, the material represented by the sample is allowed to be used. 00Cr17Ni14Mo2 improved stainless steel; the selective corrosion depth of plates, pipes, bars, forgings and welding heat-affected zones should not be greater than 70μm in the direction perpendicular to the rolling or forging direction, and should not be greater than 200μm in the parallel rolling or forging direction; 00Cr25Ni22Mo2 type stainless steel: Selective corrosion of plates, pipes, bars, forgings and their welding heat-affected zones and deposited metals b.
The depth should not be greater than 100μm in any direction; c.
The metallographic structure shall comply with the provisions of Article 4.2.2.
The heat exchange tube should also meet the following requirements:
4.2.5#
The outer diameter and wall thickness deviation of the heat exchange tube should meet the medium and high-level precision requirements of GB2270; a.| | tt | Carry out a hydraulic test, and the test pressure shall be the test pressure required by the equipment. 4.3 Welding materials
849
GB9843
88
Welding rods, wires, welding strips and fluxes used for welding of urea grade stainless steel must have quality certificates. The chemical composition of the deposited metal should comply with the requirements in Table 2.
Table 2
Welding material types
00Cr17Ni14Mo2
Improved
00Cr25Ni22Mo2
4.4 Other materials
C|| tt||0.045
Cr
17. 00~
19.50
24.00~
26.00
Ni
14 . 00~
18.00
19. 00~
23.00
Mo
Chemical compositionwwW.bzxz.Net
Chemistry
N| |tt||≥2.20
1.90~
2.40
N-containing steel
≤0.20
0.20
Si||tt| |≤1.00
0.50 | |tt | | Mn | Except as specified, the chloride ion content should not exceed 100ppm. 4.4.2 The adhesive used for sealing gaskets should be free of chloride ions and solid particles, or medical vaseline should be used. R
%
A0. 030—0. 020
4.4.3 Markings on urea grade stainless steel materials should not contain metallic pigments and sulfides. Waterproof ink with a chloride ion content of less than 25ppm or round-head virtual hard printing with a tip radius of not less than 0.15mm can be used. 4.5 Re-inspection of urea grade stainless steel materials
4.5.1 Urea grade stainless steel materials shall be re-inspected in accordance with the following regulations and must meet the requirements of Article 4.2. Recheck the chemical composition according to the furnace (batch) number:
a
b.
+.
Determine the ferrite content piece by piece;
Same Materials from the smelting furnace, the same specification, and the same heat treatment furnace number should be sampled for intergranular corrosion testing. More than two samples cannot be taken from the same material. The preparation of samples should comply with the regulations of ZBG93001. The sampling quantity is shown in Table 3. Table 3
Material category
Plate
Material
Bar or forging
Arm
Material
Total number of materials| |tt||pieces
>5
5
5
>10
10
A10
>200
200
200
Sampling quantity
pieces
Take 1 sample for every 5 pieces, and take 1 sample for the remaining less than 5 pieces2| |tt||1
Take 1 sample for every 10 pieces, and take 1 sample for the remaining 10 pieces2
-
Take 1 sample for every 200 pieces, and the remaining For less than 200 pieces, take 1 sample 2
1
Note: ① If any of the tests fails, double sampling is allowed at the original sampling location, and the unqualified items should be re-tested. If there is still one unqualified result, the plates, rolled materials or forgings shall be tested piece by piece. For pipes, 2% of the pipes represented by the unqualified samples shall be randomly inspected, and no less than two pieces shall be retested; if If there is still one unqualified sample, the batch of pipes will be deemed unqualified. ② Products that fail to pass the re-inspection shall not be used without the consent of the design unit or user. Carry out selective corrosion depth and metallographic structure inspection according to the provisions of Article 4 and 2.4; d.
Check the surface quality of lining plates and pipes one by one (root); e.
f.||tt ||The high-pressure nozzles and heat exchange tubes should be subjected to ultrasonic flaw detection one by one. However, when the heat exchange tubes have a steel factory flaw detection certificate, only 10% of the total number of flaw detection standards can be randomly inspected according to JB1151 regulations. 850 | | tt | | GB 984388 | | tt | Content, intergranular corrosion tendency test, selective corrosion inspection and metallographic inspection. 5 Hot and cold processing
5.1-General regulations
5.1.1 The welding groove of stainless steel parts should be machined. If thermal cutting is used, the overheated area should be cleared and the surface of the groove should be polished smooth Ferrite content measurement and penetrant inspection should also be carried out on urea grade stainless steel parts. 5.1.2 Penetration inspection shall be carried out after welding groove processing of carbon steel pressure components in high-pressure parts. 5.1.3 The grinding wheel used to grind the surface of stainless steel should be pure oxide material or rubber, nylon mixed with alumina. The grinding wheel used to grind carbon steel should not be used to grind stainless steel.
5.1.4 The protection of stainless steel parts during the manufacturing and transportation process should be strengthened to prevent any bumps and scratches. If there are defects that affect the corrosion resistance, they must be ground. The ground parts should have a smooth transition. The grinding depth generally shall not exceed the negative deviation of the specified thickness. 5.1.5 Tempering color is not allowed on the surface of polished stainless steel. The surface of the material that is in direct contact with the corrosive medium must be polished after grinding.
5.1.6 Urea grade stainless steel parts should not come into contact with copper and copper alloy tools during the manufacturing process. 5.2 Head
5.2.1 For split heads, a template with a chord length of not less than 2m should be used to check the curvature of the flaps of the split heads. The gap at any part should not be greater than 2.5mm.
5.2.2 The misalignment of the butt weld of the integral stamping head head should not be greater than 2mm, and the misalignment of the butt weld of the split head should not be greater than 10% of the plate thickness, and not greater than 3mm. When the plate thickness of the split head exceeds 80mm, the misalignment of the weld seam shall not be greater than 5mm. 5.2.3 For split-flap heads, the edges and corners formed by the butt welds of the flaps shall comply with the provisions of Article 5.3 of JB1127. 5.2.4 Before lining or surfacing, the inner surface of the head should be machined or polished smooth, and no defects affecting the quality of the lining or surfacing are allowed. The local unevenness should comply with the following regulations. When using a lining structure, it should not be larger than 1.5mm; when using a surfacing structure, .
b should not be larger than 2mm. 5.2.5 The inner diameter deviation of the head is ±0.35% of the nominal inner diameter, and the difference between the maximum inner diameter and the minimum inner diameter shall not be greater than 0.5% of the nominal inner diameter, and shall not be greater than 6mm.
5.3 Tubesheet
5.3.1 The maximum reduction in the width of the pipe bridge after pipe hole processing shall not exceed 1.2mm, and the verticality tolerance of the pipe hole shall not be greater than 1/1000. 5.3.2 Welding on the pipe hole The end face of the groove should be on a flat surface, and if it is uneven, it should be polished into a smooth transition (see Figure 1). Grinding parts
Picture
851
GB9843-88
5.3.3 After processing the pipe hole welding groove, the burrs should be completely removed, and the burrs should be removed hole by hole with a 5 to 10 times magnifying glass. Inspect, if defects are suspected, use water-washable penetrant inspection according to Appendix 6 of JB3741
. 5.4 Connection of heat exchange tubes and tube sheets
5.4.1 The ends of heat exchange tubes and tube sheets must be cleaned, and there must be no metal shavings, oil stains, rust and other defects that affect the welding quality. 5.4.2 Only welding is used to connect the heat exchange tube and the tube plate, and expansion joints are not allowed. Tack welding can be performed on the lower tubesheet end. 5.4.3 It is recommended to use manual tungsten arc welding for the welding of heat exchange tubes and tube sheets. Two layers should be welded, each layer should be filled with wire, and the tube should be protected by argon gas during each layer of welding.
5.4.4 Operation and inspection procedures for the connection between heat exchange tubes and tube sheets; a.
Weld the first layer of weld of the -th tube sheet (the corresponding end is the free end); b.
Weld the first layer of weld of the second tube sheet; c.
Conduct a tightness test with compressed air;
d.
The second layer of welds when welding two tube sheets;
e.
f.
Visual inspection, penetration inspection, and ferrite measurement of the welds; with Ammonia gas is used for tightness test;
shell side is used for hydraulic pressure test;
g.
h.
weld penetration test.
5.5 Simple joints
5.5.1 The upper deviation of the inner diameter of the low-pressure shell is 3, and the lower deviation is 0. 5.5.2 The edges and corners formed at the longitudinal welds of the lining simple joints shall not be greater than 1 mm. Measurement method According to Figure 6 in JB741. 5.5.3 After the lining simple sections are assembled and welded, measure the circumference based on the outer circle. Within the measurement range, the circumference difference shall not be greater than 2mm (see Figure 2). National
Figure 2
5.5.4 The straightness tolerance of lining simple sections shall not be greater than 1/1000 and not greater than 1mm. 5.6 Assembly
5.6.1 All butt welds of the lining must be inspected and qualified, and the inner and outer surfaces of the lining must be thoroughly cleaned before they can be installed into the carbon steel components. 5.6.2 The maximum gap after the lining is inserted into the carbon steel body shall not be greater than 1.5mm, and the maximum gap after the lining head is inserted into the carbon steel head shall not be greater than 2.5mm. It is recommended to use a formulated process method to achieve clearance requirements. 5.6.3 The distance between the weld edge of the weldment on the lining and the longitudinal weld of the lining should not be less than 50mm. 6 Welding
6.1 Welder
Welders who weld urea grade stainless steel materials must have a certificate for welding urea grade stainless steel materials. 6.2 Welding procedure qualification and welder examination
Pressure welds, lining welds, internal parts welds, pipe and tube sheet connection welds and urea grade material manual or strip cladding welds shall be in accordance with relevant regulations Standard welding. Process qualification, welding procedure qualification and welder examination should not only be conducted according to JB3964, but also comply with the regulations of ZBG93009, ZBG93007 and ZBG93008.
852
6.3 Welding I process
GB 9843 --- 88
Before welding all welds on pressure parts and urea grade stainless steel parts, welding process regulations should be formulated based on the qualified welding process. Welders must strictly abide by the welding process regulations when performing welding. 6.3.1 The welding of urea grade stainless steel generally uses small current, fast, linear welding beads. The interlayer temperature should not exceed 150C, and the weld surface in contact with the corrosive medium should remain in the welded state as much as possible.
6.3.2 The manual overlay welding of urea grade stainless steel should be no less than three layers (-one transition layer, the rest is corrosion-resistant layer), and the strip welding should be no less than two layers (one transition layer, the rest as a corrosion-resistant layer). The thickness of the corrosion-resistant layer of manual or strip welding (measured from the lowest point on the surface) of the lining part shall not be less than 3mm, and the sealing surface part shall not be less than 6mm after processing. 6.3.3 The weld beads for large-area manual surfacing should be arranged in strips or concentric circles, and the closing arc point of the same weld layer should be a diagonal line. The overlap between adjacent weld beads should be no less than half the weld bead width.
6.3.4 The weld beads with pole surfacing should be arranged in strips or concentric circles. The beginning and end of the concentric circle weld beads and the overlapping points should be on the same radius line. The weld bead of the corrosion-resistant layer should be parallel to the weld bead of the transition layer. The weld bead lap fusion line of the corrosion-resistant layer should be staggered with the lap fusion line of the transition layer. 6.4 Weld repair
When repairing urea grade stainless steel welds, the welding technician should formulate a repair plan. Defects can only be removed by machining or grinding. The same part should not be repaired more than twice. More than two repairs must be approved by the technical director of the manufacturing unit. The repaired parts, times and non-destructive testing results will be recorded in the quality certificate. 6.5 Weld Marking
For urea grade stainless steel welds, on-site welding records must be made. After welding, the welder should promptly make a welder mark on the specified location near the weld, but welder stamps are not allowed.
7 Heat treatment
7.1 Urea grade stainless steel parts that have the following conditions should be heat treated. 7.1.1 Cold formed urea grade stainless steel parts with a deformation rate exceeding 20% ??should be subjected to solution heat treatment. 7.1.2 All hot-formed urea grade stainless steel parts should be solution heat treated. 7.1.3 If a cladding structure is adopted, welding stress relief heat treatment should be carried out after the lining transition layer is cladded and before the corrosion-resistant layer is cladded. 7.2 The maximum temperature for heat treatment to eliminate welding stress should be as follows. 7.2.1 For 00Cr17Ni14Mo2 (improved) materials, the temperature shall not exceed 520C. 7.2.2 For 00Cr25Ni22Mo2 type materials, the temperature shall not exceed 570C. 7.3 Urea grade stainless steel parts are not allowed to undergo partial heat treatment or more than two overall solid solution heat treatments. 8 Test Plate
8.1
Welding Test Plate
The following parts of the product require a welding test plate. 8. 1. 1
a.
Longitudinal weld of low-voltage shell:
The head or pipe box is a spherical structure, manufactured separately, butt longitudinal weld; b.| | tt | Ring welds with the tube plate (or pipe box and flange), pipe box cylinder and head. e.
8.1.2 The lining welding test plate shall undergo weld appearance quality inspection, radiographic inspection, penetrant inspection, ferrite measurement, metallographic inspection, inter-product corrosion tendency test, selective corrosion inspection and chemical composition test. 8.1.3 In addition to complying with the provisions of Article 29 of JB711, the product welding test plates of pressure parts in high-voltage parts should also be added with the following inspections. a. Hardness measuring base, the measuring part should meet the requirements of a, b, and c in Figure 3; the tensile strength at the design temperature.
853
8.2 Heat treatment test plate
GB9843-88
lmr
Figure 3
>10m
8.2. 1. For urea grade stainless steel parts that need to be heat treated to meet corrosion resistance requirements, at least one heat treatment test plate must be included in each furnace (batch) number.
8.2.2 The urea grade stainless steel heat treatment test plate is heat treated in the same furnace as the product. After pickling, appearance inspection, ferrite measurement, intergranular corrosion tendency test, selective corrosion inspection and metallographic inspection are performed. 9 Inspection
9.1 Weld appearance quality inspection
All welds must be inspected for appearance quality. In addition to the provisions of Articles 16 and 17 of JB741, the inspection standards should also meet the following requirements. 9.1.1 The surface of urea grade stainless steel welds (including overlay corrosion-resistant layers) shall not have defects such as cracks, pores, arc craters, slag inclusions, incomplete penetration, and undercuts. For pores with a diameter less than 0.5mm, slag inclusions and undercuts with a depth less than 0.5mm, smooth transitions are allowed. The thickness after grinding shall not be less than the minimum thickness specified in the design.
9.1.2 The weld between the heat exchange tube and the tube sheet shall not have undercuts, tungsten inclusions, slag inclusions, cracks and pores. The pipe ends shall not be welded, burned through or overheated. The welding between the heat exchange tube and the tube sheet shall not No polishing or cleaning should be carried out without inspection. The inner wall of the tube mouth should be inspected one by one. When any depression or bulge is found on the inner wall of the tube, it should be judged:
a. During the welding process of the heat exchange tube and the tube plate, there is no Argon gas protection, this tube should be scrapped; b. During the welding process of the heat exchange tube and the tube plate, the tube is protected by argon gas. You can use sandpaper to polish the depressions or bumps on the inner wall of the tube mouth. After cleaning, use a 5 to 10 times magnifying glass to inspect. If there are no cracks, the tube is qualified. 9.2 When the weld passes the visual inspection, the following non-destructive inspection shall be carried out. 9.2.1 Radiographic inspection shall be as specified in Table 4.
854
Serial number
2
3
5
6
7
8|| tt||9.2.2
Serial number
So
9.2.3
Serial number
Inspection part
Expansion joint weld|| tt||Juri butt weld
Ring seam between expansion joint and low-pressure shell
Longitudinal ring weld of expansion box
Longitudinal seam of low-pressure shell
Low body Circumferential seam (including T-shaped joint)
Circular seam between low-voltage body and upper tube plate
Center tube butt welding
The seam is inspected twice
The inner side is welded to 8mm| |tt||Full
Welding
Ultrasonic inspection is specified in Table 5.
Inspection parts
All longitudinal circumferential welds on the pipe box
Welds of manholes, nozzles and pipe boxes
Girth seams between the low Le shell and the lower tube plate| |tt||Transition layer and corrosion-resistant layer with electrode surfacing surface
Forgings weighing more than 300kg
The penetration inspection of heat exchange tubes, central tubes, and high-pressure pipes shall be as specified in Table 6.
Inspection
Inspection
Weld groove of carbon steel pressure parts in high-pressure parts
All transition layer and corrosion-resistant layer surfaces
Department||tt ||All weld surfaces on stainless steel internal parts before and after hydrostatic test of all stainless steel lining welds
GB9843
Table 4
Inspection standards
GB3323
AB grade
Table 5
Inspection standards
JB1152
88
ZB G 93004
JB3963
JB1151|| tt | Seam surface
Outer surface of expansion joint weld after hydrostatic test Note: No defects are allowed on the surface of lining weld. Magnetic particle inspection shall be as specified in Table 7.
9.2.4
Inspection quantity
100%
20%
100%
Inspection quantity
100%
Transfer surface 100% | | tt | ||Appendix Six
Quality Grading
H
Level
According to JB755 Table 4
Number
Rat
100 %
855
Serial number
2
3
5
6
Verification
Department| |tt||The surface of the carbon steel weld in the high-pressure part after heat treatment GB 9843 --88
Table 7
position
200mm wide cross strip on the outer surface of the carbon steel head after forming Welds of pressure-bearing parts for water-repellent test scale
Welds connecting supports, hoists and equipment
The surface behind the temporary accessory weld shovel
High-pressure bolts in front of the water test
Note: All inspections except serial number 6 can be replaced by penetration method if the quality can be guaranteed. 9.2.5 Ferrite inspection
Inspection standard
JB3965
JB741 Appendix 7
Quantity
100%||tt ||The surface of all stainless steel pipes, linings, and welds (including surfacing) on ??internal parts that are in contact with corrosive media must be inspected for ferrite content. The ferrite content should not exceed 0.6% anywhere on the shaft. 9.2.6 Dimensional inspection
All dimensions should be inspected, and the dimensional inspection report should at least include the following: a.
b.
d.
e.||tt ||g.
h.
i.
10
Shape;
Connection position;
Support;||tt ||Thickness of surfacing layer;
Thickness of lining plate:
Arrangement of heat exchange tubes;
The length of the heat exchange tube extending out of the tube plate;
Thickness of explosion-proof membrane;| |tt||Sealing surface.
Pressure test and tightness test
After the equipment is manufactured, the pressure test and tightness test should be carried out. In addition to complying with the provisions of JB741 and JB1147, the pressure test and tightness test should also meet the following requirements. || tt |
10.1.2 The pipe side, shell side and coil pipes shall be subjected to hydraulic pressure tests respectively. The test pressure shall be in accordance with the drawing requirements and the pressure holding time shall not be less than 1 hour. 10.2 Tightness test
10.2.1 After the first layer of welding between the heat exchange tube and the tube sheet, the test is conducted in 0.05MPa air. The pressure holding time is not less than 10 minutes. The surface of the weld is coated with neutral soapy water for inspection. .
10.2.2 After the last layer of welding between the heat exchange tube and the tube sheet, and before the shell side hydraulic pressure test, use 15% ammonia by volume and the rest as inert gas, with a pressure of 0.23MPa and maintain the pressure. The time should be no less than 8 hours and tested with phenolic acid test paper or developing paint. 10.2.3 For lining and lining ring welds, use 100% ammonia gas with a pressure of 0.02MPa and a holding time of not less than 10 hours. Use phenolic test paper and developing paint to check.
10.2.4 After welding the simple explosion-proof membrane internal components, conduct a tightness test in 0.03MPa air. The pressure holding time shall not be less than 10 min. The surface of the weld seam shall be coated with neutral fertilizer and total water for inspection.
856
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