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This standard is the revision of QB 2551-2002 Technological Condition of Cast Iron Dryers Used in Paper Machinery.
The following technical deviations have been made with respect to the QB 2551-2002 (the previous edition):
— the outer diameter of cast iron dryer is expanded from 3800 mm to 4600 mm;
— the spheroidal graphite cast iron material is added; the design pressure of gray cast iron shall be not larger than 0.8 MPa and that of spheroidal graphite cast shall be not larger than 1.1 MPa;
— the safety coefficient of spheroidal graphite cast iron is changed to 8.
Annex A forms an integral part of this standard.
This standard was proposed by the China National Light Industry Council.
This standard is under the jurisdiction of National Technical Committee 101 on Light Industrial Machinery of Standardization Administration of China.
This standard was drafted by the National Standardization Center for Machinery of Light Industry.
This standard was issued in 1989 as first edition, was first revised in December 2002. This is the second revised edition.
This standard replaces the light industry standard QB 2551-2002 Technological Condition of Cast Iron Dryers Used in Paper Machinery issued by former State Economic and Trade Commission from the implementation date hereof.
Technological Condition of Cast Iron Dryers Used in Paper Machinery
1 Scope
This standard specifies the technical requirements, test methods and inspection rules, markings, packaging, transportation and storage of cast iron dryers used as pressure vessels in paper machinery.
This standard is applicable to dryers and felt dryers (hereinafter referred to as "dryers") with an outer diameter not larger than 4600 mm and a design pressure not higher than 1.1 MPa for paper machinery, paper board machinery and pulp board machinery.
2 Normative References
The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this standard. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 191 Packaging — Pictorial Marking for Handling of Goods
GB/T 1348 Spheroidal Graphite Iron Castings
GB/T 5782-2000 Hexagon Head Bolt
GB/T 9439 Grey Iron Castings
GB/T 13306 Plates
JB/T 7945-1999 Methods for Testing the Mechanical Properties of Grey Cast Iron
QB/T 3917-1999 Dynamic Balancing of Rolls and Dryers of Paper Machine
Supervision Regulation on Safety Technology of Pressure Vessels
3 Technical Requirements
3.1 Basic requirements
3.1.1 The design, manufacturing, inspection and acceptance of the dryers shall not only be in accordance with those specified in this standard, but also comply with the relevant laws and decrees and regulations issued in China. The designer and manufacturer of dryers shall have the corresponding design and manufacturing license of special equipment.
3.1.2 The dryers are Class I pressure vessel and shall be manufactured according to the working drawings and technical documents approved by prescribed procedures.
3.1.3 For cast iron dryers with an outer diameter larger than 3800 mm, or a design pressure larger than 0.8 MPa, or an outer diameter no less than 2000 mm, and a design pressure larger than 0.5 MPa, the stress analysis design using finite element method shall be carried out. The cast iron dryers with diameter larger than 3800 mm or design pressure larger than 0.8 MPa shall be subjected to stress test and safety evaluation during hydrostatic test, and the relevant data shall be submitted to the National Technical Committee 101 on Light Industrial Machinery of Standardization Administration of China for the record.
3.2 Material requirements
3.2.1 The materials of dryer body and end cap shall meet the requirements of GB/T 9439 and GB/T 1348.
Not less than HT200 for design pressure ≤ 0.3 MPa;
Not less than HT250 for design pressure > 0.3 MPa and ≤ 0.5 MPa;
Not less than HT300 for design pressure > 0.5 MPa and ≤ 0.8 MPa;
Not less than HT500 for design pressure > 0.8 MPa and ≤ 1 MPa.
3.2.2 The design pressure of gray cast iron dryers shall not be larger than 0.8 MPa; The design pressure of the ductile iron dryer shall not be larger than 1.1 MPa.
3.2.3 The mechanical properties of materials of the manhole cover shall not be lower than that of the end cap, and the mechanical properties of materials of the end cap shall not be lower than that of the dryer body.
3.2.4 The property classes of bolts shall meet the requirements of GB/T 5782-2000 and Table 1.
3.2.5 If there are special requirements on the materials of dryers, it can be determined by the supplier and the purchaser through negotiation, but it shall meet the designation requirements and corresponding mechanical property indexes specified in this standard.
3.2.6 The property classes of the bolts for connecting the drawing cylinder body to the end caps shall not be less than that for connecting the dryer body to the end caps.
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Table 1 Property classes of bolts
Outer diameter of dryer, D0 (mm) Design pressure of dryer, p (MPa) Bolt diameter, df (mm) Property classes not less than
800 to 1500 0.3 to 0.5 M20 to M30 5.6
> 1500 to 4600 0.3 to 0.5 M24 to M42 8.8
> 1500 to 4600 > 0.5 to 0.8 M24 to M56 8.8
> 1500 to 4600 > 0.8 to 1.1 M24 to M56 10.9
3.3 Aging treatment requirements for end caps
The end caps shall be aged after casting. Spheroidal graphite cast iron is used to cast the end capa, which can be annealed to improve the mechanical properties. Technical measures shall be taken to eliminate the residual stress of casting if it is difficult to age the end caps with diameter no less than 2500 mm.
3.4 Defect handling requirements of dryer surface
When defects larger than 0.5 mm are found in the initial grinding of dryer surface, repair is allowed. Welding repair is not allowed, only the same material riveting is allowed, and shall meet the following requirements.
The diameter of the rivet shall not exceed its length and shall not exceed 8mm;
The center distance of the adjacent two repaired holes shall not be less than the sum of the diameters of the two repaired holes;
The depth of repaired holes shall not exceed 40% of the wall thickness;
The total number of holes repaired on the dryer surface shall not exceed 8 per square meter, and the number of holes repaired in any area of 100 mm × 100 mm shall not exceed 8.
3.5 Hardness requirements
After processing, when the outer diameter of the dryer body is not larger than 2000 mm, the dryer surface hardness shall be ≥ HB170 and ≤ HB220; when the outer diameter of the dryer body is larger than 2000mm, the dryer surface hardness shall be ≥ HB190 and ≤ HB240; for the dryer body of alloy cast iron material, the dryer surface hardness shall not be larger than HB260. The hardness difference between the two ends of the dryer surface shall not be larger than HB24.
3.6 Balance requirements
3.6.1 For the dryer of the outer diameter is not larger than 2000 mm, when the speed is not larger than 300 m/min, or for the dryer of the diameter is larger than 2000 mm, when the speed is not larger than 100 r/min, the static balance check shall be carried out, and the residual unbalance shall not exceed 0.0005 of the dryer's weight.
3.6.2 For the dryer of the outer diameter is not larger than 2000 mm, when the speed is larger than 300 m/min, or for the dryer of the diameter is larger than 2000 mm, when the speed is larger than 100 r/min, the static balance check shall be carried out, and the balance quality shall not be lower than Grade G4 specified in QB/T 3917-1999.
3.6.3 The weight of each balancing block shall not exceed 25 kg.
3.7 Processing quality requirements
3.7.1 The processing quality of dryer shall meet the requirements of Table 2.
3.7.2 When the dryers used for multi-dryer paper machinery are supplied with the complete set of paper machinery, the dryers shall be organized according to the actual outer diameter size of the dryers, and the difference between the maximum outer diameter and the minimum outer diameter of the same group of dryers shall not be larger than 0.5 mm.
3.8 Other requirements
3.8.1 The processing quality of dryer shall meet the requirements of Table 2.
3.8.2 The dryer shall be provided with vent and drain holes for hydrostatic test, and the two holes shall be 180° apart.
3.8.3 After the dryer is assembled, hydrostatic test shall be carried out, and the test pressure shall be twice of the design pressure.
3.8.4 The dryer surface shall have the same luster after fine grinding, without obvious wear marks or hole-repairing marks.
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Table 2 Processing quality of dryer
Item Unit Gloss dryer Dryer for multi-dryer paper machinery
Outer surface roughness of dryer body (Ra) μm 0.2 (electroplating)
0.4 0.8
Inner surface roughness of dryer body (Ra) μm 25
Outer diameter tolerance of dryer body mm ±2 +1
0
Wall thickness tolerance of dryer body +2
0
Cylindricity tolerance of dryer surface (see Annex A) Surface width < 3m Grade 8
Surface width ≥ 3m 9
Radial runout of dryer surface to the common axis of the bearings at both ends 8
4 Test Methods and Inspection Rules
4.1 Mechanical test
4.1.1 When casting the dryer body, at least three single casting test bars shall be cast. When casting the dryer cap, at least three single casting test bars shall be cast. For the preparation of single cast test bar, gray cast iron shall meet the requirements of GB/T 9439, and spheroidal graphite cast iron shall meet the requirements of GB/T 1348. The specimen for tensile test shall be Type B specimen specified in JB/T 7945-1999.
4.1.2 For each dryer body and dryer cap, tensile test of one sample shall be carried out at least once, and the inspection rules shall comply with the requirements of GB/T 9439 and GB/T 1348. If the test is invalidated by casting defects in all three tensile test specimens, another three test specimens shall be taken from the riser for retest.
4.2 Hardness test
4.2.1 After rough machining of each dryer, hardness test shall be carried out according to those specified in GB/T 9439 and GB/T 1348. The test point shall be within the range of 80 mm to 100 mm from both ends of the dryer body. The arithmetic mean value of hardness measured at each point is taken as the dryer surface hardness value.
4.2.2 The hardness values of all measured points shall meet the requirements of 3.5. If the test results do not meet the requirements, the retest shall be carried out according to those specified in GB/T 9439 and GB/T 1348.
Foreword II
1 Scope
2 Normative References
3 Technical Requirements
4 Test Methods and Inspection Rules
5 Marking, Packaging, Transportation and Storage
Annex A (Normative) Cylindricity Tolerance of Dimension d > 500 mm
