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This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document replaces QB/T 2551-2008 Technological condition of cast iron dryers used in paper machinery and QB/T 2556-2008 Design standard in cast iron dryers used in paper machinery. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to QB/T 2551-2008 and QB/T 2556-2008:
——the document name is changed;
——the content for design pressure in “Scope” is adjusted to Clause 5 (see Clause 5; Clause 1 of QB/T 2551-2008 and Clause 1 of QB/T 2556-2008);
——the material requirements for cast iron dryers are changed (see Clause 6; Clause 3 of QB/T 2551-2008 and Clause 4 of QB/T 2556-2008);
——the relationship between the additional thickness of dryer body and the expected service life is added (see 7.3.5);
——"thermal insulation of dryer cap” is added (see 7.13);
——the requirements for relieving residual stress are added (see 7.12 and 8.1);
——the defect treatment requirements are changed (see 8.3 and 8.4; 3.4 of QB/T 2551-2008);
——“Inspection rules” is added (see Clause 10).
This document was proposed by China National Light Industry Council.
This document is under the jurisdiction of the National Technical Committee on Light Industrial Machinery of Standardization Administration of China (SAC/TC 101).
The previous editions of this document are as follows:
——the previous editions of replaced document QB/T 2551-2008 are as follows:
firstly issued as ZB Y91 003-1988 in 1988;
changed as QB 3662-1999 in 1999;
firstly revised as QB 2551-2002 in 2002, and revised for the second time in 2008.
——the previous editions of replaced document QB/T 2556-2008 are as follows:
firstly issued as ZB Y91 008-1989 in 1989;
changed as QB 3663-1999 in 1999;
firstly revised as QB/T 2556-2002 in 2002, and revised for the second time in 2008.
——this is the third revision by merging QB/T 2551-2008 and QB/T 2556-2008.
Cast iron dryers used in paper machinery
1 Scope
This document specifies the terms and definitions, general requirements, materials, design, manufacturing, test methods, inspection rules as well as marking, packaging, transportation and storage of cast iron dryers used in paper machinery.
This document is applicable to dryers and blanket dryers with an outer diameter of not greater than 4,600mm for paper machines, paperboard machines and pulp machines (hereinafter collectively referred to as "dryers").
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 35 Square head bolt with small head
GB/T 150.1 Pressure vessels - Part 1: General requirements
GB/T 150.2 Pressure Vessels - Part 2: Materials
GB/T 191 Packaging - Pictorial marking for handling of goods
GB/T 699 Quality carbon structure steels
GB/T 1348-2019 Spheroidal graphite iron castings
GB/T 3077 Alloy structure steels
GB/T 4272 General principles for thermal insulation technique of equipment and pipes
GB/T 5782 Hexagon head bolts
GB/T 6170 Hexagon nuts, style 1
GB/T 9439-2010 Grey iron castings
GB/T 13306 Plates
NB/T 47013.4-2015 Nondestructive testing of pressure equipments - Part 4: Magnetic particle testing
NB/T 47013.5-2015 Nondestructive testing of pressure equipments - Part 5: Penetrant testing
QB/T 3917-1999 Dynamic balancing of rolls and dryers of paper machine
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
pressure
force vertically applied to unit surface area of a vessel
Note: it refers to gauge pressure herein, unless otherwise indicated.
[Source: GB/T 150.1-2011, 3.1.1, modified]
3.2
operating pressure
maximum possible pressure (3.1) on the top of dryer under normal operating conditions
[Source: GB/T 150.1-2011, 3.1.2, modified]
3.3
design pressure
set maximum pressure (3.1) of dryer
Note: Design pressure, together with the corresponding design temperature, is taken as the design load conditions and is not lower than the operating pressure (3.2).
[Source: GB/T 150.1-2011, 3.1.3, modified]
3.4
design temperature
set metal temperature of element, i.e. the average temperature along the element metal cross section, under normal operating conditions of dryer
3.5
required thickness
thickness calculated using corresponding equation
Note: If necessary, the thickness required by other loads shall also be taken into account.
[Source: GB/T 150.1-2011, 3.1.10]
3.6
minimum required fabrication thickness
minimum thickness required to ensure meeting the design requirements after the pressure element is fabricated
Note: It refers to the thickness of the dryer wall at the thinnest part after machining and fabrication.
[Source: GB/T 150.1-2011, 3.1.14]
3.7
factor of safety
minimum factor for determining the allowable stress of metal materials (iron castings, studs and bolts) of dryer
4 Symbols
For the purposes of this document, the following symbols apply.
α——the angle between the dryer body conical neck and the dryer wall, °.
C——the additional thickness of dryer body, mm.
D——the calculated cross-sectional outer diameter of journal, mm.
Db——the diameter of bolt center circle on dryer cap, mm.
D0——the outer diameter of dryer body, mm.
D1——the diameter of dryer cap seam, mm.
d——the inner diameter of journal, mm.
df——the nominal diameter of connecting bolts between dryer body and dryer cap, mm.
di——the diameter of the root of connecting bolt between dryer body and dryer cap, mm.
δc——the required thickness of dryer body, mm.
δd——the design thickness of dryer body, mm.
δf——the flange thickness of dryer body, mm.
δfl——the flange thickness of dryer cap, mm.
δm——the maximum thickness of casting, mm.
FA——the bearing reaction at driving side of dryer, N (maximum load, including dead weight, condensate weight, felt load, etc.).
K——the stress intensification factor, taken as 1.2 (including temperature difference load caused by thermal stress from temperature difference between inner and outer walls of dryer body).
K1——the empirical constant, taken as 2.4.
L——the distance from the bearing center at driving side of the dryer to the calculated cross section, mm.
l——the length of conical neck at discontinuity of dryer body, mm.
l1——the distance from bolt center circle to inner wall of dryer body, mm.
n——the number of connecting bolts between dryer body and dryer cap.
p——the design pressure, MPa.
P0——the internal axial force on dryer cap, N.
R——the outer radius of dryer body, mm.
Rm——the tensile strength of cast iron material, MPa.
R1, R2 and R3——the radius of dryer cap arc, mm.
r——the radius of arc at geometric discontinuity of dryer body, mm.
σ——the calculated stress, MPa.
[σ]——the allowable tensile stress of cast iron material, MPa.
[σ1]——the allowable stress of connecting bolt, MPa.
t1——the heating or cooling rate per unit time, ℃/h.
t2——the cooling rate per unit time, ℃/h.
V1——the constant, taken as 6,250mm ℃/h.
V2——the constant, taken as 1,250mm ℃/h.
See Figure 1 for some symbols.
Figure 1 Cast iron dryer
5 General requirements
5.1 The dryers shall be manufactured according to the drawings and technical documents approved through the established procedures.
5.2 The design pressure of grey cast iron dryer shall not be greater than 0.8MPa, and the design temperature range is 10~200℃.
5.3 The design pressure of spheroidal graphite cast iron dryer shall not be greater than 1.1MPa, and the design temperature range is 0~250℃.
5.4 The designation of cast iron material used for dryer and the applicable design pressure shall meet those specified in Table 1.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 General requirements
6 Materials
7 Design
8 Manufacturing
9 Test methods
10 Inspection rules
11 Marking, packaging, transportation and storage
Annex A (Informative) Outer diameter series of dryer body
Annex B (Normative) Minimum flange thickness
Annex C (Informative) Diameter, quantity and designation of connecting bolts between dryer body and dryer cap
Annex D (Normative) Cylindricity tolerance of dryer
