1.0.1 This standard is prepared in order to regulate the design of welding neck flange manholes with davit to vertical cover, reduce the repetitive design work, assure the product quality and improve the comprehensive benefits.
1.0.2 This standard is applicable to the design of steel welding neck flange manholes with davit to vertical cover with nominal pressure of PN16~PN40 in chemical, petrochemical and other similar devices.
1.0.3 The design of welding neck flange manholes with davit to vertical cover shall not only meet the requirements of this standard, but also comply with those in the current relevant ones of the nation.
2 Type and Size
2.0.1 The structural type of welding neck flange manholes with davit to vertical cover shall meet the requirements of Figure 2.0.1.
HG/T 21521-2014 The following standards are cited：
