JB/T 6879-2021Dimensional tolerances of flow passages in castings of centrifugal pumps (English PDF)

Foreword

This Standard was drafted as per the rules specified in GB/T 1.1-2009.

This Standard replaced JB/T 6879-2008 Dimensional Tolerances of Wet Surfaces in the Castings of Centrifugal Pumps. Compared with JB/T 6879-2008, the major technical changes of this Standard are as follows:

--- Modify the scope (see Clause 1 of this Edition; Clause 1 of the 2008 Edition);

--- Modify the dimensional tolerance requirements for the wet surfaces of castings produced by precision casting method (see 3.1 of this Edition; 3.1 of the 2008 Edition);

--- Add the dimensional tolerance requirements for impellers and guide vanes produced by ceramic casting method [see 3.1c) of this Edition];

--- Modify the dimensional limit deviations of the wet surfaces of impellers with Class-B accuracy (see Table 1 of this Edition; Table 1 of the 2008 Edition);

--- Modify the dimensional limit deviations of the wet surfaces of guide vanes with Class-A accuracy (see Table 2 of this Editon; Table 3 of the 2008 Edition);

--- Add the requirements for the hydraulic dimensional tolerances of the wet surfaces of pump castings of other structural types (see 3.5 of this Edition).

1 Scope

This Standard specifies the dimensional tolerances and technical requirements for the wet surfaces in the castings of centrifugal pumps.

This Standard applies to all wet surfaces in metal castings of centrifugal pumps except light metal parts and abrasion-resistant white iron casting.

2 Basic Provisions

The dimensional tolerances of the wet surfaces in the castings of centrifugal pumps are divided into three accuracy levels: A, B, and C. The dimensional limit deviation values are shown in Tables 1 ~ 3 according to different wet surfaces.

3 Technical Requirements

3.1 The selection of accuracy levels shall meet the following requirements:

a) Level-C is a general one. For centrifugal pumps with low performance deviation requirements, Level-C can be used;

b) When Level-C is used, the performance deviation of the centrifugal pump cannot meet the requirements and needs to be met by changing the dimensional tolerance, then Level- B can be used;

c) Impellers and guide vanes that are required to be precision cast by investment casting or ceramic casting can use Level-A.

3.2 For castings that are required to be manufactured according to Level-C, the accuracy level is not marked in the drawings. For castings that are required to be manufactured according to Levels-B or -A, the accuracy level shall be indicated in the drawings or technical documents.

3.3 The impeller, guide vane, and volute castings of the centrifugal pump are shown in Figures 1, 2, and 3, respectively. The dimensional limit deviations of the wet surfaces shall comply with the provisions of Tables 1, 2, and 3, respectively. The blade misalignment of the intermediate parting is shown in Figure 4, and the maximum allowable misalignment value shall comply with the provisions of Table 4. […]