Hexagon Nut in Wind Turbine Foundation Anchor Bolt Assembly

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Environmental requirement    

WTGS(wind turbine generator system) foundation anchor bolt operating temperature range -40℃~50℃, relative humidity≤ 95%     

Outdoor weather conditions for WTGS foundation anchor bolts include air humidity, salinity and dust bowl area.    



Visual and rule measurement inspection shall be used to inspect apperance of nuts according to GB/T5779.2-2000 “Fasteners-Surface discontinuities-Nuts”, satisfying Table 1.

Nut grades Inspection standard Voids Quenchcracks Seams Forging cracks Folds
810 GB/T 5779.2-2000 Depth,h≤0.25mm Quench cracks of any depth, any length, or in any location shall not be permitted. Depth≤0.05D not more than two forging cracks, neither of which exceed a depth of 0.05D permitted

  Table 1. Surface Discontinuities on Nuts

D——nominal thread diameter 



Dimensions and tolerances of nuts shall conform to GB/T 6170-2000 “Hexagon nuts,style 1” regulations. According to GB/T 6170-2000, the nut’s thickness m value shall be 1.2-1.3 times of the “m” from the TABLE 1 of GB/T 6170-2000.Specific values are shown in Table 2.

                         Table 2 Thickness of Nuts


Thread Dimensions(d) M30 M36 M42 M48 M56 M64
Pintch P 3.5 4 4.5 5 5.5 6
GB/T6170-2000 TH m max 25.6 31.0 34.0 38.0 45.0 51.0
min 24.3 29.4 32.4 36.4 43.4 49.1
Q/AYLT 06-2016 THm max 31.5 38.5 42.0 47.0 56.0 63.0
min 30.0 37.0 38.0 45.5 54.0 61.0


Steel Materials 

Materials of nuts and washers shall conform to Table 4. Choosing of any other materials shall be approved by purchaser. 

                  Table 4 Anchor bolts, nuts, washers materials

Commodity Grade Raw materials grade Standard
Nuts grade 8、grade 10 35CrMo or 45 GB/T 3077-2015 or GB/T 699-1999
Washers HRC35-45 45 GB/T 699-1999


Manufacturing Methods

Nuts shall be hot-forged from hot-rolled steel round bars,internal threads shall be formed by screws.



Before coating on nuts and washers, clean the surface, remove oxide scale, rust, oil stain, to guarantee grade Sa2.5 cleanliness. Surface treatment and formula shall be left at the discretion of the manufacturer. Grease corrosion protecting method on nuts and washers is not included in this regulation.



Inspection items and methods for nuts and washers shall conform to Table 6.

Table 6 Inspection item, sampling and methods

Sr. Test Items Sampling Type inspection Delivery Inspection Standard
1  Appearance 3/same batch Test documents GB/T 3103.1-2002  GB/T 3103.3-2000GB/T 5779.2-2000
2  Dimension 3/same batch   Test documents GB/T 6170-2000 GB/T 3103.3-2000 GB/T 196-2003GB/T 197-2003
3  Composition 3/same batch Test documents GB/T 3077-2015GB/T 699-1999
4  Cone roof load test 3/same batch Test documents GB/T 3098.1-2010
5 Hardness 3/same batch Test documents GB/T 230.1-2009 GB/T 4340.1-2009
Note: 1.”Same batch” refers to same batch of raw materials and same batch of heat treatment.2.”Same scheme” refers to one scheme for a specified property.

3.”Same product” refers to a product model of same dimension from one specified manufacturer.

4.Test items and methods can be performed as per purchasers’ requirements.



5.1 Marking

    Marking methods for nuts and washers shall perform according to regulations, including:

a)Identification of manufacturer;

b)Property class;



Post time: May-21-2019