Disc washer, also known as Belleville spring washer, was invented by French. DIN6796 disc spring washer (HDS series) is a kind of check washer used for bolt and screw connection. It is designed and manufactured according to DIN6796, and is used to connect medium or high strength bolts and screws. The supporting load is large, and the elastic recovery makes HDS series very effective. The bolt tension can withstand the relaxation caused by the following factors: wear, creep, relaxation, thermal expansion and contraction of wearing parts, or compression of seals. HDS series improves the elasticity of screws several times, which can effectively replace ordinary spring washers, but it is not suitable for the combination of locking washers and flat washers. Because HDS series are disc springs, they can be combined or superposed. The combination mode can increase the deformation of the disc spring group and then increase the spring force of the disc spring group. The most ideal installation method is to flatten as much as possible. The closer to the flattened state, the faster the tension torque increases, and the appropriate bolt tension can be obtained without a torque wrench.

1. The application of disc washer

Used for the connection of medium or high strength bolts and screws. After the bolt and screw are connected, it can prevent the relaxation of tension, compensate for the wear and creep of wearing parts, thermal expansion and contraction and the compression of sealing parts.

2. The disc washer standard
DIN 6796
DIN 2093
JISB2706 GB/T 1972
JB/ZQ 4340-2006

3. The disc washer installation

disc washers can be installed singly or in combination. The ideal installation method is to flatten them as much as possible. The closer they are to the flattened state, the faster the tension torque increases, and the proper bolt tension can be obtained without a torque wrench.

4. Disc washer material

The production of disc washer requires the product to obtain the minimum relaxation under the premise of meeting the maximum fatigue life requirements. The selection of materials directly affects the performance of the spring. For standard use, 50CrV4 can be used as the spring material, and other materials such as 60Si2MnA and AISI 6150 can also be used. Surface treatment methods of disc spring washer: bluing, phosphating, electrophoresis, dacromet, mechanical zinc plating, etc. 

5.Disc washer test

Hardness testgenerally HRC 40 ~ 44.
Dehydrogenation treatment (considering hydrogen infiltration in the manufacturing process)
Hydrogen embrittlement test, refer to ISO 15330：1999.
Full load flattening test, refer to DIN267 part 26.

6.Application of disc washer in pressure vessel

With the large-scale design of pressure vessel and the change of alternating load of high temperature, high pressure and temperature, the pre-tightening force of equipment bolts is required. In order to ensure that the pre-tightening force of bolts is not relaxed, bolts are usually combined with disc washers in engineering, and the effect is very good. The large heat exchanger used in a power plant has a flange structure. Because the power plant is in peak-shaving operation and often starts and stops, the bolts bear great changes in temperature and pressure loads, and the rear end cover leaks after running for a period of time, which affects the operation of the power plant. According to the analysis of technicians, the bolts have creep failure for a long time under high-temperature alternating load, and the pre-tightening force cannot meet the sealing requirements, so each bolt is equipped with two disc washers after stopping, which solves the problem of bolt pre-tightening force loss well. At present, there is no leakage in the heat exchanger.