Why do rubber expansion joints need to be reinforced with welded limit bolts?

The sphere of rubber expansion joint is made of rubber, which is a flexible pipe, and is one of the common pipe products in industrial pipelines. The so-called reinforced rubber expansion joint is welded on the flange with limit bolts, so why do rubber expansion joints need to weld limit bolts to strengthen it?
 
This is because the larger the diameter of the pipe, the more obvious the elasticity of the sphere is, and the stability of large diameter rubber joints can be improved by adding such devices. In addition, in the case of overhead installation of rubber expansion joints, also in the case of large-diameter pipelines, limit devices should be installed, because the overhead rubber expansion joints can not be unloaded through the piers, only the installation of limit devices to improve the stability of the operation of rubber expansion joints.
 
There is also a situation in the bend in the pipeline to install rubber expansion joints, the same need to install a limit device, this is because the pipe under the influence of inertia will cause a strong impact on the bend and strong impact on the product, through the installation of piers and brackets and the product itself configuration of the limit device to ensure the normal operation of the bend.