The flange at the inlet of the self-priming pump is soft; why is this type of connection used here?

The design institute advises that this is done merely to reduce piping errors; when soft connections are used, the requirements regarding piping accuracy are relatively low. There are no other special reasons. In some large pumps, the oil station is located in a pit next to the pump body, and flexible connections are used for the oil pipelines of the oil station and those adjacent to the pump base. It’s just a flexible connection made of stainless steel wire, which makes piping easier.

This thing is called a rubber expansion joint. It consists of a bellows (an elastic element) that forms the main part of its structure, along with accessories such as end tubes, supports, flanges, and ducts. An expansion joint is a flexible structure installed on a vessel shell or pipeline to compensate for the additional stresses caused by temperature differences and mechanical vibrations. It utilizes the effective expansion and contraction of its main working element, the bellows, to absorb dimensional changes in pipelines, conduits, containers, etc., caused by factors such as thermal expansion and contraction, or to compensate for axial, lateral, and angular displacements of such pipelines, conduits, and containers. It can also be used for noise reduction and vibration damping, as well as for heating systems. To prevent pipes from deforming or being damaged due to thermal expansion or temperature stresses when the heating pipes heat up, compensators need to be installed on these pipes to account for their thermal expansion, thereby reducing the stress on the pipe walls as well as the forces acting on valves or support structures.

As an elastic compensation element capable of free expansion and contraction, the expansion joint boasts advantages such as reliable operation, good performance, and a compact structure, and has been widely used in industries such as chemicals, metallurgy, and nuclear energy. There are various types of expansion joints used on containers. In terms of the shape of the corrugations, U-shaped expansion joints are the most widely used, followed by Ω-shaped and C-shaped ones. As for structural compensation, the expansion joints used in pipelines are further divided into universal type, pressure-balancing type, hinge type, and universal joint type, among others.

Rubber expansion joints offer superior performance, reliability, and service life, thereby enhancing factory safety and the mechanical integrity of equipment. By inserting specially designed products into rigid piping systems, rubber expansion joints can: reduce displacement, improve thermal stability, alleviate system strain caused by temperature changes, load stresses, pump pressure fluctuations, and wear from deposits, reduce mechanical noise, compensate for eccentricity, and eliminate electrolysis between different metals

Thank you to the masters for their answers, thank you

Rubber expansion joints have a high capacity for displacement compensation, enabling them to compensate for axial, lateral, and angular movements. They also help to reduce noise and vibrations, as well as offering certain corrosion resistance.

Using expansion joint hoses for connection can reduce pipeline vibration and noise. It can also eliminate the impact of pump foundation settlement on the pipelines.

KXT expansion joint – the function of an expansion joint is to compensate for any length discrepancies that may occur during installation as compared to what is specified in the drawings

This is a soft link. It’s basically meant to address connection errors.