Crack propagation test bench

Crack propagation test bench

Client

Our customer, leader on its market, is a producer and supplier of electricity in France and Europe for companies, local authorities and individuals.

 

Tested productinstrumented models

The samples tested (instrumented models) represent labyrinth seals of nuclear primary pumps.

Labyrinth seals are part of the non-contact sealing family, the purpose of which is to prevent the transfer of a gas or liquid. 

The models consist of a stainless-steel disc drilled in its centre and welded by electron beam into a holding ring, called a complementary ring.

Instrumented model

Instrumented model

Model on machine

Model on machine

 

Objective

Study the propagation of cracks in a plasticised environment.

 

Problematic

The function of the test bench is to perform tests on the models defined above, to maintain them under a load of 2,000 kN and to apply the designated temperatures (maximum 240°C).

 

Solution and results

The tested samples are stressed by the application of a temperature differential of 100°C between the two sides, which generates stresses and causes crack propagation.

This temperature difference is obtained by circulating water at 100°C on one side and 200°C on the other, by means of two water circulation loops (one per side), each equipped with a pump, an exchanger, a heater and a diffuser (heating ring also called external crown). The circuits are pressurized to maintain the water in liquid phase.

 

Load cycles are created by reducing the entire device to 100°C and then causing the temperature differential again.

 

The complementary crown remains at 200°C on both sides. It is kept flat by a load of 2,000 kN, applied via a press equipped with a hydraulic cylinder (250 T, 300 mm stroke) and its power unit.

 

The bench has been designed symmetrically to be able to reverse the faces of the model.

Diffuser circulating water on the faces of the models

Diffuser circulating water on the faces of the models

 

Bench installed at the customer's premises

Bench installed at the customer's premises

 

Press - Test area

Press - Test area

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