In May ARAKO successfully completed type test of Globe valves with bellow and Globe valves KIP and Check valves for the nuclear power plants. Due to successful completion of the type tests, we have extended the decision of GP NAEK Energoatom to approve a supplier to Ukraine´s nuclear power plants of the ZAPOROZHYE, ROVNO, SOUTH UKRAINE and KHMELNITSKYI.
Preparation of this typing test according to regulations is very difficult, because the standard provides DN, for which we had to design, draw, produce and test individual valves. The valves must be seismically resistant and have the requirements for elements category I. of seismic resistance by NP 306.2.208-2016 and in accordance with valves group of 2nd and 3rd safety class by NP 306.2.141-2008, group B and C by PNAE G-7-008-98. For this certification, the standard requires type tests to be performed on the Valves, which are in many aspects more demanding than normal production or acceptance tests. The greater complexity of type tests compared to standard testing ensures that the undetected deviation at normal production will not affect the production’s safety of the operation, which is taken into account at maximum in the nuclear power plants.
Most of the tests took place on the premises of ARAKO under the supervision of experienced staff on test benches along with the required technical equipment. The tests were performed according to a pre-approved program and test methodology. Vibration and seismic tests also had to be performed on several test specimens. These tests took place in the testing laboratory of the Military Technical Institute in Vyškov city under the supervision of our employees from the design department.
The seismic resistance test was performed in two phases. In the first phase, the search for resonant frequencies (determination of natural oscillation frequencies) was performed without pressure and the medium was fed into the valve by scanning the frequency and continuously changing the frequency in the frequency range from 1 to 33 Hz for at least three minutes at the acceleration amplitude on the stool platform to 0.2 g, whereas recording the acceleration values were determined with the accelerometers.
The second phase of the seismic test verified the effect of the maximum calculated earthquake according to point 7.6 OTT-87 at the maximum calculated earthquake. Tests of resistance to seismic effects are performed with the supply of test medium which is under the given test pressure. In our case, the test medium was water. When performing a test with medium and pressurization, an external inspection of the valve is performed to determine or confirm whether there is any mechanical damage and to verify the functionality of the valve by performing at least 3 cycles (open-closed). Valves are considered satisfactory if they maintain their functionality in the course and after the dynamic operation of the tests.
During the test, no leaks in the moving and fixed joints above the permissible limits, metal cracking, mechanical damage or cracks were found in our fittings. Bellows Valves were recognized as satisfactory and it was again confirmed that the company ARAKO spol. s r.o. can meet even the most demanding requirements for the quality of Valves.