Abstract. Pumping station supplies water for technological process. The check valve in the station was replaced with a new one. The regular test of black out discovered the high pressure pulsations accompanied with noticeable pipeline movement of discharge pipe. It was caused by late check valve closing, probably, when the back flow reached the highest possible velocity. This statement was supported with analysis of results of pressure measurement near the check valve and with a numerical simulation of the flow in the pipeline system.

The check valves play an important role in safety and reliability of many technologies using liquid or gas flow. Check valves are elements of the hydraulic system enabling the one-way flow without a significant pressure loss and preventing the reverse flow. The ideal check valve should have an acceptable pressure loss and, when closed, there should be no undesirable dynamic phenomena like water hammer or slam. The static properties describe energy losses of the check valve, and the producers provide them as a standard. The static properties can be defined either in an experimental way or using the CFD analysis. The dynamic properties of the check valve express a relation between the maximum reverse velocity and water column deceleration. Unfortunately, the definition of dynamic properties can be obtained only experimentally, and for small pipe diameters. It is very demanding, time consuming and expensive to define the dynamic characteristic so it is why the producers do not offer it as a standard. The article deals with static and dynamic properties of different check valves with different closing principles. There was built a testing hydraulic circuit with the pipe diameter DN 100, that enables the simulation of check valve slam during the flow reversing. The attention was paid to the definition of flow deceleration, which is rather problematic and usually defined in a different way for each lab.