How to avoid water hammer when loading large diameter pipes with the valves closed

I only remember that to avoid water hammer, valves should be opened quickly and closed slowly. When I first started working, I didn’t know much about various types of valves, so I wasn’t sure which one to use

It is possible to open quickly and close slowly, or electric-hydraulic valves can be used. An electric-hydraulic valve consists of a guide rod, diaphragm, plug block, plug cover, and valve seat. The characteristic of this valve is that the longitudinal cross-section of the lower half of the plug cover is rectangular with two rounded corners. Since the gap formed between the lower half of the plug cover and the inner wall of the valve seat is rectangular or approximately rectangular in this longitudinal cross-section, when the electric-hydraulic valve is just opening or about to close, fluctuations in pipeline pressure cause the plug cover to move up and down; as a result, the cross-sectional area of this gap remains essentially constant or changes very little. Consequently, the flow rate of the fluid passing through this gap remains approximately constant, allowing the fluid to maintain a relatively stable flow rate. This in turn enables the piping system of the electric-hydraulic valve to operate stably.

Our unit uses electro-hydraulic valves; we haven’t started operations yet, so we don’t know how effective they are.

We also use electro-hydraulic valves for loading, and the results are good

Electro-hydraulic valve, a common solution.

Electro-hydraulic valves are certainly an ideal solution, but they are quite expensive. If a replacement isn’t possible for now, the flow rate of the instrument air supplied to the cylinder valve can be reduced, thereby slowing down the air intake into the cylinder and enabling a slow closure, which helps to prevent water hammer. Of course, before the installation is completed, it is necessary to ensure that the pump operator sets up a reflux system, especially in cases where such a system isn’t available automatically

Water hammer is directly related to the valve closing time. Generally, extending the valve closing time can effectively address the water hammer problem; for loading large pipes, electro-hydraulic valves with multi-stage shutdown can be used. The application effect at Yanshan Petrochemical is fairly good.

The electro-hydraulic valves used in our unit perform fairly well, but in the event of an emergency stop during loading, water hammer effects are still quite severe. Our facility has now switched to large-diameter oil loading booms, and I’m quite worried about this; I would appreciate advice from those with expertise.

Adjusting the number of closing stages of the electro-hydraulic valve to extend the closing time should help alleviate the issue.

To avoid or reduce water hammer phenomena, on the one hand, it is necessary to try to keep the discharge pipelines as short as possible from a process perspective; on the other hand, a return line should be installed; and thirdly, multi-stage valve closing should be employed, that is, extending the time taken to close the valves. :handshake :victory:

I believe that to avoid or reduce water hammer, the flow rate should be gradually reduced before the end of the loading process.

The design of the return line for the loading system is essential. It has 3 functions. 1. Prevent water hammer. 2. Prevent overpressure in the loading pump; 3. Prevent condensation.

The final flow rate can be controlled using a shut-off electro-hydraulic valve; the last few hundred liters are regulated with a low flow rate to avoid shocks. Another approach is to install a stand-alone pressure regulating valve between the inlet and outlet of the oil pump; when the electro-hydraulic valve closes, the pressure at the pump outlet increases, and the stand-alone regulating valve opens to relieve pressure, thereby reducing shock.

An electro-hydraulic valve is also installed in front of the flexible hose at our facility, used for rapid opening, slow closing, and flow regulation