JPS59133900A - Prevention against water hammer - Google Patents

Abstract

PURPOSE:To make a piping system so as to be freely selected without fear of water hammer happening as well as to prevent the occurrence of any damage to piping, by installing a safety valve, which provides a spring for a valve disc, in a side passage, while allowing abnormal high pressure only to run in the same direction of a flow in a main pipe. CONSTITUTION:A valve disc 4a of a safety valve 4 is provided with a spring 4b, and at a side passage 3, a flow of abnormal high pressure caused by a water hammer in the same direction as that of a flow in a main pipe 1, namely, an arrow 6 direction alone is allowed to run. Closing a main valve 2, when pressure waves are settled if statically determinate pressure at the valve upstream side is set down to PA while that at the down-stream side is to PB, working pressure of the safety valve 4 is to be set down to PA-PB+alpha>0 in advance. This sign alpha is of spring force for making the safety valve open when the water hammer gets statically determined. At the side passage, an auxiliary valve 2 is installed, and under usual operating conditions, both the main valve 2 and the auxiliary valve 5 are opened in advance, and when the main valve 2 is closed, the safety valve 4 is as well opened, flowing through the side passage 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing damage to a piping system due to water hammer that occurs when a valve is closed or when a pump is started or stopped.

In the piping systems of various plants, pressure waves called water hammer are generated due to the inertia of the liquid when valves are closed or pumps are started or stopped, causing many accidents that damage the piping systems. Conventionally, in order to prevent this, the size of the pressure wave was predicted using a characteristic curve, and simulated using a computer, and the closing speed of the valve was adjusted, and the order of operation of each part (pump, valve, etc.) was adjusted.

The plant's operating procedures were determined. However, this method not only requires troublesome simulations to determine valve control methods and operating procedures, but also can damage the piping system due to malfunction, so it is not a completely safe method. There wasn't. The present invention is a device for reducing the pressure caused by such water hammer.

Fig. 1 shows a system diagram of the device of the present invention in the case of a valve, where 1 is a main pipe, 2 is a main valve, 6 is a side passage of the main valve 2, and 4 is a safety valve that reduces the pressure due to water pressure. . safety valve 4
A spring 4b is applied to the valve body 4a.

The safety valve 4 is designed to only allow abnormally high pressure flow due to water pressure in the side passage 6 in the same direction as the flow direction in the main pipe 1, that is, the direction of arrow B. In such a device, when the main valve 2 is closed and the pressure wave (water pressure) subsides, the static constant pressure on the upstream side of the valve is P.
A, the downstream side is PB. At this time, set the operating pressure of the safety valve 4 to pA-pB+α〉0 (PA>PB
). α is the spring force required to close the safety valve when the water norm is stabilized. A sub-valve 5 is placed in the side passage.

Under normal operating conditions, the main valve 2 is open and the sub-valve 5 is also open. At this time, the safety valve 4 is closed because the upstream pressure and the downstream pressure are equal (the pressure at this time is PO). When the main valve 2 is closed, the upstream pressure becomes P. +f(t), and the downstream pressure is PO-g(t). Here f(t),
g(t) is the pressure fluctuation caused by water hammer, and t is time. Therefore, the force trying to open the safety valve is f
(t) + g(t), f(t)+g(t)>
When PA+PB+α, the safety valve 4 opens and the liquid flows from the upstream side to the downstream side through the side passage 3. This reduces the rise in downstream pressure due to water hammer,
At the same time, it prevents the upstream pressure from becoming negative.

In this way, pressure fluctuations due to water hammer can be reduced, and the main valve 2 can be moved at the required speed.
Moreover, damage to piping can be prevented. After the water hammer settles down, the safety valve 4 is closed and the flow of liquid on the upstream and downstream sides is stopped. The sub-valve 5 has a pressure difference pA- when the main valve 2 is normally closed.
If pB changes for some reason, it is closed and used to completely stop the upstream and downstream flows. Main valve 2° Sub-valve 5. As the safety valve 4, a commercially available one can be used.

FIG. 2 shows the case of a pump, where 10 is a pump, 11 is a suction pipe, 12 is a discharge pipe, 13 is a starting side passage, 14 is a starting safety valve installed therein, and 16 is a stopping side passage.

Reference numeral 17 indicates a stop safety valve, and arrow 19 indicates the main flow direction. A spring 14b is applied to the valve body 14a of the starting safety valve 14.

Accordingly, the safety valve 14 only allows the abnormally high pressure to flow in the opposite direction to the main flow direction 19, and the stop safety valve 17, which includes the valve body 17a and the spring 171), allows only the abnormally high pressure to flow in the same direction as the main flow 19. It is something.

The pressure in the suction pipe 11 during steady operation of the pump 10 is p
A, and the pressure on the discharge side 12 is PB (PB > PA
).

When the pump 10 is started, the pressure in the discharge pipe 12 increases rapidly, while the pressure in the suction pipe 11 decreases, causing a water hammer phenomenon. Therefore, as described above, the starting safety valve 14 is attached to the starting side path 16 for starting. The operating principle is the same as when closing the valve described above, and the operating condition of the valve may be set to PB-PA+α>0. - The component of the sudden increase in discharge pressure due to startup flows into the suction pipe 11 through the startup safety valve 14, and this causes the suction pipe 1 to
Increase the negative pressure inside 1. At the time of startup, the stop safety valve 17 attached to the stop side passage 16 remains closed because the pressure is high in the opposite direction.

Next, when stopping, the pressure on the suction side increases and the pressure on the discharge side decreases. In this case, the operating conditions for the stop safety valve 17 are normally set so that it operates at α>0 ((χ is the spring force required to close the safety valve) because the pressure on the suction side is low. By installing the side passages 13 and 16 and the safety valves 14 and 17, it is possible to prevent damage to the piping system due to water hammer when the pump is turned on and off.

Doors of valve 2 can be installed by installing the above device.

It is possible to freely select a piping system for starting and stopping the pump 10 without considering water hammer analysis and its control, and damage to the piping can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a system diagram for a valve, and FIG. 2 is a system diagram for a pump. 1 Main pipe 2 Main valve 5 Main valve side passage 4 Safety valve 4a Valve element 4b Spring 5 Sub-valve 6 Main stream direction arrow 10 Pump 11 Suction pipe 12 Discharge pipe 13 Starting side passage 14 Starting safety valve 14a Valve element 14b Spring 1
6 Stopping side path 17 Stopping safety valve 17a valve body 17b spring 1
9 Arrow in mainstream direction Applicant Mitsui Engineering & Shipbuilding Co., Ltd. Agent Kawa 1) Shigeo Figure 2 58

Claims (1)

[Claims] 1) A side passage with a safety valve is provided in the main valve, and the safety valve has a water valve with a spring imposed on the valve body so as to only allow flow of abnormally high pressure in the same direction as the flow in the main pipe. Prevention device. 2) Place two side channels on the pump, each with a safety valve,
One of the safety valves in this side passage has a spring in each valve body, allowing only abnormally high pressure flow in the same direction as the flow in the main pipe, and in the safety valve in the other side passage in the opposite direction to the flow in the main pipe. Water hammer prevention device.