Non-Water Hammer Check Valve


Non-Water Hammer Check Valve
SL series
(PAT.)

No valve closure delay means no water hammer and no noise

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Non-Water Hammer Check Valve

Patented in Japan, U.S.A., other

Bore

40-1500mm

Rated pressure

1-2MPa


The YOKOTA Non-Water Hammer Check Valve is a high performance check valve that safely and economically eliminates the danger of water hammer which is a major problem in pumping and water supply equipment.

Mining of underground resources such as coal, from hundreds of meters underground involved contending with a large amount of water. If a pump stopped operating due to a power failure, intense water hammer would occur causing an accident that could lead to pipe ruptures, pump damage, and even put the lives of workers in danger.
The YOKOTA Non-Water Hammer Check Valve clearly solved this problem.

Since then, the valve has been widely adopted in many public facilities such as water supply pumping plants, pumping stations, supply pipelines, agricultural irrigation, and sewage systems, with maximum bore reaching 1350mm. With buildings being built higher and various types of equipment requiring higher pressure, a solution to the water hammer problem has become increasingly important, and we have developed a good reputation through our many achievements in this field. Also, many of our clean-finished Non-Water Hammer Check Valves for ultra-pure water are used in the semiconductor industry.


No water hammer

Due to the patented construction of the valve which opens and closes in response to water flow, there is no delay in valve closure and water hammer does not occur. The valve operates quietly and fits well into quiet surroundings.

Superior characteristics

Head loss of the valve is equivalent to JIS swing check valves and the valve is adaptable to a variety of applications.

Easy to handle

Even the large valves feature simple, single-disk construction that eliminates breakdowns so maintenance costs can be reduced considerably.

No-Feed Detector

The valve can be equipped with the accurate No-Feed Detector (except SL-UC, NU types) facilitating the safest possible automatic pumping.



Non-water hammer principle (PAT.) ....

The YOKOTA Non-Water Hammer Check Valve adjusts to the flow so that there is no valve closure delay and water hammer does not occur.


Phenomenon of water hammer

In a pumping system without a check valve, when pump input stops suddenly, the flow in the pipe goes through stages of "normal rotation, normal flow", "normal rotation, reverse flow", and "reverse rotation, reverse flow" and reaches a stable state. In such a case, the maximum pressure increase reaches 150-160% of the total pump head, which is comparatively small. However, check valves are normally installed in actual pump systems, and the situation is entirely different.

Condition in pump immediately after power failure (without check valve)
Non-Water Hammer Check Valve / Phenomenon of water hammer

Conventional check valves

With conventional check valves, there is a tendency for valves to begin to close only when pressed by reverse flow. Instantaneous stoppage of reverse flow causes pressure to rise resulting in a water hammer noise similar to striking a pipe with a hammer, and in some cases, this causes a blowout in the discharge line.


The YOKOTA Non-Water Hammer Check Valve

Water hammer does not occur.

According to our patented non-water hammer principle, the valve disk of the YOKOTA Non-Water Hammer Check Valve is designed to be submerged in, and suspended by the water flowing in the pipes during maximum flow. When normal flow begins to slow down, the valve disk begins to close in response to this. The instant that flow reverses, in other words, when the water in the pipe stops, the valve disk closes completely and water hammer does not occur. This is similar to the shock eliminating effect of a ball that is thrown upward and caught at the moment when it begins to fall.

Concept of the YOKOTA Non-Water Hammer Check Valve

Non-Water Hammer Check Valve / Phenomenon of water hammer

Comparative test....Pressure change with time after pump operation is stopped

YOKOTA Non-Water Hammer Check Valve

Non-Water Hammer Check Valve

Test equipment

Non-Water Hammer Check Valve / Test equipment

Type of pump:

Self-priming centrifugal pump

Pump specification:

12m3/h x 50m x 3500rpm x 7.5kW

Discharge pipe:

40mm SGP13m

Recording paper feed rate:

50mm/sec

Conventional check valve

Conventional check valve


Non-Water Hammer Check Valve SL series

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Example applications

For sewage treatment plants

For water purification plants

Non-Water Hammer Check Valve / For sewage treatment plants
Sapporo City Sewage Department
SL-SH-1000
Non-Water Hammer Check Valve / For water purification plants
SL-SN-400B


For iron and steel works

More details >

"Current Topics: Steel Works"

For undersea tunnel drainage

More details >

"Current Topics: Undersea Tunnel"

Non-Water Hammer Check Valve / For iron and steel works
SL-SH-600
Non-Water Hammer Check Valve / For undersea tunnel drainage
The Kanmon Tunnel
SL-NBP-200
The Seikan Tunnel
SL-SN-300 (JIS 30K
)


For aquariums

More details >

"Current Topics: Aquarium"

For seawater intake

More details >

"Current Topics: Seawater Intake"

Non-Water Hammer Check Valve / For aquariums
SL-SN-150

Non-Water Hammer Check Valve / For seawater intake

Shrimp hatchery
SL-SN-200


For power plants

More details >

"Current Topics: Slurry Self-Priming"

For chemical/electronic industry

Non-Water Hammer Check Valve / For power plants
SL-NU-200
Non-Water Hammer Check Valve / For chemical/electronic industry
SL-SN-250


For river water intake

More details >

"Current Topics: Snow Removal"

For agricultural irrigation

More details >

"Current Topics: Irrigation Supply"

Non-Water Hammer Check Valve / For river water intake
SL-NB-200
Non-Water Hammer Check Valve / For agricultural irrigation
SL-SN-250


The valve can be applied for use with various kinds of liquid ranging from pure water to seawater, contaminated water and chemical liquid as it can be made from YOKOTA's duplex type stainless steel YST130N with high corrosion resistance.
For details of YST130N, please refer to this page.

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