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Used in draining operation at Kanmon and Seikan Tunnels ... YOKOTA pumps and valves

Undersea Tunnel

Undersea tunnels deliver us from island to island in no time.
Tunnels are convenient, but many types of equipment are under operation day and night to maintain their function. One type of equipment is for tunnel draining.

Tunnels, whether ground or undersea tunnels, are constructed across geologic or water stratums, so ground water drainage is always necessary. For large tunnels, the amount of drainage adds up to few thousand tons a day.
For ground tunnels, the down slopes toward the exit will do since water flows downward for natural drainage, but this does not work for undersea tunnels. Consequently, in addition to the tunnel shaft for the vehicle road, drain tunnels and pump compartments are constructed to collect the ground water, with drain pumps pumping it above ground immediately.

Undersea Tunnel

The requirements for a drain pump are as follows. Given the severe conditions of these places alone, a pump that meets high tech standards is required.

Must have high pump head to pump water from deep underground to above ground.

No trouble with air suction during suction operation.

Has water hammer prevention.

Durability.

Hands-off automatic operation system equipped.

Easy maintenance inspection.

Must have high corrosion resistance especially for handling seawater.


Since the impetus for company formation in 1953 was "pump and valve development for coal mining", we have created specialty pumps and valves for various tunnels, and we now have been presented the opportunity again with undersea tunnels. Thus, YOKOTA pumps and valves built with technical expertise play an active, inconspicuous role behind the scenes.


The Kanmon Tunnel ... the YOKOTA Self-Priming Pump and Non-Water Hammer Check Valve


Undersea Tunnel

The Kanmon Tunnel is an undersea road connecting Honshu and Kyushu, which began construction in 1939, and was completed in 1958.
Built for vehicle, bicycle and pedestrian traffic on National Route 2, it has a total length of 3.5km, an undersea portion of 780m, with a maximum depth from the sea surface of 56m.

Replacement work is periodically performed to prevent the Kanmon Tunnel drain pumps and pipes from wearing out.
When completed in 1958, there were conventional type drain pumps equipped in the drain pump compartments, but with the replacement work in 1973, the YOKOTA Self-Priming Pump was adopted as a replacement.
In each pump compartment, pump operation is performed in shifts with a few pumps as a precaution, furthermore, to guarantee safe drainage, each pump is equipped with the YOKOTA Non-Water Hammer Check Valve and the built-in No-Feed Detector.

Since then, the YOKOTA Self-Priming Pumps drain water in the tunnel day and night, and have received high marks for their unique features and high reliability to this very day.
From 1994 through 1995, the YOKOTA Self-Priming Pumps were renewed, at which time the YOKOTA Seawater Resistant Stainless Steel Casting YST130N material was adopted on the pump for higher durability and reduced maintenance cost.

The YOKOTA Self-Priming Pumpand Non-Water Hammer Check Valve under operation in Kanmon Tunnel
The YOKOTA Self-Priming Pump
and Non-Water Hammer Check Valve
under operation in Kanmon Tunnel


Why have the YOKOTA Self-Priming Pump and Non-Water Hammer Check Valve been adopted?

The reason why the YOKOTA Self-Priming Pump has been adopted is because of the following outstanding features in comparison to other conventional self-priming pumps.

Superior suction force

Because of the patented suction (water-air separating) mechanism, the suction force performance is superior. For general self-priming pumps, pumping malfunctions are likely to occur at the foot valve, but the YOKOTA Self-Priming Pump, with its high suction force, can perform pumping without a foot valve.

Air suction is no problem

Large amounts of air can be processed in the pump, and even if pumping becomes subject to air suction or mixture of air during water pumping operation, pumping operation continues by exhausting the air, and the pump returns to normal pumping operation as soon as conditions are restored. Even continuous suction of air-containing water (i.e., gas-liquid two-phase pumping) is possible.

Low NPSH

Even if cavitation develops due to fluctuation in suction conditions such as water level on the suction side, this pump can still continue pumping operation and does not require allowance for NPSH. Stable performance is also maintained under fluctuating suction conditions.

Intake piping across higher elevations is possible

For general self-priming pumps, care must be taken not to create air accumulation in the horizontal suction piping. Since the YOKOTA Self-Priming Pump pumps water reliably even if there is air accumulation, there are no problems even with suction piping shaped over high elevations.

Easy operation

Since there is no need for priming water operation other than filling the casing with priming water during installation, handling is very easy. Maintenance is also easy because of the simple structure.

Non-Water Hammer Check Valve

Unlike general check valves, the YOKOTA Non-Water Hammer Check Valve is a patented check valve, which has been developed according to leading edge hydraulic theory. The Non-Water Hammer Check Valve closes at exactly the moment when change in flow from the normal to the reverse direction occurs, that is, when the liquid in the pipes stops flowing after the pump is stopped. As a result, water hammer due to reversed flow does not occur, thereby preventing pipe ruptures and pump damage.

No-Feed Detector

The No-Feed Detector can be built-into the Non-Water Hammer Check Valve. The switch operates according to valve movement from water flow to stop the pump automatically when the flow rate is close to zero, preventing dry operation of the pump. Therefore, automatic operation can be performed with ease.


The following are model-based examples of the Self-Priming Pump used in the Kanmon Tunnel.
Each pump has an original structure and features.


Actual use example 1 - Multistage Self-Priming Pump USM type

Six drain pumps of this type are used for suctioning seawater accumulated at the bottom of a drain tunnel, pumping it to the ground surface located 65m above.
It is a reliable pump with a multi-stage, high pump head and patented self-priming mechanism that enables outstanding self-priming performance.

Typical pump specification

Type:

USM-3-1510

Specification:

150mm x 3.3m3/min x 85m x 1750rpm x 75kW

Auxiliary Non-Water Hammer Check Valve specification

Type:

SL-NBP-200

Specification:

Bore 200mm, JIS 10K, equipped with No-Feed Detector


 

Multistage Self-Priming Pump USM type

Multistage Self-Priming Pump USM type

Multistage Self-Priming Pump USM type

1:

Multistage Self-Priming Pump USM type

2:

Discharge valve

3:

Non-Water Hammer Check Valve (equipped with No-Feed Detector)

4:

Foot valve (Not needed normally, but it is equipped here because of
the higher frequency of activation/deactivation at this location.)


Multistage Self-Priming PumpUSM type
Non-Water Hammer Check ValveSL-NBP type
No-Feed DetectorBP type
Multistage Self-Priming Pump
USM type
Non-Water Hammer Check Valve
SL-NBP type
No-Feed Detector
BP type

Self-priming mechanism of USM type:

The self-priming mechanism consists of a 1st-stage casing with a smaller and larger passage forming a semi-double volute, and a 2nd-stage suction casing with a 2nd-stage suction port.

1. Circulation flow

During self-priming, the water discharged from passage A in the semi-double volute returns to the impeller after circulating in passage B-C, and is discharged again into passage A.

2. Removal of bubbles

This recirculation flow mixes the water and the air in the center with intense vortex D within the impeller and discharges it into passage A.

3. Water-air separation and exhaust

The water-air mixture is led from passage A to chamber B and separated. The separated air is discharged via an exhaust valve. The separated water, not entering the multistage side through the 2nd-stage suction port, returns to the 1st-stage casing to repeat the self-priming operation until separation and exhausting are completed.

Self-priming mechanism (USM type):



Actual use example 2 - Self-Priming Centrifugal Pump UHN, UHNM types

Eight pumps of these types are used for draining seawater as well as rainwater.
It is a reliable pump with a high pump head even though it is a single stage pump. The patented self-priming mechanism also enables outstanding self-priming performance.

Typical pump specification

Type:

UHN-2520

Specification:

250mm x 5.2m3/min x 21m x 1750rpm x 37kW

Auxiliary Non-Water Hammer Check Valve specification

Type:

SL-SNP-250

Specification:

Bore 250mm, JIS 10K, equipped with No-Feed Detector

Self-Priming Centrifugal Pump UHN types

Typical pump specification

Type:

UHNM-0520

Specification:

65mm/50mm x 0.5m3/min x 85m x 3500rpm x 15kW

Auxiliary Non-Water Hammer Check Valve specification

Type:

SL-NBP-80

Specification:

Bore 80mm, JIS 10K, equipped with No-Feed Detector


Self-Priming Centrifugal Pump UHN, UHNM types
Self-Priming Centrifugal Pump UHN, UHNM types
Self-Priming Centrifugal Pump UHNM types


Self-priming mechanism of UHN, UHNM types:

The pump casing consists of a smaller and larger passage forming a semi-double volute and a cavity holder in the discharge nozzle.

1. Circulation flow

During self-priming, the water discharged from passage A in the semi-double volute returns to the impeller through passage B-C, and is discharged again into passage A.

2. Removal of bubbles

This recirculation flow mixes the water and the air in the center with intense vortex D within the impeller and discharges it into passage A.

3. Water-air separation and exhaust

The water-air mixture is led from passage A to discharge nozzle B in a cyclonic state and automatically separated by centrifugal force, and then the water is recirculated through passage B-C. The separated air is then held by cavity holder E, and compressed and discharged against the back pressure.

Self-priming mechanism (PAT.)


Actual use example 3 - Self-Priming Centrifugal Pump UHPR type with submersible motor

Three drain pumps of this type are used for suctioning seawater, especially where there is a possibility of submersion by seawater.
The pump body enables outstanding self-priming performance by the same patented self-priming mechanism as described for the above UHN, UHNM types. Moreover, the submergible motor is built into the pump and is completely waterproof. YOKOTA Seawater Resistant Stainless Steel Casting YST130N has been adopted for the pump material, so there are no problems with submersion in seawater.
This highly reliable pump with its original mechanism and material has been highly evaluated.

Typical pump specification

Type:

UHPR-1520

Specification:

150mm x 3.3m3/min x 20m x 1750rpm x 15kW

Auxiliary Non-Water Hammer Check Valve specification

Type:

SL-NBP-150

Specification:

Bore 150mm, JIS 10K, equipped with No-Feed Detector

Self-Priming Pump UHPR type equipped with submerged motor


The Seikan Tunnel ... the YOKOTA Non-Water Hammer Check Valve


The world's longest undersea railway tunnel, the Seikan Tunnel connecting Honshu and Hokkaido began construction in 1964, and was completed in 1987.
The tunnel is constructed not only for the conventional railway line but also for the Shinkansen with a full length of 53.9km, an undersea portion of 23.3km, and a maximum depth from the sea surface reaching to 240m.

The high-pressure pumps pump seawater penetrating the tunnel to above ground, but the height to ground rises up to approx. 250m. Check valves have to be used to prevent counter flow in case of emergency pump stoppage, but if water hammer occurs on these check valves, an unexpected situation might occur.
Therefore, the highly reliable YOKOTA Non-Water Hammer Check Valve has been adopted for this important check valve. A total of twenty-one valves were equipped in 1986, keeping the pump equipment safe.

Non-Water Hammer Check Valve specification 1

Type:

SL-SN-350

Specification:

Bore 350mm, JIS 20K and 30K

Non-Water Hammer Check Valve specification 2

Type:

SL-SNP-300

Specification:

Bore 300mm, JIS 20K and 30K, equipped with No-Feed Detector

Non-Water Hammer Check Valve
Non-Water Hammer Check Valve SL-SNP type
No-Feed Detector NP type
Non-Water Hammer Check Valve SL-SNP type
No-Feed Detector NP type


Why has the YOKOTA Non-Water Hammer Check Valve (PAT.) been chosen?

The reason for choosing the YOKOTA Non-Water Hammer Check Valve is because of the following outstanding features compared to conventional check valves.

Due to the patented mechanism of the valve's quick response (open/close) according to the water flow, there is no delay in valve closure and water hammer does not occur.

Even with its large size, the single-disk, simple construction eliminates breakdowns. Maintenance costs can be reduced considerably.

The No-Feed Detector can be equipped as safety equipment that prevents dry operation of pumps.


Pressure change with time after pump operation is stopped

YOKOTA Non-Water Hammer Check Valve
Conventional check valve
YOKOTA Non-Water Hammer Check Valve
Conventional check valve


Regarding YOKOTA Seawater Resistant Stainless Steel YST130N

YST130N is a duplex type stainless steel alloy, which has been developed originally by YOKOTA, and it has extraordinary seawater resistance.
Results of actual field tests clearly show that YST130N has excellent crevice and pitting corrosion resistance.

Crevice corrosion resistance

Loss due to crevice corrosion
Field test with actual liquid
(seawater + hypochlorous acid (90-100ppm))
Test period: approx. 1 year and 9 months
Crevice corrosion

Test piece after field test
YST130N
SUS316
YST130N
SUS316

Pitting corrosion resistance

Loss due to pitting corrosion
5% ferric chloride 40 deg C, 50hr

Pit corrosion

Test piece after field test
YST130N
SUS329J1
SUS316

YST130N

SUS329J1

SUS316



For details of each product, please refer to
Multistage Self-Priming Pump USM, UBM, MEF types
Self-Priming Centrifugal Pump UHN series (UHNM, UHPR types)
Non-Water Hammer Check Valve SL series
Seawater Resistant Stainless Steel YST130N



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