Resolving the concerns of seawater pumping ... YOKOTA Seawater Intake Pump
The ultimate method of solving water shortages in various countries is the use of the inexhaustible supply of seawater.
In this respect, there is a growing trend for the use of seawater. Salt production is one obvious use, however, recently factories and power generating facilities are using vast amounts of seawater for cooling and, with the use of desalination equipment, major production of drinking water is being carried out. Moreover, fish farms are increasingly finding it easier to raise fish in land-based hatchery ponds by pumping in seawater rather than managing a fish farm on the sea itself.
What are the problems with seawater intake?
In the past, seawater intake was generally done using immersion type pumps such as a submerged pump or vertical pump.
The main reason for this was because of the poor seawater pumping efficiency of land-based pumps.
Difficult pumping conditions are common due to factors such as poor self-priming efficiency from the extrication of air and bubbles which occurs easily in seawater, too much distance from the water suction intake, and pipes crossing over embankments. With no strong self-priming pumps that could meet these demands, the solution closest at hand was "forced pumping operation" with submergible pumps.
However, for submerged pumps, because the pump motor is submerged together with the pump, there are concerns with the power supply, corrosion, and the danger of damage caused by rough seas. Added to this is the troublesome work of pulling up a submerged pump to perform maintenance inspection.
As for vertical pumps, because the main part of a vertical pump is submerged in water, they are prone to the danger of flood-tides and typhoons. What's more, the large size of the equipment means higher construction costs, and the added trouble of performing inspection on the main part of the pump.
Although there are land-based volute pumps equipped with a vacuum pump for priming liquid, it is usually the case that the vacuum pump is cut-off at the same time priming is finished to prevent damage to the vacuum pump from penetration of seawater. For this reason, if air suction occurs during pump operation, pumping becomes difficult.
Also, because suction power is not strong enough, pumping through suction pipes across embankments is not possible.
This situation is further problematic in areas where boring through embankments or barriers is not permitted by port and harbor regulations. Consequently, it becomes necessary to set a pump on a landfill at the same height as the embankment. This only increases the concern over loss of pumping ability due to the increase in suction height.
The newly conceived YOKOTA Seawater Intake Pumps are the clear answer to these concerns.
What is different about YOKOTA Seawater Intake Pumps?
Seawater intake pump comparative chart
YOKOTA Seawater Intake Pumps, with their patented construction of a "continuous air-bleeding" method which interlocks a bleed pump (vacuum pump) to the centrifugal pump, provide strong priming efficiency without penetration of seawater or muddy water into the vacuum pump even during continuous suction.
The YOKOTA Seawater Intake Pump has received high marks based on the above merits and is being used widely both domestically and abroad.
What is the continuous air-bleeding YOKOTA Vacuum Pump?
The greatest advantage of the continuous air-bleeding method lies in the YOKOTA's unique vacuum pump.
The patented construction of the vacuum pump with its built-in water-air separating impeller does not allow penetration of seawater or muddy water into the vacuum pump even during continuous air-bleeding.
Accordingly, the suction intake side of the main pump is always operating under conditions of maximum vacuum and bleed amount from the vacuum pump, and as a result, pumping is not interrupted because there is no air obstruction in the main pump.
The following main pumps are available in consideration of self-priming ability and pumping capacity.
The following are three example applications of the pump.
YOKOTA Seawater Intake Pumps have actually been supplied to various facilities such as experimental fishery stations, fish hatcheries, and fish farms, however, the following is an example of an application at a large-scale shrimp hatchery.
Good water maintenance is the foundation of the fishing industry, and for fish farms this literally means a stable, economic supply of seawater is what is most important. Because shrimp require especially pure seawater, it is delivered to the hatchery from a distance of 350m offshore.
At such a distance, and in consideration of possible damage caused by weather conditions such as typhoons, the safeness and manageability of submerging a pump in the sea (submerged/vertical pumps) is unsuitable.
As a result, land-based pumps have been preferable, with the installation location set across a flat surface 50m from the shoreline and at a height of 2.5m above the sea surface. However, this type of installation requires extensive piping of over 400m.
Nonetheless, stable and assured pumping is indispensable, because as far as the shrimp hatchery is concerned, pumping problems would only result in product loss.
In answer to these concerns, we have thoroughly developed a continuous air-bleeding system and created a package with even greater self-priming power in our YOKOTA Self-Priming Centrifugal Pump UHN type interlocked with the YOKOTA Vacuum Pump VP-K type. Added to this package is an assembly including the YOKOTA Non-Water Hammer Check Valve for absolute protection against water hammer and, together with the No-Feed Detector and control panel, this system provides complete automated operation.
YOKOTA Automatic Seawater Pumping System, a pump package with complete functionality
This system's operation order is as follows:
The UHN type pump itself, which is used here as the main pump, provides high performance self-priming.
Yokota Self-Priming Centrifugal Pump UHN type (PAT.) features
This example concerns a pump application at a large chemical plant.
Because a large amount of seawater is needed for cooling, the main pump that the plant uses is a large capacity YOKOTA Double Suction Volute Pump. Having adopted the continuous air-bleeding method, the convenience of a piping arrangement over higher elevations is possible without fear of air suction during pumping operation.
We have numerous pump applications for thermal power plants, however, the example we are discussing here concerns the "screen cleaning pump" that cleans the screen at the seawater intake of a thermal power plant.
The main pump used here is the medium capacity YOKOTA Double Suction Volute Pump. Having adopted the continuous air-bleeding method, it is a completely automatic, high-efficiency self-priming pump.
Moreover, with the aim of reducing inspection frequency by protecting the equipment from water hammer, the YOKOTA Non-Water Hammer Check Valve has been adopted for absolute protection against water hammer.
The main pump and Non-Water Hammer Check Valve have also been produced with the particular aim of reducing inspection frequency by protecting the equipment from seawater corrosion (such as crevice corrosion) using YOKOTA Seawater Resistant Stainless Steel YST130N.
Regarding the YOKOTA Non-Water Hammer Check Valve (PAT.)
Regarding YOKOTA Seawater Resistant Stainless Steel YST130N
YST130N is a duplex stainless steel alloy independently developed by YOKOTA with excellent corrosion resistance to seawater and chemicals.
Results of actual field tests clearly show that YST130N has excellent crevice and pitting corrosion resistance.
For details of each product that makes up the Seawater Intake Pump System, please refer to
Self-Priming Centrifugal Pump UHN series
Process Pump UB series
Double Suction Volute Pump HD type
Mixed-Flow Volute Pump YM type
Non-Water Hammer Check Valve SL series
Seawater Resistant Stainless Steel YST130N