Agricultural Irrigation Water Supply

Current Topics


Agricultural Irrigation Water Supply
Top page
& Site map
Contact us


Small tank, but no severe, intermittent operation ... YOKOTA Mini-Tank Automatic Water Supply Equipment

The tank is small and placed in the building.
The tank is small and placed in the building.

Widely adopted in Kobe district irrigation equipment projects

The irrigation system spreads across fields from Kobe City's West to North Wards and has been used continuously since 1970.
When the end valve at the field is opened, river or pond water is supplied through the pipeline. Use of water for agricultural purposes has been made as convenient as twisting open the faucet on a regular tap water supply. Moreover, construction and maintenance of agricultural irrigation ditches is unnecessary resulting in extremely low loss of water resources.

The pipeline network includes over 60 pumping stations using YOKOTA's Mini-Tank Automatic Water Supply Equipment.

The "Mini-Tank Automatic Water Supply Equipment" is an automated system based on technology developed by our company. The feed pump activates when the pressure switch built into the mini-tank is turned on, and deactivates by the No-Feed Detector built into the check valve in the water pipe. Because it is a completely hands-off automated system, use of river and pond water has been made as convenient as simply "turning on the tap".


YOKOTA's Mini-Tank Automatic Water Supply Equipment

Special features of the YOKOTA Mini-Tank Automatic Water Supply Equipment

Extremely small pressure tank

No severe, intermittent pump operation

Air supply to the pressure tank is unnecessary

No water-hammer when the pump is stopped

Excellent pump self priming

High resistance to pipe burst from winter freezing

Complete hands-off automatic operation


A good feature of our "YOKOTA Mini-Tank Automatic Water Supply Equipment" is the tank size compared with conventional automatic water supply systems. The YOKOTA mini-tank is surprisingly small at one-tenth the size or less of conventional systems, but despite the small size there is no severe intermittent operation. The equipment is favored for its convenience and minimum space requirements.

You may ask why this is possible. The following comparison chart provides an explanation.

Comparison with conventional pressure tanks
 

Conventional pressure tanks

YOKOTA Mini-Tank

Construction

Pump turns on and off by pressure switches.

Conventional pressure tanks
Conventional pressure tanks

Two pressure switches, maximum/minimum pressure switches, are built into pressure tank.

Pump activation is controlled by the minimum pressure switch and deactivation by the maximum pressure switch. As a result, the internal pressure of the pressure tank is consistently maintained between maximum and minimum.

Operation order:

When the end valve is opened, the pressure in the tank lowers due to the release of the stored water, and the minimum pressure switch activates the pump.

The pump begins feeding water and the tank's internal pressure rises, which causes the maximum pressure switch to deactivate the pump. After that, the pump repeatedly turns on and off so that the internal tank pressure is maintained between maximum and minimum.

When closing the end valve, the tank's internal pressure rises and the maximum pressure switch deactivates the pump.


The process can be conceptualized as follows: water is supplied from the tank, and when the stored amount in the tank has been reduced, the tank is recharged by what is called "indirect flow".

Pump turns on by pressure switch, turns off by No-Feed Detector device.

YOKOTA's Mini-Tank Automatic Water Supply Equipment
YOKOTA Mini-Tank

Equipped solely with a minimum pressure switch built into the pressure tank. A No-Feed Detector for detecting the presence of water flow is built into the Non-Water Hammer Check Valve in the water pipe.

Pump activation by minimum pressure switch, deactivation by No-Feed Detector.

Operation order:

When the end valve is opened, the pressure in the tank lowers due to the release of the stored water, and the minimum pressure switch activates the pump. (The similarity to conventional tanks ends here.)

The pump begins feeding water, the tank's internal pressure rises, but the pump does not stop unless the water feed rate has been lowered extremely by the closing of the end valve.

The more the end valve closes, the closer the Non-Water Hammer Check Valve comes to completely closing, upon which the No-Feed Detector deactivates the pump.


The process can be conceptualized as follows: Water is supplied directly using the pump by what is called, simply, "direct flow", and when usage ends, the pump stops.

Pressure tank size

Large

Because of a construction that controls pump deactivation through "pressure" information, if the pump's closing pressure is not set high enough so that it sufficiently exceeds the tank's maximum pressure, the pump's deactivation performance worsens, and it may cause a condition where the pump does not deactivate.

Also, if the pump's operation conditions change as a result of performance degradation or if there is a water level change on the intake side, it is necessary to lower the maximum pressure setting so that pump deactivation is assured.

As a result, the maximum/minimum pressure setting range decreases and the intermittent operation on a small sized pressure tank becomes more severe.

To avoid these difficulties, pressure tanks have been enlarged for safety assurance.

Extremely small

Due to a precision construction whereby the pump is deactivated by direct detection of a reduction in water use by the No-Feed Detector, rather than through indirect pressure information, fluctuation in internal tank pressure or pump operation conditions have no effect and the pump deactivates smoothly.

Accordingly, there is no severe intermittent operation even with a small pressure tank, and the equipment lasts a long time.

In principle, it does not matter how small the tank is. As far as practicality is concerned, for example, installing a 50-litre tank requires only one-tenth the space or less of conventional ones.

Air supply to tank

Air supply is required when needed.

Because the tank is large, troublesome work such as setting up air supply equipment or injecting air with a compressor when needed is necessary to maintain the water supply pressure.

Air supply is unnecessary.

Because the tank is extremely small, a standard rubber diaphragm (balloon) has been integrated in the tank, which is more than sufficient to do the job.
Accordingly, air supply is unnecessary.

Check valve

Water hammer occurs.

Because a conventional check valve is used, damage due to water hammer occurs easily during pump deactivation or unexpected power outages.

No worries about water hammer occurrence.

No occurrence of water hammer during pump deactivation or unexpected power outages based on the movement of the YOKOTA Non-Water Hammer Check Valve (PAT.).

Moreover, based on the function of the No-Feed Detector, the pump stops when there is no water-feed (or no occurrence of water hammer) for enhanced safety.

Pumping efficiency

Suction pumping becomes laborious when suction piping crosses over embankments or if air is sucked into the system during operation.

For conventional pumps, even if priming water equipment is used, problems remain with air being sucked into the system during operation and, as a result, water suction being interrupted. Also, this causes trouble with water suction if piping crosses over an embankment.

To supplement this lack of self-priming efficiency, a foot valve is generally installed on the intake side.

However, during the winter when the pump is stopped, water collects in the piping due to the foot valve, and
pipe burst from freezing occurs easily.

No problems with piping across embankments or air being sucked into the system.

Even if water suction is interrupted by air being sucked into the system during operation, the system automatically recovers itself because of the powerful suction force in the YOKOTA Self-Priming Centrifugal Pumps (PAT.).

Moreover, if pumping conditions become more severe such as when piping crosses over embankments, interlocking a vacuum pump will afford more stabilized automatic pumping.

Since excellent priming efficiency is provided, there is no need for installing a foot valve on the intake side.

When the pump is stopped during the winter, water does not remain in the piping because there is no foot valve. Accordingly,
pipe burst from freezing is nearly non-existent.



Self-Priming Centrifugal Pump (PAT.)

The casing consists of a simple structure made of a semi-double volute and a cavity holder. This single-suction, single-stage centrifugal pump displays outstanding pumping performance in a wide range of specifications.

The pump develops maximum vacuum of 60-90kPa (6-9m water column) and displays outstanding self-priming power.

Low NPSH. Even if cavitation develops due to fluctuations in suction conditions, this pump can still continue its pumping operation, and therefore does not require allowance for NPSH.

The pump operates continuously without any problems even if air is sucked or mixed into the system during pumping operation.

Self-priming mechanism (PAT.)


Non-Water Hammer Check Valve (PAT.)

Due to the valve response according to the water flow, there is no delay in valve closure and water hammer does not occur.

The simple, single-disk construction eliminates breakdowns and maintenance costs can be reduced considerably.


Pressure change with time after pump operation is stopped

YOKOTA Non-Water Hammer Check Valve
YOKOTA Non-Water Hammer Check Valve

Conventional check valve
Conventional check valve


Cost advantages with the YOKOTA Mini-Tank Automatic Water Supply Equipment

Based on the facts discussed above, significant cost reductions are realized in the YOKOTA Mini-Tank Automatic Water Supply Equipment as compared with conventional pressure tanks.

Low construction cost ...

The extremely small tank size requires little space.

Low maintenance cost ...

Air supply to the tank is unnecessary. Also, intermittent operation of the pump is reduced, switch contact points have long-life durability.

Electric cost is the same ...

Electric cost is the same whether the tank is large or small. The pump stoppage time with a large pressure tank is longer, but the supply water during the pump stoppage is replenished in advance. In effect, there is no total difference in electricity use as it is a matter of whether electricity is used beforehand or as needed.



Example applications

Automatic operation control panel

Vacuum pump

Strainer and priming detector
Automatic operation control panel
Vacuum pump
Strainer and priming detector

YOKOTA Mini-Tank Automatic Water Supply Equipment

1. Automatic operation control panel

5. Vacuum pump

2. Self-activation equipment and mini-tank

6. Priming detector

3. Water supply pump (Main pump)

7. Electric motor valve

4.

No-Feed Detector (Auto-stop equipment)
and Non-Water Hammer Check Valve

8. Strainer

Water supply pump UHN type

Self-activation equipment and mini-tank

No-Feed Detector (Auto-stop equipment) and Non-Water Hammer Check Valve
Water supply pump UHN type
Self-activation equipment and mini-tank
No-Feed Detector (Auto-stop equipment)
and Non-Water Hammer Check Valve


Automatic operation procedure

When the end valve is opened, water stored in the mini-tank is released and the pressure switch, which detects the decrease in pressure, sends a signal to activate the vacuum pump.

When the priming detector detects that the suction piping is at full capacity, it activates the number 1 main pump, water feed begins, and the vacuum pump stops.

If further water supply is needed, the number 2 main pump activates.

When the end valve is closed, the amount of water passing through the Non-Water Hammer Check Valve approaches zero. The built-in No-Feed Detector detects this condition and stops the main pump.


Even with the YOKOTA Mini-Tank Automatic Water Supply Equipment, be aware that if small amounts of water are used intermittently or there is leakage from the piping, the pump is stopped more frequently.


Actual application

61 pumping stations and 104 pumps (delivered from 1988 to 2003) mainly in the Kobe area, including the Kobe Minorino Public Corporation River Improvement Project and Goryoda Pump Facility.


For details of Self-Priming Centrifugal Pump or Non-Water Hammer Check Valve, please refer to
Self-Priming Centrifugal Pump UHN series
Non-Water Hammer Check Valve SL series


© Yokota Manufacturing Co., Ltd. Tel: +81 82-241-8672 E-mail: yokota@aquadevice.com Terms of Use