The battery-operated vacuum pump is designed to provide vacuum to suction lysimeters installed in the field. Suction lysimeters are frequently installed at locations where line power is not available. This small vacuum pump will draw enough vacuum (maximum vacuum 340 mbar) to extract pore water into suction lysimeters when the soil or porous matrix are relatively moist (matrix potential greater than -200 mbar). In reality if the soil or porous material is dryer than a water content equivalent to –200 mbar matrix potential, the hydraulic conductivity of the soil immediately around the lysimeter is so low as to make extraction of soil pore water very difficult. This is especially true for sandy soils, and coarse textured materials.
The battery and vacuum pump are enclosed in a strong container. It measures 23 x 20 x 10 cm and weighs 2.7 kg. On a fully charged battery the pump can run continuously and draw vacuum for 3 to 4 days.
Frequently Asked Questions
How many lysimeters can I connect to one vacuum pump?
If all tubing to the lysimeters is airtight and if all connections are airtight, one pump can maintain an approximate negative pressure of 300 mbar in many lysimeters. However, even small leaks can severely reduce the efficiency of the system. Thus great care is required in installing lysimeters in the field. Leak testing is done by applying positive pressure to the tubing and connectors, and by holding all connections under water. Appearance of air bubbles in the water is proof of leaks.
How quick can the pump create partial vacuum?
This pump can reduce the pressure in a 1 liter bottle to -100 mbar in 11 seconds. It takes approximately 30 seconds to reduce the air pressure in a 1 liter bottle to -200 mbar.
Are there any precautions one should take when using this pump?
One should always place an overflow bottle in the fluid return tube right before the vacuum pump. This ensures that no water from the lysimeters can enter the pump. Water will damage the pump.
Are these pumps suitable for permanent installations?
For permanent installations line powered pumps (110V or 220V) are preferable. The portable, battery powered pump is particularly suitable for intermittent pore water collection, and/or where suction lysimeters are widely dispersed in the field.
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