Maintenance of FlowTrac II
There are no scheduled maintenance requirements for the FlowTrac-II equipment. However, we do have some recommendations (as described below) for keeping your equipment in the best possible working condition. The FlowTrac-II system comprises durable but precision components. As with any precision laboratory equipment, it should be operated with care and only by a skilled user. Have every person who will use the system become familiar with the functioning of the equipment through a study of this manual and the software manual, or through training by another skilled user. Strongly discourage the curious worker who drops by and wants to see by trial and error what the system will do.
*NOTE: When you are not using your pump, please empty them and turn off.
Flow Pump
- Clean the exterior of the FlowTrac-II unit with water and a mild dishwashing detergent. Do not use abrasives or any cleaner that reacts with aluminum, such as those containing ammonia. Do not use any abrasive scrubbing cloth.
- Avoid water dripping into the interior of the FlowTrac-II unit. Electronics inside could be damaged.
- Avoid sliding objects, which might cause scratches, over the FlowTrac-II case.
- Do not remove the FlowTrac-II case unless you have been instructed to do so and know exactly what you are doing.
- The fan slots on the back of the FlowTrac-II unit may collect a lot of dust. If this happens, turn off the FlowTrac-II power switch (on the back panel) so that the fan is off. Use a vacuum cleaner to carefully clean the dust from the slots.
- The FlowTrac-II pump cylinder should be flushed after extensive use. Flushing is done by first emptying the cylinder. Use the keypad and LCD menus to do this (see section 2.1.2.1 for details). The cylinder must be emptied into a container separate from the one you fill from. After draining the cylinder, fill it with clean, de-aerated water. You should repeat this operation several times or until you can see that the drained water is clear.
- The FlowTrac-II pump cylinder should be left empty if the unit will remain idle for a prolonged period of time.
FlowTrac-II Solenoid Valves
There are two solenoid valves; a supply valve on the back connected to a 6.35 mm ( ¼ in) diameter tube, and an output valve on the front connected to a 3.17 mm ( 1/8 in) diameter tube. The supply valve is normally closed and the output valve is normally open. There are two conditions throughout all phases of all tests:
- Undrained condition: The high-precision stepper motor keeps the volume constant by either increasing or decreasing the pressure to keep the volume at the same value. The increase/decrease in pressure is the sample pressure change during the undrained shear phase. The changes are related to the soil behavior of being contractive (positive excess pore pressure) or dilative (negative excess pore pressure). See critical state diagram below.
- Drained condition: Similarly the high-precision stepper motor keeps the pressure constant by either increasing or decreasing the volume to keep the pressure at the same value. The increase/decrease in volume is the sample volumetric change during the drained shear phase. The changes are related to the soil behavior of being contractive (positive volumetric strain) or dilative (negative volumetric strain). See critical state diagram below.
During a test, the stepper motor is always stepping one way or the other. Therefore the manual valves on the triaxial cell, the permeability cell or the Rowe cell must be always open; everything is happening at the location of the FlowTrac-II unit.
Occasionally the solenoid valves get clogged (see picture below).
If this happens, they need to be taken apart and flushed with a high pressure air source. If this does not clear them, they should be replaced. To keep the valves from clogging, you should flush the pumps after each use by emptying and filling the pumps several times while watching the quality of the water coming out. Ideally, you should change the water after each flush to ensure that you are not getting the fine particles back into the pump.
Supply Valve
To see if the supply valve is clogged, follow these steps:
- Close the supply valve (using either keypad or software control).
- Open the output valve.
- Make sure that the 1/8” (3 mm) tube at the end of the output valve is connected to a valve that is closed so that you can apply and maintain a pressure within the tube.
- Using software control, apply and maintain about 350 kPa (50 psi).
- Check the flow pump activity. If the pump is not stabilizing because the pressure is dropping, then check to see if water is dripping out of the supply line tubing coming out of the back of the FlowTrac-II unit. (Clogging of the supply valve will result in it not sealing completely when closed.)
If water is dripping from the supply line, then for the time being you will need to use a manual valve on the back of the FlowTrac-II unit to close the line when a test is running. Open the valve only when you fill the pump with water at the beginning of a test.
Eventually you will have to replace the solenoid valve. Please see the article called " How to replace solenoid valves" for step by step instructions.
Output Valve
If the output valve is clogged, it will be obvious since no water will be coming out of the output line when the valve is open.
As a temporary measure you can remove the solenoid valves and replace them with manual valves. The manual output valve should always be open except when filling and emptying the pump; conversely the supply valve should always be closed except when filling and emptying the pump.
To summarize:
- Filling the pump: Supply valve open and output valve closed.
- Emptying the pump: Supply valve open and output valve closed.
- Running a test: Supply valve closed and output valve open.
Computer
- Keep the computer and monitor screen free of dust.
- Clean the exterior of the computer with water and mild dishwashing detergent.
- Avoid getting liquids inside the computer.
- Avoid spilling liquids onto the keyboard.
- In dusty environments, cover the keyboard when not in use.