Maintenance Experiments

Hydrostatic circuit simulation

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Hydrostatic circuit simulator

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Suggested exercises and observations

Enter your username, complete the exercises below then post to your LRS using the email button.

System operation screen

1. From the home screen select button 2 (How electro-hydraulic control systems work) to move to screen 2.

2. Select dropdown 5 (Contamination entry point review).

Move the mouse over or click on each triangle to see the relevant information for that area.

3. Select dropdown 6 (Drag icons to show contamination entry).

Click on and drag the dirty fluid triangle to locations where dirt may enter the system.

♦ Your score is shown on the righthand side.

♦ The nodding or shaking head will indicate if you are correct or incorrect.

4. Select dropdown 7 (Components sensitive to contamination review).

♦ Move the mouse over or click on each triangle to see the relevant information for that area.

5. Select dropdown 8 (Drag icons to show contamination failure points).

♦ Click on and drag the dirty fluid triangle to locations where components are sensitive to contamination failures.

6. Select dropdown 9 (Leakage or flow loss points review)

♦ Move the mouse over or click on each triangle to see the relevant information for that area.

7. Select dropdown 10 (Drag icons to show leakage points).

♦ Click on and drag the fluid leak triangle to locations where internal leakage might occur.

8. Select dropdown 11 (Heat source, high-pressure drop review).

♦ Move the mouse over or click on each triangle to see the relevant information for that area.

9. Select dropdown 12 (Drag icons to show heat source points).

♦ Click on and drag the temperature triangle to locations where a heat source would appear.

Exercise: Explain why each heat source is occurring and make a typical power loss calculation to gauge the how much energy is being lost.

10. Select dropdown 13 (Dangerous risk points review).

♦ Move the mouse over or click on each triangle to see the relevant information for that area.

11. Select dropdown 14 (Drag icons to show dangerous risk points).

♦ Click on and drag the ! triangle to locations that could be high-risk areas.

Exercise: Discuss the need to always turn off and isolate equipment and always leave in a safe condition with loads supported and safe.

12. Select dropdown 15 (Air ingress points review).

♦ Move the mouse over or click on each triangle to see the relevant information for that area.

13. Select dropdown 16 (Drag icons to show air ingress points).

♦ Click on and drag the air bubble triangle to locations where air might enter the system.

Exercise: Calculate how often the fluid is recirculated with a flow rate of 30 L/min and a 40L reservoir and two 2L total volume cylinders, extended and retracted.

Experiment 1: Over 80% of hydraulic failures are caused by contamination.

Question 1: How is contamination in hydraulic fluid measured?

Inline particle counters are relatively low cost and can monitor the fluid while the vehicle is being used. Fluid can also be removed and sent away for analysis.

Experiment 2: Fluid contaminants are generally so small that they cannot be seen by the human eye.

Question 2: What standard is used to classify how dirty the fluid is, and should be?

The latest fluid contamination standard is ISO4406

Experiment 3: Keeping hydraulic fluid clean is vital for a long, reliable, working life.

Question 3: How would you clean hydraulic fluid if it does not meet the required standard?

Pump the fluid through an external filter system until it is clean to the standard required.

Circuit diagram screen

1. Click the Home (house) button to return to the menu page.

2. Select screen 3 (How hydrostatic drive circuits work)

3. Select dropdown 6 (Learn how to check and maintain components).

♦ Move the mouse-over or click on each component to see typical maintenance instructions.

4. Select dropdown 7 (Drag icons to identify regular maintenance checks).

♦ For the first few seconds, the regular maintenance checks are displayed. Move back and forward to see them again.

♦ Click on and drag the required test meter icons for regular daily maintenance checks.

♦ Your score is shown on the righthand side.

♦ The nodding or shaking head will indicate if you are correct or incorrect.

5. Select dropdown 8 (Drag icons to identify planned maintenance checks).

♦ For the first few seconds, the planned maintenance checks are displayed. Move back and forward to see them again.

♦ Click on and drag the required test meter icons for planned maintenance checks.

6. Select dropdown 9 (Learn how to setup and commission equipment).

♦ Move the mouse-over or click on each component to see typical setup and commissioning instructions.

Experiment 1: Filter clogging indicators work by displaying the pressure drop across the filter element. As the element retains more dirt the pressure difference across it will increase.

Question 1: Will the indicator display the save reading at hot and cold temperatures?

No. Indicators can display dirty when cold but fine when the fluid is hot. Cold start levels provide a good measure of deteriorating condition.

Experiment 2: Non-contact, digital thermometers can read pipework or component temperatures without having to touch the equipment.

Question 2: Name two areas that are useful for monitoring changes in the system's condition?

Fluid reservoirs will show if the system is working outside of normal operating conditions. Pump and motor case drain line temperatures are likely to increase as the pump fails. Valve drain lines can also show if components are passing fluid when they should not be.

Circuit diagnostic exercises

1. Select dropdown 10 (Diagnose clunking noise when changing direction).

♦ Drag the test meters over each component in the same way you would test them with real instrumentation.

♦ Study the results from each meter and use this information to diagnose what might be causing the problem.

♦ When you understand the fault click on the component that should be changed to repair the fault. This is not necessarily the component where the fault appears but the one that is causing the fault to appear.

2. Select dropdown 11 (Diagnose high reservoir and case drain temperature).

♦ Drag the test meters over each component to identify the cause of the fault. As per the exercise above.

♦ Click on the component that should be repaired to stop the fault occurring.

3. Select dropdown 12 (Diagnose cavitation cracking sounds at pumps).

♦ Drag the test meters over each component to identify the cause of the fault. As per the exercise above.

♦ Click on the component that should be repaired to stop the fault occurring.

Further reading and diagnostic answers

Diagnostic answers (for after youÃÆ'¢â‚¬â„¢ve tried to find them yourselves):

a) Reservoir cleanliness is high 20/18/16. Flushing valves is likely to be sticking. Flush reservoir with external filter pack. Check/change air and fluid filters. Address any signs of pump wear. Establish why fluid is dirty and improve procedures accordingly.

b) Charge pump relief valve is operating too close to the flushing relief valve meaning less flow is going through the cooler. Re-adjust relief valves to stop flow across charging relief valve.

c) High aeration in the reservoir. Air bubble collapsing causes cracking noise. Small air leak in gear pump suction line means fluid drains from pipes when stationary, causing noise/damage at startup. Soapy water can highlight air leaks in suction lines.