Target Audience
Maintenance Technicians, Service Engineers, and Automation Specialists working with ABB IRB 6700 robots.
Introduction: The Critical Final Check
You've just completed a motor replacement or gearbox refit on an ABB IRB 6700 – a complex task requiring precision and care. Before you refill the oil and return the robot to its demanding duties, there's one crucial step you absolutely cannot skip: the leak-down test. While seemingly simple, this test is the unsung hero of post-repair validation, safeguarding the integrity of your seals and preventing potentially costly future failures. This article goes beyond the basic manual steps to explain why this test is vital, how to perform it correctly and safely, and what to do based on the results.
Why is the Leak-Down Test Non-Negotiable?
The primary purpose of the leak-down test after a motor or gearbox repair is to verify the integrity of all seals enclosing the gearbox oil. Even minor imperfections during reassembly – a slightly misaligned seal, incorrect torque on a bolt, or microscopic damage – can lead to oil leaks.
Skipping this test can have significant consequences:
Oil Leakage
The most obvious outcome, leading to contamination of the work area, potential environmental hazards, and slippery conditions.
Component Damage
Insufficient oil due to leaks will cause increased friction, overheating, and premature wear or catastrophic failure of expensive gearbox components and bearings.
Downtime
An undetected leak will inevitably lead to future breakdowns, resulting in unplanned downtime far more costly than the time taken for the leak-down test.
Process Contamination
In sensitive applications (e.g., food processing, cleanrooms), leaking oil can contaminate products or the environment.
Warranty Issues
Failure to perform post-repair checks correctly might impact warranty claims if a related failure occurs later.
Where Does the Leak-Down Test Fit in the Repair Workflow?
Understanding the sequence is crucial for efficiency and effectiveness. The leak-down test should be performed:
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1
After the mechanical reassembly of the motor or gearbox is fully complete, including the final torquing of all relevant mounting bolts.
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2
Before refilling the gearbox with lubricating oil. Performing the test with air is cleaner and makes leak detection with spray much easier than trying to spot oil seepage.
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3
Before reconnecting complex wiring harnesses or auxiliary equipment that might obstruct access to potential leak points for spraying and inspection.
Performing the test at this specific juncture ensures that if a leak is detected, disassembly for correction is minimally disruptive.
When is the Test Required?
As the manual states, the leak-down test must be performed:
Mandatory Test Scenarios
- After refitting any motor.
- After refitting any gearbox.
Essentially, any time the oil-containing cavity of a gearbox has been opened and resealed, this test is mandatory before proceeding (e.g., before refilling oil).
Essential Equipment
You'll need specific tools for this test:
Leak-Down Tester
(e.g., ABB Part No. 3HAC0207-1)
This specialized tool allows you to apply a controlled, low pressure air supply to the gearbox. It typically includes a pressure gauge and regulator.
Leak Detection Spray
A surfactant solution (like soapy water in a spray bottle, though dedicated sprays are often better) used to visually identify the source of leaks by forming bubbles.
Compressed Air Source
A clean, regulated air supply, free from excessive moisture or oil that could contaminate the gearbox interior.
Safety First: Handle With Care!
Pressurizing the gearbox, even at low levels, requires caution:
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Pressure Limit is CRITICAL: NEVER exceed 0.25 bar (25 kPa). Over-pressurizing can permanently deform or damage seals, potentially creating leaks or compromising the seal's long-term integrity. Apply pressure slowly and monitor the gauge carefully.
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Prior Safety: Ensure all electrical, hydraulic, and pneumatic power was properly locked out and verified before starting the repair work that necessitated this test.
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PPE: Always wear safety glasses during the test to protect against potential spray or debris.
Step-by-Step Guide to Performing the Leak-Down Test
Follow these steps meticulously:
Complete Component Refitting
Ensure the motor or gearbox you serviced is fully reassembled and all fasteners are torqued according to the specific repair procedure specifications. Do not proceed if the refit is incomplete.
Access the Oil Plug
Identify and carefully remove the topmost oil plug on the specific gearbox being tested. (Using the topmost plug ensures you are pressurizing the air cavity above the potential oil level). Clean the port area.
Connect the Tester
Attach the leak-down tester fitting to the oil plug port, ensuring a good seal. If necessary, connect regulators included with the tester kit to your compressed air line.
Apply Pressure CAUTIOUSLY
Slowly open the air supply and use the tester's regulator knob to gradually increase the pressure inside the gearbox. Monitor the gauge constantly. STOP increasing pressure immediately once you reach 0.2 - 0.25 bar (20 - 25 kPa). DO NOT EXCEED 0.25 BAR.
Isolate the System
Once the target pressure is reached and stable on the gauge, disconnect the compressed air supply from the leak-down tester. This isolates the gearbox, allowing you to observe if it holds the applied pressure.
Wait and Observe
Let the system sit undisturbed for 8 to 10 minutes. Carefully monitor the pressure gauge on the leak-down tester during this period.
Interpret the Results
Success
If there is no noticeable pressure drop after 8-10 minutes, the seals are considered intact. Proceed to remove the leak-down tester and refit the oil plug (using appropriate torque and sealant if required). The test is complete. You can now proceed to the next step, which is typically filling the gearbox with the correct type and quantity of oil.
Failure
If the pressure drops significantly during the waiting period, a leak exists. Proceed to step 8.
Localize the Leak (If Pressure Dropped)
- Reconnect the air supply and maintain the pressure at ~0.2 bar.
- Generously apply the leak detection spray to all potential leak points:
- The main seal/interface between the motor and gearbox (a very common area for leaks if assembly wasn't perfect).
- Any mating surfaces, gaskets, or covers that were disturbed during the repair.
- Around all oil plugs (fill, drain, level), including the one where the tester is fitted.
- Seals around output shafts or flanges.
- Look closely for bubbles forming, which indicates the exact location of the air leak. Be patient, as small leaks might form bubbles slowly.
Correct the Leak
Once the leak source is identified, you must:
- Safely release the pressure and remove the leak-down tester.
- Disassemble the necessary components again.
- Carefully inspect and replace the faulty seal, gasket, or O-ring. Ensure mating surfaces are perfectly clean, free of scratches or old sealant, and that components (like seals) are correctly oriented and seated. Re-check fastener torque values.
- Re-run the entire leak-down test from Step 1 after correcting the potential issue. Do not assume the leak is fixed without re-verification.
Leak-Down Test Process Flow
Troubleshooting Common Leak-Down Test Failures
If your leak-down test fails, consider these common culprits during your inspection and re-repair:
Seal Damage During Installation
This is perhaps the most frequent cause. Seals (especially lip seals or O-rings) can be easily nicked, cut, or rolled during assembly if not properly lubricated or if forced over sharp edges or threads without protection.
Solution: Always use new, undamaged seals specified for the application. Lubricate appropriately and use protective sleeves or tape over potential snag points during installation.
Contamination on Sealing Surfaces
Even tiny particles of dirt, debris, old gasket material, or metal shavings trapped between mating surfaces or under a seal can create a leak path.
Solution: Meticulous cleaning of all mating surfaces before reassembly is paramount. Use lint-free cloths and appropriate solvents if necessary.
Incorrect Seal Seating/Orientation
Some seals are directional or must sit perfectly square in their groove. An improperly seated or reversed seal will not function correctly.
Solution: Double-check the orientation and ensure the seal is fully and evenly seated in its designated groove or bore before mating components.
Damaged Mating Surfaces
Scratches, gouges, or corrosion on the surfaces where the seal makes contact can prevent a proper seal.
Solution: Inspect surfaces carefully. Minor imperfections might sometimes be polished out, but significant damage often requires component replacement.
Incorrect Fastener Torque
Under-torqued bolts may not provide enough clamping force to compress gaskets or hold components securely. Over-torqued bolts can distort housings or damage threads.
Solution: Always use a calibrated torque wrench and follow the specific torque values and tightening sequences outlined in the ABB repair procedures.
Using Old or Incorrect Seals/Gaskets
Reusing old seals or gaskets is generally not recommended, as they may have taken a permanent set or suffered invisible damage. Using the wrong part number, even if it looks similar, can lead to failure.
Solution: Always use new, correct ABB-specified replacement seals and gaskets for the specific component being repaired.
The Importance of Cleanliness (Beyond the Test)
While cleaning mating surfaces just before assembly is vital, maintaining a clean working environment throughout the entire repair process significantly reduces the risk of contamination-related leaks.
Clean the Exterior First
Before disassembling any gearbox component, thoroughly clean the exterior of the robot around the work area to prevent dirt from falling into open cavities.
Protect Openings
Immediately cover any open ports or cavities with clean, lint-free cloths or appropriate caps/plugs after disassembly to prevent ingress of contaminants.
Clean Tools
Use clean tools. Avoid transferring grease or debris from other jobs onto sensitive gearbox components.
Handle New Parts Carefully
Keep new seals and bearings in their protective packaging until the moment of installation. Handle them with clean hands or gloves.
Important Considerations & Pro Tips
Temperature Fluctuations
As noted in the manual, a significant temperature difference between the compressed air and the gearbox can cause minor pressure fluctuations (increase if air is warmer, decrease if colder). Allow components to normalize to ambient temperature as much as possible before testing for best results. Minor, stabilizing fluctuations are usually acceptable; a continuous, steady drop indicates a leak.
Thorough Spraying
When searching for leaks, be systematic. Spray generously and observe carefully. A flashlight and sometimes a small mirror can help inspect hard-to-see areas.
Listen
Sometimes, a significant leak can produce an audible hiss, helping to pinpoint the general area before spraying.
Documentation
Always document the successful completion of the leak-down test in your maintenance logs for the specific robot and component repaired. Include date, technician, component repaired, and test result (Pass/Fail, pressure held). This provides a crucial record of proper procedure adherence and aids future troubleshooting.
Conclusion: Protecting Your Investment
The leak-down test is a fast, simple, yet indispensable procedure for ensuring the long-term health and reliability of your IRB 6700 robot after motor or gearbox repairs. By verifying seal integrity before refilling oil and returning the robot to service, you prevent leaks, protect expensive components from lubrication starvation, avoid unplanned downtime, and maintain a safe working environment. Don't let this crucial final check become an oversight – make it a standard, non-negotiable part of your post-repair workflow. A few minutes spent here, backed by meticulous assembly practices, can save hours, or even days, of costly corrective action later.
Related Resources
Checking IRB 6700 Gearbox Oil Levels (Axes 1-6)
Visual guide for routine maintenance of gearbox oil levels across all axes.
Replacing the Axis Motor on Your IRB 6700
Step-by-step guide for motor replacement procedures.
IRB 6700 Maintenance Schedule & Component Life
Essential maintenance timeline and component lifespan information.