Who This Is For
If you're responsible for maintaining a fleet of Demag cranes—whether overhead, mobile, or crawler—this checklist is designed for you. I've used variations of this list on our shop floor and in the field for the last four years, reviewing over 200 crane maintenance reports annually. It's not a theoretical guide. It's what I actually check.
This works best if you have a crane that's in regular use (say, 40+ hours per week) and you're trying to decide between a deeper inspection or just a routine service. It also helps if you're comparing maintenance quotes from different service providers and want to know what's actually essential versus what's fluff.
Total steps: 5. Each one has a clear pass/fail check.
Step 1: Visual Structural Inspection
Start with what you can see. This is the step most people rush through because it feels obvious. But what you're looking for isn't just 'does it look okay.'
I check for three specific things:
- Cracks near weld joints on the main beam. Not on the beam itself—near the welds. That's where stress fractures start. If I see a hairline crack longer than 1/8 inch on an overhead crane, I flag it.
- Deformation on the runway rails. On a bridge crane, the rails take a beating. If the rail head is flattened more than 5% of its original height, that's a wear indicator. Normal tolerance is less than 3%.
- Loose or missing bolts on end trucks. This one is surprisingly common. I rejected a batch of eight end trucks in Q1 2024 because the vendor had skipped lock washers on every unit. The bolts looked tight, but without the locking mechanism, they'd vibrate loose within 200 hours.
Take photos of each area. If you can't get a clear angle with a phone camera, use a borescope or mirror.
Checkpoint
Pass: No visible cracks > 1/8 inch, rail wear < 5%, all bolts present and torqued to spec. Fail: Any of these are out of range.
Step 2: Hoist and Wire Rope Inspection
Here's something vendors won't tell you: the hoist is the most commonly underestimated wear point on a Demag crane, especially on mobile units. People assume if the hook moves and the brake holds, it's fine. The reality is different.
What I look for:
- Wire rope condition. Not just 'any broken strands.' I count them. OSHA allows up to 6 broken wires in one rope lay length for running ropes, and 3 for standing. But I've found that once you hit 4 broken strands in a single lay on a hoist rope, the degradation accelerates. If I see that, I recommend replacement within the next 30 days.
- Hoist brake free travel. On a Demag hoist, you should feel the brake engage within the first 1/4 inch of the control lever travel. If it's more than 3/8 inch, the brake lining is likely worn past 50%. The cost of replacing it now is about $150 in parts. If it fails mid-lift, the repair cost is easily ten times that.
- Hook throat opening. Measure it. If the opening has increased by more than 10% from the original spec, the hook is fatigued and needs replacement. I learned this the hard way after ignoring it once—that quality issue cost us a $22,000 redo and delayed our launch by three weeks.
Checkpoint
Pass: < 4 broken strands, brake engages within 1/4 inch, hook opening < 10% over spec. Fail: Any of these are exceeded.
Step 3: Electrical System Check (The One People Skip)
This is the step that catches most people off guard. On a Demag crane, the electrical system is robust, but the connections are where failures happen. I've rejected 12% of first deliveries in 2024 due to poor electrical connections.
I run a blind test: same crane model, one with properly torqued terminals and one with hand-tightened connections. 80% of my team identified the one with proper connections as 'more reliable' without knowing the difference. The cost increase for proper torquing? About $40 per connection point. On a crane with 6 key terminal points, that's $240 for measurably better safety.
Check these:
- Control panel terminal screws. Use a torque driver. Spec is usually 1.5 Nm. Hand-tight is often 0.8 Nm. Loose terminals cause arcing, which causes heat, which causes failures.
- Limit switch wiring. I see this wrong all the time on Demag overhead cranes. The limit switch wires should be in a flexible conduit, not zip-tied to the frame. The vibration loosens them.
- Emergency stop button. Does it lock properly? Does it require a twist to release? If it pops back up when pressed, it's faulty. Replace it. They cost about $25.
I want to say the most common failure I see is the limit switch wiring—but don't quote me on that exact number; it might be confirmation bias from the last few audits.
Checkpoint
Pass: All terminals torqued to spec, limit switch wiring in conduit, E-stop locks and requires twist release. Fail: Any terminal is hand-tight or E-stop doesn't lock.
Step 4: Operational Load Test (Under Full Load)
This is where you separate maintenance from real assurance. Don't skip this step just because the crane 'seems fine' during no-load operation.
I run a load test at 100% of the crane's rated capacity. If I can do it at 110% (under controlled conditions), even better. The standard procedure:
- Lift the test load slowly — about 6 inches off the ground.
- Hold for 2 minutes. Listen for any unusual sounds from the hoist, the gearbox, or the brake. A whining sound from the gearbox often indicates low oil, which costs almost nothing to top up but can cost thousands if ignored.
- Check for drift. Does the load stay in place? If the hook drops more than 1/4 inch in those 2 minutes, the brake is slipping. That's a fail right there.
- Trolley travel under load. Move the load horizontally along the bridge. Listen for grinding in the wheels. If you hear it, check the wheel flanges—they might be worn unevenly.
After 5 years of managing maintenance for our facility, I've come to believe that the load test is the single most revealing check, but it's the one people skip most often because it requires setup time.
Checkpoint
Pass: Load holds steady, no unusual sounds, no drift > 1/4 inch. Fail: Drift > 1/4 inch, any unusual mechanical noise.
Step 5: Documentation and Service History Review
Most people stop after the physical checks. The fifth step is about the paperwork—and I've rejected maintenance sign-offs because the documentation didn't match the physical inspection.
Check these:
- Service logs. Do the dates match the hours of operation? If a crane was serviced on June 1st but logged 400 hours by July 1st, someone didn't record the actual operating hours. This is a red flag for poor record-keeping.
- Part numbers. Are replacement parts genuine Demag or aftermarket? I don't automatically disqualify aftermarket parts, but I verify that they meet OEM spec. If the part number doesn't match a Demag cross-reference, I flag it. That's a quality issue I've caught more than once — a $200 counterfeit motor cost us a $5,000 crane downtime.
- Latest inspection certificate. Is it signed by a qualified inspector? Does it include the date, the crane serial number, and the specific tests performed? If any of these are missing, it's not a valid inspection.
Then again, I'm probably more paranoid than most about documentation. But I've never had to retract a rejection because the paperwork was correct. It's saved us from larger issues.
Checkpoint
Pass: Service logs match operating hours, replacement parts are verified, inspection certificate is complete. Fail: Missing dates, unverified aftermarket parts, or incomplete certificate.
Common Pitfalls and What They'll Cost You
Based on what I've seen, here are the most common mistakes and their real costs:
- Skipping the load test. The most expensive shortcut. A failed brake mid-lift on a 10-ton Demag overhead crane costs about $8,000 in repair, plus lost production time. The load test takes 15 minutes.
- Ignoring limit switch wiring. I've seen three cranes where the limit switch came loose and the crane operator couldn't stop the hoist at the top. The damage to the roof structure was about $12,000. The fix was a $30 conduit clamp.
- Trusting the 'ballpark' quote. When you get a maintenance quote that's 20% lower than everyone else, ask what's NOT included. That 'low' price might cover only basic lubrication, not the inspection steps above. The hidden cost is the rework later.
Bottom line: If your inspection covers these five steps, you'll catch about 90% of the reliability issues before they become costly failures. I'd start with Step 1 and Step 3 if you only have an hour. If you have two hours, do all five. The certainty is worth more than the time it saves.
