In incidents of heavy machinery breakdowns, downtime costs can rack up in hours. Industrial equipment maintenance is extremely sensitive since manufacturing depends on machines without which they fail, to do so quick and effective repair solutions are a must. In-situ crankshaft grinding and Onsite rotor shaft fixes are two important repair processes that are applicable to multiple industries.
Both these drivers are helping organizations avoid costly disassembly, transportation and extended downtimes, and are therefore incredibly popular in sectors like power generation, marine, manufacturing and oil and gas.
This blog aims to help Industrial Managers, Maintenance Heads, and Plant Operators in knowing the differences, advantages, processes, and applications of the two.
This blog provides insights into making a coherent decision on the best repair method choosing by comparing In-situ crankshaft grinding and Onsite rotor shaft fixes considering specific machinery, downtime tolerance and repair budget.
What is In-situ Crankshaft Grinding?
In-situ crankshaft grinding is a procedure involved in repairing a crankshaft at the site of treatment without the need of removing the crankshaft from the engine block or machines.
Portable grinding machinery designed for onsite grinding can be performed for the restoration of crank shaft size, correcting alignment, and the removal of surface imperfections, without extensive disassembly.
The Latin term “in-situ” translates, literally, to “in place” – so the term refers to the repair done at the location at which the equipment is installed.
Process of In-situ Crankshaft Grinding
The in-situ Crankshaft grinding process is a systematic and precision-centric workflow, which encompasses the following:
- Crankshaft Inspection — First Steps: Engineers check the crankshaft for cracks, wear, surface damage, or misalignment. Tools such as micrometers and laser alignment systems measure the true condition of the crankshaft.
- Specific to Interference Internal Combustion Engines: Align Check — When grinding happens, the alignment on the crankshaft and joining parts are checked.
- In-Situ Crankshaft Grinding – A portable crankshaft grinding machine is placed on the crankshaft. This devices can spin and mill the shaft while the engine itself still exists.
- Grinding Operation: Precise and controlled removal of material brings the crankshaft back to proper shape, size, and surface finish.
- Final Check: Engages engineers to reset tolerances to ensure crankshaft meets OEM (Original Equipment Manufacturer) specifications.
Testing: In testing (after the repair process), the crankshaft ran smoothly.
Benefits of In-situ Crankshaft Grinding
Downtime Reduction
The major benefit of In-situ crankshaft grinding is no need for full engine disassembly.
Conventional crankshaft repairs involve removing the crankshaft, transporting it to a machine shop, getting it repaired and reinstalling it — a process that can stretch over weeks. On the other hand, In-situ crankshaft grinding saves this time down to merely days.
Cost Savings
Using no disassembly, no heavy lifting, and no out-sourcing of machining, companies can save thousands of dollars on labor cost as well as transport and logistics costs.
RA Power Solutions claims that this in-situ crankshaft grinding reduces the overall cost of crankshaft repair by as much as 60%.
Precision Repairs
Conventional onsite grinding tools produce sub-return to zero accuracy and ensure that the crankshaft meets manufacturer specifications. Portable equipment can even measure to tolerances of 0.02 mm.
Suitable for Large Equipment
In-situ crankshaft grinding is especially applicable to marine vessels that have large engines or pipes, as well as power plants and manufacturing setups, where removing the engine is often impractical or costly.
Limitations of In-situ Crankshaft Grinding
- Requires highly skilled technicians.
- Not suitable for severely damaged crankshafts requiring welding or metal spraying.
- Space constraints inside engine rooms may limit equipment access.
What are Onsite Rotor Shaft Fixes?
Onsite rotor shaft repairs are repair methods used to fix rotors shafts of turbines, compressors, and other rotating machinery at the same location as the equipment.
In such cases the fixes mostly include rotor shaft grinding and journal repair, metal spraying and dynamic balancing amongst others.
Process of Onsite Rotor Shaft Fixes
Onsite rotor shaft fixes process includes:
- Condition Assessment: Engineers utilize state-of-the-art measurement tools to evaluate shaft wear, scoring, and alignment problems.
- Portable Grinding and Balancing Equipment Layout: Precision portable grinding and balancing machinery framework surrounding rotor shaft.
- In the controlled grinding process, the geometry of the shaft is restored and the wear is removed, restoring the surface finish.
- Balancing: Every grinding process is followed by a dynamic balancing to guarantee vibration-free operation.
- Alignment: Laser alignment tools help verify coupled component concentricity.
Testing: Vibration and thermal analysis assures trouble free operation.
Benefits of Onsite Rotor Shaft Fixes
Minimized Downtime
Since Onsite rotor shaft repairs & fixes do not involve the removal of rotor, repairs are completed much faster as compared to traditional offsite repairs.
Significant Cost Reduction
Moving substantial rotors is very costly. Onsite rotor shaft repairs eliminate these expenses completely.
High Precision Repairs
According to various sources, onsite rotor shaft fixes achieve tolerances as low as 0.01 mm, ensuring industry-standard accuracy for high-speed rotors.
Limitations of Onsite Rotor Shaft Fixes
- Environmental factors (dust, humidity) can affect precision.
- Requires highly experienced technicians.
- In cases of deep scoring or fractures, grinding alone may not be enough — metal spraying may be required.
Key Differences Between In-situ Crankshaft Grinding and Onsite Rotor Shaft Fixes
| Aspect | In-Situ Crankshaft Grinding | Onsite Rotor Shaft Fixes |
|---|---|---|
| Application | Crankshafts in engines | Rotor shafts in turbines, compressors |
| Transport required | No | No |
| Downtime | Minimal | Minimal |
| Precision tolerances | 0.02-0.05 mm | 0.01-0.02 mm |
| Typical industries | Marine, power generation, manufacturing | Power plants, oil & gas, manufacturing |
| Cost savings | Significant | Significant |
| Additional processes | Metal spraying if needed | Balancing, alignment verification |
Which Repair Method is Best?
Factors to Consider
- Machinery type: In-situ crankshaft grinding for engines having a crankshaft having rotatable machinery Onsite rotor shaft fixes The crankshaft has a shaft that rotates within a cylindrical cavity.
- Damage Grade: Shallow damage can be removed using either method, but deep damage may need further processes.
- Downtime Tolerance: Both have rapid repair, but rotor fixes for turbines may be slightly faster.
Case Study Example
Background
A global shipping company that ran a fleet of container vessels experienced a critical mechanical failure on a ship in its fleet while it was docked in a port.
The crankshaft journal experienced excessive damage as a result of lubrication failure and minor misalignment to the rotor shaft associated with the marine propulsion system.
The company offered two options for repair, in-situ crankshaft grinding for the crankshaft and onsite rotor shaft fixes for the rotor. In this case study, we look into the company’s steps and successfulness of either repair method.
Problem Statement
The ship was scheduled to deliver an important cargo, and its downtime would incur heavy penalties from late delivery and operational disruptions.
The scoring and surface irregularities on the damaged crankshaft journal were so bad that it would require repair as close to OEM specs as possible.
The rotor shaft misalignment created vibrations that may lead to additional damage if the vibration is not addressed.
There were two primary obstacles for the company:
- Reducing down time for no delays.
- Make sure repairs are high quality to ensure operational reliability.
Approach
In-Situ Crankshaft Grinding
To fix the damage to crankshaft journal, the company chose in-situ crankshaft grinding. A specialist team mobilized portable grinding equipment with customizable high-precision machining capabilities, capable of being performed in situ.
Steps Taken:
- Non-destructive testing (NDT) methods were used to evaluate the wear extent on the damaged crankshaft journal.
- Engine block by portable grinding and re-established the journal surface dimensions.
- Post-repair measurements verified adherence to OEM tolerances to ensure proper fix.
Onsite Rotor Shaft Fixes
To fix the rotor shaft misalignment, a field repair crew utilized laser alignment and portable machining equipment.
Steps Taken:
- It was also examined for rotor shaft wear, rotor shaft alignment and rotor shaft structural integrity.
- Movement and intervention were informed by laser alignment tools.
- Portable machining tools were used to eliminate surface wear and realign them.
- Last minute checks were done to make sure everything was functioning.
Results
In-Situ Crankshaft Grinding
- Time Saving: The crankshaft was repaired, within 48 hours, as opposed to weeks estimated for workshop repairs.
- Cost Saving: It saved around 60% in terms of cost as there was no need for transportation and the disassembly/ reassembly costs would be eliminated.
- Precision: After the crankshaft was repaired, it was measured and confirmed to be within OEM specifications, providing confidence in the engine.
Conclusion
In-situ crankshaft grinding and Onsite rotor shaft repairs are essential repair techniques for industries that operate large and expensive machinery. Each is optimal for specific machines and types of repairs, and has unique benefits.
Recognizing these differences and consulting with experienced service providers can help organizations identify when minor maintenance is appropriate, saving valuable resources.
FAQs
In in-situ crankshaft grinding, it is only for engine crankshafts, while Onsite rotor shaft fixes applies for turbines and compressors.
Onsite rotor shaft fixes may be faster in specific high speed rotors, but both solutions have minimal downtime.
Yes, both slashed transport and disassembly costs
Rare, because crankshafts and rotor shafts are doing different things.
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