Planning, foundations and cost
The best alignment job is decided before the machine arrives. A sound base, a pipe that does not pull, and a plan for the first start give you an alignment that stays.
Foundation and baseplate
| Item | Good practice |
|---|---|
| Base stiffness | A heavy, stiff base resists distortion. Thin skids and light tube frames flex when bolts tighten |
| Flatness | Mounting pads machined or ground flat and in one plane. Check with a straightedge before the machine goes down |
| Grouting | Fill the baseplate with grout so it carries the load evenly. An empty or partly filled plate rocks |
| Pipe and conduit | Connect pipework last. Check that flanges meet without force, and re-check alignment after each connection |
| Bolt holes | Centre the machine in its holes so it can move both ways |
| Jacking points | Weld or bolt in jacking blocks before the machine is set, not afterwards |
Pipe strain
Take the pipe flange bolts off and watch an indicator on the shaft. If the shaft moves more than about 0.05 mm (2 mil), the pipe is pulling the machine. Fix the supports and the flange fit, not the alignment.
When to check alignment
- At installation, before and after the pipework.
- After any repair that touches the feet, the bearings or the coupling.
- After the first week of running, when a new base settles.
- On a schedule that fits criticality. Many sites check every year on critical machines and after any vibration alarm.
- After a change in operating temperature or load.
What does it cost, and what does it save?
The figures below come from published studies and trade reports. They are reported values, not guarantees, and your plant will be different.
| Item | Reported range | Notes |
|---|---|---|
| Energy | About 1% to 10% less power after precision alignment | Large variation; measure your own before and after |
| Bearing and seal life | Often reported as several times longer | Depends on how bad the starting point was |
| Alignment job | From under an hour for a small pump to a day or more for a train | Most of the time goes on soft foot and hardware, not on the readings |
| Tool | Dial set, straightedge, or laser system | A laser system pays for itself on repeat work |
How to justify it
- List the machines that fail most often on bearings, seals or couplings.
- Take a quick vibration reading and a coupling check on each.
- Pick the worst three and do them properly.
- Record the before and after vibration, temperature and the following 12 months of repairs.
- Use that record, not a generic figure, to decide on the rest.
Skills and standards
Alignment is a skill. A trained technician with a simple tool beats an untrained one with an expensive tool. Write a plant standard for tolerances, thermal offsets, shim practice and records, so every job is done the same way.
Questions
How often should shaft alignment be checked?
At installation, after repairs, after pipework changes and on a schedule that matches criticality. Many sites check critical machines yearly and after any vibration alarm.
How do I know if pipe strain is moving my machine?
Loosen the pipe flange bolts with an indicator on the shaft. More than about 0.05 mm (2 mil) of movement means the pipe is pulling the machine.
Is precision alignment worth the cost?
For machines that repeatedly fail on bearings, seals or couplings, usually yes. Measure before and after on a few machines and decide from your own results.
Does grouting matter for alignment?
Yes. A baseplate that is not fully grouted can rock and distort, and alignment will not hold.
General good practice for horizontal machines driven through a coupling. The machine maker's manual, the coupling data and your site standard come first. Lock out and isolate the machine before any alignment work.