A pump or compressor is only as stable as the base it sits on. A baseplate with voids under it, a foundation that was grouted before it was ready, or piping bolted up before the grout cured will show up as vibration and repeated misalignment for the life of the machine. This article is for project engineers, maintenance planners and installation teams, and covers the sequence from foundation handover to connecting the pipework.
Foundation checks at handover
Before any equipment is set, the civil contractor's foundation should be checked against the drawings:
- Dimensions and elevations of the top of concrete, allowing for the grout gap shown on the drawings
- Anchor bolt positions, projection, thread condition and protection
- Concrete age and strength: the foundation must have reached the strength required by the design before grouting
- Cracks, honeycombing or damage that need repair first
- Records: concrete test results and the as-built survey
Problems found now are cheap to fix. Problems found after grouting are not.
Anchor bolts and sleeves
Anchor bolts are often cast into sleeves so that the top part of the bolt can move slightly to suit the baseplate holes and stretch along its length when tightened. Sleeves should be clean and dry before grouting and filled or sealed as the specification requires, so that grout doesn't run into the sleeve and lock the bolt. Where bolts are installed after the concrete is cast, the anchor type, embedment and installation method follow the design and the anchor manufacturer's instructions.
Setting and levelling the baseplate
Baseplates are set on jacking (levelling) screws bearing on steel pads, or on shim packs placed beside each anchor bolt. The baseplate is levelled across the machine mounting pads, not across the frame, using a precision level, to the tolerance in the specification or the manufacturer's instructions. The underside of the baseplate must be clean, and on many specifications it is blast-cleaned and primed with a coating compatible with the grout. With jacking screws, the screw tips are greased or sleeved so they can be backed off after the grout has cured, leaving the baseplate supported by the grout rather than by point loads.
Cementitious or epoxy grout
| Property | Cementitious grout | Epoxy grout |
|---|---|---|
| Typical use | Static equipment, lower-speed machines, general baseplates | Reciprocating and high-speed rotating machinery, dynamic loads |
| Bond to concrete and steel | Moderate | High |
| Chemical resistance | Limited | Good against many oils and chemicals |
| Concrete surface condition | Pre-soaked, saturated surface dry | Dry |
| Placement limits | Fluidity and minimum gap | Pour depth and temperature limits because of curing heat |
| Cost | Lower | Higher |
Both types must be non-shrink grouts suitable for machinery, mixed and placed strictly to the manufacturer's data sheet. Temperature matters: hot weather shortens working time and cold weather slows curing, which is a real factor on South African sites in summer and on Highveld winter mornings.
Surface preparation and placing
- Remove laitance and weak concrete by chipping or scabbling until sound aggregate is exposed
- Clean off dust, oil and loose material
- Prepare the surface for the grout type: pre-soak for cementitious grout, keep dry for epoxy
- Build tight, sealed formwork with a head box on the pouring side
- Pour continuously from one side so the grout flows under and pushes air out ahead of it
- Fill until grout appears at the vent holes in the baseplate and on the far side
- Finish exposed edges as specified, usually with a chamfer
Never vibrate grout vigorously or pour from two sides at once: both trap air under the baseplate.
Curing and post-grout checks
Cure the grout as the data sheet requires, protecting it from sun, wind, rain and early loading. Once it has reached the strength the manufacturer specifies:
- Back off or remove jacking screws as the procedure requires
- Tap-test the baseplate to find hollow-sounding voids; voids are usually filled by drilling and injecting grout
- Tighten anchor bolts to the specified value
- Re-check the mounting pads for level and flatness, and check the machine for soft foot
Connecting the piping
Pipework is connected after the grout has cured and the anchor bolts are tight, never before. Each flange should meet the machine nozzle parallel and centred without force. Check alignment with indicators on the coupling while the flange bolts are tightened, then do the final alignment once all piping is connected and supported. If the shaft moves as the pipework is bolted up, the problem is in the piping or its supports, and that is where it is fixed.
How Redsafe helps
Equipment setting, levelling and grouting, and laser shaft alignment form part of Redsafe's mechanical installation scope, with ITPs compiled into QCP data books at handover. Send us the equipment list and drawings.
For general guidance only. The equipment manufacturer's instructions, the grout data sheet and the project specification govern.
