Damage found on arrival: transport, offloading and storage

A centrifugal fan leaves the works assembled, balanced and run-tested. Between that test bench and its first start on your foundation it is lashed to a truck, lifted two or three times, sometimes trans-shipped, and often parked in the open for weeks. Much of what a fan suffers, it suffers in that window. This guide is about finding that damage before you energise the motor.

What you're seeing

Two quite different presentations.

Visible mechanical damage — no run needed. A dented or crushed motor/fan cover. A bent silencer section. A deformed inlet cone. A torn expansion bellow. A cracked mounting foot, a bent shaft guard. Thin sheet-metal accessories are the first casualties because they protrude and they are light — the pressure casing and the rotating core usually survive what the cover does not. Rust bloom on machined faces and shaft extensions after weeks of unprotected outdoor storage belongs here too.

Consequential dynamic symptoms on start-up. The unit runs, but not as it did on the test bench: broadband noise, a scrape or rub, elevated vibration, running current above nameplate FLA with no process change, or motor protection tripping on start.

Reach for numbers early, and state the mounting when you quote them. Vibration acceptance to ISO 14694, general-purpose category BV-3:

Two more thresholds worth having in the notebook: bearing-housing temperature rise above roughly 40 °C over ambient, and oil weep at a plummer block. Balance grade is a separate question under a separate standard — ISO 21940, G6.3 typical for this class of rotor.

What it usually means

Ranked by how often it turns out to be true in the field:

1. Rough loading, road shock or rough offloading — an unsecured load, or a forklift/crane lift taken on the wrong points.
2. Inadequate packaging — thin components shipped without crate, frame or edge protection.
3. Installation handling — slinging on the shaft, cone or guard instead of the lifting lugs; commissioning on an incomplete structural support.
4. Foreign object ingress during open handling — hardware, packing material or debris left inside the casing.
5. A dimensional or forming error at build — less common, but it exists, and it presents identically to a handling-induced rub. A rotating run test will not reveal a static dimensional error, so "it passed the run test" is not a licence to book everything as transit damage. Confirm the mechanism.

How to diagnose it

Isolate first. Lock out and tag out the motor supply, confirm dead, let the impeller come to rest. Nothing below needs a running machine until step 8.

1. Do not start the fan. Photograph it as-found from all sides — packaging remnants, crate, lashing, and the trailer bed if it is still on it. These photographs are your only evidence and they exist for about ten minutes.
2. Compare against dispatch photographs. The works' dispatch photographs against the transporter's delivery photographs is the one comparison that decides transit versus site. Ask for both, in writing, on the day.
3. Visual and tactile survey: covers, cone, silencer, bellow, foot and base, guards, terminal box. Crush and scrape marks have a direction — read them like a crash investigator. They place the impact at loading, in transit, or at unloading.
4. Turn the impeller by hand. Free rotation with no scrape rules out a gross jam. A rub, hard spot or catch means clearances and shaft straightness next.
5. Measure the inlet-cone-to-impeller-ring gap at 4–8 points around the periphery with feelers and compare against the GA drawing. An uneven or closed gap is a rub source — but do not assume handling caused it: check impeller-ring runout with a dial gauge on the same setup before you decide.
6. Check mounting and support. Is the fan on its designed structural support, levelled, grouted and bolted? An unsupported fan strains the flexible connection and the bearing pedestals.
7. Alignment and drive. Recheck coupling alignment, or sheave alignment and belt tension, after any road move. Both shift with road shock.
8. Run test with a vibration meter — only once 1–7 are clear. Readings at each bearing, horizontal / vertical / axial, against the factory run-test figures on the test certificate. A clean factory reading with a rough site reading tells you the fault entered downstream of dispatch. A rough reading with a good cone gap and good runout points at bearings, balance or a bent shaft instead.
9. Foreign-object check for any jam complaint: open the inspection door and look inside the casing before turning anything.

One misdiagnosis to avoid: blaming ducting (system effect) or condemning bearings when a clearance rub — broadband noise plus a strong 1× line — is staring at you. Confirm the mechanical clearance first. Ten minutes, and it settles the argument.

The usual root causes

Transport and handling — Unsecured load, road shock: thin covers and silencers dent or crush; confirm by crush direction plus a dispatch photograph showing the part intact. Rough offloading: bent cones, cracked feet, disturbed coupling, with impact marks at the lift and contact points. No crate or edge protection: protruding light parts take the hit. Handling that closes a running clearance: cone-to-impeller-ring rub, presenting as noise and vibration — confirm by gap measurement against the drawing, after ruling out runout. Typical of the pattern: on a 4,250 CMH / 1,220 mmWC / 40 HP blower for a pharma process-equipment OEM, the silencer and motor cover arrived crushed while the casing and rotor were untouched.

Installation — Erection or storage without the structural support: bellow tear, plummer-block leak, base strain. A 91,800 CMH / 178 mmWC / 100 HP project fan on an oil-and-gas site, run roughly a year on incomplete supports, tore its expansion bellow and wept oil at the plummer block. That is an installation finding, and it is preventable. Improper slinging: local deformation, sling marks visibly off the lifting lugs. Reassembly of transport-split parts done wrong: a misaligned cover or silencer forcing a rub.

Commissioning — starting before the cone gap, hand rotation and alignment have been re-verified post-transport. That converts a repairable deformation into a wrecked impeller in about four seconds.

Operation and process — rarely the origin, but a handling-induced rub left uncorrected accelerates into bearing and impeller wear, and eventually motor tripping.

Maintenance and wear — damage during shifting for maintenance, or a refit after service with no re-check of clearance and alignment. Same mechanism as install-stage handling; it just happens later.

How to fix it

• Crushed cover, guard or silencer section: one-to-one replacement, frame-sized to the motor nameplate. Recover cost from the transporter where transit fault is proven on photographs.
• Deformed inlet cone or closed clearance: fabricate and fit a new cone. Do not field-bend a hot-formed cone — it will not take the form, and it cracks. Re-measure the gap and re-run vibration afterwards.
• Torn bellow or plummer-block weep from unsupported mounting: install the designed support structure first, then replace the bellow, re-seat and re-seal the plummer block, recheck alignment, and only then hand back.
• Impeller damage or jam: clear the foreign object; if the impeller is bent or cracked, replace it — balanced to ISO 21940 and run-tested, not straightened in situ.
• Motor damage: for IE-class motors, route the repair through the OEM-authorised service centre. The local rewind is faster and it costs you the efficiency class you paid for.
• Surface rust from storage: clean back and re-coat before assembly, not after.

How to stop it coming back

• Package for the road, not the shed. Crate or frame every unit; edge-protect and separately box the thin parts. Block the impeller against free rotation in transit on direct-drive units.
• Photograph at both ends. Dispatch photographs from the works, delivery photographs from the transporter. Two minutes, and it settles liability in one comparison.
• Ship lifting and storage instructions with the unit — designated lifting points, "do not sling on shaft, cone or guard," "do not commission without the structural support in place."
• Post-transport pre-start check in the commissioning SOP: cone gap against the GA, hand-rotate the impeller, recheck alignment and belt tension, confirm the support structure is complete — before first start.
• Inspect and report within 48 hours of receipt. Damage reported on the day is a transporter claim; damage reported after eight weeks in the yard is an argument.
• Store under cover, on dunnage, inlet and outlet blanked — a tarpaulin and two sleepers prevent most storage damage. Brief the freight agency on top-heavy, clearance-sensitive equipment, and insure export shipments accordingly.

When to call a specialist

Jitamitra services fans of any make, not only our own. If a unit arrives damaged, or comes up rough after a shift and you would rather have the diagnosis than the argument, we do on-site vibration diagnosis and balancing, bearing and coupling replacement, clearance and alignment correction, and re-rating where the duty has moved. Performance is verified to IS 4894 / ISO 5801 / AMCA 210 method; our quality system is certified to ISO 9001:2015, and CE / ATEX (Zone 2/22) conformity is self-declared.

Contact: sales@jitamitrablowers.com · Jitamitra Help Desk +91 83291 72325.

— Jitamitra Electro Engineering · Technical Services

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