A transformer radiator selected only by the transformer's MVA rating may provide insufficient cooling during hot, full-power hours. This can restrict electricity export or trigger temperature alarms.
Begin comparisons with confirmed transformer losses, site conditions, and an approved equipment layout.
Define Transformer Heat Losses and Solar Plant Operating Conditions
Request the transformer's no-load losses, load losses, ambient temperature range, altitude, and operating profile.
Solar output and reactive-power support requirements can both affect transformer current and the resulting losses.
Consider an illustrative transformer with the following characteristics:
| Parameter | Assumed value |
|---|---|
| No-load losses | 3 kW |
| Load losses at rated current | 27 kW |
| Operating current | 80% of rated current |
The estimated total losses at 80% rated current are:
Total losses = 3 + (0.8² × 27) = 20.28 kW
At rated current, total losses rise to 30 kW.
This calculation holds the loss reference temperature constant. Temperature changes and harmonic effects require separate consideration.
These figures do not directly determine radiator size. The transformer designer must allocate heat rejection between the tank and cooling equipment, then evaluate the complete installation.
Select the Cooling Arrangement and Required Heat Dissipation Capacity
For a power transformer radiator, confirm whether the transformer uses ONAN or ONAF cooling.
| Cooling arrangement | Oil circulation | Air movement |
|---|---|---|
| ONAN | Natural | Natural |
| ONAF | Natural | Forced by fans |
When comparing transformer radiator types, check that the connection arrangement, panel geometry, and space for fans suit the transformer design.
Request cooling performance data that state the oil temperature, ambient temperature, airflow conditions, and surface finish. Similar-looking assemblies may have been rated under different conditions.
If fans are required, agree on their controls, auxiliary power supply, and maintenance access. Also establish the transformer's permissible loading when forced cooling is unavailable.
Match Radiator Dimensions, Flanges, and Connection Centres
A radiator may bolt into position while obstructing a valve or maintenance access. Review its drawing against the complete transformer arrangement.
Check the following details before approving fabrication:
| Item | Details to confirm |
|---|---|
| Overall dimensions | Height, width, and installed projection |
| Panels | Number, dimensions, and spacing |
| Headers | Diameter and connection arrangement |
| Flanges | Dimensions, bolt-hole pattern, and orientation |
| Connection centres | Distance between upper and lower connection centres |
| Handling provisions | Lifting points, supports, and transport restraints |
| Maintenance access | Clearance around isolation valves and removable connections |
Connection centre distance is not the radiator's overall height.
For pressed steel radiators for transformers, confirm that lifting and transport arrangements protect the panels from deformation.
Replacement orders require measurements from the existing installation. Photographs can reveal obstructions, but they cannot replace an approved fabrication drawing.
Assess Airflow, Panel Spacing, and Dust Exposure
Dust accumulation between panels can obstruct airflow and reduce heat transfer. A desert solar plant therefore needs a practical cleaning arrangement alongside the cooling assessment.
Do not assume that adding more panels within the same footprint will increase cooling capacity. Narrow panel spacing, nearby obstacles, and fan positioning can restrict airflow.
Review the radiator banks in relation to fences, acoustic screens, buildings, and adjacent equipment.
Provide access to inspect and clean both sides of each bank.
Any roof or shading structure also needs review by the transformer designer. It may reduce direct sunlight while obstructing the upward movement of heated air.
Compare Painted and Hot-Dip Galvanized Finishes for the Site Environment
Describe the actual exposure before selecting a finish. Relevant conditions include inland dust, coastal salt, industrial pollution, humidity, and combinations of these factors.
A coastal installation may justify hot-dip galvanizing or a duplex system-a compatible paint coating applied over galvanized steel.
For painted radiators, specify:
- Surface preparation.
- Coating products.
- Dry film thickness.
- Curing requirements.
- Repair procedures.
Dry film thickness means the thickness of the coating after drying.
For galvanized radiators, identify the applicable standard, coating acceptance criteria, and treatment of mating surfaces.
Neither finish alone establishes cooling performance. Request thermal data applicable to the selected finish and confirm that any internal coating is compatible with the insulating liquid.
Review Materials, Weld Quality, and Internal Cleanliness
Ask transformer radiator manufacturers to identify the steel grades and thicknesses used for panels, headers, flanges, and supports. Require approval of material substitutions before production.
Review how the factory controls panel seam welding, header joints, distortion, and weld repairs.
Automatic welding supports consistent production, but inspection must also cover manually welded connections and attachments.
Internal cleanliness matters because the radiator forms part of the transformer's oil circuit. Agree on the removal of welding debris and process residues, drying requirements, and protection of openings before shipment.
For galvanized radiators, confirm which surfaces receive zinc. The manufacturing sequence must also address venting, drainage, and oil-side cleanliness.
Specify Leak Testing, Inspection Records, and Acceptance Criteria
IEC 60076-22-2:2019 addresses removable radiators for liquid-immersed transformers, including service conditions, interchangeability, and testing. Identify the contractual requirements applicable to the design before fabrication.
ZHIHE lists a conventional radiator procedure using 150 kPa air pressure for 20 minutes, with immersion in a leak-test tank to check for bubbles.
This is a stated factory procedure, not a universal requirement for every radiator design.
Agree on the inspection requirements before placing the order:
| Inspection item | Requirements to establish |
|---|---|
| Leak-test method | Test medium and method of detecting leakage |
| Test pressure | Specified pressure and pressure basis |
| Holding time | Required duration |
| Acceptance criteria | Conditions for passing or rejecting the test |
| Testing sequence | Stages before or after coating or galvanizing |
| Repairs | Approved repair method and retesting requirements |
| Post-test condition | Drying, internal cleanliness, and protected openings |
| Documentation | Dimensional checks, coating measurements, identification, and test records |
Leak testing does not verify thermal capacity. Cooling performance requires separate supporting data and verification.
Compare Price per Kilogram, Supply Scope, and Production Time
Compare transformer radiator price using the same drawing revision, coating specification, and billable weight basis.
Establish whether the quoted weight refers to bare fabricated steel, the finished assembly, or another agreed basis.
The following figures are illustrative and are not market quotations. Both offers cover the same approved design.
| Cost item | Supplier A | Supplier B |
|---|---|---|
| Agreed billable weight | 1,000 kg | 1,000 kg |
| Unit price | USD 3.00/kg | USD 3.20/kg |
| Base amount | USD 3,000 | USD 3,200 |
| Required coating upgrade | USD 300 | Included |
| Comparable subtotal | USD 3,300 | USD 3,200 |
Freight and taxes are excluded.
Supplier B's higher price per kilogram produces a USD 100 lower comparable subtotal because the required coating is already included.
ZHIHE lists the following starting production times, subject to drawings, technical requirements, and quantity:
| Radiator type | Production time |
|---|---|
| Conventional transformer radiators | From 8 days |
| Hot-dip galvanized transformer radiators | From 11 days |
Confirm the production schedule for the specific order and establish shipping time separately.
Before ordering, send each bidder the same technical package and request a priced deviation list. Attach the agreed drawings, inspection plan, weight basis, supply scope, and production schedule to the purchase order.
