Obtain the required thermal duty from the supplier
Ask the gearbox designer to establish the heat-rejection requirement for the accepted operating cases and lubricant conditions. Identify the measurement and connection boundaries used in the cooling assessment. Do not select an exchanger from transmitted engine power alone or assume every gear unit generates the same loss. Keep the cooler selection tied to the actual offered transmission and duty rather than to a generic accessory capacity from another installation.
Define usable ambient-air conditions
For an air-cooled proposal, provide the installation environment, ventilation constraints and relevant ambient design cases. Identify electrical supply and the proposed fan or drive arrangement. Ask the supplier to state clearance, access and environmental support requirements for the actual cooler. A unit selected for unobstructed air circulation should not be assumed suitable inside a tightly enclosed package. Include site conditions that can influence maintenance or sustained heat rejection in the commercial comparison.
Define the available cooling-water service
For a water-cooled option, obtain the site supply conditions and quality information required by the exchanger designer. Identify what the supplier expects at its connection and who provides distribution, return routing and conditioning where needed. A statement that water is available does not establish adequate usable service. Review construction and maintenance requirements against the specified water duty, and make external infrastructure visible before comparing the cooler option as a complete lower-cost installation.
Include the oil-side circuit and maintenance scope
List pumps, filters, control components, instruments and piping associated with the cooler arrangement. Ask which items are supplied with the gearbox and which remain external. Review access for cleaning, removal and servicing under the actual layout. Compare the complete installed circuits, not just the exchanger bodies. A change in piping or component selection should be coordinated with the responsible designers so the agreed oil-system and thermal conditions remain supported.
Review loss of the selected cooling resource
Ask the equipment and process designers to establish the consequences of unavailable air movement, cooling water or electrical supply. Identify the required monitoring and any supported operating restrictions through approved documentation. Do not assume a different cooler can be substituted without revisiting the design basis. The purchase should define dependencies and acceptance evidence, including the site work needed to demonstrate the assembled oil system under the agreed load and utility conditions.
Compare ongoing utility and service obligations
Include electricity, cooling-water services, cleaning resources and maintenance access where they affect the project cost. State the operating assumptions behind estimates rather than promising a universal cost saving for one cooling method. A suitable arrangement at a permanent facility may not suit a mobile rig with different resources. The selected package should have a documented thermal basis and a practical support plan, with purchaser work and utility limitations visible beside the equipment price.
Put these items side by side in the bid review
| Purchase item | Question to resolve | Evidence to request |
|---|---|---|
| Heat duty | Which gearbox operating cases apply? | Supplier thermal design basis |
| Utilities | What air, water or power is available? | Defined connection conditions |
| Complete scope | Which oil-circuit components are included? | Tagged cooling and service boundary |
Suggested wording for the quotation request
Compare air-oil and water-oil options against the agreed gearbox heat duty and site utilities. State supported conditions, included oil-circuit equipment, external piping, maintenance access and resource-loss dependencies. Separate equipment price from purchaser infrastructure and ongoing utility assumptions.
Assess each option within the complete gearbox drive train: prime mover, transmission, couplings, driven equipment, mounting and supporting oil system. Preserve the accepted load schedule and interface drawings when comparing suppliers or approving changes. A component rating should not be treated as proof of the complete installed arrangement. Obtain configuration-specific documents from the responsible designers, and retain the agreed exclusions and verification records with the equipment order. Installation, shifting, testing and maintenance must follow approved equipment instructions and site procedures rather than a procurement comparison.
For the wider equipment scope, consult the Oilfield Transmission Box: Utility Planning. Use the RFQ checklist to collect the supporting documents before requesting a configuration-specific quotation.
Buyer questions
Can a cooler be selected from engine nameplate power alone?
No. Use the gearbox supplier thermal duty and the actual cooling and oil-side conditions.
Does a water-cooled option include the site water system?
Not necessarily. Identify supply, return, quality and distribution responsibilities explicitly.
Background and supplier contact
Gear-unit oil supply and cooling system background offers related background, not certification of the equipment in a quotation. Applicability must be checked for the project and destination.
Explore the oilfield transmission box, browse all technical resources, or visit Vance Petroleum for company information. Request a gearbox proposal with the load schedule, interface drawings and required shaft speeds.