For a substation transformer conservator and breather, the quotation and approved drawings should identify the preservation arrangement, oil-expansion basis, air-separation element, breathing path and complete accessory supply boundary. Confirm which components are included, factory fitted or shipped separately, and who completes and accepts the remaining assembly. A line reading “conservator with breather” leaves important design and purchasing questions unanswered.
This guide is for EPC engineers and procurement teams buying a mineral-oil substation transformer for an IEC-based industrial project. It addresses quotation and drawing approval; the equipment designer and responsible project engineer retain the design and acceptance decisions.
AI-generated illustration of a conservator-equipped substation transformer; not a photograph of a HEAKOR unit or an approved project drawing.
Identify the offered preservation arrangement first
The word “conservator” does not establish whether an air cell or diaphragm is included. A conservator accommodates changes in oil volume. In a free-breathing conservator, an oil-to-air interface remains. In the bladder or diaphragm arrangement described in the U.S. Bureau of Reclamation's 2005 transformer guide, the flexible element separates the oil from atmospheric air while its air side breathes through a desiccant dryer. The desiccant dryer addresses incoming-air moisture; it does not provide oil-expansion space. These are physical distinctions, not a recommendation to select one arrangement for every project.
Ask the supplier to name the actual construction and show the oil and air paths on the proposed drawing. An external photograph cannot establish the internal separation arrangement. If an alternative offer proposes a sealed-tank design without a conservator, treat it as a configuration change requiring engineering review rather than carrying the conservator accessory schedule across unchanged.
Use a conservator and breather supply-scope schedule
Compare the offered package against the required functions and delivery boundary. The following is a suggested purchasing schedule, not a mandatory IEC form or a component-sizing method.
| Scope item | Evidence to request | Decision to record |
|---|---|---|
| Preservation arrangement | Named construction, drawing reference and listed deviations. | Does the offered arrangement match the project requirement? |
| Oil expansion | Designer-confirmed conservator capacity and operating-level basis for the specified liquid quantity, temperature range and duty. | Has the equipment designer confirmed the basis rather than supplied only a tank dimension? |
| Air separation | Air-cell or diaphragm identity and applicable component documentation, where specified. | Is the separation element included, and does the drawing identify its arrangement? |
| Breathing path | Selected breather reference, quantity, connection drawing and the compartment served. | Does the documented air path match the preservation design? |
| Mechanical connections | Schedule covering the conservator, connecting pipes, supports, mating parts and supplied connection hardware. | Who supplies each item and resolves each interface? |
| Oil-level indication | Proposed indicator and drawing showing its association with the conservator arrangement. | Are the requested indication features identified in the offer? |
| Delivery and completion | Factory-fitted and separately shipped lists, assembly responsibility and acceptance-document schedule. | Who supplies, completes, checks and accepts each outstanding item? |
Add columns for the supplier's response, document revision, open point and responsible party. Use “to be confirmed” for missing information; an empty cell should not silently become an accepted exclusion.
For example, two quotations may both list a conservator and breather while only one identifies the connecting pipe and support package. The buyer cannot compare the complete supply price until the other offer states whether those parts are included, excluded or supplied by the site contractor. This is an illustrative purchasing gap, not a description of a HEAKOR delivery.
Separate IEC references from project-specific requirements
A reference to IEC 60076-22-7:2020 does not, by itself, identify the supplied preservation package. Its published scope covers selected accessories and fittings for liquid-immersed transformers and reactors, with or without conservators, including service, mechanical and device-specific requirements and testing. The IEC listing states that the June 2023 corrigendum is incorporated.
Purchaser specifications can be more explicit. For example, POWERGRID's June 2021 transformer specification, Revision 13, sections 6.5–6.7, separately addresses the conservator, air cell, manuals, piping and breather. This is a named utility's up-to-400-kV specification; its materials, dimensions and operating criteria are not universal IEC requirements.
State the destination, applicable standards and editions, and project or utility specification revision in the purchase file. Ask the engineer to resolve conflicts and approve deviations. Do not infer project acceptance from an accessory catalogue or a standard number in a quotation.
Agree the drawing, manual and handover package
The document schedule should make the approved assembly traceable and its remaining responsibilities visible. Use HEAKOR's technical document checklist to specify the records requested for the actual offer, then confirm availability and delivery milestones.
- Drawing package: the general arrangement, preservation-system detail and accessory schedule should identify the same configuration and revisions.
- Access review: ask for the space and access provisions needed for the selected components' inspection and maintenance, and have the site designer review the surrounding layout.
- Equipment instructions: request the applicable conservator, air-separation-element and breather manuals, including the manufacturer's inspection and maintenance requirements.
- Delivery record: identify separately packed parts and associate them with the relevant transformer and assembly drawing.
- Completion record: agree who performs outstanding assembly, what qualified supervision is required, and which records the responsible party will accept.
Do not assume that delivery, assembly supervision and final acceptance are the same contractual service. Record the agreed scope explicitly. This checklist provides no field assembly, filling or operating procedure; those activities require the equipment-specific instructions and authorized personnel.
Frequently asked questions
Does an air cell eliminate the need to specify a breather?
No. In the cited bladder or diaphragm arrangement, the air side still has a breathing connection. Ask the designer to identify the intended breather and air path; the presence of a flexible separation element alone does not settle accessory scope.
Can the buyer select conservator capacity from transformer MVA alone?
MVA alone is not a complete design basis. Request the designer's confirmation against the offered oil quantity, temperature conditions and operating duty, together with the relevant drawing and level information. This article supplies no universal sizing percentage.
Can the same breather schedule cover separate oil compartments?
Do not assume that it can. If the transformer includes a separate tap-changer oil compartment, ask the designer to identify its preservation arrangement and any separately required accessories. Record which compartment each quoted component serves.
What if the offer uses a different air-cell or breather component?
Request a documented substitution review. The supplier and project engineer should resolve the affected connections, dimensions, instructions, documentation and any contractual requirements before accepting the revised component schedule.
Does a desiccant breather establish a maintenance-free package?
No. Use the selected equipment's current instructions to define maintenance and access requirements. Neither the presence of a breather nor this procurement checklist establishes a service-life or moisture-free guarantee.
Include preservation scope in your HEAKOR enquiry
Use HEAKOR's substation transformer configuration review as the category starting point. The requested preservation arrangement, accessories and document package require written confirmation for the proposed transformer.
Submit Your Project Specification to request a quotation addressing the required scope. Include destination, phase, frequency, kVA or MVA, full winding voltages, operating duty, site conditions, governing specification and revision, required preservation arrangement, document requirements, delivery and assembly responsibilities, quantity and schedule. Identify unresolved inputs explicitly.