Who Does What in a Japanese Plant: EPC, Owner, Maintenance

You are supplying a compressor package, a licensed process, or a control system to a plant project in Japan. In the same week, three Japanese engineers send you comments: one from the engineering contractor's rotating-equipment team, one from the plant owner's equipment engineering section, and one from the maintenance company that will look after the unit for years to come. All three have the same job title on their business cards: plant engineer. Whose comment wins?

The answer depends on which side of the plant each engineer works for. On a Japanese plant project, "plant engineer" covers three very different jobs. The EPC contractor builds the plant, the owner runs it, and the maintenance contractor keeps it running. Each side decides different things at different stages, and each one becomes your main contact at a different point in the plant's life.

This guide explains what each side does and decides, how the EPC's engineering disciplines map to the people who will contact you, and when each side typically gets involved. It ends with a decision map, kickoff questions, and an email template you can adapt.

Build, Own, Maintain: The Three Sides of a Japanese Plant

In Japanese oil, chemical, gas, power, and water treatment plants, the engineers fall into three groups by employer:

• EPC contractor (engineering company): designs a new plant or a major revamp, procures the equipment, builds it, commissions it, and hands it over. Japan's large EPCs include JGC, Chiyoda, and Toyo Engineering.
• Owner: the chemical company, refiner, or power utility that owns and operates the plant. Its equipment engineers (often called setsubi gijutsu, 設備技術, "equipment engineering") decide what the plant should be and stay with it from planning to decommissioning.
• Maintenance contractor: inspects and repairs the plant once it is running, and carries out the planned shutdowns. Sankyu is one example.

A mechanical engineer at each of the three does a different job. At the EPC, they design equipment and piping. At the owner, they write the specifications and supervise the contractors. At the maintenance company, they plan inspections and repairs. They work on the same equipment, but at different times and with different responsibilities.

The EPC Contractor: Designs, Buys, Builds, Hands Over

An EPC splits a project among engineering disciplines. Each discipline team owns its own drawings and specifications, and together they cover everything from the pre-award estimate through design, equipment purchasing, site construction management, and commissioning. What sets EPC engineers apart is that their job ends only when the plant delivers its contracted performance and is handed over.

A JGC job posting for an instrumentation and control engineer, for example, lists design, procurement, construction, and commissioning as one scope of work. The same posting mentions site postings of about one to one and a half years and frequent overseas trips for vendor and client meetings and factory inspections. For a profile of one of the big three, see our guide to Toyo Engineering as a Japanese EPC contractor.

EPC Disciplines and Who Will Contact You

If you sell equipment or a package to an EPC, you will mostly hear from the discipline that owns your item. The table below shows the usual split.

At the owner and the maintenance contractor, mechanical, electrical, and instrumentation staff are usually not split this finely. One person often covers several disciplines.

The P&ID cuts across all of these teams. Chiyoda describes its P&ID engineers as building broad knowledge of process, control, piping, and equipment, and growing into project engineers through coordination with other departments. In practice, the person who manages the P&ID is often a good contact when a question touches more than one discipline. For how Japanese projects use these drawings, see PFD vs. P&ID on Japanese projects.

During detailed design, the EPC checks the drawings that vendors submit for the equipment it has ordered, to confirm they match the specification. This is where the Japanese approval-drawing process comes in. See approval drawings (shonin-zu) for how the stamps and return codes work.

The Owner: Sets Requirements and Lives With the Plant

The owner's equipment engineers decide how the company's own plants are built, modified, and kept running, and they manage the work. Typical tasks at a chemical company include equipment layout and P&ID studies, design of heat exchangers, pressure vessels, pumps, and instrumentation, budgeting, permit applications to local authorities such as the fire department and the prefecture, and construction management.

The owner is involved for the whole life of the plant. On a new project, it acts as the buyer: it gives specifications to the EPC, compares bids, reviews the design, and supervises construction. Once the plant runs, the owner writes the maintenance plan and plans upgrades of aging equipment and capacity revamps. Even when the design is outsourced, the owner keeps the responsibility for deciding what the plant should be.

Owner engineers travel less than EPC engineers, but they coordinate every day with production, safety and environment, and purchasing. Plants that handle high-pressure gas must also appoint licensed safety staff under Japan's High Pressure Gas Safety Act, so safety questions on those units go through people the owner has formally appointed. For how the owner's departments split responsibilities, see Japanese factory departments: who is who.

The Maintenance Contractor: Keeps It Running and Runs the Turnaround

Maintenance contractors protect a running plant without stopping it, and they stop it on schedule to repair it. Sankyu lists four types of maintenance work:

• Routine maintenance: checking running equipment for abnormalities and wear, using the senses and inspection tools
• Preventive maintenance: time-based and condition-based
• Breakdown maintenance: repairs after a failure
• SDM (shutdown maintenance): the scheduled turnaround, called teishu (定修) in Japan

The turnaround is the heaviest load. The whole plant is shut down, and according to Sankyu, several thousand people can be working at once on peak days. Engineers at maintenance contractors earn their keep by finishing inspections and repairs within a fixed outage window. Our guide to teishu, the Japanese plant turnaround, covers the timeline and the contracting layers, and hozen in Japanese plants explains the maintenance terms you will hear.

Some maintenance engineers are resident at one plant. Others move from site to site with each turnaround.

Who Is Involved at Each Stage of the Plant Life Cycle

Put the three side by side and the pattern is simple: the EPC works up to handover, the maintenance contractor works after startup, and the owner is there from start to finish.

When the EPC Will Contact You During a Project

An EPC engineer's work changes with the project phase, and so does what they need from suppliers. Desk work at the office and hands-on work at site alternate, as Figure 3 shows.

For suppliers, this means:

• Before award, the EPC builds its cost estimate from a rough equipment list and quantities, so it may ask you for budget quotes and technical data on short notice.
• In detailed design, a change in one discipline ripples into others. Rerouting one pipe can move supports and instruments. Telling the EPC early about any change on your side that affects other disciplines, such as nozzle positions, loads, or utilities, helps everyone avoid rework.
• At site, the day starts with a morning meeting and KY (kiken yochi, hazard prediction) activity, followed by installation checks, coordination with construction contractors, and witnessed tests such as pressure tests and instrument checks; the evening goes to planning the next day's work and safety measures. During commissioning, crews may work night shifts because the equipment cannot always be stopped.

On overseas projects, Japanese EPC teams often hold calls with clients and engineering offices in other time zones from late afternoon onward, Japan time.

Who Decides What: A Decision Map for Suppliers

The table below shows the usual pattern on a lump-sum project where the owner has hired an EPC. Your contract and the project's coordination procedure always take precedence.

Two points cause the most confusion. First, the owner's engineer who comments on your drawings during design is often the same person who will call you about spare parts years later, so their preferences matter beyond the project. Second, the maintenance contractor usually works under orders from the owner. They can tell you what they found, but changes to scope, parts, or cost normally need the owner's approval.

Kickoff Checklist: Questions to Ask the Japanese Side

Ask these at the kickoff meeting or in your first clarification list, before the first drawing goes out:

• Who is our technical contact for this item, and in which discipline?
• Who handles commercial matters: EPC procurement, or the owner's purchasing department?
• Will the owner review our drawings directly, or only through the EPC? Which documents need owner approval?
• Which owner standards, specifications, or preferred-vendor lists apply to our scope?
• Who decides on deviations, and how should we submit them?
• Which documents do you need from us for permit applications to Japanese authorities, and by when?
• Who will attend factory inspections and witness tests: the EPC, the owner, or both?
• After handover, who is our contact for spare parts, service, and turnaround work: the owner's equipment section or a maintenance contractor?
• Will there be a site visit or commissioning support, and who will coordinate it on site?

Email Template: Confirming Roles at Project Start

Edit the bracketed parts before sending.

Subject: [Project name] – [Your item]: Contacts and approval flow

Dear [Name],

Thank you for the purchase order for [item, tag number]. To keep
document reviews on schedule, could you confirm the following?

1. Technical contact for this item (name, discipline)
2. Commercial contact (EPC procurement or owner purchasing)
3. Documents that need the owner's review or approval, if any
4. Owner standards that apply to our scope
5. How to submit deviations, and who approves them
6. Documents you need from us for permit applications, with due dates
7. Attendees for factory inspection and witness tests

We plan to submit the first drawings on [date].

Best regards,
[Your name]
[Company]

Limits of This Guide

• The three-way split is a simplification. Some EPCs also maintain plants, some maintenance contractors build them, and some owners do much of their own design.
• The decision map assumes a typical EPC project in Japan. Owner-furnished equipment, licensor packages, joint ventures, and overseas projects run by Japanese EPCs can follow different lines of authority. Check your contract and the project's coordination procedure.
• Discipline names, team boundaries, and who goes to site vary by company.
• Permit requirements depend on the plant, the substances handled, and the local authority. This guide does not describe how to apply for any permit.

FAQ

What Is the Difference Between an EPC Contractor and the Owner?

The EPC designs, procures, builds, and commissions the plant and hands it over at contracted performance. The owner decides what the plant must do, buys the project, accepts the plant, and then runs and maintains it for its whole life.

Who Approves Vendor Drawings on a Japanese Plant Project?

Usually the EPC's discipline engineer for your item. The owner may also review key drawings, depending on the contract. Ask at kickoff which documents need owner review.

What Does a Maintenance Contractor Do in a Japanese Plant?

Routine, preventive, and breakdown maintenance, plus the scheduled shutdown maintenance called teishu. They normally work under orders from the owner, who sets the scope.

Should a Foreign Supplier Contact the Owner Directly?

During an EPC project, usually not without the EPC's agreement, because the contract runs through the EPC. After handover, the owner's equipment or maintenance section typically becomes your main contact.

Sources

• EPC instrumentation and control engineer scope, site postings, overseas travel: JGC Group careers, "Instrumentation and Control Engineer (JGC Global)" (Japanese)
• P&ID engineer role and growth into project engineering: Chiyoda Corporation careers, "Plant Design Engineer (P&ID)" (Japanese)
• Maintenance types and turnaround scale: Sankyu Inc., "Maintenance" (Japanese)
• High-pressure gas safety licenses and appointed roles: High Pressure Gas Safety Institute of Japan (KHK), national qualifications and scope of duties (Japanese); High Pressure Gas Safety Act (Japanese Law Translation)