Field service and in-house maintenance

A maintenance technician in a bottling plant and a service engineer for a packaging machine maker may fix the same fault on the same kind of machine. Their jobs still look very different. One works for the company that owns the machine. The other works for a company that sells or services it. That changes who plans the work, who pays for it, and what the technician knows when they arrive.

In-house maintenance

In-house maintenance teams look after the equipment of their own company. The machines are in one plant or a few sites. Technicians walk to the job. They often know the machines well, sometimes for years, and they talk to the operators every day.

The work is mostly planned around production. Preventive tasks run on schedules, faults are reported by operators, and big jobs wait for planned shutdowns. The main measures are downtime, OEE, and maintenance cost. A CMMS is the usual system.

Field service

Field service teams do the work at a customer's site. They may work for the machine's manufacturer, a dealer, or an independent service company. A technician may cover a large region and visit dozens of different sites a month.

The work starts from a customer call or a service contract. A dispatcher assigns a technician by skill, location, and availability. The technician travels, often for hours, does the job, and records it so it can be billed or booked against a contract. The main measures are first-time fix rate, response and resolution times under an SLA, jobs per day, and service revenue. FSM software is the usual system.

The main differences

	In-house maintenance	Field service
Who owns the machine	The same company	The customer
How the technician gets there	Walks across the plant	Drives or flies to the site
How well they know the machine	Often very well	May see it once a year
Who pays	Internal cost center	Customer, contract, or warranty
Main measures	Downtime, OEE, cost	First-time fix, SLA, revenue
Cost of a missing part	A walk to the store	A second trip

What they share

Both work on assets. Both use work orders, spare parts, manuals, and safety procedures such as lockout/tagout. Both depend on knowing what happened to the machine last time.

The boundary is also blurrier than it looks. Many plants use outside contractors for specialist work, which turns part of their maintenance into field service from the contractor's side. Many machine makers offer service contracts that take over maintenance of their machines entirely. And the same machine is often worked on by both: the plant's own team handles daily issues, and the manufacturer's engineer comes for major faults and overhauls.

Why history matters more in the field

An in-house technician who has fixed the same press ten times carries much of its history in their head. That knowledge is fragile, because it leaves with the person, but it is there.

A field service engineer rarely has that. They may arrive at a machine they have never seen, at a site they do not know, with a fault description from a phone call. What helps them most is what earlier visitors recorded: what was wrong, what was replaced, which settings were changed, and what the customer said. Without that, the first hour of the visit is spent rediscovering it.

The handover also crosses a company boundary. The plant's technicians know what they did last week; the service engineer often does not, unless someone wrote it down where both can see it.

Choosing tools

Plants often run a CMMS, and service companies run an FSM system. When a service company and its customer use different systems, the history of one machine ends up split between them. A shared record at the machine, such as a label that leads to the asset's history, is one way to keep both sides working from the same facts.