The ABCs of Structured Maintenance

Order In – Order Out, Order In – Order Out, Order In – Order Out… is the life breath of a manufacturing business. And the effective maintenance of the equipment, processes and systems that convert Orders In to Orders Out are foundational to the success of that business. This post is an update to a post from five years ago that focuses on the critical importance of structure in keeping maintenance effective. – C.H.

Structured Maintenance (From 1/12/2012)

Sustainability goes far beyond concern for the environment. Adam Werbach* says that “being a sustainable business means thriving in perpetuity”. To thrive in perpetuity requires constant attention to the present and the future on the factory floor, within the business as an organization, within the industry in which the business operates, within global economic and social realities, and within the natural world we all rely on.

For manufacturers, that begins with efficient production and timely delivery of high quality products — all the time. And that requires production equipment that reliably performs as intended. It is the function of the maintenance program to assure that the equipment performs reliably. As extreme examples, think about what “reliably performs” means to passengers in jet aircraft or to sailors in nuclear submarines, not to mention astronauts. The sign on the shop wall that said “If It Ain’t Broke, Don’t Fix It” was retired some time ago.

To be clear on terms, that which is to be maintained, I refer to as a “maintained item”, or, more simply, “item”. An item may be a machine (such as a lathe), a system (e.g. electrical power distribution) or anything else that you may want to declare as a unit for the purposes of maintenance and performance records keeping.

ABC BlocksIt is convenient and useful to divide maintained items into three classes:

Class A Items – The failure of a Class A item can shut down or significantly impair production, or create a serious safety condition, in the entire facility. Most Class A items are utilities or similar services, such as a main power transformer, a boiler, materials conveying system or critical ventilation unit.

Each of these critical items needs both a plan to keep it performing reliably and a plan for its rapid repair or replacement, in case it does fail. The “keep it performing” plan might include a scheduled inspect / clean / service routine, pre-emptive parts replacement based on service hours or proactive parts replacement based on throughput or on monitored machine condition (for example, vibrations analysis).

The corresponding rapid repair / replacement plan might involve in-line spare capacity, critical spare parts inventory, rental equipment (for example, an air compressor) and/or fast response third party service (examples: digital control systems or boilers). Since parts for critical items are often quite expensive, spare parts inventory costs must be weighed appropriately during the planning process.

For critical items, Failure Mode and Effects Analysis (FMEA) may be of significant use in formulating both plans. FMEA is a technique for evaluating the probable occurrence of various failure modes and the likely effects of such failures. FMEA is widely used in the automotive, aerospace and other industries for product and process design and improvement. It works well for critical item maintenance planning too. If you aren’t familiar with FMEA, start with a free power point presentation from Purdue University at 381_Chap_7.ppt. There is a lot more on FMEA on the web. Don’t confuse FMEA with FEMA, the federal agency that is supposed to respond to natural disasters.

Class B Items – Class B includes most primary production equipment, failure of which can shut down or significantly impair operation of a single production line, or create a localized safety concern.

The “keep it performing” plan for each of these less critical items might, as with Class A items, include a scheduled inspect / clean / service routine, pre-emptive parts replacement based on service hours or proactive parts replacement based on throughput or on monitored machine condition.

Appropriate repair / replacement plans might include common spare parts, reconditioned parts (e.g. gear boxes or rewound motors), prearranged “order as needed” parts from reliable suppliers or specialized third – party service calls (preferably with pre-arranged vendors).

Class C Items – Repairs or replacement of Class C items, taken individually or in small groups, are less urgent. Scheduled inspect / clean /service routines are often appropriate. For some high wear parts or for items that require other items to be down while maintenance to be performed, scheduled preventative maintenance may be the best route. Run to failure is an acceptable strategy for some Class C items.

The real point to this post is that effective and cost efficient equipment maintenance requires item–by–item planning, to keep the equipment performing reliably and to correct failures when they do occur. Grouping items by criticality helps make maintenance planning easier.

There is a lot more to maintenance planning than any one post can even hope to cover – look for more on maintenance in future posts.

Chuck at ReneThoughtful comments and experience reports are always appreciated.

…  Chuck Harrington (

This blog and associated website ( are intended as a resource for smaller manufacturers in the pursuit of Sustainability. While editorial focus is on smaller manufacturers, all interested readers are welcome.

* Werbach, Adam, Strategy for Sustainability, Harvard Business Press, Boston (2009), page 9.