The mystery of the maintenance backlog explained

There may not be any one correct way to measure backlog, but it is always advised to find that shortlist of backlog calculations that work for you, and measure them consistently. Measuring the size and makeup of your backlog can give you some keen insight into how you are managing your workload in your maintenance organization.


There may not be any one correct way to measure backlog, but it is always advised to find that shortlist of backlog calculations that work for you, and measure them consistently. Measuring the size and makeup of your backlog can give you some keen insight into how you are managing your workload in your maintenance organization.The question:

Which of the following groups is overloaded with work, and which one can handle more work?

  • A work group with 250 work orders
  • A work group with 50 work orders

Which work group had better performance?

  • A ten-person crew that completed 40 work orders
  • A ten-person crew that completed 17 work orders

The answer:

It depends. One cannot gauge the workload facing a group by a simple count of work orders. Not all work orders are equal; each requires a different amount of effort and resources. Thus the mystery of the backlog.

The backlog calculation is the trick to unravelling this mystery. 

What is backlog?

Backlog is a method of calculating the workload based on required resources and available resources.

The formula for calculating backlog is:

Backlog = Required Hours / Available Hours

Backlog is expressed in weeks of backlog

By itself, the backlog calculation means very little. But when we look at trends and targets, we can reach some very helpful conclusions.

Total backlog calculation

Suppose you manage a 10-person organization (8 mechanics and 2 electricians) and when you add up the required man-hours on all work orders, you arrive at 2000 hours total. To make the math simple, let’s suppose that everyone works 40 hours per week (in reality we would subtract lunch, breaks, training, etc.).

10 People X 40 Hours = 400 Available Hours per Week

2000 Hours / 400 Hours = 5 Weeks

Backlog = 5 Weeks

Total backlog target

So your next question is going to be, “So what?” What do you do with this backlog calculation? Let’s look at a couple of targets:

Total Backlog Target: 4-6 Weeks

My experience shows that you should strive to maintain 4-6 weeks of total backlog at all times. There are two factors driving this target:

  1. Having enough work identified to keep the workforce gainfully engaged.
  2. Moving work off of the backlog so that requestors see action being taken on their requests.

If the backlog is too large or too small, then you will not be able to satisfy both of these requirements.

Making decisions based on total backlog

As you can see from the example, the final backlog number can be affected by adjusting either of the two variables:

  • Adjusting Required Hours
  • Adjusting Available Hours

Given the two choices, adjusting the Available Hours component is always the better choice. This can be accomplished through overtime, contracted labor, and strategic changes in the staffing levels.

Derivations of backlog

The base formula provided for backlog calculation (Backlog = Required Hours / Available Hours) can be adjusted to measure different aspects of the organization. Take a look at the various permutations of backlog listed below. Each is derived by filtering out the Required Hours and Available Hours based on the requirements of the work order.

Derivations of the backlog calculation include:

  • Total Backlog (calculated in our example)
  • Mechanical Backlog
  • Electrical Backlog
  • PM Backlog
  • PdM Backlog
  • Corrective Backlog
  • Outage/Turnaround Backlog
  • Ready (WSCHED) Backlog

How would you adjust the base backlog formula to calculate for each of these derivations?

Planners remain focused on future work and the ready backlog

  • Ready Backlog Target: Minimum 2 Weeks at All Times

I never like to miss an opportunity to make this point. The prime measure of the planner’s output is ready backlog – total amount of work that has been planned, parts obtained, and ready to be placed on the schedule.

When people ask me if it is ok for the planner to do x, y, z – my first answer is always “as long as we have 2 weeks of ready backlog, then maybe.” 2 weeks of ready backlog gives the scheduling team the data they need to project a schedule 1 week in advance. Of course, if we are attempting to project further into the future, then we will require even more ready backlog to pull this off.

If we believe that planners are focused on future work, then the ready backlog is a solid way to measure our execution on this belief.

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Safety for 18 years, warehouse maintenance tips, Ethernet and the IIoT, GAMS 2016 recap
2016 Engineering Leaders Under 40; Future vision: Where is manufacturing headed?; Electrical distribution, redefined
Strategic outsourcing delivers efficiency; Sleeve bearing clearance; Causes of water hammer; Improve air quality; Maintenance safety; GAMS preview
SCADA at the junction, Managing risk through maintenance, Moving at the speed of data
Safety at every angle, Big Data's impact on operations, bridging the skills gap
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Applying network redundancy; Overcoming loop tuning challenges; PID control and networks
Driving motor efficiency; Preventing arc flash in mission critical facilities; Integrating alternative power and existing electrical systems
Package boilers; Natural gas infrared heating; Thermal treasure; Standby generation; Natural gas supports green efforts

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role of plant safety and offers advice on best practices.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me