Industry Experts Respond to 'Let’s Kill Wrench Time' – A Deep Dive into Maintenance Metrics

Following the publication of the column “Let’s Kill Wrench Time” in the May/June 2007 issue of Reliable Plant, a diverse group of maintenance professionals shared their insights on the value (or lack thereof) of wrench‑time studies. The comments reveal contrasting perspectives on predictive maintenance, preventive maintenance targets, workforce allocation, and the broader context of lean manufacturing.

Comment 1

In a major automotive stamping and welding plant, the maintenance team uses oil analysis, vibration analysis, and infrared thermography to anticipate failures and curb energy use. Three competing pressures shape their decision‑making:

• Maintenance planners schedule overtime based on predictable workloads and resist using spare parts for adjustments that could be avoided.
• Production insists on keeping equipment running, fearing insufficient inventory for just‑in‑time demands and losing backup lines.
• Plant leadership, drawn from skilled trades, supports heavy “wrench‑time” because visible activity is perceived as productive.

Infrared studies are the most accepted tool—visible thermal anomalies are hard to ignore. The plant proudly reports that more than 94 % of maintenance effort is preventive, driven by repetitive procedures such as monthly retightening of all electrical connections. While this boosts PM metrics, the author argues it masks a lack of strategic direction and hinders competitiveness.

Comment 2

Wrench‑time studies are criticized as outdated metrics that focus on effort rather than outcome. The author recommends shifting focus to metrics like maintenance rework, MTBF, and chronic failure rates, which align better with reliability engineering. They argue that excessive emphasis on wrench time can lead to the illusion of efficiency while ignoring root causes.

Comment 3

In 2006, a plant conducted a wrench‑time audit to determine available work hours. The audit excluded planning, parts procurement, and travel—treating them as part of “wrench time.” Non‑productive hours such as sick leave, vacation, and training were identified as the true “non‑wrench” time. By quantifying available time, the plant aimed to improve scheduling accuracy and reduce idle labor. Subsequent initiatives focused on refining work‑task definitions and enhancing preventive maintenance efficiency.

Comment 4

Responding to the same column, an engineer shared a practical approach: gather maintenance staff, list obstacles that reduce productivity, and prioritize solutions through collaborative workshops. This bottom‑up “areas for improvement” list received full field buy‑in, illustrating that engagement can turn a seemingly rigid metric into a catalyst for change.

Comment 5

Observations highlighted the direct correlation between low planned work ratios and poor wrench‑time scores. The author noted that collecting 4,000 observations—often requiring eight observers over two weeks—was costly and suggested that better‑maintained technical databases could reduce the need for extensive field time. They concluded that wrench time measures utilization, not productivity.

Comment 6

The article resonated with maintenance teams now operating lean, multi‑skill rosters. With one technician per 100 production employees, technicians must juggle preventive, corrective, and support tasks. The author argues that wrench‑time studies can distort performance assessments and impede resource optimization, yet management continues to rely on them for staffing decisions.

Comment 7

Another response emphasized that measurement tools alone cannot solve systemic issues. Without factual data, discussions about wrench time become ideologically driven rather than evidence‑based. The author called for a holistic approach that considers all maintenance facets—from parts inventory to workforce accountability.

Comment 8

Support for the article’s stance was strong. The writer noted that focusing on wrench time is often cheaper and easier than addressing underlying problems such as supply chain accuracy or preventive maintenance planning.

Comment 9

A maintenance mechanic from a chemical plant described the challenges of a lean environment: reduced staff, expanded responsibilities, and a lack of clear leadership. The narrative detailed how critical path work was fragmented among personnel, leading to production shortfalls. The author highlighted the disconnect between management’s expectations and on‑the‑ground realities, arguing that counting wrench time becomes meaningless without managerial engagement.

Comment 10

Supporters of targeted wrench‑time studies acknowledged their utility in specific contexts, such as rebuilding facilities where disassembly and reassembly dominate. However, the author warned that excessive focus on such studies can divert valuable time from safety and reliability improvements.

Comment 11

Advocates for craftspeople as continuous improvement drivers emphasized that high reliability (over 96 %) can be achieved by empowering technicians to perform inspections, plan scheduled downtime, and innovate. They argued that wrench time should not exceed 25 % for skilled labor, otherwise it signals systemic issues.

Comment 12

Drawing from three decades in the electric utility sector, the writer stressed the importance of process design, clear goals, and proper training over measurement alone. They cautioned that management’s focus on wrench time can demotivate staff, and suggested alternative performance metrics that truly reflect productivity and engagement.

Collectively, these responses paint a nuanced picture: while wrench‑time studies can provide visibility into labor activity, they risk obscuring deeper reliability and efficiency challenges if not coupled with strategic data, robust planning, and engaged leadership.