The New Paradigm of Industrial Time Study in 2025: OHS and Productivity

Methods and time engineering faces a critical turning point in 2025. The convergence between climate change—manifested in recurrent heat waves—and the tightening of Occupational Health and Safety (OHS) regulations has transformed the calculation of relaxation allowances. What used to be a theoretical exercise based on static tables is today a legal and operational necessity to guarantee the viability of OEE (Overall Equipment Effectiveness).

From the technical perspective of Cronometras, data analysis demonstrates that production standards calculated under “normal” conditions (ISO standard, 20°C - 24°C) are becoming obsolete during 30-40% of the operating year in sectors without forced climate control. Ignoring workplace thermodynamics not only distorts the workload but generates an unacceptable negative variance in direct labor costs.

Regulatory and Technical Reference Framework (Spain and EU)

The current regulatory framework demands bidirectional integration between Process Engineering and Industrial Hygiene. For a plant engineer, calculating times without considering these regulations is a compliance risk.

Update of Royal Decree 486/1997

Legislation has evolved to severely limit work in thermal stress conditions (AEMET orange or red alerts) if corrective measures are not guaranteed. For time study, this implies recalculating metabolic load and recovery periods intrinsic to the cycle.

Essential UNE-EN ISO Standards for Standard Time Defense

To establish a defensible Standard Time before works councils and inspections, allowances must be based on scientific standards, not arbitrary estimates:

• UNE-EN ISO 7243: Thermal stress estimation based on the WBGT count (Wet Bulb Globe Temperature). It is not enough to measure ambient temperature; radiation and humidity are determinants.
• UNE-EN ISO 7933 and 8996: Thermal ergonomics and analytical determination of metabolic rate. These standards allow calculating the estimated thermal overload and the maximum permissible exposure time.

Technical Analysis: Integration of Environmental Variables in Standard Time

Standard Time ($T_{std}$) is classically defined as:

$T_{std} = T_{basic} \times (1 + \%Allowances)$

The common error in the industry is treating the environmental component as a fixed and linear percentage. However, the Rest Coefficient ($K_d$) behaves non-linearly in extreme conditions.

Metabolic Load vs. Intrinsic Recovery

Traditional ILO (International Labour Organization) tables assign linear percentages that fail when the thermal homeostasis threshold is exceeded. When the body’s internal temperature rises, the cardiovascular system diverts blood flow to the skin for thermoregulation, reducing muscle oxygenation. This causes fatigue to appear exponentially faster.

Technical Note: Before redefining the standard, it is recommended to validate the actual frequency of unofficial breaks that operators are already taking due to thermal fatigue. Sampling tools like WorkSamp are indispensable for capturing objective data on time distribution (work vs. recovery) and scientifically justifying the adjustment of allowances.

Breakdown of Environmental Factors and their Impact on MTM/MOST Systems

The application of predetermined time systems (MTM-1, MTM-2, MOST) must be audited under the lens of environmental conditions.

1. Thermal Stress (Heat + Humidity)

An operator working at 32°C with 70% relative humidity experiences a drop in psychomotor efficiency of 15% to 20%.

• Impact on Motions: In high-concentration tasks, Reach and Position micro-movements slow down.
• Sweat Factor: Loss of friction on the skin requires greater Grasp force, which fatigues forearms prematurely. The allowance must include time for constant hydration.

2. Extreme Cold and PPE

In cold chain environments (< 10°C), the critical factor is not just temperature, but clothing.

• Altered MTM Codes: The use of thick thermal gloves invalidates standard MTM codes for “Grasp”. A G1A (simple grasp) can functionally become a complex manipulation equivalent to G4 or G5.
• ISO 11079: This standard regulates the thermal recovery needed to avoid numbness affecting fine dexterity.

3. Air Quality and Respiratory Protection

The use of masks or industrial respirators increases inhalation resistance, raising the metabolic cost in watts (W) generated by the body.

• Noise (>80 dBA): Even with hearing protection, constant noise generates nervous fatigue, requiring a 2-5% allowance for attentional cognitive load to maintain quality.

Proposed Methodology: Allowances Calculation Matrix

To differentiate from generalist consultancies, we recommend abandoning “eye-balling” and applying a matrix model in Cronometras.

Critical Variables

1. H (Hygrothermal): WBGT Index. If WBGT > 28, the allowance scales dynamically according to workload (Light/Medium/Heavy).
2. V (Ventilation): Negative correction factor if effective forced ventilation directly to the operator exists.
3. L (Lighting): Precision work under < 300 lux or with glare requires eye micro-pauses (Allowance +2% to +5%).

Composite Rest Coefficient Integration Formula

The final coefficient is not a simple sum, but a weighted integration:

$K_{d} = K_{physiological} + K_{force} + (K_{thermal} \times Factor_{PPE}) + K_{environmental\_others}$

Operational Solutions for Plant Managers and Analysts

Bioclimatic Productivity Audit

Do not accept a time study if boundary conditions have not been recorded. Measurement must be in-situ, accompanying timing with luxmeters and WBGT monitors.

Implementation of Dynamic Standards

It is unfeasible to maintain the same standard in August as in February in a non-climate-controlled hall. The solution lies in Seasonal Standards.

• Winter: Base Standard (100% theoretical efficiency).
• Summer (Heat Wave): Adjusted Standard (Automatic application of environmental correction factor).

This is vital for management control. If we do not adjust the standard, OEE will artificially drop, demotivating the team. To monitor how these adjusted standards impact real factory profitability and visualize efficiency loss in real-time, we recommend integrating data into production control platforms like Induly, which allow segregating losses due to reduced speed (environmental) from technical stops.

Technical Justification

A time study conducted with Cronometras, which explicitly includes environmental allowance calculation based on ISO standards, is the most powerful tool before a union negotiation or a labor inspection. It demonstrates that the company not only seeks productivity but protects the physiological health of the worker.

Conclusions: Towards Thermodynamic Time Engineering

Modern time engineering can no longer operate in a vacuum. Allowances for environmental conditions are not a “margin of error” or a gracious concession; they are a quantifiable thermodynamic variable that directly affects the company’s Bottom Line.

Adopting rigorous calculation methodologies (WBGT, ISO 7933) and advanced digital tools is the only way to maintain competitiveness and social peace in the industrial environment of 2025.