How to Prevent Bottlenecks in Industrial Maintenance?

The PIEU Method Helps You Prioritize Company’s Assets

Knowing how critical every piece of equipment is at your plant will help you identify potential bottleneck machines. These are the highly critical assets on which the entire production depends and if they break down production stops or bottlenecks occur. Equipment criticality assessment analysis in industrial maintenance can help you identify these pieces of equipment and support you in the creation and deployment of successful preventive and predictive maintenance strategies.

A bottleneck in a manufacturing process occurs when a key asset is unable to reliably produce the required output. The goal of industrial maintenance is to categorize your piece of equipment according to its importance in order to mitigate the negative effects and help you cope with the problem. Assessing the criticality of your assets will help you identify the equipment that should be observed the most.

Moreover, evaluating the criticality of assets contributes to improved spare parts management.


Why It Is Important to Identify Bottleneck Equipment?

Each manufacturing process is composed of equipment of different criticality, but they are not always well identified. A bottleneck machine could be defined as a critical piece of equipment of your production unit, a vital element of your production tool which requires a particular surveillance. This asset affects the overall output the most by usually using the highest percentage of its capacity.

If this machine doesn’t have enough capacity, breaks down frequently or has an operator who needs training, the entire production line will get stuck. And the situation can get even more complex with several bottlenecks at different process steps. In this case you should know which machine has the highest priority.

Mismanagement of these assets can result into dramatic consequences for your business, including a complete shutdown of your production system and unhappy customers.


The PIEU Method

The PIEU method is a fairly well known method in industrial maintenance for determining the level of criticality of your equipment. It was developed by the French engineer Lavina to prioritize company’s assets. In order to calculate the criticality of the your equipment, you have to determine the value of the following letters for each machine.


P - fr. pannes / en. failures; P corresponds to the machine’s failure index

I - fr. importance de l’équipement, / en. the importance of the equipment; I stays for the machine’s importance rate

E - fr. état de l'équipement / en. the condition of the equipment; E describes the condition of the asset

U - fr. utilisation / en. the using rate; U is the use rate.


The failure index (P), the importance of the equipment (I), the condition of the equipment (E) and the use rate (U) are the four criticality indexes which can be contributed to different groups of assets and thus classify the equipment in several sets.

Consequently, criticality assessment is performed according to the following criteria.

Criteria   0.01 1 2 3
P - Incidence of failures   Serious consequences Impact on quality and waste generation Possible repairs No impact on quality
I - Importance of equipment  

Strategic, no load-shedding on other equipment, subcontracting impossible

Important, no load-shedding, subcontracting possible

Secondary, load-shedding possible Emergency equipment
E - Condition of Equipment   To be fixed To be revised To beobserved Specified Equipment

U - Equipment use rate

  Saturated High Medium Low


Once the different elements have been determined, you only need to calculate the criticality of the machine according to the following formula:

Criticality of your equipment = P*I*E*U

Then you just need to classify your critical equipment following this rule:

Pieu < 1: very critical
1<Pieu< 10: moderately critical
Pieu > 10: less critical

Try Mobility Work CMMS - 14 days free Watch our demo


The table below shows some examples of criticality on a melting production line at a foundry:


Incidence of failures

Importance of equipment Condition


Cupola Küttner 0,01 0,01 3 2 0,0006
Cooling tower Küttner 0,01 0,01 3 2  
Filter Lürh 0,01 0,01 2 2 0,0004
ADC Loading bridge 1 0,01 3 2 0,06
Küttner Recovery tower 0,01 0,01 3 2 0,0006
Shovel Fuchs Terex MHL340 3 2 1 3 18
Bucket granulator 1 1 3 1 3
Conveyer 3 0,01 3 1 0,09
Bracket SAS 2 2 3 3 36



How to Identify the Critical Equipment in Your CMMS?

Once you have completed the PIEU method for all your processes, you have determined all of your critical equipment. The next steps will be to identify it in your CMMS software.

To do this, simply use the tag or label function present in CMMS Mobility Work application. You can create different types of equipment families via the tags. Here are some examples of possible tags:

Category A – Bottleneck or very critical equipment

Category B – Equipment that should be regularly observed

Category C – Equipment that is not very important


Equipment criticality assessment methods as the PIEU method can help you identify and integrate relevant adjustments to your maintenance strategy. By prioritizing equipment, bottlenecks in industrial maintenance can be successfully prevented and reliability improved.

Sign-up to receive our newsletter