RCM Systems - Basics

To assess the reliability of a production unit, we need to know what the Functions and Functional Failures are of the production process.
For the Functional Failures of the production process we need to specify a Product Loss Equation (PLE).

As a unit can hold a lot of Functions and Functional Failures, we often like to split up the unit in smaller pieces.

If the unit is big and/or complicated, you can create as many Systems as needed.

RCM reliability assessment asks for: What can cause a functional failure of your System?
To answer that question a 'Failure Mode and Effect Analyses' (FMEA) is done on the System.

For an effective FMEA the engineers need to be able to relate equipment Failure Modes to the system Functional Failures.
Here, both equipment knowledge is needed involving what Failure Modes are credible to occur, as also production process knowledge is needed to determine the effect of the broken equipment towards the system Functional Failures.
This is the reason we recommend to execute the FMEA with a multi-disciplinary team, involving process engineers, operation, discipline engineers and maintenance.

In the end, if the systems are too big, one might find too many functional failures and it can be difficult to do the FMEA.
As such, the systems might be split up into smaller systems to enable effective FMEA.

For guidance on FMEA work, we point out to International Standard IEC 60812 on FMEA:

Relevant paragraphs are for instance:

• IEC60812 – 5.2.2.1 Information on System Structure:
• IEC60812 – 5.2.2.2 Defining System boundary for the analyses

Process engineers - involved in process design - typically map logical process steps onto the individual P&ID pages, where the process unit can have multiple P&IDs in series.
For utility systems, like a compressor lub oil system or the furnace burner control - parallel P&IDs can be involved. See picture below:

In above example, there are 6 P&ID's.
The P&ID's 1.1, 1.2, 1.4 and 1.6 are in series covering the main production process (by the Red line)
P&ID 1.3 is the lub oil system of the compressor, also called a sub-unit.
P&ID 1.5 is the burner control system of the fired heater (furnace), aslo called sub-unit.

In this example:

• System 1 involves P&ID's 1.1 and 1.2
• System 2 involves P&ID's 1.4 and 1.6
• System 3 involves P&ID 1.3: the lub oil system
• System 4 involves P&ID 1.5: the burner control

As the P&IDs are typically detailed diagrams, they are a good base to register the Systems boundaries. The system boundaries can be draw in on the P&ID's, in case a P&ID involves multiple Systems. The marked up P&IDs become a quality registration for the System boundaries.

Typical points for determining System boundaries may involve:

• Main changes in product specification and product quality requirements
• Inputs and outputs of the production process, covering the main product stream, recycle streams, utility streams (in and out) including energy.

Although an FMEA approach is not a RCM analyses, it can be well used to prioritize the Floc/Eq in the System.
Basically the question should be raised: can a Floc/Eq with one Failure Mode cause a Functional Failure of the System?
Based on the consequences regarding the Asset or Environment, a priority can be registered to get better focus on the follow up work, like detailed RCM analyses or not.