Design for Reliability
What does Design for Reliability really mean?
Reliability is a critical attribute of every asset.
Can Maintenance achieve zero downtime after the asset is commissioned?
Where is the opportunity to maximize Reliability?
Common claims about Maintainability & Reliability
Maintenance owns unreliability.
No maintainer would ever agree with this statement. In many organizations, they are Supermen & Superwomen to the Rescue in the event of a failure.
Failures do occur and at great cost to the organization —
cost of lost production
credibility with the customer
reputation
Maintenance shares ownership for reliability with all internal stakeholders.
True. Production / Operations, Stores, Procurement, Engineering, IT, Finance, HR are all connected. Don’t forget the Senior Management Team!
Invisible walls exist between these areas of responsibility and departments. That’s why siloed departments and siloed data bases exist.
Maintenance shares ownership for safety with all internal stakeholders.
Everyone would agree with this statement.
A plant’s Safety Record is posted at the gate for all who pass through to be reminded of this top priority.
It’s very difficult for a brownfield site to ‘maintain’ its way to zero downtime.
What?! This is the promise and the goal of many maintenance organizations.
Here’s what’s so: The ability to do anything beyond achieving reliability over what has been specified and designed is almost impossible.
Limitations and constraints are unknowingly specified and designed into the asset unless innovation and clear thinking are applied.
Everything-is-connected-to-everything-else. If we are aware of this fact, all known weaknesses can be eliminated.
Reliability and availability are determined by the specification and design of the asset far more than maintenance is able to influence reliability after the asset has been commissioned and is in operation.
Noooooo! Who said that? What does this mean?
It’s not true … or is it?
This is true.
Maintainability is chiefly influenced by planning and execution.
Well, that’s true. Of course. That’s how we get to zero downtime … isn’t it?
Planning and execution is the best way to maintain the asset given its predetermined limitations and constraints.
But getting to zero downtime give the asset’s built in constraints is an uninformed lofty goal.
What is Design for Reliability?
Design for Reliability is a business process that ensures a product, or system, performs a specified function within a given environment over its expected lifetime.
Successful Design for Reliability initiatives require the integration of product design and process planning into a cohesive, interactive practice known as concurrent engineering. It’s less expensive to Design for Reliability than to Test for Reliability. When reliability considerations are implemented in the concept feasibility stage, you then make all future decisions with reliability in mind.
Design for Reliability Best Practices
Design for Reliability best practices can apply to the development of any project. These best practices guide the business processes throughout the life cycle of the asset.
Set reliability goals based on survivability. This is often bound by confidence levels, such as 95% reliability with a 90% confidence level over 15 years.
Avoid mean time to failure (MTTF) and mean time between failures (MTBF) because they do not measure reliability. Historically, MTBF has been calculated using empirical prediction handbooks that assume a constant failure rate that is not always correct.
Acquire a deep understanding of how the proposed lifetime and environment affect the design. This takes substantial effort, but there is valuable return.
Determine average and realistic worst-case scenarios, identify all failure-inducing loads, include all environments.
Keep dimensions flexible to avoid mistakes driven by arbitrary size constraints.