Equivalency & Substitution: A Controlled Method

Substitution can save cost and lead time—but it can also damage performance if handled casually.

Use a controlled method:

1. Define what is critical (must not change): performance limits, compatibility, safety constraints

2. Define what is flexible: brand, non-critical dimensions, packaging, minor specs

3. Compare like-for-like: map parameters side-by-side

4. Assess risk: operational impact, maintenance, warranties, compliance

5. Approve formally: record the basis of acceptance and revision impact

A strong equivalency review asks:

• Does it meet the same standard?

• Does it create interface issues?

• Does it alter operating envelope or reliability?

• Are documents and traceability equivalent?

• Does the change trigger re-approval or licensing impacts?

Substitution should never be “whatever is available.” It should be engineered acceptance.

Takeaway: Alternatives are fine when controlled. Protect critical requirements, document decisions, and keep approvals traceable.