# FMEA, FTA, HAZOP and Other Risk Analysis Methods: Which One to Use

> Source: https://netray.co/tools/risk-analysis-method-selection-reference
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

A searchable comparison of risk and reliability analysis methods, showing whether each works bottom-up or top-down, what it suits and which standard describes it.

## Category

quality

## Audience

- Quality engineer
- Reliability engineer
- Safety engineer

## Tool

**Kind:** worksheet

**Mode:** reference

**Columns:**

#### Method

**Key:** method

**Type:** text

#### Approach

**Key:** approach

**Type:** text

#### Best used for

**Key:** best

**Type:** text

#### Typical output

**Key:** output

**Type:** text

#### Related standard or source

**Key:** reference

**Type:** text

**Rows:**

#### Inductive, bottom-up

**Method:** DFMEA

**Best:** Finding how product functions could fail in design

**Output:** Ranked failure chains with design actions

**Reference:** AIAG-VDA FMEA Handbook; SAE J1739; IEC 60812

#### Inductive, bottom-up

**Method:** PFMEA

**Best:** Finding how process steps could fail to deliver requirements

**Output:** Ranked failure chains, controls and actions

**Reference:** AIAG-VDA FMEA Handbook; SAE J1739; IEC 60812

#### Inductive, bottom-up

**Method:** FMECA

**Best:** FMEA plus criticality ranking, common in defense and aerospace

**Output:** Criticality matrix or numbers

**Reference:** MIL-STD-1629A (cancelled, still cited); IEC 60812

#### Inductive, bottom-up

**Method:** System FMEA (SFMEA)

**Best:** System-level functions and interfaces

**Output:** System failure effects and mitigations

**Reference:** AIAG-VDA FMEA Handbook

#### Inductive, bottom-up

**Method:** FMEA-MSR

**Best:** Monitoring and system response in electronic and software-heavy systems

**Output:** Failure chains with monitoring and response

**Reference:** AIAG-VDA FMEA Handbook

#### Inductive, bottom-up

**Method:** FMEDA

**Best:** Failure rates and diagnostic coverage for safety hardware

**Output:** Safe, dangerous, detected and undetected failure rates

**Reference:** IEC 61508; ISO 26262

#### Deductive, top-down

**Method:** Fault tree analysis (FTA)

**Best:** Finding combinations of events leading to one unwanted top event

**Output:** Fault tree and top event probability, minimal cut sets

**Reference:** IEC 61025

#### Inductive, forward-looking

**Method:** Event tree analysis (ETA)

**Best:** Following consequences after an initiating event

**Output:** Outcome branches with frequencies

**Reference:** IEC 62502

#### Structured team review with guide words

**Method:** HAZOP

**Best:** Process plants and flow systems, deviation from design intent

**Output:** Deviation, cause, consequence and safeguard table

**Reference:** IEC 61882

#### Semi-quantitative

**Method:** LOPA

**Best:** Deciding if safeguards give enough risk reduction

**Output:** Scenario frequency against tolerable frequency

**Reference:** CCPS LOPA guidance; IEC 61511

#### Early qualitative

**Method:** Preliminary hazard analysis (PHA)

**Best:** Identifying hazards early in concept

**Output:** Hazard list with initial risk ranking

**Reference:** SAE ARP4761 (aircraft); ISO 31010

#### Brainstorming

**Method:** What-if analysis

**Best:** Quick review of procedures or small changes

**Output:** Question and answer list with actions

**Reference:** ISO 31010

#### Visual barrier model

**Method:** Bow-tie analysis

**Best:** Showing threats, barriers and consequences around one hazard

**Output:** Bow-tie diagram

**Reference:** ISO 31010

#### Iterative questioning

**Method:** 5 Whys

**Best:** Simple root cause of a single problem

**Output:** Cause chain

**Reference:** Lean and 8D practice

#### Brainstorming by cause category

**Method:** Ishikawa (fishbone) diagram

**Best:** Listing possible causes of one problem

**Output:** Cause categories diagram

**Reference:** ISO 9004 and quality tool literature

#### Quantitative structure model

**Method:** Reliability block diagram (RBD)

**Best:** Availability of series and parallel systems

**Output:** System reliability or availability

**Reference:** IEC 61078

#### Function-based maintenance analysis

**Method:** Reliability-centred maintenance (RCM)

**Best:** Choosing maintenance tasks for assets

**Output:** Maintenance strategy per failure mode

**Reference:** SAE JA1011 and JA1012; IEC 60300-3-11

#### Statistical life data

**Method:** Weibull analysis

**Best:** Modelling wear-out or infant mortality from failure data

**Output:** Shape and scale parameters

**Reference:** IEC 61649

#### Task-based hazard review

**Method:** Job safety analysis (JSA)

**Best:** Hazards in a work task

**Output:** Step, hazard and control table

**Reference:** OSHA guidance on job hazard analysis

#### Ongoing qualitative scoring

**Method:** Risk register

**Best:** Tracking project and business risks over time

**Output:** Ranked log with owners and actions

**Reference:** ISO 31000; PMI practice

**Notes:** Standards and handbooks change by edition. Confirm the current edition and your customer's requirements before citing one in a deliverable.

## Content

**Intro:** Choosing the wrong risk method creates a lot of paperwork and little insight. This table compares the common methods side by side: does it start from components or from an unwanted event, what is it good at, what does it produce and where is it described.

**Sections:**

#### Bottom-up versus top-down

**Body:** FMEA works bottom-up: take each item or step, ask how it could fail and trace the effect upward. It is thorough for single failures and ties neatly to controls. Fault tree analysis works top-down: pick one unwanted event and ask which combinations of lower events cause it. It handles combinations and redundancy well, which FMEA does not. Many safety cases use both: FMEA to find single-point failures, then an FTA on the few top events that matter most.

#### Matching the method to the question

**Body:** Start with the question, not the template. If the question is how a product or process could fail and what controls exist, use DFMEA or PFMEA. If it is whether two failures together could cause a hazard, use FTA. If it is deviation in a flowing process, HAZOP fits. If you need to prioritise a long project risk list, use a risk register. If you need the cause of a single event that has happened, use 5 Whys or an 8D with a fishbone.

**Bullets:**

- Single failures in design or process: DFMEA or PFMEA
- Combinations and redundancy: fault tree analysis
- Process plant deviations: HAZOP, then LOPA if needed
- Maintenance planning: RCM using FMEA outputs
- Past events: 5 Whys, fishbone, 8D

#### Common mistakes

**Body:** Teams run FMEA to answer questions it cannot answer, such as the likelihood of two simultaneous failures. They also treat a risk register as a hazard analysis, scoring vague items with no structure. Another trap is using a method because the customer form asks for it, without checking that it suits the risk. Where a customer or regulator specifies a method, follow it, and add a complementary method if it leaves gaps.

**Cta:** If your risks and failure data sit across ERP, quality and maintenance systems, Netray can talk through how to bring them into one view without moving the data.

**Faq:**

#### Is FMEA better than fault tree analysis?

**Answer:** Neither is better; they answer different questions. FMEA is a systematic bottom-up review of single failures. FTA models how several events combine to cause one top event. Safety-critical programs often use both.

#### What is the difference between FMEA and FMECA?

**Answer:** FMECA adds a criticality analysis to FMEA, ranking failure modes by severity and probability or failure rate. It is common in defense and aerospace programs, historically under MIL-STD-1629A.

#### When should I use HAZOP instead of FMEA?

**Answer:** HAZOP suits process plants and flow systems where deviations from design intent, such as no flow or high pressure, are the natural way to explore risk. FMEA suits discrete products and manufacturing steps.

#### Which standard describes FMEA?

**Answer:** IEC 60812 describes FMEA and FMECA generally. For automotive, the AIAG and VDA FMEA Handbook is the reference, and SAE J1739 has been widely used. Your customer may specify which applies.

## Search terms

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