Objectives of HAZOP (Hazard and Operability Study)
The Hazard and Operability Study (HAZOP) is a structured and systematic technique used to identify hazards and operability issues in process systems. Its objectives go beyond regulatory compliance; HAZOP is a cornerstone of process safety, operational reliability, and informed decision-making. Each objective is focused on proactively identifying and controlling risks before they result in incidents, losses, or operational disruptions.
1. Identify Hazards
The primary objective of HAZOP is to identify potential hazards arising from deviations from normal operating conditions. These deviations may involve parameters such as pressure, temperature, flow, level, composition, or reaction conditions.
If left unaddressed, such deviations can lead to fires, explosions, toxic releases, equipment damage, environmental harm, or fatalities. By systematically applying guidewords (e.g., No, More, Less, Reverse) to process parameters, the HAZOP team is able to uncover both obvious hazards and hidden or non-intuitive risks that may not be detected during routine design reviews.
Example:
A deviation such as “No Flow” in a cooling line may appear minor, but in a reactor system it can cause overheating and thermal runaway, potentially leading to catastrophic failure.
2. Examine Operability Problems
Beyond safety hazards, HAZOP also aims to identify operability issues, conditions that may not immediately cause accidents but can disrupt stable plant operation. Addressing operability issues during the HAZOP stage helps organizations reduce downtime, avoid production losses, improve efficiency, and enhance maintainability.
These issues may include:
- Low or unstable flow rates affecting product quality
- Incorrect material composition leading to off-spec products
- Poor equipment layout causing maintenance or access difficulties
- Frequent equipment trips or failures due to design limitations
Example:
Identifying a potential pump cavitation scenario at low flow conditions allows design or operational changes that prevent repeated shutdowns and maintenance problems.
3. Improve Safety and Reliability
Another key objective of HAZOP is to enhance overall process safety and system reliability. By identifying hazards and operability weaknesses early, HAZOP ensures that the process is designed and operated within defined safe limits.
This proactive approach:
- Reduces the likelihood of equipment failure and human error
- Prevents escalation of abnormal situations
- Improves confidence in plant performance
- Enhances organizational reputation and workforce trust
Example:
If a HAZOP study identifies that a relief valve is undersized for worst-case scenarios, corrective action can be taken during the design phase, making the system more robust and dependable.
4. Determine Causes (Why the deviation happens)
Causes are the initiating events that lead to a deviation from the design intent. They generally fall into a few main categories:
Common types of causes
- Equipment failure
(valve stuck, pump trip, instrument failure) - Human error
(wrong valve alignment, incorrect setpoint, bypass left open) - Control system failure
(controller in manual, wrong logic, signal loss) - Utility failure
(power loss, cooling water failure, instrument air loss) - External factors
(ambient temperature, upstream upset, maintenance activity)
5. Evaluating Existing Safeguards
In a HAZOP study the current protective measures are assessed—such as control loops, alarms, interlocks, shutdown systems, relief devices, and procedural controls—are capable of effectively preventing identified deviations or mitigating their consequences if they occur. This evaluation is not about merely listing safeguards, but about judging their effectiveness, independence, reliability, and suitability for the specific scenario under review.
6. Suggesting Recommendations
In HAZOP, the team should recommend practical actions to either eliminate the cause, prevent the deviation, or reduce the consequences, and also suggest any uncertainties or information gaps that require deeper investigation. Recommendations may include design changes, instrumentation and control improvements, mechanical protection, procedural and human-factor controls.
5. Determine Consequences (What happens if deviation continues)
Consequences describe the credible outcome if the deviation occurs assuming no safeguards work.
They are described qualitatively, not numerically.
Consequences may include:
- Safety impacts: fire, explosion, toxic exposure, injury, fatality
- Environmental impacts: spill, release, contamination
- Asset damage: equipment rupture, catalyst damage
- Operational impacts: unit trip, production loss, shutdown
7. Assist in Decision-Making
HAZOP is not only a hazard identification tool—it is also a powerful decision-support mechanism. The study provides management with structured insight into:
- Process vulnerabilities
- Credible worst-case consequences
- Effectiveness of existing safeguards
- These insights support informed decisions related to:
- Design modifications
- Selection of control and protection systems
- Development or revision of operating procedures
- Emergency response and mitigation strategies
Example:
If a HAZOP identifies a high risk of pipeline overpressure, management can objectively evaluate options such as installing additional relief devices, changing materials of construction, or revising operating limits—ensuring that safety investments are targeted and effective, not reactive.
8. Ensure Compliance with Standards and Regulations
A further objective of HAZOP is to ensure compliance with legal and industry requirements. Many regulatory frameworks and standards mandate systematic risk assessments, including:
- OSHA Process Safety Management (PSM) – USA
- COMAH Regulations – UK
- IEC 61882 – International HAZOP standard
Conducting HAZOP:
- Demonstrates regulatory compliance
- Reduces legal and financial exposure
- Supports project approvals and insurance requirements
- Reinforces stakeholder and public confidence
- Compliance through HAZOP reflects an organization’s commitment to safety, environmental protection, and responsible operation.
Top References:
- The HAZOP Leader’s Handbook by Phil Eames
- https://ifluids.com
- HAZOP in Practice: A Guide to Safer and Smarter Operations by Remy Thomas
- https://senwork.com
Certified Functional Safety Professional (FSP, TÜV SÜD), Certified HAZOP & PHA Leader, LOPA Practitioner, and Specialist in SIL Verification & Functional Safety Lifecycle, with 18 years of professional experience in Plant Operations and Process Safety across Petroleum Refining and Fertilizer Complexes.
