An Interactive 5-Day Training Course
Relief, Flare and Blowdown Systems Design (API 520/521)
Practical relief, flare and blowdown system design guide.
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Duration
5 Days
Price
$ 4,000
Starting From
18 Oct 2027
Relief, Flare and Blowdown Systems Design (API 520/521)
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Relief, Flare and Blowdown Systems Design (API 520/521) - SF-RFBS-PEA27
| Code | Date | Time | Duration | Location | Currency | Early Bird Fee Per Person |
|---|---|---|---|---|---|---|
| SF-RFBS-PEA27 | 18 - 22 Oct 2027 | 10 AM CST | 5 Days - 4 Hours / Day |
Online |
USD |
4000 |
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Relief, Flare and Blowdown Systems Design (API 520/521)
This training covers pressure relief, flare and blowdown system design to recognised code practice. It works through overpressure scenario identification, relief load calculation for each scenario, relief device selection and sizing, header and flare hydraulics, knockout drum and flare stack design, radiation and dispersion assessment, depressurisation requirements and the revalidation of existing relief systems.
Description
Pressure relief is the last engineered barrier before a pressure vessel fails. Everything upstream of it, control systems, alarms, operator response and shutdown functions, can fail, and the relief device must still protect the equipment. That protection depends on a chain of engineering decisions: whether the credible overpressure scenarios were identified, whether the relief load for each was calculated correctly, whether the device was sized and selected for that load, whether the inlet and outlet piping allows it to function, and whether the header and flare can accept the discharge without imposing back pressure that defeats it.
This training covers each step to the practice set out in API 520 and API 521. Scenario identification is developed systematically across blocked outlet, fire exposure, control valve failure, thermal expansion, tube rupture, utility failure, reflux failure and other credible causes, with the governing case determined for each protected system. Relief load calculation follows for each scenario type, including the fire case for both wetted and unwetted vessels. Device selection and sizing covers conventional, balanced bellows and pilot operated valves, rupture discs and combined arrangements, with the sizing equations for gas, liquid, two-phase and steam service. Inlet pressure drop, built-up back pressure, chatter and instability are then addressed. The training closes with relief header hydraulics, knockout drum and flare stack design, radiation and dispersion, depressurisation philosophy and the revalidation of relief systems on operating plants.
Relief system deficiencies are widespread and largely invisible. Facilities are modified over their lives: throughput increases, feed composition changes, equipment is added, control schemes are altered and operating pressures drift. Each change potentially alters relief loads or adds a scenario, and unless the relief system is revalidated the protection quietly becomes inadequate. Industry relief system audits routinely find undersized devices, unassessed scenarios, excessive inlet pressure drop and headers that cannot accept simultaneous relief.
The fire case is the scenario most often decisive and most often argued. It sets relief load through the heat input to a vessel exposed to a pool fire, and that heat input depends on wetted area, environmental factors, drainage, insulation and the fire zone assumed. Small differences in these assumptions produce large differences in required relief area, and the decision on whether a vessel is protected by relief or by depressurisation frequently rests on them. API 521 provides the framework, but applying it requires judgement that has to be understood rather than copied.
Inlet and outlet piping defeat more relief valves than undersizing does. Excessive pressure drop in the inlet line causes the valve to chatter, which destroys the seat and can prevent the valve from relieving at all. Excessive built-up back pressure in the discharge line reduces capacity in a conventional valve. Both are avoidable at design and both are common in installed systems, particularly where valves have been replaced with larger units without revisiting the piping.
Depressurisation is a distinct requirement from relief. Relief protects against overpressure; blowdown reduces inventory and vessel wall temperature during a fire so that the vessel does not fail below its relieving pressure. The two are designed to different criteria and a system that satisfies one does not necessarily satisfy the other.
By the end of this training, participants will be able to:
- Identify credible overpressure scenarios for each protected system and determine the governing case
- Calculate relief loads for blocked outlet, control valve failure, thermal expansion, tube rupture, utility failure and other scenarios
- Apply API 521 fire case methodology including wetted area, environmental factors and heat input determination
- Select relief device type appropriate to the service, back pressure and fluid conditions
- Size pressure relief valves for gas, liquid, two-phase and steam service using API 520 methods
- Evaluate inlet pressure drop, built-up back pressure and their effect on device stability and capacity
- Design relief headers and calculate hydraulics for simultaneous relief scenarios
- Size flare knockout drums, flare stacks and assess radiation and dispersion
- Specify depressurisation and blowdown requirements and distinguish them from relief requirements
- Revalidate relief systems on existing facilities and identify and prioritise deficiencies
The training follows the design sequence from scenario identification through load determination, device sizing, piping and header hydraulics to flare and blowdown design, with each step worked through numerically on facility examples. Relief load and sizing calculations are performed for gas, liquid, two-phase and fire scenarios using the code methods. Existing relief system documentation, including scenario tables, sizing calculations and header hydraulic results, is examined and checked for deficiency. Case histories of relief system failure and of overpressure incidents are analysed for the design or revalidation step that was missed.
Organisations sending participants to this training will:
- Reduce overpressure risk through identification and correction of relief system deficiencies
- Improve compliance with API 520, API 521 and associated regulatory expectations
- Strengthen management of change so that modifications trigger relief revalidation
- Improve the technical quality of contractor relief studies and their review
- Reduce unnecessary flare capacity investment through better load determination
- Build internal capability to perform relief calculations and revalidation studies
Participants will:
- Identify overpressure scenarios systematically rather than relying on a previous study
- Calculate relief loads and size devices independently against code method
- Recognise inlet, outlet and back pressure problems in installed relief systems
- Assess flare and header capacity for simultaneous relief
- Specify depressurisation requirements correctly
- Build a specialist capability central to process safety in facilities
- Process and facilities engineers responsible for relief system design
- Process safety engineers and practitioners
- Design and project engineers on facility projects and modifications
- Operations and technical support engineers responsible for installed relief systems
- Mechanical and static equipment engineers
- Inspection and integrity engineers covering relief devices
- Technical staff reviewing contractor relief and flare studies
Module 1 - Overpressure Protection Framework
- Role of pressure relief within the layers of protection
- Code framework: API 520, API 521, ASME Section VIII, and regional requirements
- Design pressure, MAWP, set pressure, accumulation and overpressure definitions
- Relieving pressure and accumulation limits for different scenarios
- Protected systems, relief system boundaries and isolation
- Documentation requirements: scenario tables, sizing calculations, datasheets
- Relationship between relief design and hazard studies
- Common deficiencies found in relief system audits
Module 2 - Overpressure Scenario Identification
- Systematic scenario identification methodology
- Blocked outlet and closed discharge
- Control valve failure, open and closed
- Thermal expansion of trapped liquid
- External fire exposure
- Heat exchanger tube rupture
- Utility failure: power, instrument air, cooling, steam
- Reflux failure, cooling failure and column scenarios
- Chemical reaction, vapour generation and abnormal heat input
- Gas blowby from upstream high pressure systems
- Scenario credibility, double jeopardy and their treatment
- Determining the governing scenario for each protected system
Module 3 - Relief Load Determination
- Relief load calculation for blocked outlet scenarios
- Control valve failure load and its calculation basis
- Thermal expansion relief load
- Gas blowby load determination
- Tube rupture: two-thirds rule, load calculation and treatment options
- Utility failure load determination across a facility
- Column and separation system scenarios
- Vapour and liquid load, and two-phase relief determination
- Dynamic simulation for complex relief load determination
- Credit for instrumented protection and its qualification
Module 4 - Fire Case Methodology
- Fire scenario definition and fire zone determination
- Pool fire and jet fire exposure
- Wetted area determination and elevation limits
- API 521 heat input equations for wetted vessels
- Environmental factor, drainage credit and insulation credit
- Adequacy requirements for fire proofing insulation
- Unwetted vessel fire exposure and wall temperature rise
- Vessel rupture below relieving pressure and the case for depressurisation
- Storage tank fire venting requirements
- Fire case relief load for two-phase and supercritical conditions
- Fire case assumptions and their sensitivity
Module 5 - Relief Device Selection
- Conventional spring loaded relief valves and their back pressure limits
- Balanced bellows valves and their application
- Pilot operated valves: advantages, limitations and failure modes
- Rupture discs: types, burst tolerance, and applications
- Combined rupture disc and relief valve arrangements
- Buckling pin and other specialist devices
- Thermal relief valves for liquid expansion
- Vacuum relief and combined pressure vacuum devices
- Materials, trim and seat selection for service conditions
- Selection against fluid, temperature, corrosivity, fouling and back pressure
Module 6 - Relief Device Sizing
- API 520 sizing methodology and required parameters
- Vapour and gas sizing: critical and subcritical flow
- Liquid sizing and the effect of viscosity
- Two-phase and flashing flow sizing methods
- Steam sizing
- Coefficient of discharge, back pressure correction and combination capacity factor
- Standard orifice designations and device selection from calculated area
- Rupture disc sizing and combination arrangements
- Sizing for supercritical and high pressure conditions
- Worked sizing calculations across service types
Module 7 - Inlet and Outlet Piping Design
- Inlet pressure drop limits and the three percent rule
- Valve chatter mechanism, damage and prevention
- Inlet line sizing, routing and isolation valve requirements
- Built-up back pressure and its effect on capacity
- Superimposed back pressure and variable back pressure
- Outlet line sizing and reaction force
- Support and reaction load design
- Drainage, pocketing and liquid accumulation in relief piping
- Car sealed and locked open isolation arrangements
- Multiple device installations and staggered set pressures
Module 8 - Relief Header and Flare System Hydraulics
- Relief header design philosophy and segregation
- High pressure, low pressure and cold flare header separation
- Simultaneous relief scenario definition and load summation
- Header hydraulic calculation methods
- Back pressure profile and its effect on individual devices
- Sonic velocity, noise and vibration limits in headers
- Liquid handling and header slope requirements
- Header material selection and low temperature considerations
- Header capacity as a facility throughput constraint
- Debottlenecking an existing relief header
Module 9 - Flare Systems and Knockout Design
- Flare system configuration: elevated, ground, enclosed, marine
- Knockout drum sizing for droplet removal
- Liquid seal drums and their function
- Flare tip selection, capacity and pressure drop
- Pilots, ignition systems and flame detection
- Purge requirements and flashback prevention
- Molecular seals and their operation
- Flare radiation calculation and permissible exposure limits
- Flare stack height determination
- Dispersion of unignited releases and cold vent design
- Smokeless operation, steam and air assist
- Flare gas recovery and its interaction with flare system design
Module 10 - Depressurisation and Blowdown
- Purpose of depressurisation and its distinction from relief
- Depressurisation criteria and the fifteen minute guidance
- Vessel wall temperature during fire and its calculation
- Rupture prevention as the depressurisation objective
- Blowdown valve sizing and restriction orifice selection
- Low temperature effects during depressurisation and material selection
- Depressurisation of liquid filled and two-phase systems
- Sectionalisation, isolation and inventory limitation
- Dynamic simulation of depressurisation
- Emergency shutdown interaction with blowdown initiation
- Operating and testing requirements for blowdown systems
Module 11 - Revalidation of Existing Relief Systems
- Drivers for revalidation: modification, throughput change, code update, audit
- Establishing the current design basis and its documentation gaps
- Field verification of installed devices against records
- Reassessing scenarios against current operation
- Recalculating loads for current conditions
- Assessing inlet and outlet piping against current requirements
- Header hydraulic reassessment
- Classifying and prioritising identified deficiencies
- Interim measures and risk acceptance while deficiencies are corrected
- Relief valve testing, maintenance intervals and pop testing records
- Sustaining relief system integrity through management of change
Upon successful completion of this training course, delegates will be awarded an official Certificate of Completion issued by the Petroleum Engineers Association (PEA), an ISO 9001:2015 certified training organization. The certificate carries 10 Credits and formally records the total learning hours completed.
Each certificate is signed by the Course Facilitator and the CEO of the Petroleum Engineers Association, and serves as verifiable proof of professional training that delegates can present to employers and professional bodies worldwide.
This course is led by a pressure relief systems specialist with more than 20 years in the oil and gas industry, built on sizing the systems that stand between overpressure and loss of containment.
He currently holds process safety and relief systems engineering leadership responsibility with a major operator managing pressure protection across production and processing facilities, covering overpressure scenario identification, relief device sizing and flare system design — the disciplines that prevent overpressure from becoming a loss of containment event. Earlier in his career he served as a process safety engineer on major facility developments, leading relief system design and revalidation work to API 520 and API 521 standards on some of the industry's most safety-critical facilities. Across two decades he has taken several relief and flare systems from design through revalidation on existing operating facilities.
That operating background shapes how he teaches. Delegates learn not only how relief systems are designed to work, but how they perform when called upon — where overpressure scenarios actually get missed, why relief load determination is often underestimated, what drives correct device sizing and selection, how relief header hydraulics affect system performance, and how engineering and operations teams manage depressurisation, blowdown and revalidation of relief systems together. Every module is anchored in real relief system data, design decisions and lessons from safety-critical facilities.
His subject coverage spans the full relief systems chain: overpressure scenario identification, relief load determination, device sizing and selection, relief header hydraulics, flare stack sizing and radiation, depressurisation and blowdown, and the revalidation of relief systems on existing facilities.
He has delivered relief, flare and blowdown systems training for many years across the Middle East, North Africa and Southeast Asia, working with mixed groups of process safety engineers, process engineers and technical management at every level of experience. He is an active contributor to industry forums on process safety and pressure relief systems.
His approach is practical, discussion-led and grounded in real relief system engineering — not the textbook.
Frequently Asked Questions
All course bookings made through PEA are strictly non-refundable. By registering for a course, you acknowledge and accept that all fees are payable in full and are not subject to refund under any circumstances, including changes in personal or professional commitments or partial attendance.
PEA reserves the right to make reasonable adjustments to course content, trainers, or schedules where necessary, without entitling delegates to a refund. Comprehensive details of each course — including objectives, target audience, and content — are clearly outlined before enrolment, and it is the responsibility of the delegate to ensure the course's suitability prior to booking.
For any inquiries related to cancellations or bookings, please contact our support team, who will be happy to assist you.
