Pressure Relief ValveHector Nguema Ondo

Pressure Relief valves

• Safety is the most important factor in designing a process system.

LOPA

Pressure Relief valves

Define Protected System:

Design considerations

Important an understanding of the operation. One relief valve can protect more than one equipment

Locate Relief Devices:

Pressure Relief valves

Define overpressure scenarios

Design considerations

• Double jeopardy design not required• Latent failures• Overpressure protection and instrumentation

MEGPL Basis (Z0210-09-PE-RT-00001-00)• HP Flare system: 900 MMSCFD with back-pressure of 75 Psig

• LP Flare system: 40 MMSCFD with back-pressure of 15 Psig

• Propane Flare system: 20-22 MMSCFD with no back-pressure

• Butane Flare system: 29-36 MMSCFD with no back-pressure

“Alba_Hysysrun.HSC” (Dated 08/27/2009).

MEGPL Considerations

Fire - The relieving pressure is 121% of MAWP Operating - The relieving pressure is 110% of MAWP

Pressure Relief valves

Causes of overpressureA. Blocked Discharge

Design considerations

Max design pressure: 1350 Psig @150F

Pressure Relief valves

B. Fire Exposure

Design considerations

Max design pressure: 1350 Psig @150F

Pressure Relief valvesDesign considerations

C. Check Valve FailureCauses:

• Stuck Open• Broken flapper• Check valve seat leakage

Pressure Relief valvesDesign considerations

D. Thermal Expansion

Pressure Relief valves

Conventional pressure relief valve

Type of relief valves

Working principal of the conventional relief valve is the inlet pressure to the valve is directly opposed by a spring force

Conventional Pressure Relief Valve

Pro: Wide range of materials High Temperature version available Lowest cost

Contra: Prone to leak Long simmer > 95% valve opening Sensitive to back-pressure, < 10% Vulnerable to inlet pressure lost

Pressure Relief valvesType of relief valves

Balanced Relief Valves

Pro: Better handling of corrosive fluids. Less sensitivity to back-pressure Wide range of materials High Temperature version available

Contra: Prone to leak Long simmer > 95% valve opening Higher maintenance cost Limited bellows life

Pressure Relief valvesType of relief valves

Pilot Operated Relief Valves

• Low pressure applications for tanks

Pro: Smaller & Lighter than other valves Easily testable on site Not affected by back-pressure Can address high inlet losses

Contra: Dirty service limitations When soft-seat or O-ring is used, limited

chemical compatibility

Pressure Relief valves

• Sizing for liquid service

• Sizing for gas service

Sizing relief valves

FlareNet Model

Pressure Relief valves

• Designed pressure relieving devices should be certified and approved under Code.

ASME- Boiler and Pressure Vessel Code Section I, Power Boilers, and Section VIII, Pressure Vessels.

ASME- Performance Test Code PTC-25, Safety and Relief Valves.

ANSI B31.3, Code for Petroleum Refinery Piping.

Application of Codes, Standard and Guidelines

• API are recommended practices for the use of Safety Relief Valves in the petroleum and chemical industries are:

API Recommended Practice 520 Part I - Sizing and selection of components for pressure relief systems in Refineries.

API Recommended Practice 520 Part II - Installation of pressure relief systems in Refineries.

API Recommended Practice 521 - Guide for Pressure-Relieving and Depressuring Systems.

API Recommended Practice 527 - Seat Tightness of Pressure Relief ValvesAPI Standard 526 - Flanged Steel Pressure Relief ValvesAPI Standard 2000 - Venting Atmospheric and Low-Pressure Storage Tanks:

Nonrefrigerated and RefrigeratedAPI Standard 2001- Fire Protection in Refineries.

Pressure Relief ValvesAlternative relief path (ARP)

Questions?

Hector Nguema Ondo