What Has Changed In Api 521 6ed 3xc72

What’s Changed in API STD 521 6th ed. - Issued January 2014 Eli Vatland Johansen - Leading Advisor Process Safety Classification: Internal

2014-11-07

Overview: • Introduction to American Petroleum Institute (API) • Some main changes in API STD 521 6th ed. • Other API standards in subcommittee Pressure Relieving Systems updated lately

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Classification: Internal

2014-11-07

American Petroleum Institute (API) • Petroleum Safety Authority Norway (Guideline to facilities regulations § 34): “Overpressure protection should be designed in accordance with API RP 520/NSEN ISO 4126 and API 521/NS-EN ISO 23251” • ISO 23251 1st ed. and API STD 521 5th ed. were cobranded

− Sadly this cooperation has ended API 521 6th ed. issued as API standard − Reason: Restriction from OFAC (Office for Foreign Assets Control - USA) − API committee and API staff regret this, and hope that things will change • Statoil has been member of API Pressure Relieving Systems committee for 10 years. • The API Pressure Relieving Systems committee meets twice a year.

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Classification: Internal

2014-11-07

Sec. 3.1 General update of and definitions • Examples, changes or new definitions: − Blowdown drum − Lift – off (replaces blow-off) − Choke valve − Combustion efficiency − Confined fire − Lateral − Open fire − Pressure-relief device / pressure relief valve − Pressure system − Rated capacity − Required relief rate 4

Classification: Internal

2014-11-07

Sec. 4.2.5 Operator Error / Effect of Operator Response Section “Effect on operator response” and “Operator error “ has been combined

New paragraph added on items to consider when credit is taken for operator intervention: − An alarm is required − Sufficient time for operator to intervene − Operator training − Understanding of consequences of operator failure − Evaluation of probability of alarm failure and / or ineffective operator intervention

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Classification: Internal

2014-11-07

Section 4.4.9.3: Check Valve Leakage or Failure (1) New text 6th edition: . . .overpressure protection should be considered where the maximum operating pressure of the high pressure system is greater than the low pressure equipment's corrected hydrotest pressure.

Old text 5th edition: Required overpressure protection if the operating pressure of the high pressure system are greater than the design pressure

Note: New edition is less strict and more in line with the 4th edition

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Classification: Internal

2014-11-07

Section 4.4.9.3: Check Valve Leakage or Failure (2) • New paragraph under Severe Check Valve Leakage: For certain rotating equipment such as reciprocating compressors and positive displacement pumps, the may determine that significant reverse flow trough the machinery will not occur. • 5th edition “allowed” reverse flow through check valves to be less than “a orifice area equal to 1 % of the nominal flow area” for series check valves provided a condition-monitoring system where installed. − This has been deleted in 6th edition, API 521 6th ed. now recommends either: • orifice area equal to 1 % of the nominal flow area • orifice that is sized to 10 % of the normal forward flow

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Classification: Internal

2014-11-07

New sec. 4.4.8.6 Choke valve Failure (Choke Collapse) Statoil have provided the API committee with: - Norsok P-100 section 16.2.2 Choke Valve Collapse

Section 4.6.8 Choke Valve Failure in API STD 521 6th ed. is more or less the same as “old” Norsok P-100.

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Classification: Internal

2014-11-07

New sec 5.4.4 (Flare) Header Segregation • Flare header streams should be segregated based on: − Pressure − Temperature − Fluid properties • New list with aspects to consider when making flare relief headers • Water-wet fluids should be segregated from cold fluids to prevent ice/hydrate • List of what to consider when deg the relief discharge from rupture discs…

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Classification: Internal

2014-11-07

New Sec. 5.5.12 Acoustic Fatigue • 5.5.12.1 Background − High pressure drops across e.g. PRV, orifice cause noise downstream − High-energy, high-frequency noise cause high-frequency vibration in pipe wall that can result in rapid fatigue − Fatigue screening method  Carucci and Mueller «Sound Power level»

• 5.5.12.2 Sound Power Level − Guidance on calculation the Sound Power Level

• 5.5.12.3 Mitigation Options

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Classification: Internal

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Sec. 5.7.9: Flare Knockout Drums • 5th edition: − Outlet nozzles should have a deflection plate or baffle to minimize carry over • 6th edition: − In general, vapor outlet nozzles should not be fitted with any devices (e.g. deflection plates, baffles, demister pads, vane packs, etc.), because of the potential for such devices to fail or plug and obstruct the outlet. Such devices should be used only if the drum is equipped with an alternate outlet nozzle sized for the drum’s design vapor flow rate and fitted with a rupture disk (or buckling pin device) whose burst pressure is selected both to protect the drum against overpressure and to permit proper operation of the drum and relief system in the event the normal vapor outlet becomes obstructed.  Input from Visund accident where baffle plate blocked the flare stac http://www.ptil.no/getfile.php/z%20Konvertert/Helse,%20milj%C3%B8%20og%20sikkerhet/Hms-Aktuelt/Dokumenter/report20063098rev02_komprimert.pdf

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Classification: Internal

2014-11-07

521: 5.7.9.4 Droplet Size Criteria for Flare Drums • Flare knockout drums can be sized for droplet size 400 m (sub-sonic tip), 1000 m (sonic) • API 5th edition − In general, a flare can handle small liquid droplets. However, a knockout drum is required to separate droplets larger than 300 μm to 600 μm in diameter in order to avoid burning liquid outside the normal flame envelope.

• API 6th edition − Although the presence of burning rain may result with liquid droplet sizes, conditions or loadings in excess of the values noted in a) through c) below under steady-state conditions (read: 600 micron for sub-sonic, 1000 micron for sonic), the occurrence of burning rain is often associated with transient flare load conditions where slugs of liquid may be carried over from the flare knockout drum, liquid seal drum, or re-entrainment of liquid accumulated within the flare piping or the flare gas riser…. Liquid droplets exceeding 1,000 m can readily lead to burning rain regardless of flare type. Burning rain can occur at smaller droplet sizes for some flare types. • The focus is more on smoke than burning rain, i.e. smoke is an issue before burning rain. Although not explisitly said, the new droplet sizing requirements are 400 m and 1000 m with respect to burning rain.

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Classification: Internal

2014-11-07

521: 5.7.9.8 (New Section) Knockout Drums for Oil and Gas Production Facilities • Describes the challenges with deg Knockout drums for overfill protection for oil and gas platforms compared to refineries. − Sizing a knockout drum to contain 20 min to 30 min of this flow (the sizing basis suggested in 5.7.9.5 for a “typical” facility) is frequently impractical for both transportation to and installation in an oil and gas production facility, whether onshore or offshore. • Gives design recommendations for overfill protection: − … the knockout drum surge capacity may be based on 1 min to 2 min of continued flow starting once the point is reached where the automatic shutdown is initiated by the flare knockout drum instrumentation. − In addition to the emergency case described above, the flare knockout drum should have sufficient surge capacity (e.g. 20 min between the normal level and the LAHH (high-high liquid level alarm)) to avoid spurious trips during normal flaring. 13

Classification: Internal

2014-11-07

New Annex 1: Fire depressurisation (1) • API521 has for several years required fire rupture calculation to be done,

− API521, rev 4 1997: • «The required depressuring rate depends on the metallurgy of the vessel, the thickness and the initial temperature of the vessel wall, and the rate of heat input»

− API521, rev 5, 2007: • «If a depressurization system is installed to protect vessels and/or piping against fire, the need for ive fire protection is determined by the capacity of the depressurization device, the type, size and intensity of the fire, the availability of firewater and fire fighting equipment, the type and layout of the drain system. The need for ive fire protection also depends on wall thickness, the vessel/pipe material and the prevailing acceptance criteria for the specific installation»

• Reference to Scandpower Report 27.207.291/R1, Version 2, Guidelines for the protection of pressurised systems exposed to fire, March 31, 2004 In other words: Both the 1997 and 2007 revisions say: «Do the work!» ….but not how to do it. 14

Classification: Internal

2014-11-13

New Annex 1: Fire depressurisation (2) • A «How to do it» is now included in the API521 6th edition, Appendix A − This is a short version of Statoil’s TR3003 and Scandpower «guideline», and includes e.g. • The fire equation + typical input data to this equation • The need for criteria for unacceptable ruptures (included in the 2005 version)

• The stress equations • The work flow chart including guidance

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Classification: Internal

2014-11-13

Other changes in API STD 521 6th ed. • Substantial changes in structure and organization • Change in section 4.4.7 Overfilling • New section 4.4.16 Overpressure Prevention During Maintenance • New section 5.2.2 (Disposal system) Temperature • New section 5.7.2.4 Flame Stability • New sec. 5.7.3.2.11 Noise Caused by Smokeless Flaring • ……

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Classification: Internal

2014-11-07

Summary changes in API STD 521 6th edition • Substantial changes in structure and organization • and definitions updated • A number of technical changes API STD 521 have increased from 196 (5th ed.) – 248 (6th ed.) pages

Disclaimer: • There may be errors in this presentation or important changes made to API STD 521 6th ed. that are missed • It has not been possible to either identify or list all changes

Therefore please familiarize yourself with API STD 521 6th ed.

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Classification: Internal

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API pressure relief systems • API Pressure Relieving Systems − API STD 521 Pressure-relieving and Depressuring Systems -2014 − API STD 520 part 1 Sizing and Selection of Pressure-relieving Devices -2014 − API STD 520 part 2 Installation of Pressure-relieving Devices – -2014 (?) − API STD 2000 Venting Atmospheric and Low-pressure Storage Tanks -2014 • API Heat Transfer Equipment − API STD 537 Flare Details • Inspection − API RP 576 Inspection of Pressure-Relieving device

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Classification: Internal

2014-11-07

Presentation title: What’s Changed in API STD 521 6th ed. Eli Vatland Johansen E-mail [email protected] Tel: +4748072946 www.statoil.com

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Classification: Internal

2014-11-07