Offshore Oil and Gas Safety: Protection against Explosions

Offshore oil and gas operations carry a high risk of explosions, which can be efficiently prevented in many cases. The two most used approaches for prevention are: (1) the “International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres” (IECEx) and (2) European “Atmosphere Explosible” (ATEX) schemes. The main shortcoming for the IECEx scheme is in the fact that it does not cover nonelectrical equipment, while for the ATEX scheme, it is due to the allowed self-certification for a certain category of equipment in areas with a low probability of explosions, as well as the fact that it explicitly excludes mobile offshore drilling units from its scope. An advantage of the IECEx scheme is that it is prescribed by the US Coast Guard for protection against explosions on foreign mobile offshore drilling units, which intend to work on the US continental shelf but have never operated there before, with an additional requirement that the certificates should be obtained through a US-based Certified Body (ExCB). Therefore, to avoid bureaucratic obstacles and to be allowed to operate with minimized additional costs both in the US and the EU/EEA’s offshore jurisdictions (and very possibly worldwide), all mobile offshore drilling units should be certified preferably as required by the US Coast Guard.


Introduction
The offshore oil and gas industry involves many risks of explosions for personnel and installations. Explosions can occur under certain conditions in the presence of a mixture of air and released hydrocarbon gases due to a number of different reasons, including blowouts, the use of inadequate equipment or its malfunction, negligence, lack of training, poor or incomplete maintenance, etc., while sources of ignition can include naked flames, electrical sparks, static electricity, hot surfaces, friction, ionizing radiation, ultrasound, hot gases, etc. (e.g., methane is capable to cause an explosion in concentration between 4.4% and 16.5% in its mixture with air, while the ignition temperature for methane should be ≥595 • C).
Protection against explosions on mobile offshore drilling units needs to be arranged through worldwide accepted regulations at the lowest possible cost, which will be accepted by most host countries, while on fixed platforms, it needs only to fulfill legislative requirements of the host country. Two main approaches for protection against explosions are the "International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres" (IECEx) [1] and the European "ATmosphere EXplosible" (ATEX) schemes (the ATEX approach can be treated as a regional European version of the IECEx approach, while certain differences can be noted) [2][3][4].
Offshore oil and gas operations typically start with a relatively short one-off drilling phase performed by mobile offshore drilling units [5], which is shortly after replaced with a long-lasting exploitation phase that can take several years and even decades and is performed from fixed production platforms. Legislative requirements for protection against explosions on fixed platforms and offshore drilling ships are very often different (also, the legislatures treats a certain type of ships as fixed platforms, e.g., floating production storage and offloading units are typical ships in terms of shape, navigation, and propulsion, but they are treated as fixed facilities in terms of legislative requirements for protection against explosions because, as a rule, they are settled for a long time or even permanently at one place; although anchored in a similar way as ships).
The EU/EEA and the USA require different levels of protection against explosions for oil and gas mobile offshore drilling units compared with their related requirements imposed for fixed offshore platforms and offshore (Table 1). Both the ATEX and IECEx schemes provide a high level of protection against explosions but with some differences that are described in this note [6,7].

Main Certification Schemes for Protection against Explosions
The principles for the classification of equipment proofed for use in areas with a higher risk of explosions are similar in most countries, and they are based on requirements introduced by the International Electrotechnical Commission (IEC) [8]. Despite this fact, many local modifications and variants exist.
ATEX protection is described in Section 2.1 and IECEx in Section 2.2. Although based on the almost same principles but with some modifications, as described in Section 2.3, various certification schemes for protection against explosions are available and required for use in different countries. Section 2.3.1 describes the situation in the USA, Section 2.3.2 in Canada, Section 2.3.3 in the Eurasian Union (Armenia, Belarus, Russia, Kazakhstan, and Kyrgyzstan), Section 2.3.4 in China, Section 2.3.5 in Brazil, and Section 2.3.6 in Australia, together with New Zealand.

European "ATmosphere Explosible" (ATEX)
Two European ATEX directives are available for protection in explosive atmospheres (ATEX is a French acronym for "ATmosphere EXplosible"): (1) 1999/92/EC ATEX directive for the protection of the user (personnel and workers)-"Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres"; (2) 2014/34/EU ATEX directive for product safety-"Equipment and protective systems intended for use in potentially explosive atmospheres," a new version of 94/9/EC.
Using the ATEX scheme, equipment shall be certified through one of the European notified bodies listed in the "New Approach Notified and Designated Organizations" (NANDO) database. The obligatory certification has been in force since 1 July 2003 through the 94/9/EC directive and since 20 April 2016 through the related recast 2014/34/EU of the previous directive. Both ATEX directives for product safety (2014/34/EU) and the protection of the user (personnel and workers) (1999/92/EC) are mandatory in the EU/EEA.
The new goal-oriented European approach [2], which has been in force since 2000, allows the use of any available technical standard that can assure application of the obligatory directives, such as ATEX. Instead of referring to a certain list of harmonized standards (the European Standards Committee (CEN) and the European Committee for Electrotechnical Standardization (CENELEC) define the harmonized standards), the directives prescribe Essential Health and Safety Requirements (EHSRs) that shall be fulfilled. The use of harmonized technical standards gives only a presumption of conformity to the directives, while compliance only to the Essential Health and Safety Requirements (EHSRs) is considered full conformity (to achieve that, any appropriate available technical standard can be used).
The ATEX directive for product safety covers electrical equipment, nonelectrical equipment such as mechanical, hydraulic (pumps), and pneumatic equipment, including assemblies, protective systems, components (push button, relays, valves), controlling and regulating devices, etc. The ATEX directive for product safety deals with both electrical and nonelectrical equipment. Such equipment is divided into (i) Groups and (ii) Categories and can be placed in (iii) Zones, as shown in Table 2.: Table 2. Groups, Categories, and Zones prescribed by the "ATmosphere EXplosible" (ATEX) directive.

(i) Groups
Group I Relevant to underground coal mines, where the occurrence of dust and methane firedamp is frequent [9][10][11][12][13][14] Group II Relevant to the oil and gas industry and refers to potentially gaseous explosive atmospheres

Category 1 Most strict and intended for use in areas with the highest risk of explosions Category 2
For use in areas in which explosive atmospheres are likely to occur Category 3 For areas with a low probability for explosions

(iii) Hazardous Zones
Zone 0 An explosive atmosphere is present continuously, for long periods, or frequently Zone 1 An explosive atmosphere is likely to occur occasionally in normal operation

Zone 2
An explosive atmosphere is not likely to occur during normal operations (if it occurs, it only persists for a short period) For Categories 1 and 2, the procedure to affix the CE marking following appropriate type-examination procedures shall be issued by a notified body, while for Category 3, the manufacturer can ensure full conformity. The European auxiliary "Ex" mark, together with the European general mark for conformity "CE," shall be affixed on the certified equipment.
Group II of equipment for use in offshore oil and gas installations is divided into Categories, which can be used or installed in hazardous Zones, as given in Table 3. Table 3. Use of Group II of equipment in Hazardous Zones depending on its Category.

Zone Category
Zone 0 Category 1 Zone 1 Category 1 or 2 Zone 3 Category 1, 2, or 3 Categories of equipment and Hazardous Zones [15][16][17][18][19] can be determined by using any of the available technical standards. For electrical equipment, IEC 60079: Explosive atmospheres-CENELEC 60079 series can be used, and for nonelectrical equipment, EN 13463 series (EN ISO 80079) can be used. The types of protection are given in Table 4. Zones are determined by the grade of release: (1) continuous grade, (2) periodically or occasionally, and (3) normally not to expect; by the degree of ventilation: (1) high, (2) medium, and (3) low; and by availability of ventilation: (1) good, (2) fair, and (3) poor. The potentially explosive atmosphere can be prevented from igniting if the surface temperature of the item of equipment is lower than the ignition temperature of the surrounding gas, while the temperature classes for Europe and the USA are maximal (T 1 = 450 • C, T 2 = 300 • C, T 3 = 200 • C, T 4 = 135 • C, T 5 = 100 • C, and T 6 = 85 • C (subcategories exist in the USA)). The gas groups are I-methane, IIA-propane, IIB-ethylene, IIC-acetylene, and hydrogen, etc. (ignition energy is I-280 µJ, IIA-160 µJ, IIB-80 µJ, and IIC-20 µJ) [20,21].
Use of the 2014/34/EU directive for product safety is obligatory in the EU/EEA, both onshore and offshore, with the exception of mobile drilling units operated on the EU/EEA continental shelf. On the other hand, the 2013/30/EU directive for overall oil and gas offshore safety requires the use of all the best worldwide available technical standards [22] and prescribes the use of the IMO MODU Code, "Code for the Construction and Equipment of Mobile Offshore Drilling Units" by the International Maritime Organization, which, in practice, requires the use of the IECEx scheme for protection on mobile drilling units.

"International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres" (IECEx)
The "International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres" (IECEx) scheme is not mandatory [1], but it is widely used in the offshore oil and gas industry and especially on mobile offshore drilling units in the US and EU/EEA's offshore jurisdictions.
The IECEx certification scheme is operated by International Electrotechnical Commission (IEC), and it is based on its technical standards [23][24][25][26]. Around 30 nations participate in the IECEx scheme for protection against explosions, and many are based on it, such as the already described European ATEX, as well as many others described in Section 2.3. A nation without its own national scheme for protection against explosions can adopt the IECEx scheme to fill its legislative gaps using a pretailored model for regulation in the sector of equipment used in environments with an explosive atmosphere through the United Nations Economic Commission for Europe (UNECE) [27].
The offshore oil and gas industry under the IECEx scheme uses the same classification of equipment as under the ATEX protective scheme: Groups, Categories of equipment, and Hazardous Zones (Technical Committee 31 of the IEC is responsible for equipment for explosive atmospheres). The IEC 60079 series of Technical Standards can be used, but in the offshore industry, the Recommended Practice by the American Petroleum Institute API505 "Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2" is more used (a similar approach is used in the US onshore industry through the NEC505, as described in Section 2.3.1) [16]. The requirements between these two approaches for Hazardous Zones are similar; the IEC 60079 is more analytical, while the RP API505 is more prescriptive [6].
Certificates issued by the IECEx scheme are listed on its website; therefore, their validity can be verified in a very convenient way. Under the IECEx scheme, four types of certificates can be issued: (1) Equipment-Only technical standards issued by Technical Committee 31 "Equipment for explosive atmospheres" of the International Electrotechnical Commission (IEC) can be used for the certification of equipment (only electrical equipment can be certified), while the certification through an IECEX Certification Body (ExCB) is required for all Categories of equipment (Categories 1, 2, and 3 in IECEx Ga, Gb, and Gc, respectively) (ATEX allows for the self-certification of equipment by the manufacturer in Category 3); (2) Service Facilities-In addition to the certification of equipment, the IECEx scheme allows the certification of the repair and overhaul of equipment (nothing similar is available in the ATEX scheme); (3) Persons-Certification for qualified persons who were properly trained and meet the prerequisites to implement safety requirement required by the IECEx scheme (nothing similar is available in the ATEX scheme); (4) Conformity Mark-It is issued by approved IECEx Certification Bodies (ExCBs) for the equipment manufactured and tested using appropriate IEC technical standards.

Other Main Certification Schemes for Protection against Explosions
Possession of the IECEx or ATEX certifications cannot replace the obligatory certification imposed by most countries but can facilitate and support a procedure to apply for it. The IECEx Test Report is likely to be accepted as a base for national certification in the USA, Canada, Russia, Ukraine, Belarus, China, South Korea, India, Brazil, Argentina, Chile, South Africa, etc. Some countries, such as China, also accept the ATEX certificate as a base for its national certification. On the other hand, the ATEX Test Report can be used as a base for a national certificate in Hong Kong (special administrative region of China), Taiwan (de facto different legislation apply, but de jure part of China), Vietnam, Indonesia, etc. Finally, in some countries, such as in Japan, many domestic tests are required, and the IECEx or the ATEX Test Reports cannot facilitate the procedure.

USA
The Occupational Safety and Health Administration (OSHA) requires certification against explosions through one of its Nationally Recognized Testing Laboratories (NRTLs). In the National Electrical Code and National Fire Protection Association prescript NEC/ NFPA 70 for hazardous areas, NEC500 is based on a two-division classification of hazardous locations, while NEC505 is based on a three-zone classification. The three-zone area classification system is compatible with the IEC 60079 series of technical standards for explosive atmospheres; such an approach is compatible with the IECEx scheme and can be used as a basis for obtaining certification for the protection of equipment installed/or used on mobile offshore drilling units on the US offshore continental shelf. Certified equipment for use in areas protected against explosions shall be marked with a label of a Nationally Recognized Testing Laboratory (NRTL). In the offshore sector in the USA, the Bureau of Safety and Environmental Enforcement (BSEE) has authority over fixed platforms and the United States Coast Guard (USCG) over mobile units (ruling published in the Federal Register (Vol. 80, No. 61) on 31 March, 2015, and came into force on 2 April 2018). The IECEx certificates are not directly accepted under the National Electrical Code (NEC) in the USA, but the IECEx Test Report can facilitate appropriate US certification (only electrical equipment can be certified against explosions).

Canada
Similar rules for protection against explosions as in the USA are in force in Canada. The Standards Council of Canada (SCC) requires certification through one of its recog-nized certification bodies, while product approval related to electrical safety is under the jurisdiction of Provincial Governments. Classification of hazardous areas is based on the three-zone classification, as prescribed by the Canadian Electrical Code (CEC) (two-division classification is also accepted) and is compatible with the IEC 60079 series of technical standards for explosive atmospheres. Certified equipment shall be marked with a label of a recognized Canadian certification body. The IECEx certificate can be used as a basis for obtaining Canadian certification.

Eurasian Union
The Eurasian Union (ex. Customs Union; Armenia, Belarus, Russian Federation, Kazakhstan, Kyrgyzstan) requires technical regulations GOST/CU-TR on the safety of equipment in explosion hazardous environments issued by the Euro-Asian Council for Standardization, Metrology, and Certification (EASC). Only electrical equipment can be certified (in practice, only equipment that satisfies at least the ATEX level of protection can be certified). The appropriate product conformity mark of the Eurasian Union shall be affixed on the certified equipment.

China
The Chinese State Administration for Market Regulation (SAMR) requires a China Compulsory Certificate (CCC) Ex certification for protection against explosions (ATEX and IECEx certificates are not accepted, but if they exist, they can significantly reduce the work and preparation effort for the CCC certification). The China Compulsory Certificate mark, commonly known as a CCC mark, shall be affixed on the certified equipment.

Brazil
The Brazilian Ministry of Development, Industry and Foreign Trade, requires a certification against explosions by the National Institute of Metrology, Standardization and Industrial Quality (INMETRO). Brazilian certification bodies accept IECEx tests as a base for the certificate [28]. The INMETRO mark shall be affixed on the certified equipment.

Australia and New Zealand
In Australia and New Zealand, an ANZEx certification against explosions is required. To obtain it, an IECEx certificate is sufficient, and only certain national differences need to be tested additionally (the IECEx certification will be directly accepted for Group II equipment).

Differences between the ATEX and IECEx Certification Schemes
Historically, the National Electrical Code (NEC), established in 1947 as a concept of areas with two Divisions, followed by the American Petroleum Institute (API), which started related work in 1951 on its area classification document API500 based on Divisions (API500A for electrical installations in petroleum refineries was finalized in 1955, initially without the suffix "A;" API500B for electrical installations at drilling rigs and production facilities on land and marine platforms was finalized in 1961; and API500C for electrical installations at pipelines was finalized in 1966. These merged in 1991 into a single API 500 document [29]). API 500 is based on a hazardous area classification based on two Divisions, while API 505, introduced in 1997 [30], is based on three Zones (both the ATEX and IECEx schemes are based on Zone classification) [31] (Table 5 and Figure 1). After these early efforts, which were made in the USA and followed by many countries, the first international system for protection against explosions is dated in 1996 when IECEx was established and in 2003 when the first certificates were issued (IEC-60079-10-1 is compatible with US API 505 for the classification of hazardous areas). In Europe, the history of ATEX directives started also in the 1990s.  Categories of equipment in the ATEX and IECEx schemes are equivalent are given in Table 6, where G refers to gaseous potentially explosive atmospheres. Table 6. Categories of equipment in the ATEX and IECEx schemes.

IECEx Group Ga Group Gb Group Gc
The main differences between the ATEX and IECEx protection schemes are: • In the EU/EEA, the ATEX scheme is mandatory, and it is developed by the European Commission (government), while the IECEx scheme is operated by the International Electrotechnical Commission (IEC), i.e., regulated through an industry representative at international level. • Safety of personnel is regulated under the ATEX scheme through the mandatory use of a separate directive, 1999/92/EC, while nothing similar is available through the IECEx. • A certificate through an ATEX Notified Body is mandatory for equipment in Categories 1 and 2, while self-certification by the manufacturer is allowed for equipment in Category 3 (on the other hand, the IECEx scheme requires attestation of all categories of equipment through its Certified Bodies (ExCBs)).

•
The ATEX scheme requires certification through any available technical standards that can meet Essential Health and Safety Requirements of the ATEX directives, while the IECEx requires use of the technical standards developed only by the International Electrotechnical Commission (IEC).

•
Although the ATEX scheme uses terms "equipment" and "protective systems," it covers both electrical and nonelectrical equipment (EN 13463 and EN ISO 80079 "Non-electrical equipment for explosive atmospheres"), while the IECEx covers only electrical equipment. • Protection of certain Categories of equipment is sometimes different in the ATEX and IECEx schemes (every individual case should be studied if different protections are required) [32][33][34].

•
The ATEX scheme explicitly does not include mobile offshore drilling units in its scope.
Different marking of equipment is required using the ATEX and IECEx schemes ( Figure 2).

Conclusions
All European Directives are designed to protect the European single market in the first place, but in respect to protection against explosion on mobile offshore units for oil and gas drilling in the EU/EEA offshore continental shelf, some concerns exist if the European market is fully protected. Furthermore, mobile units in the EU/EEA offshore jurisdiction are excluded out of the scope of the ATEX Directive 2014/34/EU-ATEX by Article 1, Section 2(e): "This Directive shall not apply to: seagoing vessels and mobile offshore units together with equipment on board such vessels or units." On the other hand, the US market is fully protected due to the fact that the US Coast Guard requires the use of domestic protection scheme on the US offshore continental shelf for foreign mobile drilling units, while foreign-flagged vessels that have never operated, but intend to operate under the US offshore jurisdiction, should be certified through the IECEx scheme against explosions by a domestic US-based Certified Body (ExCB). In all other cases, full compliance with US regulations is obligatory.
No main differences between the ATEX and the IECEx systems for protection against explosions are detected. A shortcoming for the ATEX scheme is due to the allowed selfcertification for the equipment Category 3, which should be placed in Hazardous Zone 2, while for the IECEx in the fact that it does not cover nonelectrical equipment.
Mobile offshore drilling units [35][36][37][38] should be preferably certified through a USbased Certified Bodies (ExCB)) using the IECEx protective scheme against explosions because such units will be allowed to operate with minimized additional costs, both in US and EU/EEA's offshore jurisdictions (and very possible worldwide). On the other hand, fixed offshore platforms should be certified strictly following the rules of host countries.