The first facility 1n

zone classified oil and gas North America

by W. Berner, H. Biickle und R. Seitz

Figure 1: Alpine Oil Field in Ala ska

This article discusses the Alaska Alpine Project, distinguished as the first major new complete oil production facility in North America to utilize the Zone concept of area clas­sification using National Electrical Code (NEC) Article 505. Insight into the process that led to the use of the Zone classification system is provided, as well as the opportunities, challenges and problems encountered in implementation of products using the protec­tion techniques for the Zone system. The conclusion will show what actions are required to allow the Zone concept to be fully implementable, and provide justification for continu­ation of the effort to adopt the methods described.

Introduction

1. Classification of Hazardous Areas in the USA

In the USA hazardous areas are defined as .haz­

ardous (classified) locations'and include areas

in which combustible gases, vapors, dusts or

fibers and flyings may occur in amounts that

considered hazardous.

Until recently the traditional Class and Divi­

sion system was the only possible method for

area classification and equipment installation

32

in North American industries. The introduction

of the International Electrotechnical Commis­

sion (IEC) based Zone system into the 1996

NEC Article 505, and further developed in the

1999 and 2002 NEC is a new development

and orientation for the USA.

2. Classes, Divisions and Zonen

Under the traditional North American system,

hazardous areas are classified into three

Classes offlammable materials. Class I hazards

include gases, vapors, and liquids that can

burn or explode. Class II contains combustible

dusts such as flour, sugar, aluminum or mag­

nesium. Class Ill includes ignitable fibers or

flyings such as cotton.

Each of these three Classes is further subdi­

vided into two Divisions, with Division 1 encom­

passing hazards that are continuously, intermit­

tently or periodically present in the atmosphere

under normal operating conditions. Division 2

includes hazards that can exist under .unusual'

circumstances.

In the new system, the practice of area

classification is refined even further within the

Class I area, based on the American implemen­

tation of the IEC (International Electrotechnical

Commission) area classification and standards

for hazardous locations into Article 505 of the

NEC. Application of the IEC system divides U.S.

Class I areas into three Zones: Zone 0, 1. and 2

- one more than the traditional North American

Division classification. Class I, Division 1 is sub­

divided into Zone 0 and Zone 1. Zone 0 defines

those locations in which an explosive gas-air

mixture is present continuously or for long peri­

ods during normal operation. By isolating the

worst hazards within a Zone 0 classification,

designers are allowed to use less restrictive

and less costly systems in the remainder of

Division 1, defined as Zone 1. Class I. Zone 2 is

essentially the equivalent of Class I, Division 2.

Zone 2 is an area in which an explosive gas-air

mixture is not likely to occur and if it does occur,

it will exist only for a short time.

3. Protection Techniques

Zone products differ greatly from Division prod­

ucts. The Zone system offers to the product

specifier a much wider range of protection

•

•

Table 1: Area Classification, Comparison of Divisions and Zones

IEC/ CENELEC

NEC (U.S.) Article 505 Class I

Article 500 Class I Class II Class Ill

IEC classification per IEC 60079-10 CENELEC classification per EN 60079-10

present continu­ously or for long peroiod

Zone 0 - gas Zone 20 - dust

Zone 0

Explosive Atmosphere

present occasionally

Zone 1 - gas Zone 21 - dust

Zone 1

Division 1

not likely to occur or present for short period only

Zone 2 - gas Zone 22 - dust

Zone 2

Division 2

US classification per ANSl/NFPA 70 National Electrical Code INEC) Article 500 and Article 505

Table 2: Comparision-Protection Technique Acceptability

Type of Protection

Division System Intrinsic Safety Explosionproof Purged and Pressurized

Zone System Intrinsic Safety, ia Intrinsic Safety, ib Increased Safety, e Flameproof, d Encapsulation. m Oil Immersion, o Pressurized, p

Zone 0

x

x

Zone 1

x x x

x x x x x x x

Division 1

x x x

x

techniques than does the Division system. With the exception of flameproof (a contain­ing technology), all of them make use of the physics of the combustion triangle; eliminating one of the elements, fuel, ignition source, or oxygen. A comparison of the protection tech­niques used in Class I, Zone 0 and 1 versus Class I, Division 1 is shown below in Table 2. The greatest advantage to the user in Zone 1 locations is recognized by the type of protec­tion increased safety, AEx e. Increased safety is the type of protection that can be applied on products which are normally not arcing devices such as terminals, potential and current trans­formers, moving iron ammeters and voltme­ters, capacitors and squirrel cage motors. In comparison to ordinary location equipment, the product standards require increased clear­ances, and creepage distances and additional construction improvements.

Ex-Magaz ine No. 28/2 002

The Alpine Project

1. Basic Data and Development of the Project

The Alpine Development Project is now a 90,000 Barrel per day crude oil production facility located near the Colville River on the North Slope of Alaska and is approximately twenty-five miles west of the existing l<uparuk Oil Field. This remote facility is only accessi­ble by air using the private runway at the facil­ity and by a winter ice road as there is no permanent road to the Alpine facilities . There is a thirty-five mile pipeline routed to the exist­ing l<uparuk facilities to export the crude oil, and import arctic heating fuel (diesel) and sea­water for injection.

The development of the marginal North Slope Alaskan Oil Fields demands that the costs to produce the oil, including building the facilities, required to process the crude oil, has to be reduced to better ensure approved fund­ing for the project. Time to develop a project must also be reduced to further justify project funding.

Although oil and gas producers had tra­ditionally classified the enclosed oil and gas processing modules as Class I, Division 1, the Alpine Project Management Team (PMT) requested consideration for classification of the facility as Class I, Division 2. Due to the extreme environmental conditions on Alaska's North Slope, increased ventilation rates would add considerably to the requirements for build-ing heat. In July of 1995, user's electrical engi­neer recommended that the PMT should con­sider the use of the NEC Article 505 ,Zone Con­cept of Electrical Area Classification' for the project. The PMT response was enthusiastic. The project group was supposed to .think out­side the box'and develop new ideas, new tech­nology, and cost-effective alternatives to the traditional somewhat conservative engineer-ing design used for the existing North Slope facilities. The use of the Zone concept of classification for the Alpine Project was ten­tatively approved in 1995 prior to the first printing of the 1996 NEC. A challenge to the -+

33

The first zone classified oil and gas facility in North America

acceptance of Article 505 to the NEC did cause some concern.

Alliances were established with several engineering companies, construction compa­nies, and a drilling company to accomplish the project. An engineering company based in Calgary, Alberta, Canada was chosen as the central facility engineering contractor and registered Professional Engineers from Alaska

3. Challenges using the Zone System

The new technique of products and installa­tion practices for the zone system required the education of all parties involved, includ­ing everyone, from the electrical designers, the electrical engineers, and the electricians to the Authority Having Jurisdiction's electri­cal inspector.

Traditional wiring methods allowed for use were brought to Calgary to oversee the engi- in Class 1, Division 1 areas were found to neering design. not be directly applicable to installation with

2. Major Construction Activities

The typical process module of the facility con­sists of an electrical building that is an unclas­sified area and a much larger process area that is classified. The electrical rooms were pur­chased as turn-key, ,design and build'buildings and transported to the fabrication sites. These electrical buildings were installed onto the structural platform of the large process mod­ule. The electrical power, control and instru­ment interconnections were then installed between the electrical and process buildings at the fabrication sites.

The large modules were barged to the North Slope of Alaska during the summer of 1999 from fabrication sites in Corpus Christi, Texas and Kenai, Alaska. Smaller modules were fabri­cated in Anchorage, Alaska and trucked up the haul road to the North Slope. The large mod­ules were unloaded at l<uparuk and awaited the winter freeze and construction of an ice road to permit transportation for the final 50 miles.

Although some of the process modules could have been classified as Class I. Zone 2 locations, a decision was made to keep all of the facilities classified Class I, Zone 1 and use Zone 1 equipment throughout the classified areas. Unlike the Division system, where there is a big difference between equipment rated for Class I. Division 1 and Division 2, there is not that much difference between Class I, Zone 1 and Zone 2 rated junction boxes and control enclosures.

Zone 1 products. Much interaction between the engineers, manufacturer and the Nation­ally Recognized Testing Laboratories (NRTLs) was required to work out the proper methods and accessories. Even the use of metal clad, hazardous location cable (MC-HL), and Class I, Division 1 cable fittings required a new design approach different from traditional conduit installations.

3.1 Wiring Methods

The use of MC-HL cable in Class I. Division 1, and Class I Zone 1 locations brings with it some advantages over the traditional con­duit systems, however, the MC-HL cable did represent some significant challenges. The Zone rated enclosures selected for the Alpine project were constructed of fiberglass rein­forced polyester and for ground continuity, they require an internal bonding system.

The MC cable for the Alpine project was required to be suitable and Listed for Class I, Division 1 locations. The 1996 NEC does not have any Zone 1 wiring methods other than those permitted for Class I. Division 1. With the introduction of MC-HL cable in the 1996 NEC for Class I. Division 1 and Class I. Zone 1, a standard was developed by Underwriters Laboratories Inc. (UL) for listing of the cable and fittings as required by the NEC.

Many of the terminal boxes and control stations and panels were engineered to spe­cific configurations which made it possible to specify enclosures that contained all of the openings for installing the cable in the factory

polyester enclosures contain a brass bonding plate with pre-drilled and threaded openings. The armor of the cable is grounded through the cable fitting, and the metal plate, which has an increased safety terminal. wire-connected to the ground bar.

Since it is impossible to cover all contin­gencies for MC-HL cable, provisions had to be made for terminating the MC-HL cable fittings when there is no metal plate in the enclosures. Future additions would be difficult if the metal bonding plates were installed. An entry open­ing can easily be added to an increased safety enclosure with a knockout punch if there is no metal plate installed. This is only possible since the increased safety enclosure is not designed to contain an explosion because the internal components are explosion protected in their own right. Therefore, enclosure open­ings do not require a flameproof joint. This is far simpler than attempting to drill and tap a cast aluminum explosionproof/flameproof enclosure.

When there is no metal plate, a special locknut is provided that contains a set screw to maintain a tight connection between the fitting and the locknut. The locknut also con­tains a special increased safety terminal for wire connection to the ground bar. A washer between the cable fitting and the enclosure maintains the level of ingress protection required for increased safety, minimum IP 54.

3.2 Education

The first education effort was to familiarize the electrical engineers and designers with the Zone requirements of the 1996 NEC and the fundamentals of the types of protection permitted by the Zone concept. Instructions were also provided for specifying and dealing with these different types of products.

Most of the electricians had not installed MC-HL cable before this project and therefore the initial reception for this installation method was not entirely enthusiastic. The MC-HL cable termination fittings approved for use in Zone

installed openings in the walls of the enclo- 1 areas were different than other cable con-sures. The walls of the fiberglass reinforced nectars. All of the electricians were required

34

•

•

Figure 2 (above): terminal box 8146/ 1. with Exe terminals Figure 3 (below): terminal box 8146/ 1. with entries for MC-HL cables

to attend a seminar where they participated in a ,hands on' demonstration of installing a listed, sealing type, MC cable fitting. These seminars, conducted by the manufacturer of the Zone type products also included an intro­duction to the fundamentals of the Zone sys­tem. A comparison was provided between the Division and Zone system including terminol­ogy, area classification, gas groups, types of protection, marking, and installation require­ments. Each electrician was given a Seminar Attendance Card to document completion of the training.

3.3. Approvals

In order to use Zone rated equipment the National Electrical Code and, therefore, the Authority Having Jurisdiction require that product listings be from a Nationally Recog­nized Testing Laboratory. The laboratories are accredited by the Occupational Safety and Health Administration (OSHA). European Zone type equipment certified by a European Test­ing Laboratory does not meet the NEC defini­tion for ,Listed'. These products must be certi­fied by a NRTL. The first step in the process

of obtaining listings for the R. STAHL products was to identify the needs and requirements for the Alpine Project.

The following products were selected for Zone listings:

• Terminal boxes Series 8146/1 fiberglass reinforced polyester for control and intrin­sically safe circuits

• Control stations Series 8146/5 fiberglass reinforced polyester containing contact blocks with various actuators. pilot lights, selector switches, ammeters. or illuminated push buttons

• Plug and socket devices CES Series 8575-8581

• Fluorescent light fittings with and without battery back up Series EXLUX 6000 and 6008

• Cable connectors for MC-HL cable Series MCX

For a large portion of R. STAHL products, NRTL Class I, Zone 1 listings were in place or in process. Some of the products selected had already been listed for Class I, Division 2 prior to the introduction of Zones in the NEC.

It is important to recognize that Interna­tional Standards for Zone protection tech­niques as specified in the IEC 60079 Series were harmonized as United States Standards, but there are deviations between these stand­ards and the International Standards. Some of these deviations are a result of differences in wire sizes, entry threads, voltages and frequencies. The electrical products selected for the Alpine project had to meet ordinary area requirements in addition to hazardous area requirements to be approved for use in the US.

Besides the requirements for listing, some products had to be modified in order to be suitable for the extreme cold weather environ­ment of Alaska's North Slope.

3.4 Procurement

Prior to development of the actual facility design, proposals were solicited for the supply

Ex-Magaz ine No. 28/20 02

of the US Zone rated electrical products for a hypothetical module or building. It has shown that

• none of the packaged equipment vendors were prepared to supply Zone rated equip­ment with their assembled skids and they quoted unreasonably large extra costs

• there were several types of electrical equip­ment that were not yet available with Nationally Recognized Testing Laboratory approvals for Zone applications.

Since the engineering contractors had a strong preference towards Zone rated com­ponents because of their advantages and the owner was simply not willing to pay extra, an agreement was established for the entire project with one manufacturer - R. STAHL -that applied to the manufacturer's entire cata­log of parts to international standards. Since there were many types of electrical equipment that were not available with NRTL approvals for Zone applications, Division type products could be offered.

For products which were not Zone approved at that time the Alpine Project purchased motors, instruments (process transmitters and switches). and valves limit switches approved for Class I, Division 1 locations.

The manufacturer of terminals for the project was selected early in the design phase of the project. At that time, only one manu­facturer of terminals had an NRTL listing for increased safety terminals as individual com­ponents. This brand and specific style of ter­minals was used throughout the entire project, even in unclassified area instrument terminal boxes and control panels.

3.5 Unclassified Locations

The electric power system equipment includ-ing the generators, the medium voltage switch­gear, low voltage switchgear, and panelboards were all installed in unclassified locations. Because the Zone 1 rated terminal boxes and control stations were rated for environmental protection to dust and water as IP66, were -+

35

The f irs t zo ne c lass if ied o il and gas fac il ity in Nor t h America

.-+ light weight and rated for -55 degC, and in order to reduce inventory, these products were used in unclassified locations indoors and outdoors. They were used in all areas of the production facility.

Conclusions and Future Development

To utilize the Zone Method of Classification in the USA is considered the best choice for new

metallic and stainless steel are available for locations where corrosion is a concern. Most explosionproof enclosures are only available in aluminum. Control enclosures with small volume flameproof components with increased safety terminals also present a significant advantage over the traditional explosionproof method. These are suitable for the highest gas group, i.e. Group llC (all gases) to NEC Article 505. The pressures resulting from small vol­umes makes containment of the explosions

installations in hazardous (classified) loca- easier and pressure piling is not a factor. tions. Despite the lack of several types of equipment specifically listed for Zone classi­fied applications, the preference for the Zone Classification remains for any new facility. The use of the Zone Classification System would probably not be an advantage for small addi­tions to existing Division Classified facilities. The cost to change and educate the affected parties would probably not be justified.

The advantages of the Zone System are made possible because it separates the loca­tions of highest risk (Zone 0), making it pos­sible to use additional types of protection and wiring methods in Zone 1 locations. The treat­ment of installation/termination in Class I, Zone 1 locations using cable and increased safety, provides several distinct advantages over the traditional metho1ds used in Class I, Division 1 for the explosionproof enclosures and raceways. Reduction of the number of sealed fittings at hazardous area boundaries through the use of cable is one great savings in time. Elimination of sealed fittings at increased safety (type ,e') enclosures is another great savings in time.

Explosionproof installations are typically suitable for gas groups C and D to NEC Article 500. Since it is a containing technique, it is dif­ficult to design for Groups A and B, because of high pressure and flame propagation require­ments. In contrast, with increased safety, gas groups are not a consideration. Increased safety equipment protects by eliminating the ignition source, regardless of the kind of gas.

Because increased safety does not use con­tainment, additional material choices of non-

Further distinct advantages of increased safety cable installations are lower weight, fewer bolts, less corrosion, no maintenance of joints, and no seals.

When the National Electrical Code is modi­fied and amended in the future additional Class I, Zone 1, installation methods could be added. NEC Article 505 defines the Zone Classifica­tion System and the approved products fur use in zones, but mainly refers to the Division System wiring methods. One example for the difficulties with the Class I, Division 1 wiring methods is the MC-HL cable with listed explo­sionproof cable glands for use with increased safety enclosures. At least this has been changed in the 2002 NEC - explosionsproof cable glands are not necessary anymore. This is an enormous reduction in time and cost for the installation. Unfortunately this was not possible when planning and installing the Alpine Project so that there were no additional savings in this because of the incomprehensi­ble NEC requirements.

An important consideration for future code changes would be to permit the use of cables in Zone 1 locations without an armor jacket to be connected to increased safety enclo­sures. There are more cost effective tech­niques of providing protection to cables sub­ject to mechanical abuse other than an armor jacket. The armor makes installation more dif­ficult especially because of the type of fit­tings and bonding aspects. Zone 1 installations require specific installation rules to take full advantage of their cost and safety benefits. One hinderance to fully adapting the Zone

methods of protection in the USA, is the lack of a full range of US approved Zone products, especially motors. Once the NEC Article 505 is fully harmonized with the IEC 60079 Series and used more often by the end users in the USA there will be more Zone approved products available. With an ~xtended range of Zone products available and more experi­ence made with the Zone system and products cheaper, safer and more flexible installation will be possible in the future .

References

[1] National Fire Protection Association NFPA 70-1996, .The National Electrical Code'

[2] National Fire Protection Association NFPA 70-1999, .The National Electrical Code'

[3] W. G. Lawrence and W. Berner . .The Zone System in The USA', Ex-Magazine 1999 (page 30)

[4] W. Berner, .Installation Technology in Haz­ardous Areas', Ex-Magazine 1997 (page 4)

[5] M. T. Cole, J. S. Stoyanov, P. Volker, .The Quest for Change in North America', Ex­Magazine 1996 (page 38)