International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 Applying a HAC study on an LPG/SNG system in a steel factory 1Khaled Habib Ezzat, 2Moustapha Salem Mansour, 3Ibrahim Ismail Ibrahim, 4Fathy ahmed Shoukry 1Chemical Engineering department Faculty of Engineering, EL-Minia University, El-Minia, Egypt 2Chemical Engineering department, Faculty of Engineering, Alexandria University, Alexandria, Egypt 3Chemical Engineering department Faculty of Engineering, EL-Minia University El-Minia, Egypt 4Petrochemical Engineering department Faculty of Engineering, Pharos University Alexandria, Egypt Abstract: As a global trend, safety has become the number 1 priority in all industries worldwide. This leads any organization either It's in the design phase or already in production, to design or modify –respectivelyits layout and Installations to comply with safety standards. One of the most important hazards that are common in most industries, either it is petrochemical, nonpetrochemical or even FMCG (Food Manufacturing & Customer Goods) industries, is the Explosion Hazard. According to the most recent fire statistics from the National Fire Protection Association (NFPA): An average of 37,000 fires occurs at industrial and manufacturing properties every year. These incidents resulted in: • 18 civilian deaths, • 279 civilian injuries, and • $1 billion in direct property damage. It is a smart step to take a preventive action towards explosions, rather than a corrective action. As a matter of fact, as every industry requires a type of fuel – which is usually flammableto run its operations, one of the most common units in all industries nevertheless what category it falls into, is the LPG/SNG unit. As much as this unit is important and mandatory to any industry, it is considered one of the most potential areas of explosions as well. Hazard area classification (HAC) is a study in which an industrial area is divided into zones according to the probability of the presence of combustible or flammable material in that zone. There are different standards for applying the study, and different outcomes according to the condition of the zone, this includes the material, pressure and temperature. In this paper we will discuss the HAC study of one of the most common units in industry, which is the LPG/SNG system. The aim of the study is to be a good reference for industries that have this unit or have a need to install it, and needs to apply a preventive HAC study on it to mitigate explosion risk Keywords: Hazard, Area Classification, ATEX, SNG,LPG 1. INTRODUCTION ATEX (French: ATmosphere EXplosibles (English: Explosive Atmospheres))is a study is specialized in studying the causes of explosions and how to evade the root cause, starting from the design phase of a plant or a unit, passing by the operation phase.[1] The Triangle of fire consists of (Fuel-Heat – Oxygen); eliminating one side of the triangle prevents the occurrences of fire, so ATEX study consists of three studies inclusively: [2] • (HAC – Hazard Area Classification) – Focuses on the (Fuel) side of the triangle; it is specialized in studying each area of the plant, and classifying it according to the flammable material present in it. • (EPD – Explosive Proof Document) – Focuses on the (Heat/source of ignition) side of the triangle; it is specialized with studying the source of ignition in the ATEX classified areas • (EX Equipment) It is the study concerned with equipment to be installed in the ATEX areas In this paper we will apply the first part of the ATEX study, which is the HAC study. www.ijeais.org/ijaer 9 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 The first step in the applying the HAC study is gathering info starting with: • MSDS – Material Safety data Sheet • Plant lay out • Process description. Then, the flammable materials are pointed out and their usage is spotted on the plant layout After that, HAC study is applied, and each area is classified under one of three categories, according to the presence of the flammable material and its usage. [3][4] Each classified area has a range in which it is spotted out on the layout, this area is considered the hazardous area, where there is a probability of Explosion to a certain extend depending on the several aspects will be discussed below. Classifying an industrial area into explosive atmosphere (ATEX) zones gives a better vision of several aspects. First of all the equipment's to be installed in this area, also the instruction to the personnel who have assigned tasks in or around an ATEX classified area. Finally this may require an action regarding this area like a change in condition, ventilation or even could be a design in the layout of the zone. [5][6] . 2. HAZARD AREA CLASSIFICATION: 2.1CONCEPT HAC study aims to classify the areas with a factory, building or any area of operation into zones depending on the probability of formation of an explosive atmosphere. Putting most of the vital factors in consideration to classify an area; this includes ventilation, materials being used in this area, type of operation and sometimes the layout. [7] 2.2-Methodolgy aclassification of zones: Zones are classified into (0, 1 or 2) for areas of flammable gases & vapors • Zone 0: An area in which an explosive gas atmosphere is present continuously or for Long periods or frequently. • Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation occasionally. • Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it does occur, it will exist for a short period only.[8] Zones are classified into (20, 21 or 22) for areas of combustibles dusts: • Zone 20: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently. • Zone 21: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally. • Zone 22: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.[4] bSources of release: For an explosive atmosphere to occur there should be a flammable or explosive material to occur in a space, being mixed with air to give an explosive mixture. The concerned substances most probably will be included in process equipment. This equipment may or may not release the substances, so it is important to identify the areas where there could be a possibility to release this substance in the atmosphere. Also important to consider, that if an equipment cannot expectably contain a combustible or flammable substance, or there is no probability for it releasing a flammable substance it should not be identified as a source of release (for example, a welded pipe may not be considered as a source of release, but a flange on this line shall be considered) [9] Release of flammable or combustible materials should be classified either (Continuous, primary or secondary) sources of release: • Continuous: it's a type of release where material is expected to be released for a long period or frequently. • Primary: a type of release where material is expected to be released occasionally during operation • Secondary: a type of release where material release is not expected to occur in normal operation conditions, and if happened, it does happen for a short period of time. cVentilation: Ventilation is an important factor while applying HAC study, it could decrease the grade of a classified zone or either eliminate it, it could be identified as the volume of air change around the source of release. This is includes two factors, first is the degree of ventilation, the better the degree of ventilation is available in a place , the lower is probability of an ATEX media to occur.[10] The degree of ventilation could be classified to (high, medium or poor) ventilation as below: www.ijeais.org/ijaer 10 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 • High: it is the type of ventilation which if acquired will decrease the concentration of a flammable or combustible material to below its lower explosive limit. However if the availability of this ventilation is not permanent, a HAC area could occur. • Medium: the type of ventilation which could result in a stable zone boundary. • Low: it's the type of ventilation which could not decrease the concentration of the substance during or after the release. The other factor is the availability of ventilation, the more the availability of ventilation the less is the probability of HAC area is to be formed and vice versa, the availability of ventilation could be classified as either (Good, Fair and Poor) [12][13] • Good: ventilation is present continually • Fair: ventilation present during normal operations, and may be not available for short period of times • Poor: any other case that does not match good or fair is poor class The relation between ventilation, its availability & release type could be summarized as: Grade of releas e Ventilation Degree High Medium Low Availability Good Fair Poor Good Fair Poor Continuous

Zone 0 N E Zone 0NE + Zone 2 Zone 0NE + Zone 1 Zone Zone 0 + Zone 2 Zone 0 + Zone 1 Zone 0 Primary Zone 1 N E Zone 1NE + zone 2 Zone 1NE + zone 2 Zone Zone 1 + Zone 2 Zone 1 + Zone 2 Zone 1 or Zone 0 Secondary Zone 2 N E Zone 2NE Zone 2NE Zone Zone 2 Zone 2 Zone 1 or Zone 0 No release Non-hazardous Area Notes: Symbol (+) means 'surrounded by' Zone o NE, 1 NE or 2NE, indicates theoretical zone which could be of negligible extent under normal conditions, they could be negligible [14] DExtent of the Zone. It is the distance starting from the source of the release to the point where the material is diluted below its lower explosive limit. This could be figured out from standards: • EI 15 Model code of safe practice. Part 15: Area classification code for installations handling flammable fluids (Formerly referred to as IP 15). • NFPA 497. Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. • NFPA 498 Recommended Practice for the Classification of Combustible Dusts and of Hazardous Locations for Electrical Installations in Chemical Process Areas. www.ijeais.org/ijaer 11 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 • UNE 202007 IN. Application guide of UNE-EN 60079-10. Electrical apparatus for explosive gas atmospheres. Classification of hazardous areas.[15] . 1Case study: 3.1description of the system This unit is used to provide LPG to a steel fabrication factory, where the presence of LPG & SNG is essential to the industrial process. The system consists of storage tanks for Liquefied petroleum gas (LPG), they are filled by trucks that unloads the LPG through the truck station, then there is LPG pumping station that does pumps the LPG to a synthetic natural gas (SNG) creation unit, where part of the LPG is vaporized and mixed with air to produce SNG, and the other un-vaporized part is pumped as it is to the industry, also part of it is directed to the flare. 3.2 simple layouts for the unit: 3.2.1 Process Description: The LPG plant has four tanks which do contain LPG to be fed to the industry; the four tanks are filled with trucks through the truck station. The LPG is kept under pressure in the tanks, and then is sent to an SNG unit by a pump where it is vaporized and mixed with air to produce the SNG (synthetic Natural Gas) which is then sent to the production area by a compressor to be ignited. Another output from the SNG unit is sent to the flare. 3.3-Findings: # Area of operation Sources of ventilation /release Classification 1 Identification: Four LPG storage tanks Ventilation: Installed outside with natural ventilation Substance: LPG (70%Propane-30% Butane mixture) Surrounding conditions: Ambient temperature Tanks pressure around 5.5 bar Continuous: Not identified Primary: Not identified Secondary: Leaks in instruments, flanges & valves, Safety valves at 20 bar Ventilation assessment: Degree: High Availability: good ZONE 1: 1.2 m high above the tanks pool 1.7 m around each instrument 3.2 m around each valve 3.2 m around each flange ZONE 2: 7.7 m around tanks pool 3.2 m around each safety vent GAS GROUP & TEMPERATURE CLASS: IIBT2* Comments: As LPG is a flammable liquid under pressure, they are expected to cause an ATEX Explosive area; this will almost be around the flanges and vents, the areas which do have a high probability of leakage. Beside the area below the tanks also in case any of the tanks failures and create a pool of LPG below the tanks. 2 IDENTIFICATION LPG compressor unit CONTIONUOUS: Not identified ZONE 1: 0.4 m around each pump's connection www.ijeais.org/ijaer 12 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 VENTILATION: Installed outside with natural ventilation SUBSTANCE: LPG (70%Propane-30% Butane mixture) NORMAL CONDITIONS: Ambient temperature Around 5 bar PRIMARY: Pump's connections SECONDARY: Leaks from instruments, flanges & valves VENTILATION ASSESSMENT: Degree: High Availability: Good ZONE 2: 11 m around the whole unit GAS GROUP & TEMPERATURE CLASS: IIBT2* Comments: LPG compressor does pumps a flammable liquid so it also shall be classified, especially around the area where the flammable liquid could leak like the sealing of the pump. Also due to the high pressure of the liquid inside, the compressor, the area around the compressor with a radius of 11m is considered hazardous, as any leakage would have a wider range of spreading 3 IDENTIFICATION: Gas flare VENTILATION: Outdoors Natural SUBSTANCE: LPG (70%Propane-30% Butane mixture) NORMAL CONDITIONS: Ambient temperature Around 4 bar CONTIONUOUS: At the flare output, but it is ignored due to continuous ignition PRIMARY: Not identified SECONDARY: Around gas seal VENTILATION ASSESSMENT: Degree: High Availability: Good ZONE 2: 1.3 m around every gas seal among the pipeline . GAS GROUP & TEMPERATURE CLASS: IIBT2* Comments: As flare is a part of the unit where the LPG will always be present in order to keep the flare lit. It will be considered an ATEX area on the areas of high leakage probability. This will include the gas seals on the pipeline to the flare. The area is slightly reduced than the valves of the tanks, due to lower pressure present in the piping to the flare than the pressure inside the compressor. 4 IDENTIFICATION: LPG unloading station VENTILATION: Installed outside with natural ventilation SUBSTANCE: LPG (70%Propane-30% Butane mixture) NORMAL CONDITIONS: Ambient temperature Pressure around 5 bar CONTIONUOUS: Not identified PRIMARY: level indicator SECONDARY: Connections for LPG unloading Pump connections Safety valve VENTILATION ASSESSMENT: Degree: High Availability: Good ZONE 1: 1.7 m around the level indicator ZONE 2: 4.5 m around the pump connections 0.4 m around the safety valve 1.7 m around any temporary connection GAS GROUP & TEMPERATURE CLASS: IIBT2 * Comments: LPG unloading station is the place where the trucks does unload the LPG into pumps directed to the LPG tanks. Areas of considerations here will be the connections of thee hose which is used to unload the LPG, as well as the pump and safety valve in the truck. Level indicator is also considered as a primary source of release 5 IDENTIFICATION: SNG system inside the cabinet VENTILATION: CONTIONUOUS: Not identified PRIMARY: Zone 2: 1.3 m around each flange 1.3 m around each Valve 1.3 m around each Instrument www.ijeais.org/ijaer 13 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 Indoors Forced SUBSTANCE: LPG (70%Propane + 30%Butane) NORMAL CONDITIONS: Air conditioner Up to 2.5 bar Not identified SECONDARY: Leaks from instruments, flanges & valves VENTILATION ASSESSMENT: Degree: Medium Availability: Good GAS GROUP & TEMPERATURE CLASS: IIBT2* (Minimum) Comments: SNG unit is the place where the synthetic natural gas is produced by mixing vaporized LPG with air; the areas which shall be considered as well are the areas of potential leakage, like flanges, valves & instruments along the pipeline. 6 IDENTIFICATION: Flame sensor/ Ignitor unit VENTILATION: Indoors forced SUBSTANCE: SNG (Methane) NORMAL CONDITIONS: Ambient temperature 150 mb Up to 3.7 bar CONTIONUOUS: Not identified PRIMARY: Not identified SECONDARY: Leaks from instruments, flanges & valves VENTILATION ASSESSMENT: Degree: Medium Availability: Good ZONE 2: 0.6 m around each flange 0.6 m around each Valve 0.6 m around each Instrument GAS GROUP & TEMPERATURE CLASS: IIAT1* (Minimum) Comments: It's the place where the SNG is ignited to be used in the industry, same areas of potential leakage are considered, with a lower range due to the lower pressure. * This is a gas group classification according to the minimum ignition energy (MIE) as follows (I for mining, IIA MIE>250 μJ ,IIB MIE>96 μJ, IIC<96 μJ) N.B. Some areas around the considered instruments are extended 10% than the recommended standard due to variety in wind speed and direction, as well as wide variety in ambient temperature due to changeable weather condition. 3.4 Recommendations: # Situation Recommendation Additional information 1 The unloading hose usually leaks traces of LPG during transferring the fluid from the truck to the tanks through the station The hose should be replaced to prevent leakage of the LPG 2 The ambient temperature some days of the year rise in the summer, the truck used in loading usually not covered under the umbrella covered in the unloading unit Better to extend the umbrella in the unloading station to cover the part where the truck park to unload The umbrella better to be extended to cover the whole truck, also better to schedule the unloading in early morning to avoid the peak hot hours of the noon. 3 By visual inspection the earthing of the unloading unit it appears that it needs to be rechecked as some cables appear loose. The earthing needs to be checked that it is well connected 4 No sign is hang with instructions for unloading the LPG precautions could be taken to hang some signs labeled (Mobile phones prohibited)(no smoking) (work permit required at this area) All workers should be instructed with these precautions and new comers to have induction training www.ijeais.org/ijaer 14 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 5 Several common electric devices are present with the range of classified ATEX area around the pipeline All electric devices should be replaced by alternative ATEX certified devices, or could be removed out of range of ATEX zone Minimum requirements for zone 2: Synthetic Natural gas Category 3 Gas group IIA Temperature class T1 6 There were several ATEX classified junction boxes that do miss a fixing nail or two Junction boxes should have all fixing nails in place. 7. There is an emergency plan present, but with no details for an explosion scenario One ATEX oriented emergency plan should be set into place Expected scenarios that could cause an ATEX explosion: -leak on a flange or instrument on the NG pipe line -Spillage of LPG during unloading 8 Any change of the following should have a change in the HAC classification accordingly: -change in plant layout -change in Material used (especially adding new flammable or combustible materials) -change in operation conditions -change in process that may cause change in material used or relocating of devices or pipelines Incase no change occurs that requires updates in the HAC study, it should be updated on a three year period. Surveys should be performed in ATEX classified areas for any unconformities. 3.5 Properties of material Properties unit LPG SNG CAS Number 68476-85-7 68410-63-9 Molecular weight - ≈46 ≈15 Flammability limit %v/v 1.9/9.5% 2.0/10.0% Flashpoint oC 104.4 -184 Boiling point oC <-40 <0 Auto-ignition Temper ature oC 430 537 Temperature class T2 T1 Gas Group IIB IIA Vapor density 1.5 ≈0.5 Cp/Cv J/kg*K 1.13 1.31 3.6 Drawings of the zones (referring to standard IP15) [16]: LPG storage tanks Zones in the diagram above are a screen shot of the standards, listed below: ZONE 2 of 3 m around the safety vents. ZONE 1 of 3 m around every valve or flange. ZONE 1 of 1.5 m around every instrument. The standard is based on that in case of leakage there will be a pool created below the tank; this area will be classified as zone 2. Around each valve or instrument there will be Area 1 in case any leakage occurs. Also a Zone 2 area will be classified www.ijeais.org/ijaer 15 International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 5, May – 2018, Pages: 9-16 around the safety valve of the tank as mentioned in the drawing As mentioned, some of these areas are extended in the finding due to ambient conditions of the plant 4. CONCLUSION: The case study discussed is meant to be a good reference for those who are willing to install an LPG/SNG unit in their industry, or already have it installed but need to apply a HAC study to it. It is considered a shortcut instead of going through standards to find the right zones; this paper would save lot of effort, money & time. From the study we conclude that: 1The areas we need to consider while dealing with a liquid fuels in a pipe line: Around valves Around flanges Around each instruments installed on the pipeline Around the sealing of the pumps 2The areas to be considered when dealing with liquid fuel in tanks: Around safety valve Around draining pot Creating a pool around the tank with a height of 1 m 3Ventilation is one of the most important mitigation factors either it be natural or forced 4The radius of the classified area around a pressurize system depends on the pressure inside the pipes 5HAC does not consider the probability of an accident (like a forklift hitting the pressurized pipe causing leakage) 5. ACKNOWLEDGMENT I would like to thank dr. hassan farag, Dr. Ibrahim Ismail and Dr. Mostafa Salem for their guidance through my research and their close attention to my work. i would also like to appreciate the hosting university, al mina university faculty of engineering, for hosting my work and providing the knowledge that i needed through my research. REFERENCES 1. Technical Note: AN-925-1, ATEX Considerations: the possibility of ignition in installations Employing FPT850 Near-Infrared Transmission Probes in Conjunction with Explosive Atmospheres, March, 2017 2. Revista Facultad de Ingeneria (Rev. Fac. Lng.) Vol. 26 (45), pp, 47-60, Maya Agosto, 2017, Tunja-Bayaca, Colombia 3. Korbinian Kramer, Guideline on testing procedure s for collectors used in solar process heat, Technical report, May (2016) research gate DOI:10.13140/RG.2.1.3837.2725 4. Hofer, A.; Valenzuela,L.; Janotte,N.;Burgaleta,J.I.:Arraiza,J.;Montecchi,M. et al. 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Tommasini, 'Zone con pericolo di esplosione determinate da una Pozza di sostanza Infiammabile", N.T. Tecnica e tecnologia n. 11/98, ISNN 0392-4521, November 1998. 16. IP code, Area Classification code for installations Handling Flammable Fluids,Part 15,July 2005, 3rd edition www.ijeais.org/ijaer