4.9.1 INTRODUCTION
This heading covers a wide variety of chemical products; some of the more potential dangers to personnel are covered in the following paragraphs. Normally, those used in specific process will be delivered in highly concentrated form. It is therefore necessary that their toxic and other properties should be known and understood before the
materials are used. These are detailed on the MSDS which are available for all chemicals used in ADGAS in the Hazardous Substances Manual.
4.9.2 METHANOL
Methanol is a poison with a vapour toxicity comparable with that of many common solvents. It burns with a colourless flame. Prolonged exposure to methanol at relatively low concentrations (200ppm) can have some physiological effects. Blindness can occur from severe exposure and very large doses can be lethal.
Methanol is toxic to humans through ingestion, inhalation or skin absorption and harmful on repeated skin contact. Methanol shall not be dumped into the sea. Special emphasis is placed on the requirements involving the use of personal protective equipment while handling Methanol and Methanol inhibitor.
Personnel assigned to this handling operation shall wear chemical goggles, chemical gloves and full chemical protective suits.
Eye wash and emergency shower station shall be in the immediate vicinity of the Methanol handling areas.
Self Contained Breathing Apparatus shall be readily available for use should vapour escape into the atmosphere during this operation.
Entry to a Methanol tank, vessel or pipeline shall be governed by the conditions and precautions as stated in the MSDS. Entry to a tank or vessel is permitted only when covered by a valid Entry Permit.
The areas of Methanol handling, tanks, pipelines, vessels and heat exchangers shall be free from any source of ignition including any mechanical equipment used during this operation that may cause any spark.
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Methanol shall only be allowed to enter the pipelines, vessels or heat exchangers that have been purged with nitrogen and the oxygen content has been reduced to below 2%.
Dry powder fire extinguishers shall be placed at the Methanol tanks, pipelines and vessels.
Fire hoses shall be readily available and stand-by watch shall be provided during this operation.
Electrical earthing/bonding shall be provided to all Methanol associated tanks, equipment and piping.
Self-Contained Breathing Apparatus shall be used when cleaning up spills of Methanol to avoid inhalation of vapours emitted.
An absorbent shall be readily available for use should a spill occur.
Personnel shall make every effort possible to prevent Methanol from entering the sea.
4.9.3 CAUSTICS AND ACIDS
Caustics, hydrochloric and other acids used for acidising are dangerous in that they can destroy normal clothing fabric and rapidly affect the skin, causing severe burns.
Breathing of the acid fumes should be avoided as they are asphyxiants, and even in small quantities can be injurious to the membrane of the nose. When diluting always add acid to water, and not the reverse.
Personnel handling acids should be equipped with protective clothing, including hoods, PVC/Neoprene gloves and rubber boots.
All chemicals shall be clearly marked and labelled (preferably on two sides) with the contents, nature of associated hazards and recommended means of safe handling.
During acidising operations no person other than the crew directly employed should be allowed nearby.
A quantity of lime should be made available and utilised to neutralise any acid spilled.
Pumps, lines, tanks, etc., through which acid and caustic substances are handled should be thoroughly washed out with water upon completion of the operations.
A check valve should normally be installed in the treatment lines as close to the work as practicable. All pressure lines and related connections shall be pressure tested before operations commence.
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Acid carboys shall be stored in single tiers. They shall not be lifted by the neck of the carboy. Spilt acid shall be neutralised under supervision or washed away with water from a safe distance. Discharge should be by pouring, mechanical siphoning, pumping or by means of an approved discharge device. Galvanised iron drums shall not be used for the storage or transport of acid solutions.
Overhead acid tanks shall have adequate overflow pipes to a safe location, where any spillage may drain away. The area below the tanks should be bunded.
Closed tanks shall be provided with air vents which cannot be shut off.
Drums or carboys of acid shall not be discharged by the application of any gas pressure to the container.
If there is an accident with acid, first-aid treatment should be carried out immediately according to the instructions, which should always be contained in each adjacent first-aid kit.
4.9.4 AMMONIA
Ammonia is usually stored as an anhydrous liquid under pressure in cylinders from which it can be released either as a liquid or as a gas. It is also supplied as an aqueous
solution in various concentrations. The gas is colourless and has pungent easily
detectable odour even in low concentrations. Its density relative to air is 0.771, and it will rapidly disperse in open locations.
The flammable range is from 16% - 25% by volume in air with an auto-ignition temperature of 650°C.
It is extremely irritating to the eyes, nose throat and lungs and all moist parts of the body.
The TLV is 25ppm.
Whenever ammonia is used in quantity, protective equipment should be readily available.
Air line masks or self-contained breathing apparatus should be used for all
concentrations of ammonia. Severe skin irritation will result from prolonged work in a contaminated area unless full body protection or a chemical suit is also worn.
Since ammonia is extremely soluble in water, water fog or spray can be used to good effect as a dispersant where large leakages occur.
4.9.5 CAUSTIC SODA
Caustic Soda is a water soluble alkali used in the treatment of hydrocarbon products for the removal of undesirable sulphur products. It is mainly supplied as a solution in special containers.
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It is non-flammable, but spent caustic soda may contain entrained hydrocarbons, and should not be exposed to an ignition source.
Caustic soda is highly toxic, as an irritant or if ingested. the chemical acts quickly upon tissue causing burns and deep ulceration.
In the handling of small quantities of caustic soda solution, in addition to normal work clothing e.g. overalls, chemical goggles, PVC gloves and rubber footwear shall be used.
When making up large quantities of solution from solid drummed caustic soda full PVC protective clothing shall be worn including full face protection.
4.9.6 MIXED LIGHT HYDROCARBONS
As well as being highly flammable the vapours from petroleum are toxic and, if inhaled in sufficient concentration will ultimately result in death. They vary considerably because of the large variety of component substances present in crude oil and refined products, but with the exception of certain aromatic compounds, may be considered as similar in having the same harmful effects.
Comparatively small quantities cause symptoms of dizziness with headache and irritation of the eyes. These effects can occur well below the limits of flammability.
The TLV for petroleum vapour is not uniform because the constituents can vary in their proportions but a figure of 500 ppm is generally accepted.
It should not be necessary to expose personnel to concentrations above the TLV but for short periods, e.g. to shut off an escape of gas/vapour from a leaking flange or pump, an air line mask or self-contained breathing apparatus shall be worn.
4.9.7 CARBON DIOXIDE AND NITROGEN
Although not toxic, both are asphyxiants and in sufficient concentration will quickly produce unconsciousness from lack of oxygen. They are particularly hazardous in that they have no smell and there are no physical symptoms preceding unconsciousness.
4.9.8 ACETYLENE
Acetylene has a distinctive garlic-like smell. It will ignite and burn instantly from a spark or piece of hot metal. Lighter than air, acetylene will collect in roof spaces and confined spaces such as vessels. To prevent the build-up of acetylene becoming an explosion hazard, constant and thorough ventilation is necessary.
4.9.9 MERCURY
Mercury is highly toxic and shall be handled with care. Precautions shall be taken to prevent contact with the skin. Gloves shall be worn when handling.
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Exposure to mercury vapour for short periods requires only removal from exposure to rectify but if mercury is swallowed, medical attention should be sought.
Mercury is volatile at room temperature and dangerously high concentrations can build up in a non-ventilated area (TLV 0.0005ppm).
4.9.10 MERCURY RECOVERY UNITS 4.9.10.1 INTRODUCTION
Trains 1 and 2 have both been provided with Mercury Recovery Units (MRU). Each MRU consists of 2 vessels, one for treating the vapour stream and the other for treating the liquid condensate stream. The vapour treating vessel 3-C-150/250 contains a single bed of 10.2 Tons of Chemivron (HGR) granulated sulphur impregnated activated carbon. The liquid condensate treating vessel 3-c-151/251 contains a single bed of 3.6 Tons of PROCATALYSE CMG 273 granulated alumina impregnated with copper
sulphide.
Each mercury guard vessel is followed by a dust filter to remove any particulate matter escaping from the vessel.
The mercury guard beds are of a non-regenerative type and are expected to be disposed of after 3 to 6 years of continuous service. Train 3 has a gas bed of 18 tons of
Chemivron (HGR).
4.9.10.2 HANDLING OF FRESH MERCURY GUARD MATERIALS
Absorbent materials must be handled with care to avoid formation of dust. Persons involved in handling of the absorbent materials must be suitably attired with protective clothing consisting of :
· Long Sleeved
· Boiler Suit
· Rubber Gloves
· Goggles
· Filter type face mask
Dust contact with the eyes must be avoided and a supply of water or drench shower must be available at all times at the work place.
4.9.10.3 HANDLING OF SPENT MERCURY GUARD MATERIALS
Mercury contaminated absorbents must be handled with extreme care. Full protective clothing must be worn when removing and handling the spent absorbents.
Protective clothing shall consist of :
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· A long sleeved boiler suit
· Rubber gloves
· Long Rubber Boots
· Goggles
· Filter type face mask (for correct type, contact HSED)
· Face mask with air supply if person has to enter vessel.
A supply of water or drench shower must be available at all times at the work place.
For handling and disposal procedure. See HSED Waste Disposal Manual.
4.9.10.4 WRITTEN PROCEDURES/TASK RISK ASSESSMENT
All aspects of work shall be covered by a Task Risk Assessment that should include:
· Containment of contamination as near as possible to its site of production.
· Limiting the possibility of ingestion or inhalation
· Controlling and restricting direct exposure of workers
4.9.11 PYROPHORIC MATERIAL HANDLING STORAGE AND DISPOSAL PROCEDURE
4.9.11.1 DEFINITION
Pyrophoric material is a complex ferrite type compound and is formed when iron scale or corrosion debris combines with sulphur compounds, (in particular H2S), often with
organic materials. This compound is stable when kept wet. On drying, it will combine vigorously with the oxygen in air producing considerable heat reaction, which will result in spontaneous ignition. The reaction takes place below about 45oC and hence the
hazards arising from the use and handling of such materials involve fire, either from direct contact with the pyrophoric material or as a result of secondary fires following ignition. Oxidisation of the pyrophoric will, in any case cause sufficient temperature rise to ignite a flammable vapour/air mixture in its vicinity.
4.9.11.2 CONTROL MEASURES
Before opening any equipment on the LNG plant the possibility of pyrophoric material presence must be assessed and precaution taken as follows;
· The sludge 1 deposits must be wetted down with water and, when removed from plant equipment must be kept wet.
· The material must be immediately put into empty dedicated drums, they must contain at least 15 cm of water in the bottom and all times the contents must maintain a 15 cm level of water above the level of pyrophoric material.
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· The metal drums should be black with the identification "pyrophoric material"
Stencilled in white. If possible drums should be used on a "once only" basis.
· All Supervisors must ensure that no pyrophoric material is spilled on platforms walkways, into drains etc. If this occurs the spillage must be kept damp and cleaned up immediately. Drains and sewers must be adequately covered to prevent any material failing into them.
· The drums must be immediately removed from the site and to be temporarily stored in the waste disposal area (plant 19). They must not be allowed to dry out within process area. In no circumstances will pyrophoric material be allowed to remain on or about the job-site.
· Once in Plant 19, pyrophoric drums shall be unloaded and spreaded evenly on the ground. The waste should be kept moist for 30 days. Level the date of waste dump.
Every forthright the waste should be mixed and re-spreaded.
· After 30 days, collect the weathered waste in the metal drums. Cover the waste with sand/earth material. Seal and level as "PYROPHORIC" hazardous waste.
· Fill waste disposal form and inform ADGAS civil when the waste drums are sealed and labelled. Civil will arrange to pick up and organise with store for onward dispatch to Ruwais.
· All pallets used to transport the drums must be cleaned and removed from storage area.
· If a vehicle, skip, or containers is used for disposal of pyrophoric material, all parts, which may have been in contact with the material must be thoroughly hosed down with water before it leaves the disposal area. If this is not done, there is a very high risk of the vehicle catching fire.
Further Information
Operations- Standing Instructions C-14 (Potential sources of Pyrophoric Material)
Note
Pyrophoric sludge MUST be carefully segregated from other materials being stored in the dedicated area (Plant 19).
4.9.11.3 PERSONNEL PROTECTION
To prevent contamination of personal clothing with pyrophoric material disposable masks and overalls, gloves of PVC material and boots should be worn by personnel employees during its removal. Anyone handling pyrophoric material which could result in airborne dust must wear goggles for eye protection.
All disposable overalls etc., must be dumped with the pyrophoric material into the same dedicated area. The PVC gloves and boots must be washed with water to remove any adhering pyrophoric material at the end of each work period.
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4.9.11.4 TRAINING
Supervisors must ensure that all persons who are engaged on operations involving pyrophoric material are properly instructed on, and constantly reminded of the dangers related to the job and the proper precautions which must be taken to minimize the risk.
· Wash skin/eye with large amounts of water (emergency showers), continuously for at least 15 minutes.
· Remove contaminated clothing whilst in the shower.
· If swallowed, wash mouth, drink plenty of water.
· Do not induce vomiting, summon medical assistance.