«1998 Edition Issue 2014 GUIDANCE FOR TRANSPORTING NITRIC ACID IN TANKS Contents 1. INTRODUCTION 4 2. PROPERTIES AND CLASSIFICATION OF NITRIC ACID 5 ...»
GUIDANCE FOR TRANSPORTING
NITRIC ACID IN TANKS
GUIDANCE FOR TRANSPORTING NITRIC ACID IN
1. INTRODUCTION 4
2. PROPERTIES AND CLASSIFICATION OF NITRIC ACID 5
2.1 General 5
2.2 Chemical properties 5 2.2.1 Acidic properties 5 2.2.2 Oxidizing properties 5
2.3 Physical properties 6
2.4 Hazards and classification of nitric acid 7
3. DESIGN AND CONSTRUCTION OF TRANSPORT EQUIPMENT 10
3.1 Design and construction of railway tank wagons 10
3.2 Design and construction of road tankers 12 3.2.1 Bottom openings 12 3.2.2 Materials 12 3.2.3 Pumps 13
3.3 Design and construction of tank containers 13
3.4 Design and construction of inland waterway tank vessels 13
4. SAFETY AUDIT OF BULK HAULAGE CONTRACTORS AND
BULK TANK OPERATORS 14
4.1 Suitability of the haulage contractor:
Assessment and monitoring 14
4.2 Safety audit of the haulage contractor 14
5. PRODUCT TRAINING FOR DRIVERS OF ROAD TANKERS AND
TANK CONTAINER VEHICLES AND FOR THE SHIPOWNER’S PERSONNEL 15
5.1 General training requirements for road tanker drivers 15
5.2 Specific requirements for nitric acid road tanker drivers 15
5.3 Driver criteria for transporting nitric acid 16
5.4 Requirements for shipowner’s personnel on inland waterways 16
6. PROTECTIVE CLOTHING AND PERSONAL SAFETY EQUIPMENT 17
7. LOADING AND UNLOADING OPERATIONS 18
7.1 Requirements for loading and unloading 18 7.1.1 Equipment for the loading and unloading stations 18 7.1.2 Working platform 18 7.1.3 Filling arm 18 1 7.1.4 Loading area
1998 Edition Issue 2014 © Fertilizers Europe 2014
This document has been produced for the benefit of the members of Fertilizers Europe. The information and guidance provided in this document is given in good faith.
Fertilizers Europe, its members, consultants and staff accept no liability for any loss or damage arising from the use of this guidance. As regulations are up-dated from time to time, readers are advised to consult the up-to-date information.
This guidance for the transport of nitric acid have been drawn up by Fertilizers Europe, a sector group of CEFIC, with the help of expertise from members in order to ensure high safety standards in operations involving nitric acid transport. The guidance deal exclusively with the transport of nitric acid in tanks within Europe and do not deal with the transport of packaged product in small parcels or containers, or with transport on the high seas. However, it should be borne in mind that even though only transport is considered, nitric acid is subject to other European regulations amongst which are those concerning occupational health and safety and the packaging and labelling of dangerous substances.
Although nitric acid is classified as “dangerous” because of its particular chemical properties, it can be transported and handled safely provided the appropriate precautions are taken.
The transport of nitric acid is subject to stringent national and international rules which must be complied with by all those involved. This guidance go beyond the strict application of the existing rules and all those involved in the transport of nitric acid are recommended to adopt them. However, every user of this guidance has the responsibility to evaluate and apply them, giving due regard to all the specific circumstances in his particular situation. No part of this guidance should be applied or interpreted in such a way that it clashes with existing national and/or international laws. In all cases, legal regulations must always prevail over any part of this guidance.
52. PROPERTIES AND CLASSIFICATION OF NITRIC ACID
2.1 General Nitric acid (CAS No 7697-37-2) is a chemical of major industrial importance. It is a very strong acid, a powerful oxidizing agent and has the ability to nitrate organic materials, thus making it essential for the production of numerous chemicals. Its main use however remains the production of ammonium nitrate in the fertilizer industry.
For the sake of simplicity, regulatory classification categories relate to the physical characteristics of the product but the requirements also take account of all the physical, chemical and toxicological properties of the product.
2.2 Chemical properties Nitric acid is a strong, monobasic acid and a powerful oxidizing agent which also nitrates many organic compounds.
2.2.1 Acidic properties Being a typical acid, it reacts with alkalis, basic oxides and carbonates to form salts, the most important of which is ammonium nitrate. Due to its oxidizing nature, nitric acid does not (with some exceptions) liberate hydrogen on reaction with metals and the resulting salts are usually in the higher oxidized state. For this reason, heavy corrosion can be expected and should be guarded against by the appropriate use of corrosion resistant metals or alloys (see section 3).
Nitric acid is considered to be a strong acid since in dilute solutions it is practically
while as a base, nitric acid is extremely weak.
2.2.2 Oxidizing properties Being a powerful oxidizing agent (electron acceptor), nitric acid reacts violently with many organic materials and the reactions may be explosive. Any of the following reactions may occur depending on the acid concentration, temperature and the
reducing agent involved:
As a general rule, oxidizing reactions occur primarily with the concentrated acid, favouring the formation of nitrogen dioxide (NO2). The acidic properties tend to dominate with dilute acid, coupled with the preferential formation of nitrogen oxide (NO). However, the oxidative reaction in relation to other substances appears only with those having an oxidation potential below +0.96V.
Reaction takes place with all metals except the precious metal series and certain alloys.
Although chromium, iron and aluminium readily dissolve in dilute nitric acid, the concentrated acid forms a metal oxide layer that protects (passivates) the metal from further oxidation. In general, reaction with metals from the electrochemical series below hydrogen tends to yield nitrogen dioxide and nitrogen oxide whereas those above hydrogen produce nitrogen, ammonia, hydroxylamine or nitrogen oxide.
Reaction with non-metallic elements, with the exception of nitrogen, oxygen, chlorine and bromine, usually oxidizes them to their highest oxidation states as acids.
2.3 Physical properties Pure anhydrous nitric acid (100%) is a colourless liquid with a density of 1522 kg/m3 which solidifies at -41.6°C to form white crystals and boils at 84.1°C. When boiling in light, even at room temperature, there is a partial decomposition with the formation
of nitrogen dioxide following the reaction:
2HNO3 H2O + 2NO2 + 0.5O2
which means that anhydrous nitric acid should be stored below 0°C to avoid decomposition. The nitrogen dioxide remains dissolved in the nitric acid colouring it yellow, or red at higher temperatures. While the pure acid tends to give off white fumes when exposed to air, acid with dissolved nitrogen dioxide gives of reddishbrown vapours, leading to the common name "red fuming acid".
Nitric acid is miscible with water in all proportions and distillation gives an azeotrope with a concentration of 69.2% HNO3 and a boiling temperature of 121.9°C at atmospheric pressure. Two solid hydrates are known; the monohydrate (HNO3.H2O)
Nitrogen oxides are soluble in nitric acid and this property influences more or less, all the physical characteristics depending on the concentration of the oxides. These mainly include the vapour pressure above the liquid and the boiling temperature, as well as the colour mentioned above.
Nitric acid is subject to thermal or light decomposition with increasing concentration and this may give rise to some non-negligible variations in the vapour pressure above the liquid because the nitrogen oxides produced dissolve partly or completely in the acid.
There is no clear definition of ‘red fuming nitric acid’ other than that given in ‘Sax’s Dangerous Properties of Industrial Materials’*, where the product is said to contain more than 17% NO2 with a density of more than 1480 kg/m3.
2.4 Hazards and classification of nitric acid The table I summarises the transport classification, EU product classification, the behaviour of the different products in various circumstances and the health hazards.
The indications in the table are a summary and must be taken as initial indications which must be enhanced by the careful consideration of the relevant literature and regulatory texts. These indications are intended only as a broad framework and do not absolve the user from the obligation to explore every aspect in order to comply fully with all safety, health and environmental requirements. In addition, even though harmonisation has taken place in the European Union regarding transport, this harmonisation is not yet total and individual national regulations may still retain some requirements which must be followed at national level.
3.1 Design and construction of railway tank wagons Railway tank wagons for transporting nitric acid must meet the requirements of the
following regulations with regard to their design and construction:
• Any national provisions or the regulations of the respective railway company for national transportation.
• Any international provisions, such as the International Regulations for the conveyance of Dangerous Goods by Rail (RID) for international transportation.
In addition, railway tank wagons for nitric acid should not have any openings or valves below the liquid level. A special risk assessment must be carried out if bottom valves are used.
The wall thickness of the tank must meet the requirements of the generally applicable rules for rail transport containers made of special steel or aluminium, in accordance with Annex XI of RID.
Railway tank wagons which are emptied from the top have filling and emptying equipment at the tank crown. They have no further connections located elsewhere in the outer surface, in the base or in the liquid phase of the filled tank. The filling and emptying device at the top includes the rising pipe (8), the pressure nozzle (10) and the filling nozzle (12), (see Figures 1 and 2)
11 (12) (8) (10)
Rising pipe (8) The rising pipe, which is usually red, is used for emptying and is closed with a blind lid.
A shut-off valve may also be fitted. The nominal bore of the rising pipe may be 50 mm or 80 mm. The rising pipe nozzle has a nominal bore of 100 mm or 125 mm.
Warning! Never open the rising pipe first!
Pressure nozzle (10) The pressure nozzle, which is usually blue, is used to apply compressed air to the tank for pressure relief during the leak detection test and for general aeration and venting of the tank. The nominal bore of the pressure nozzle should be at least 40 mm. The pressure nozzle must be fitted with a shut-off valve.
Filling nozzle (12) The tank wagon is generally loaded using the filling nozzle, which is normally grey. The nominal bore should be at least 100 mm. The filling nozzle must be able to be closed with a blind lid and may additionally be fitted with a shut-off valve.
3.2 Design and construction of road tankers Road tankers for the transport of nitric acid must meet the requirements of the
following regulations with regard to their design and construction:
• Any national regulations for national transportation
• Any international regulations such as the European Agreement on the international conveyance of dangerous goods by road (ADR) and/or the transport provisions for conveying dangerous goods by sea (IMDG) etc., for international transportation.
3.2.1 Bottom openings Road tankers for transporting nitric acid with an acid content below 70% may have openings and valves below the level of the liquid. In this case, the haulier must demonstrate, prior to loading, that the tank material, the fittings and the seals meet the requirements for nitric acid duty (See Annex 2).
Road tankers with no openings and valves below the liquid level are preferred for transporting nitric acid with an acid content of 70% or more. However, there may be good reasons for using tanks with openings and valves below the liquid. For example, the consignee may use gravity for unloading. A special risk assessment must be carried out when a tank with openings and valves below the liquid level is used. In addition the
following points must be followed:
• The haulier must check the maintenance of the valves on a regular basis and inform the producer of each check.
• The producer must check all closing devices for tightness. This applies in particular to the bottom and discharge valves.
3.2.2 Materials Tanks to contain nitric acid below 70% concentration must be made of special steel
which is resistant to nitric acid. Suitable materials include:
V2A DIN/EN 1.4306 UNS S 30403 (AISI 304L), DIN/EN 1.4541 UNS S 32100 (AISI 321) DIN/EN 1.4550 UNS S 34700 (AISI 347) DIN/EN 1.4465 UNS S 31050.
Antinite DIN/EN 1.4361 UNS S 30601 (recommended for concentrations above 85%).
Warning! Materials DIN/EN 1.4301 or 1.4401 = UNS S 30400 or S 31600 (AISI 304 or
316) are not suitable for nitric acid tanks and should be avoided.
All hoses carried must be made from a material which is resistant to nitric acid.