Guidance on the Design, Construction and Testing of Standard Rail Tank Cars for the Transport of Chemicals in Bulk

Issue 2   
May 2016  

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INTRODUCTION

This document provides guidance on the design and construction of Rail Tank Cars (RTC’s) and associated equipment commonly used for the transport in bulk of chemicals.
This document does NOT address the transport of solids or of products with specific requirements e.g. ethylene oxide, chlorine, ammonia, etc.

The design and construction of RTC’s must, as a minimum, be in compliance with the international regulations concerning the Carriage of Dangerous Goods by Rail (RID) (see OTIF - Dangerous Goods ) and with the European Directive 2010/35 on Transportable Pressure Equipment and other domestic regulations where applicable.

This guidance contains recommendations on top of what is already legally required.

The document is split into 2 columns:

A. Liquids (with a focus on chemicals i.e. non-oil products) B. Gases (limited to liquefied flammable gases e.g. LPG, propane, butane, butadiene, propylene, etc. but excluding gases that have specific requirements such as ethylene oxide, chlorine, ammonia, etc.)

Text that is common to both liquids and gases has been shading in blue.

New text with regard to the previous version is in blue.

This document replaces the previous version of the Cefic Guidelines issued in 2003.

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Disclaimer

This document is intended for information only and sets out guidance for the design, construction, and testing of standard rail tank cars for the transport of chemicals in bulk. The information contained in this guidance is provided in good faith and, while it is accurate as far as the authors are aware, no representations or warranties are made with regard to its completeness. It is not intended to be a comprehensive guide to all the detailed aspects of rail transport equipment. No responsibility will be assumed by Cefic in relation to the information contained in this guidance.

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CONTENTS

A. LIQUIDS

B. GASES (liquefied flammable)

1. Tank design and construction
2. Equipment
   1. Manhole/manlid
   2. Pressure/vacuum relief
   3. Earthing
   4. Bottom discharge
   5. Top discharge
   6. Thermometers/manometers
   7. Controlled ventilation valves (Auto vent system)
3. Walkways/platforms
4. Heating/insulation
5. Underframe
6. External painting/cladding
7. Placarding and marking
8. End protection
9. Testing, inspection and certification
10. Information/data to be submitted to the lessee (consignor) prior to putting into use RTC’s

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A. LIQUIDS

B. GASES (liquefied flammable)

CONTENT

1. TANK DESIGN AND CONSTRUCTION

   • See RID requirements in RID 6.8.2.1

   • Materials of tank construction, including coatings, valves, fittings, gaskets etc. shall be suitable for the specified products.

   • For the shells of RTC's, which are intended for carrying different products, suitable stainless steel is recommended because of its resistance to a wide variety of chemicals.

   • Compared with carbon steel, stainless steel might, in some cases, also have a positive influence on the product quality (e.g. colour) and leak-proofness of the bottom outlet/valve system of the RTC (no rust in seats of valves).

   • The materials of shells (or protective linings), including all other components, which are in contact with the product, shall not contain substances liable to react dangerously with the product, or form dangerous compounds or degrade the material properties or quality of the carried products.

   • New or treated stainless steel tanks must be properly pickled and passivated.

   • For new tanks, all load bearing attachments shall have backing plates of a material compatible with the tank shell, thick enough to distribute incoming forces to an uncritical limit. Backing plates shall be fully welded to the shell and shall have all corners well rounded. Also, a small boring is recommended for stress release.

   • The tank must be designed for a calculation pressure as required by RID (see RID 6.8.2.1.14). It is recommended to have a design pressure of not less than 4 bar gauge. Atmospheric (vented) tanks even if allowed by national and international regulations, are not recommended.

   • Vacuum relief valves shall not be fitted.

   • Hermetically closed shells without vacuum relief valves shall be designed to withstand a minimum underpressure of 0.4 bar.

1. TANK DESIGN AND CONSTRUCTION

• See RID requirements in RID 6.8.2.1 and 6.8.3.1

• Materials of tank construction, including coatings, valves, fittings, gaskets etc. shall be suitable for the specified products.

• The materials of shells (or protective linings), including all other components, which are in contact with the product, shall not contain substances liable to react dangerously with the product, or form dangerous compounds or degrade the material properties or quality of the carried products.

• For new tanks, all load bearing attachments shall have backing plates of a material compatible with the tank shell, thick enough to distribute incoming forces to an uncritical limit. Backing plates shall be fully welded to the shell and shall have all corners well rounded. Also, a small boring is recommended for stress release.

• The tank must be designed for a calculation pressure as required by RID (see RID 4.3.3.2.5).

• Measures should be taken (see RID 6.8.2.1.7.) to protect the shells against the risk of deformation as a result of a negative internal pressure (vacuum). It is highly recommended that the tanks are designed to withstand an underpressure of 1 bar.

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A. LIQUIDS

B. GASES (liquefied flammable)

1. INTERNAL COMPONENTS

   • Internal components such as baffle plates, internal reinforcements, internal ladders, shall not be fitted. Internal heating coils should be avoided if external heating is sufficient for the products carried.

   • RTC's without underframe (“Selbsttragende Kesselwagen”) and RTC's, of which the tank is welded to the underframe over the full length, are not recommended.

   • Tanks must have drainage with flush welding seams at the surface of the bottom.

   • The tanks shall be designed to be explosion-proof.

   • The identification plate has to be properly fixed on the outside of the tank shell and all information has to be readable. The initial test data may not be overwritten by other test data (see RID 6.8.2.5.1 and EN 12561-1).

2. EQUIPMENT

• See RID requirements in RID 6.8.2.1

• The following standards are recommended:

  • EN 12561-1:2011 Marking of tank wagons for the carriage of dangerous goods
  • EN 12561-2:2011 Bottom emptying devices for liquid products including vapour return
  • EN 12561-4:2011 Top emptying and filling devices for liquid products
  • EN 12561-5:2011 Devices for bottom emptying and top filling of liquid products
  • EN 12561-6:2011 Manholes
  • EN 12561-7:2011 Platforms and ladders
  • EN 12561-8:2011 Heating connections
  • UIC leaflet 573 Technical conditions for the construction of tank wagons

• When one of these standards or leaflets is updated or replaced, the new version automatically applies.

• RTC's without underframe (“Selbsttragende Kesselwagen”) and RTC's, of which the tank is welded to the underframe over the full length, are not recommended.

• Tanks must have drainage with flush welding seams at the surface of the bottom.

• The identification plate has to be properly fixed on the outside of the tank shell and all information has to be readable. The initial test data may not be overwritten by other test data (see RID 6.8.2.5.1 and EN 12561-1).

2. EQUIPMENT

• See RID requirements in RID 6.8.3.2

• The following standards are recommended:

  • EN 12561-1:2011 Marking of tank wagons for the carriage of dangerous goods
  • EN 12561-3:2011 Bottom filling and emptying devices for gases liquefied under pressure
  • EN 12561-6 :2011 Manholes
  • UIC leaflet 573 Technical conditions for the construction of tank wagons

• When one of these standards or leaflets is updated or replaced, the new version automatically applies.

2.1 Manhole/manlid

• There are no specific requirements in RID.

• Minimum diameter of the manhole must be 500 mm. Manlids with swing bolts and butterfly nuts have to comply with standard EN 12561-6:2011. For RTC’s, not loaded via the manhole, a closure with nuts is recommended.

• The closing mechanism of the manlid shall be designed in such a way that internal pressure in the RTC can be released safely before the lid can be fully opened.

• The manlid must be secured properly when opened to less than 120 degrees. No obstacles shall prevent proper closure of the manlid.

• The manlid shall be fitted with a joint ring, which must be compatible with the product being carried.

• The manlid shall be gas tight, complying with RID 6.8.2.4.3.

• Fittings or other pieces of equipment on hinged manlid covers are not acceptable.

• Hinged manlids must be sealable.

2.2 Pressure/vacuum relief

• See RID requirements in RID 6.8.2.2 and 6.8.2.2.3

• Pressure/vacuum relief valves shall NOT be fitted if not required.

2.3 Earthing

• See RID requirements in 6.8.2.27 and section 5.5 of EN 12561-2.

• All parts of the tank wagon shall be bonded by equipotential connections and shall be capable of being electrically earthed.

• Earthing lugs must be available on both sides of the RTC, next to the outlet nozzle.

• In order to ensure proper bonding with the RTC, the earthing lug shall consist of a stainless steel plate of at least 40 mm x 80mm x 5mm , which must be welded directly onto equipment that is connected to the tank e.g. cradle for tee pipe, “Sattelleiste” (saddle bar) .

• The earthing plate may never be painted and must be properly marked with the international “earthing” symbol.

• For top loading/unloading, an extra earthing close to the top connections is recommended.

2.4 Bottom discharge

2.4.1 Bottom valves and operating mechanism

• See RID requirements in RID 6.8.2.2

• The tank shall be fitted with discharge pipework in the form of an outlet tee piece. The arm of the tee shall be directed to each side of the RTC and shall have a horizontal position.

• Each bottom-filling or bottom-discharge opening shall be equipped with at least three mutually independent closures, mounted in series, comprising:

  • An internal bottom-valve, i.e. a stop-valve mounted inside the shell or in a welded flange or companion flange;
  • An external stop-valve or equivalent device, one at the end of each pipe;
  • A closing device at the end of each pipe, which may be a screw threaded cap, a blind flange or an equivalent device.

• The internal bottom-valve shall be operable from below. Its setting – open or closed – shall be capable of being verified. Internal bottom valve control devices shall be so designed as to prevent any unintended opening through impact or inadvertent act.

• The internal bottom valve shall continue to be effective in the event of damage to the external control device.

2.4.2 Bottom discharge connections

• See RID requirements in RID 6.8.2.2.2

• The outlet piece shall be fitted at each end with an outlet (side) valve which may be a globe valve (“Schrägsitz”), plug valve or a ball valve.

• The types of the outlet valves must be the same on both sides.

• The discharge end of the outlet tee piece may terminate in a 5 ½” Whithworth screw-thread which is commonly used, and a screw (blank) cap and chain.

• Flanges may also be fitted.

• The use of dry disconnect couplings is recommended. However, dry disconnect couplings should not be used on tanks with crystallisable or highly viscous substances and also not on carbon steel tanks as a second closure.

• For bottom loading and unloading systems, dry disconnect couplings may be used as secondary closure instead of the outlet valve.

• If special couplings are not yet fitted, adequate spacing must be foreseen to connect these onto the outlet valves in a later stage. Adaptors of 5 ½ Withworth thread to dry disconnect couplings are NOT recommended. Dry disconnect couplings should be fitted to a flange.

2.4.3 General – bottom discharge

• The leakproofness of the service equipment shall be ensured even in the event of the RTC overturning (see RID 6.8.2.2.1).

• Gaskets shall be made of a material compatible with the substance carried (see RID 6.8.2.2.1).

• Outlet valves and bottom valve operation mechanisms shall be capable of being secured and sealed.

• All parts of valves, in contact with the product, must be free of grease.

2.5 Top Discharge

• The top connections shall, as a minimum, consist of:

  • Liquid phase (dip tube): DN 80
  • Vapour return: DN 50

• Both connections shall be fitted with:

  • a ball- or butterfly-valve and a blank flange, or
  • a dry break coupling.

• However, dry disconnect couplings should not be used on tanks of crystallisable or highly viscous substances. These connections should be marked with the following codes:

  • Red for the liquid phase
  • Blue for the vapour return

• As additional top connection a filling nozzle with flange DN 150 is recommended.

• Other connections may be foreseen (e.g. for future fitting of an overfill protection system, temperature- or pressure gauges). Therefore an extra DN 80 flange connection is recommended. Where blind flanges, which are not preceded by a valve, are fitted on filling or discharging devices, the blind flanges shall be equipped with splash rings.

• If reasonable, inadequate spacing (approximately 140 mm) should be foreseen to connect future couplings onto the top valves (e.g. dry disconnect couplings)

2.6 Thermometers/manometers

• Thermometers/manometers shall not be fitted except when specifically requested by the customer.

2.7 Controlled ventilation valves (Auto vent system)

• The RTC may be equipped with an auto vent valve, which opens simultaneously, or preferably before the bottom valve is opened. The system may be of a mechanic and/or hydraulic design.

• The auto vent valve (“Zwangsbelüftungsventil”) shall be connected onto a branch pipe with a diameter of not less than 50 mm, which extends from the top to the bottom of the tank. This vapour return line shall, at the bottom, be connected with a T-line which is fitted, on both sides of the RTC, with a blind flange DN 80 or a quick coupling with blind cap. A vacuum relief valve, fitted directly on the vapour line, may also be fitted to prevent implosion during discharge.

• For existing RTCs, the use of an external reinforcement ring, as a vapour line, on the tank is not recommended. If it is used, a special attention must be paid to the compatibility between the material of the line and the vapour. For new RTCs a separate return line has to be installed.

• It is recommended that vapour return lines are fitted with a device preventing liquids from entering the vapour return line.

• It must be clearly displayed (e.g. with white stripe or in writing) that an auto vent system is installed and active.

• For RTC’s which are equipped with vapour return lines, which are not (yet) connected onto an auto vent valve, a clear indication near the vapour return line must show that it is out of use.

3. WALKWAYS/PLATFORMS

• There are no specific requirements in RID.

• At least one walkway/platform of ‘anti-slip safety grating’ construction and a kick plate shall be provided on top of the tank to give safe access to the equipment and fittings.

• The platform must cover the workplace around domes and connection points, if reasonable, and guarantee access to valves, connections

4. HEATING/INSULATION

• See RID requirements in RID 6.8.2.1.25.

• For RTC’s carrying products which may require heating (e.g. with a high freezing point or high viscosity), the tank, outlet line and bottom valve shall be insulated and heatable. Consideration should be given to indirectly heating the bottom valve by making use of the external heating coils of the tank.

• The vapour return line shall be insulated or integrated into the tank insulation.

• The recommended type of insulation is 100 mm thick standard insulation (Rockwool, glasswool or equivalent). The insulation must be of such material that it cannot react dangerously with the chemicals to be carried.

• Preferably, only external heating coils shall be used.

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B. GASES (liquefied flammable)

TANK DESIGN AND CONSTRUCTION

• Materials of tank construction, including coatings, valves, fittings, gaskets etc. shall be suitable for the specified products.

• The materials of shells (or protective linings), including all other components, which are in contact with the product, shall not contain substances liable to react dangerously with the product, or form dangerous compounds or degrade the material properties or quality of the carried products.

• For new tanks, all load bearing attachments shall have backing plates of a material compatible with the tank shell, thick enough to distribute incoming forces to an uncritical limit. Backing plates shall be fully welded to the shell and shall have all corners well rounded. Also, a small boring is recommended for stress release.

• The tank must be designed for a calculation pressure as required by RID (see RID 4.3.3.2.5).

• Measures should be taken (see RID 6.8.2.1.7.) to protect the shells against the risk of deformation as a result of a negative internal pressure (vacuum). It is highly recommended that the tanks are designed to withstand