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Guidance on Risks and Precautions to be Considered for Bulk Liquid Loading and Unloading Operations in Road Transport

**Issue 1 NOVEMBER 2009**

Table of Contents​

  1. Introduction
  2. Objective and Scope
  3. Different Types of Loading and Unloading Schemes
    1. Loading Schemes
    2. Unloading Schemes
  4. Recommended Schemes for Products with Certain Hazards
  5. Operational Risks Associated with Each Scheme
  6. Precautions

Introduction​

Continuous efforts to enhance safety during transport of chemicals and the associated handlings are part of the overall aim to improve the safety performance of both the chemical industry and the transport industry.

Analysis of accident statistics indicates that a substantial number of transport-related incidents happen during loading and unloading operations. It is therefore essential that proper use is being made of appropriate equipment during these operations.

This guidance should be considered as complementing the “Behaviour Based Safety (BBS) Guidelines for the Safe Loading and Unloading of Road Freight Vehicles”, issued by CEFIC and ECTA in March 2007 (2nd issue), which concentrate on clarifying the roles and responsibilities of the different parties involved. Reference is also made to guidelines for specific products such as styrene, chlorinated solvents, etc., which can be found here.

This guidance is of a voluntary nature and individual companies may decide to apply the guidance in full or partly in accordance with their own judgment and taking into account the specific circumstances and requirements.

Applicable national and international regulations, in particular Chapters 4.2 and 4.3 of ADR should always be complied with as they take precedence over the recommendations made in the present guidance.

Objective and Scope​

The objective of the present guidance is to provide recommendations on the risks and precautions to be considered during the loading and unloading of chemicals, whereby particular attention is given to different loading and unloading schemes that may require specific precautions. The present guidance is therefore providing illustrations of these different loading/unloading schemes and identifies the product-related hazards and operational risks associated with these schemes. It also provides recommendations on general precautions as well as on precautions specific to certain schemes, to be taken during loading and unloading operations.

This guidance should help in selecting an appropriate loading/unloading scheme and in taking the necessary safety precautions. It offers both general and more scheme-specific advice, which can be used in training sessions, etc.

The scope of this guidance is limited to equipment used for the loading and unloading of bulk liquids in tank transport operations.

This guidance does, however, not aim to provide an exhaustive overview of all existing transport equipment or loading/unloading schemes and of all possible risks and precautions that may need to be considered.

Different Types of Loading and Unloading Schemes​

1.1 Loading Schemes​

The following loading schemes are being considered in this guidance (see also illustrations in Appendix 1):

  • L1: top loading through open manhole
  • L2: top loading through dome with cone and with vapour recovery
  • L3: top loading with dip tube and with vapour recovery
  • L4: top loading with dip tube and with inert gas blanketing
  • L5: bottom loading with open manhole
  • L6: bottom loading with closed manhole and with vapour recovery
  • L7: bottom loading with closed manhole and with blanketing

1.2 Unloading Schemes​

The following unloading schemes are being considered in this guidance (see also illustrations in Appendix 2):

  • U1: bottom unloading by pump with open manhole
  • U2: bottom unloading by gravity with open manhole
  • U3: bottom unloading by compressed air or inert gas
  • U4: bottom unloading by pump with closed manhole and with intake of air
  • U5: bottom unloading by gravity with closed manhole and with vapour return
  • U6: bottom unloading by pump with closed manhole and with vapour return
  • U7: bottom unloading by pump with closed manhole and with inert gas
  • U8: top unloading by pump with closed manhole and with vapour return

A number of hazard categories of products are listed in the first column of Table 1. For each of these categories, the table indicates the recommended loading/unloading schemes. If a product exhibits more than one hazard, a loading/unloading scheme should be selected that is recommended for each hazard.

Table 1: Recommended Schemes for Product Hazards

Product HazardsL1L2L3L4L5L6L7U1U2U3U4U5U6U7U8
Smelly or Toxic by Inhalation Products✓✓✓✓✓✓✓✓✓
Hot or Corrosive Products✓✓✓✓✓✓✓✓✓✓✓
Products with Low Flashpoint (< 23°C)✓✓✓✓✓✓1✓✓✓✓
Products with Extended Release of Vapour✓✓✓✓✓✓✓✓✓✓✓✓
Products with Short Release of Vapour✓✓✓✓✓✓✓✓✓✓✓✓
(1) only unloading with inert gas, not with air

Operational Risks Associated with Each Scheme​

The main risks that may occur during loading/unloading operations are listed in the first column of Table 2. For each loading/unloading scheme, the risks that require particular attention have been marked with a “✓”.

Table 2: Operational Risks

Operational RisksL1L2L3L4L5L6L7U1U2U3U4U5U6U7U8
Overpressure Tank✓✓✓✓✓✓✓
Overpressure Hoses✓✓✓✓✓✓✓✓
Underpressure (Tank Collapse)✓✓✓✓✓
Product Residue (Previous Load)✓✓✓
Overfilling✓✓1✓1✓1✓✓1✓1
Leaks through Open Bottom Valve✓✓✓✓✓
Leaks through Manlid✓✓✓✓✓✓✓✓✓✓✓✓
Leaking Hose✓✓✓✓✓✓✓✓✓✓✓✓
Load Repartition (Multi-Compartment Tank)✓✓✓✓✓✓
Run-away of Loading Arm/Hose✓
Dropping Object in Manhole✓✓✓✓
Distance Tank to Truck (Avoid Long Hoses)✓✓✓✓✓✓✓✓✓✓✓
Leaks through Connections below Liquid Level✓✓✓✓✓✓✓✓✓✓✓
Residues of Inert Gas (N2) after Discharge✓✓
(1) Extra attention should be given

Precautions​

Two different types of precautions should be taken during loading and unloading operations:

  • General Precautions that apply to all loading and unloading schemes (e.g., use hoses compatible with the product)
  • Specific Precautions that apply only to a number of loading or unloading schemes (e.g., use of dry couplings)

4.1 General Precautions​

Table 3 provides a non-exhaustive list of general precautions that apply to all loading and unloading schemes. Reference is made to ADR and the CEFIC/ECTA Guidelines for the Safe Loading and Unloading of Road Freight Vehicles, where appropriate.

Table 3: General Precautions

General PrecautionsComments
Ensure compatibility of tank and equipmentNone
Empty hoses after operationNone
Prevent unintentional movement of vehiclesSee BBS Loading/Unloading 1.2.2.3 and ADR (2009) 8.3.7
Only open valves after…See BBS Loading/Unloading 1.2.2.14
Ensure safe conditions for access to top of tank and for working at heightUse safety gantry of site, a handrail, a harness, or operate remotely
Take preventive measures to avoid static electricitySee ADR (2009) 8.5 S2 (3) and CENELEC Technical Report CLC/TR 50404
Ensure tightness of all valves and dome coversVisually control proper closure
Use liquid lines with appropriate diameter (DN 80)Recommended equipment specification
Ensure correct connection of couplings (e.g., bolts in all holes)See BBS Loading/Unloading 1.2.2.12
Use hoses tested for pressure appliedSee BBS Loading/Unloading 1.2.2.12
Use hoses compatible with productSee BBS Loading/Unloading 1.2.2.12
Check tank capacity to avoid overfillingSee BBS Loading/Unloading 1.2.2.9
Check correct line-up of valves before starting loading/unloadingSee BBS Loading/Unloading 1.2.2.12

4.2 Precautions Specific for Each Scheme​

Table 4 lists a number of precautions that should be taken and indicates to which schemes they are applicable.

Table 4: Specific Precautions

NoteSpecific PrecautionsL1L2L3L4L5L6L7U1U2U3U4U5U6U7U8
(1)Carry out pre-loading test on tightness✓✓✓✓✓✓✓
(2)Use vapour lines with appropriate diameter (DN 50)✓✓✓✓✓
(2)Use compressed air or N2 lines with appropriate diameter (DN 25)✓✓✓
(3)Use personal respiratory protection device✓✓✓✓✓
(4)Safety devices not to be used for coping with pressure variations during loading/unloading✓✓✓✓✓✓✓✓✓✓
Bottom valve to be opened as last operation for products with high melting point✓✓✓✓✓✓✓
Ensure that maximum vapour/air/N2 pressure does not exceed working pressure of the tank✓✓✓✓✓✓✓✓✓✓
Release pressure after discharge or loading✓✓✓✓✓✓✓✓✓✓
Use dry couplings (4)✓✓✓✓✓✓✓✓✓✓✓

Appendix 1: Illustration of the Different Loading Schemes​

Loading Scheme L1: Top Loading through Open Manhole​

Loading Scheme L1

Loading Scheme L2: Top Loading through Dome with Cone and with Vapour Recovery​

Loading Scheme L2

Loading Scheme L3: Top Loading with Dip Tube and with Vapour Recovery​

Loading Scheme L3

Loading Scheme L4: Top Loading with Dip Tube and with Inert Gas Blanketing​

Loading Scheme L4

Loading Scheme L5: Bottom Loading with Open Manhole​

Loading Scheme L5

Loading Scheme L6: Bottom Loading with Closed Manhole and with Vapour Recovery​

Loading Scheme L6

Loading Scheme L7: Bottom Loading with Closed Manhole and with Blanketing​

Loading Scheme L7

Appendix 2: Illustration of the Different Unloading Schemes​

Unloading Scheme U1: Bottom Unloading by Pump with Open Manhole​

Unloading Scheme U1

Unloading Scheme U2: Bottom Unloading by Gravity with Open Manhole​

Unloading Scheme U2

Unloading Scheme U3: Bottom Unloading by Compressed Air or Inert Gas​

Unloading Scheme U3

Unloading Scheme U4: Bottom Unloading by Pump with Closed Manhole and with Intake of Air​

Unloading Scheme U4

Unloading Scheme U5: Bottom Unloading by Gravity with Closed Manhole and with Vapour Return​

Unloading Scheme U5

Unloading Scheme U6: Bottom Unloading by Pump with Closed Manhole and with Vapour Return​

Unloading Scheme U6

Unloading Scheme U7: Bottom Unloading by Pump with Closed Manhole and with Inert Gas​

Unloading Scheme U7

Unloading Scheme U8: Top Unloading by Pump with Closed Manhole and with Vapour Return​

Unloading Scheme U8

Contacts​

The following persons participated in the development of these guidelines:

Disclaimer​

This document is intended for information only and sets out recommendations on risks and precautions to be considered during the loading and unloading of bulk chemicals in tanks and tank containers. The information contained in this guidance is provided in good faith and, while it is accurate as far as the authors are

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