Cargo securing: concepts, rules and forces


(No.1, year 2010)

 

Heading premiere:
«School of captain Shmelev»

 

 

When Anatoly Shmelev stepped down from the captain’s bridge of cargo ship to shore he learned that his colleagues engaged in transport business on the land were not interested in cargo securing. It’s absurd for a seaman because the life of the crew and ship floatation during sea voyage depend on cargo securing. Any mistake of a captain is punished here not by a fine of the Road police but ship crash, cargo destruction and crew would go to feed the fish. Though the same laws of physics are in force on land and anyone has canceled neither law of gravity, nor laws of inertia and acceleration. But there are no any regulations on cargo securing upon transportation within all countries of former Soviet Union. After sea life Anatoly Shmelev became a surveyor. And since then he tried to direct “land captains” to the path of truth: the same laws of physics act on roads and the cargo on road transport should be secured in such safe manner as on deck or in the hold of cargo ship.
Today, the magazine “Avtoperevozchik” opens a new heading “School of captain Shmelev” which we intend to keep for at least the coming year. In his articles, Anatoly Shmelev would explain how and why various cargoes should be secured during road transportations.

 

Anatoly Shmelev
Photos by the author and Andrew Makhotin

 

What should be guided by?

Definitions of the forces causing cargo displacement should be determined by rules and regulations and used for calculations of the securing. Only the knowledge of these regulated forces would empower carriers to provide safe securing and a driver to comply with clause 23.2 of the Road Traffic Regulations in accordance with which a driver should control stowage, securing and condition of cargo before and during transportation in order to avoid cargo falling down and hampering of road traffic. All questioned persons referred to the absence of regulatory framework in the Russian Federation under which calculation of cargo securing could be completed. However, I dare to confirm that the questioned document is in force. We will not consider in this release my favorite European standard EN 12195-1 “Load restraint assemblies on road vehicles. Part1. Calculation of lashing forces” on which the regulations of the Republic of Belarus had been developed. Despite the comprehensibility the Standard could be applied within territory of the Russian Federation only in the reference order. Moreover, standard EN12195-1 will be harmonized with other standards.

 

 

«Guidelines for packing of cargo transport units” was adopted in 1997.

We consider the document drawn up by the United Nations Economic Commission for Europe; the Russian Federation has been a member of the Commission since its establishments and participated in each meeting. The famous guide IMO/ILO/UN ECE Guidelines for Packing of Cargo Transport Units (CTUs) was adopted in 1997. The guideline was drawn up by the working group on multimodal transport. During its XXI and XXII sessions the working group completed the first draft of the guidelines for packing of cargo into containers and transport means covered requirements of whole transport (railroad, road, maritime and inland waterway transport) – TRANS/WP.24/R. 72 and Add.l. Subsequently this draft was transferred to the International Maritime Organization (IMO) for further consideration and integration of the requirements on cargo packing during maritime transportation. The Guidelines was approved by the International Labor Organization (ILO). The Russian Federation is a member of all the three mentioned international organizations, and therefore it is possible nowadays to monitor compliance with the provisions of the given Guidelines. Guidelines for Packing of Cargo Transport Units (CTUs) hereinafter Guide IMO / ILO / Un ECE is actively used for container loading in Russian ports but for some reasons is not used for loading of road transport. Since the beginning the aims of the Guide are clear,, the translation into Russian can be found on the Internet. Preamble of the Guide IMO/ILO/UN ECE says: «While the use of freight containers, swap-bodies, vehicles or other cargo transport units substantially reduces the physical hazards to which cargoes are exposed, improper or careless packing of cargoes into/onto such units, or lack of proper blocking, bracing and securing, may be the cause of personnel injury when they are handled or transported, In addition, serious and costly damage may occur to the cargo or to the equipment. The person who packs and secures cargo into/onto the cargo transport unit (CTU) may be the last person to look inside the unit until it is opened by the consignee at its final destination.

Consequently, a great many people in the transport chain will rely on the skill of such persons, including:
- road vehicle drivers and other highway users when the unit is transported;
- rail workers, and others, when the unit is transported by rail;
- crew members of inland waterway vessels when the unit is transported on inland waterways;
- handling staff at inland terminals when the unit is transferred from one transport mode to another;
- dock workers when the unit is loaded or discharged;
- crew members of the ship which may be taking the unit through lis most severe conditions during the transport operation; and
- those who unpack the unit.
All persons, such as the above and passengers, may be at risk from a poorly packed container, swap-body or vehicle, particularly one which is carrying dangerous cargoes.

Scope of Guide IMO/ILO/UN ECE:

These Guidelines, which are not all-inclusive, are essential to the safe packing of CTUs by those responsible for the packing and securing of the cargo and by those whose task it is to train people to pack such units. Training is essential if safety standards are to be maintained.

These Guidelines are not intended to conflict with, or to replace or supersede, any existing regulations or recommendations which may concern the carriage of cargo in CTUs. They do not cover the filling or emptying of tank containers, portable tanks or road tank vehicles, or the transport of any bulk cargo in bulk packaging.”
The fact that the Guidelines IMO/ILO/UN ECE should be applied for road transport follows the list of definitions.
Cargo transport unit (CTU) means “cargo container”, swap body, transport means, railway wagons or any other similar unit; “transport means” is defined as any road transport means or railway wagon placed on frame and wheels and which is being loaded or unloaded as one unit; it is also included trailer, semi-trailer or any other identical unit excluding those designed only for loading and unloading purposes. Let’s quote two very important items of clause 1 of the Guidelines:
1.4. . Road transport operations may generate short-term longitudinal forces upon the cargo and the CTU. They may also cause vibrations that may vary considerably due to different suspension systems, different road surface conditions and different driving habits.
1.7. The following table provides an example of the accelerations in g's which could arise during transport operations; however, national legislation or recommendations may require the use of other values.

 

Mode of transport

Forwards

Backwards

Sideways

Rode

1,0g

0,5g

O,5g

 

Thus, everything takes its place. Already now we can require Russian participant of road transportation to accomplish requirements of the Guidelines. The most serious problem is that no one of Russian participants of the road traffic as well as Road Police, inspectors of Rostransinspection have no any understanding on that account. Let’s try as far as possible to fill in this gap.


This could be shown in the following way:


According to Guidelines for packing of cargo transport units:

 

(Abb: www.tis-gdv.de)

According to Standard EN 12195-1:

 

(Abb: www.tis-gdv.de)

How could risks be minimized?

European Directive No.2003/59/EC entered into force on 10th of September 2003. According to it all professional drivers should be trained in proper manner in order to minimize risks and maintain road safety.
Training program should include such obligatory topics as safety factors concerning loading of vehicles, cargo supervising (stowage and securing), dangers relating to various kinds of cargoes (i.e. liquids), supervising of loading, unloading and usage of loading facilities. Minimal quantity of hours has been set.
Thus, International Maritime Organization (IMO) recommends the following quantity of hours requested for training of certain groups of trainees:

Так, например, Международная морская организация (IMO) рекомендует следующее количество часов для подготовки определенных групп обучаемых:

No

Subject area

 

Target groups

 

 

 

Management Forwarders

Lorry drivers Railway workers

Stevedores Terminal packers Surveyors Authorities

1

Consequences

1

1

1

2

Responsibilities

1

0,5

0,5

3

Forces

0,5

0.5

0.5

4

Basic principles with quick lashing guide

1

1,5

2

5

CTU types

0,5

0,5

1

6

Cargo care

-

0,5

1

7

Methods of packing and securing

0,5

0,5

1

8

Securing equipment

0,5

0,5

0,5

9

Unitized cargoes

-

0,5

1

10

Break bulk

-

0,5

1

11

Paper products

-

0,5

1

12

Special techniques

-

0,5

1

13

Dangerous goods

0,5

0,5

1

14

Theoretical exercises

-

1

2

15

Practical exercises

-

3

3

16

Inspections

-

0.5

3

17

Evaluation

-

1

1

 

TOTAL

5,5

13,5

21,5

 

Lack of studying hours regarding to some types of cargoes for management and forwarders does not mean that there is no necessity to them to be trained on subjects “Paper cargo”or “cargoes required special technique of transportation”. It means that trainees are obliged to be trained prior entering into the office. Let’s begin from point No.3 “Forces arising during transportation”. Please find below a table of definitions which will be used further:

 

 


Why are cargoes shifted, why do they tip over and fell down out the transport means? Let’s remind Newton’s law: “After any body has changed parameters of movement it tries to preserve initial speed and direction under influence of inertial forces”. To prevent destructive influence of these forces upon the cargo is the aim of proper cargo securing. Firstly, I would like to pay your attention to to unit used almost in all documents concerning cargo securing. This is deca-Newton or daN.


Standard GOST 8.417-2002 "State system for ensuring the uniformity of measurements. Units of quantities” sets units of quantities applied in a country: name, definitions, determination and rules of their appliance. Unit of measurement of force in modern option of system SI is newton (N) but earlier it was kilogram-force. Kilogram-force is convenient to be used due to the fact that weight is equal to mass that is why for anybody it is easily to realize what force 5kgf is. According to system SI 1 Newton is equal to force giving to body with weight of 1 kg acceleration of 1m/s² in the force direction; 1 decaNewton is equal to 10 newtons, thus, 1kgf =  9,80665 Newtons or around 10N or 1 decaNewton.


That is why appliance of unit “decaNewton” is rather convenient to calculate cargo securing. The example is given on marking of lashings and securing points what will be discussed later.

 

Example of proper marking

 

 

Example of inadequate marking

 

 

Examples of other markings applied on the vehicle body

 

We would talk on the following forces:

 

Weight of cargo

Abb: Verlag Gunter Hendrisch



In modern science weight and mass are different definitions. At the same time the difference in definitions of weight and mass has become known not long ago, and sometimes word weight is being used while speaking about mass. For example, when weight of 20t is stated in documents we consider weight FG = mg = 20000 daN.

Enertia force

 

 

The cargo is affected by forces arising in three axes: longitudinal Fx, transversal Fy and vertical Fz. The forces are applied to the center of gravity that is why it is important to know its position to provide adequate securing. Coefficients multiplied weight of cargo or acceleration of gravity force are used to mark inertia forces for different regulations. These coefficients we will use marking them as cx, cy, cz.

 

The below figure is taken from North-American Standard: cx = 0,8, cy = 0,5, cz = 0,2

 

 


The force directing along axle of transport means is marked as Fx. The greatest force affecting the cargo arises due to braking of transport means. Acceleration is negative, force directs forward. What explanations are given by our drivers then?
«Saving lives I applied heavy braking. Unknown transport means (or pedestrian) disappeared. The cargo shifted. I’m not guilty”. Heavy braking is integral part of the driving. Those who do not know that drives for nothing. Definition “emergency braking” is applied in Standards and means only braking purpose of which to decrease speed of the transport means sharply. This could occur and it is inevitable as storm weather at sea or air-pocket in the air. To prepare cargo and transport means for emergency braking is obligation not only of Carrier.

 

 

Requirement to place cargo tightly to the headboard is stipulated by force arising due to heavy braking.

 

 

Let’s consider it on example with roll weight of which in documents as stated as 10mt. For our calculation we take

FG = 10000 daN,

As per Guideline IMO/ILO/UN ECE

cx = 1,0.

Upon braking the highest force affecting the cargo is equal to

Fx = cx x FG = 1,0 x 10000 daN.

 

It is meaning and direction of this force to determine requirements to strength and condition of the headboard of the vehicle body. Particular requirements to place cargo tightly to the headboard are requested under influence of this force arising upon emergency braking. (the cargo is easier to be kept at place than stop it in motion). Upon starting movement and increasing speed identical but less by meaning force arises.

As per Guidelines IMO/ILO/UN ECE

сx = 0,5,

it means that the highest force affecting the roll with weight of 10000 daN is equal to:

Fx = cx x FG = 0,5 x 10000 daN = 5000

This is the force to shift and tip over the last packages stowed at the rear doors. Not many drivers manage to secure the last package.

 

 

Upon starting movement and increasing speed identical but less by meaning force arises.


 

When transport means turns or simply change road line, the means and cargo are subjected to influence of centrifugal force directed from the center of the turn to sideways: Fy = m v2/r. It should be reminded that the centrifugal force is directly proportional to speed square, that is why twice decrease of speed would decrease that force in 4 times. As per Guideline IMO/ILO/UN ECE cy = 0,5, it means that the highest enertia force affecting the roll with weight of 10000 daN is equal to:

Fy = cx x FG = 0,5 x 10000 daN = 5000.

 

 

During transportation there is vertical force acting on the transported cargo.

 

 

While proceeding along the rough road vertical force acts on cargo. This force is relatively small but it decrease cohesion between cargo and the floor of the cargo compartment and consequently decreases friction force which prevents cargo shifting. Many regulations introduce cz = 0,2 (see figure from North-American Standard). But Guidelines IMO/ILO/UN ECE (as well as Standard EN 12195-1) does not take into consideration vertical forces for road transportation.
Condition of our roads suggests that we should use coefficient cz ranged from 0,2 to 0,5, that practically leads to zero of summarizing force of securing by lashings, but it is topic for the next articles.

All described forces act on the cargo in complex. Insufficient attention to one of the named factors could entail such influence that cannot be compensated by proper cargo securing against other kinds of forces.


 

 

Friction force

Friction force between cargo and floor of the cargo compartment is an ally in fight with forces. Friction force is calculated as weight multiplied on friction coefficient. Various regulating documents require usage of coefficient of static or sliding friction. Friction force is acting in opposite direction.

FF = µ FG

Correct appliance of such physical effect as friction influences considerably on safe transportation, safety of cargo and reducing of expenses on cargo securing. For example, placement of rubber mats between cargo and cargo surface of the transport means reduces quantity of securing devices. It should be considered that Guidelines IMO/ILO/UN ECE recommends to use coefficient of static friction to calculate friction force, at the same time Standard EN 12195-1 requires usage of coefficient of sliding friction. It is supposed that while moving there is no cohesion between cargo and platform due to constant vibration and it is necessary to use sliding friction coefficient, which is equal to 70% of static friction coefficient.


Thus, the following is used for calculations:


Guidelines IMO/ILO/UN ECE – static friction coefficient µS;
Standard EN 12195-1 – sliding friction coefficient µD = 0,7 µS.
The best way to determine sliding friction coefficient when it is unknown is to measure it.

The most frequently used method is a method of platform incline till the moment when cargo starts sliding. Static friction coefficient (S) is equal to tangent of the sliding start.

 

This method was recommended to Manufacturers at the places of numerous cargo shipments. For example, we strongly recommend to Belarusian metallurgical plant to measure this magnitude for cargo of metal cord. Maybe then they could see the dangerous features of their shipments.


Very often information on sliding coefficient could be found out in various reference books.

When the friction coefficient m is

the cargo starts to slide at an angle fo

Equal to the heights h (cm)   (if L=200 cm)

0,2

11,3

39

0,3

16,7

57

0,4

21,8

74

0,5

26,6

89

 

The general requirements to maintain cargo securing during transportation are:

- sum of forces in each direction should be equal to zero;

- sum of moments in each plane should be equal to zero.

To secure cargo from shifting it is necessary to compensate the difference between forces and friction forces through securing means.

 

 

 

The given formula is used to secure cargo by means of blocking, i.e. securing of roll with weight of 10000 daN and static coefficient equal to 0,3 it is necessary to apply securing means with securing force equal to 7000 daN compensating difference between static force and friction force in order to compensate static force arising upon heavy braking.

 

 

Securing force by means of top-over lashing

(Picture taken from Alfred Lampen book)

My unfavorite method of cargo securing by means of top-over lashings is calculated in some other way.
After lashing tension through tensioner the weight of the secured cargo allegedly increases tension force shown by lashing from the side of location of the tensioner (F1) and tension force of lashing from the other side of the secured cargo (F2).


Thus, the following is used for calculations:
Guidelines IMO/ILO/UN ECE – F2 = F1 = STF (tension force of a tensioner);
Standard EN 12195-1 – F2 = 0,5 F1.

Inthat way each tensioned lashing is likely to add weight to cargo equal to 2,0хSTF (IMO/ILO/UN ECE ) or 1,5хSTF (EN12195-1). Coefficients 2,0 и 1,5 are called transfer coefficient and marked by symbol k and used in general formulae.

Method of calculation of top-over lashing will be given in the next articles. So, we could assert that we have normative document that could be applied in Russian Federation without future tragedies and financial losses entailed by shifting of cargoes.
This is IMO/ ILO/ UN ECE Guidelines for Packing of Cargo Transport Units (CTUs).
While proceeding along territory of Germany the given cargo securing could be considered as inadequate due to some differences in two documents, but the most differences concern calculation of top-over lashings which could not be efficient within territory of Russian Federation.

 

Cargo securing: concepts, rules and forces