Standards & Codes

UNIT 1.2 - STANDARDS AND CODES OF PRACTICE Contents Introduction

1.

Codes of Practice

1.1 1.2 1.3 1.4

2.

Standards

2.1 2.2 2.3

3.

British Standards ISO Standards CEN/CENELEC CEN/CENELE C (euronorm) Standards

The use of standards and codes

3.1 3.2 3.3 3.4

4.

Approved Codes of Practice Trade or Professional Professiona l Codes of Practice Recommended Codes of Practice Technical Publications and Safety Information Information

Testing and examining Construction Marking and identification WLL, SWL, Proof Load

The cor rect use of metric and imp erial

4.1 4.2 4.3 4.4 4.5 4.6 4.7

Why change from imperial to metric? Expressing metric units Metric multiples and sub-multiples Length Mass, force, weight and load Practical conversions for use in rating lifting equipment Conclusion

© Lifting Equipment Engineers Association 2013 – Unit 1.2

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Introduction

The law places duties on manufacturers, suppliers, repairers and hirers of equipment to meet certain minimum requirements. Legal duties are also imposed on the owners and users of lifting equipment and on those who make the tests and examinations to verify the equipment. The purpose is to ensure that lifting equipment is designed and manufactured to be safe and that it is regularly maintained and examined whilst in service to ensure that it remains safe. The verification of lifting equipment is the duty of the tester and examiner. The legal requirements tend to be of a general nature. Detailed guidance to assist the tester and examiner is provided by standards, codes of practice and manufacturer’s instructions. This unit looks at standards and codes of practice in a general way and considers how they apply to the duties of lifting equipment engineers. Particular attention is paid to the units of measurement used.


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1.

Codes of Practice

Various types of codes of practice are available to guide the tester and examiner. 1.1

Appr oved Codes of Practice (ACoP)

In the UK, to have this status, a code must be approved by the Health and Safety Commission with the consent of the Secretary of State. ACoPs have a quasi legal status. An ACoP gives practical advice on how to comply with the law. If you follow the advice you will be doing enough to comply with the law in respect of those specific matters on which the code gives advice. You may use alternative methods to those set out in the code in order to comply with the law. There is no obligation to comply with an ACoP but if a person is prosecuted for a breach of health and safety law and it is proved that they did not follow the relevant provisions of the code, then they will need to show that they complied with the law in some other way or a court will find them at fault. Most modern UK legislation, such as LOLER and PUWER, is published with an ACoP. An ACoP is often accompanied by guidance which does not form part of the ACoP and does not have the same status but is used to give further explanation to the requirements of the ACoP and to illustrate good practice. Such guidance is published for both PUWER and LOLER. It is important that students are familiar with the ACoP and guidance that accompanies LOLER as it contains much useful information for the competent person. The regulations ACoPs and guidance are published combined in book form by HSE Books and can be purchased by mail order telephone: +44 (0) 1787 881165 fax: +44 (0) 1787 313995. The references are as follows: For PUWER - Safe use of work equipment L22 For LOLER – Safe use of lifting equipment L113 1.2

Trade or Professio nal Codes of Practice

Another type of code of practice is the trade or professional code of practice. These lay down minimum standards and requirements considered necessary by the industry or profession to perform certain duties or practice certain functions in a correct and proper way. Although these have no legal status it is necessary to meet their requirements to be considered competent to carry out certain work. The LEEA has such a document reference LEEA 042 which is the Association’s Technical Requirements for Members. This document contains the minimum requirements for equipment, personnel qualifications and quality systems which a lifting equipment company must maintain. Members of the LEEA must comply with these requirements.


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The Association carries out regular technical audits of its member organisations to ensure that they are complying with the Technical Requirements in the areas applicable to their scope of work. 1.3

Recomm ended Codes of Practice

A recommended code of practice has no legal status. However, they are recommended by the HSE as a way of meeting certain requirements of the Health and Safety at Work Act or of significantly adding to safety. A person could be called upon to prove they were working to such a code, or that what they were doing was equivalent to or better than the recommendations of the code. The LEEA publishes such a code - The Code of Practice for the Safe Use of Lifting Equipment (COPSULE). This is intended as a source of reference for organisations using lifting equipment. The code is in sections and section 1 deals with general matters applicable to most types of lifting equipment. These include definitions, legal requirements, selection of equipment and the information needed to do so, marking, storage, handling and in-service inspection of the equipment, safe use and training of users. There are also appendices to section 1 dealing with matters of particular importance. These include estimation of weight, load security and stability, planning of lifting operations, crane signals and guidance on examination schemes. Each of the subsequent sections deals with one particular type of equipment and provides more detailed information. This information is presented under standard headings in all the sections. The headings group the information relevant to the various departments in the user organisation. So, for example, there is the information needed for the engineer to select or specify the item, the information the purchasing department will need to buy it, the information required for the maintenance department to install, commission and maintain it, the requirements for storage and, for the training department, the information required to use it safely. Each section includes information on the relevant manufacturing standards and lists the faults and defects which can occur in use. As well as giving guidance on the correct way to use the equipment the section includes the known bad practices to be avoided. Study of this code is an important element of this course and students should be familiar with its requirements. 1.4

Techni cal Public ations and Safety Inform ation

This covers a wide range of documents and textbooks, including manufacturer’s product installation and maintenance manuals, books covering workshop practices, product catalogues and training manuals. Under this heading the LEEA publishes a range of training materials, including this course. The LEEA also publishes Lifting Equipment – A User’s Pocket Guide which is based on COPSULE and acts as a quick reference for the rigger and slinger. Another important document published by the LEEA is The Lifting Engineer’s Handbook. This is intended for the lifting equipment engineer, tester and examiner and students. It contains guidance and reference material on which work procedures should be based. To support its members, LEEA also publishes a range of single sheet safety information leaflets. These are suitable for issue with every item of lifting equipment


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supplied or hired. The provision of safe use information is required by the Health and Safety at Work etc Act and the Supply of Machinery (Safety) Regulations. Students should try to obtain their own copies of the documents mentioned above. In any event students need free access to them, particularly LOLER with its associated ACoP and guidance and the Code of Practice for the Safe Use of Lifting Equipment, to use as a reference in day to day duties and for study purposes. 2.

Standards

2.1

Bri tis h Standards

Of prime concern to the student of this course are British Standards, which specify particular products. Product standards take one of two forms: •

•

fully specified standards, which fully specify dimensions, tolerances, materials and safe working loads. (eg BS 4278 – Eyebolts). performance standards, which specify the performance criteria that the product must meet but leave as open as possible the dimensions, material specification etc. For compatibility purposes, such dimensions as are included are specified as maximum or minimum. (eg BS EN 13889 - Shackles).

Modern standards for new products are written as performance standards. Some standards take the form of recommended Codes of Practice, covering the use, maintenance or application of specific products or the conduct of certain processes. British Standards are published directly by the British Standards Institute (BSI). Most of the products with which the student of this course is concerned are covered by British Standards. However the tester and examiner should be familiar with the other types of standard available so we will briefly outline them here. 2.2

ISO Standard s

ISO standards (or International Standards Organisation Standards) generally take the form of performance standards. They are agreed internationally by a majority vote but, because ISO members include some less technologically developed countries, these standards do not always reflect the latest technology. ISO standards are published directly by ISO in Switzerland. They are often used as the basis for writing national standards which may include more stringent requirements. Where the UK accepts an ISO standard as written, they are published as a British Standard. At one time, such standards were given their own BS number. Now the practice is to use the ISO number and add the prefix BS. For example, ISO 2330 Fork lift trucks - Fork arms - Technical characteristics and testing, is published as BS ISO 2330.


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In the past, where the UK accepted some, but not all, of the contents of an ISO standard, a British Standard was published which omitted those parts to which objection was made, or amendments were made which added to the requirements. These standards appear only with a BS number and it is necessary to refer to the British Standard catalogue to see the relationship with the International Standard. Not every ISO standard was taken up by BSI. If it was decided that the ISO standard was of no value, it contained mainly unacceptable requirements, the subject was already adequately covered by a British Standard or demand would not have warranted a British Standard, then no action was taken. If the tester and examiner are required to work to these standards, their status can be checked by reference to the BSI Standards catalogue which can be accessed online at www.bsi-global.com. The catalogue shows any relationship between the BS standard and an ISO standard. Information on ISO standards can be found in the ISO Standards catalogue which can be accessed online at: www.iso.org/iso/iso_catalogue.htm In more recent times, cooperation between the various standards bodies has led to changes. This will be considered later. 2.3

CEN/CENELEC Stand ards

Within Europe, CEN and in the case of electrical equipment, CENELEC are the bodies responsible for European Standards. Prior to the completion of the Single European Market in 1992, these standards, then known as euronorms, were treated for publication in the same way as ISO Standards. Those accepted by the UK were published as dual numbered British Standards, which have both BS and EN numbers. With the introduction of the Single European Market (European Union), it became necessary for goods to pass freely throughout the member states. For example, an item made and tested in the UK must be accepted in any of the other states of the Union as complying with their standards and legal requirements. European Directives (see Unit 1.1) were introduced to provide common legal requirements for various products. The first such Directives had long technical annexes specifying the requirements for the products but the process of drafting them was taking far too long. What was called the ‘new approach’ was adopted. The technical annexes of the new approach directives were restricted to the ‘essential health and safety requirements’. These are the goals to be achieved rather than the method of achieving them. The method of achieving those goals was left to a new system of standards prepared by CEN and CENELEC. They are called harmonised European standards and carry the prefix EN. These harmonised EN standards have a quasi-legal status. When a manufacturer makes a product to the relevant EN standard it is deemed to comply with the ‘essential health and safety requirements’ of the Directive in so far as the standard addresses them. Each standard includes information on which of the essential health and safety requirements is relevant to the product and whether they are addressed. Wherever possible, the EN standard does cover all the relevant


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essential health and safety requirements and that is the case for the standards relevant to this course. These manufacturing standards are all performance based and wherever possible avoid being prescriptive about dimensions, materials, processes etc. This is to allow for technical innovation. They are high quality standards, meaning that it should not be possible to manufacture an unsafe product which genuinely complies with the standard. To achieve the status of a harmonised standard, an EN must be vetted on behalf of the European Commission to ensure that it does address the relevant essential health and safety requirements and is verifiable. Once approved, its acceptance is published in the Official Journal of the European Union. It is mandatory that member states adopt these harmonised standards as national standards, without alteration, and that they withdraw any existing or conflicting standards. CEN does not publish standards directly. They are published by the national standards bodies in each state. In the UK this is BSI which does so with a BS prefix, ie as a BS EN standard. Working to harmonised standards is the easiest way for manufacturers to demonstrate that they meet the legal requirements imposed by the Directive. Manufacturers do not have to comply with a harmonised standard. However, where a harmonised standard has been published, it acts as a benchmark by which the authorities can judge any other specification. In effect, once a harmonised standard is in place, its requirements become the legal minimum. Manufacturers that claim to be working to such standards but fail to meet them in full and are unable to show that they have achieved an equivalent result by other means are liable to prosecution. A more recent move is under way to bring standards throughout the world to the same high levels. CEN and ISO are working together with national standard bodies from around the world with the aim of bringing all of the standards into line. Their approach follows that taken in Europe. Manufacturers can use the standards to demonstrate that they are meeting all necessary legal requirements. This family of standards is being published by ISO, as harmonised standards by CEN as EN ISO, and by the British Standard Institute as BS EN ISO. Other national standards bodies follow the same format. For example, in Germany the standard is published as DIN EN ISO. In this way, no matter which version of the standard is read, the requirements are the same. 3.

The use of Standards and Codes

3.1

Testi ng and examining

From the above, we can see that reference to current British Standards ensures compliance with accepted ISO standards and euronorms, and with all CEN harmonised standards. Therefore in most cases, a UK based tester and examiner will only have to concern themselves with British Standards.


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Note: When dealing with existing equipment it is important that reference is made to the standard, or edition of the standard, to which the equipment was manufactured. This may not be the current British Standard. LEEA document reference 015 Reference Library - British, European and International Standards - lists most of the relevant standards, including some which have been withdrawn or declared obsolescent. It is updated on a regular basis. However, it is the duty of the tester and examiner to ensure they are referring to the correct standard/edition for the product being tested or examined.

Standards specify the verification methods which may include type tests, sample tests, individual load tests, non-destructive tests (NDT) and other tests. They also give the acceptance and rejection criteria to be applied. For BS EN standards, the methods of verification must be specified in a way that gives repeatable results. In other standards, including older British Standards, it is often left to the tester and examiner to decide how to apply the test and what the examination procedure should be. Here guidance may be obtained from the LEEA’s The Lifting Engineer’s Handbook. This gives general details of the various tests available and the information they will reveal. Depending on the item, age and the source of the standard, the required accuracy of test machines or applied loads/forces will vary. LEEA technical requirements call for all test machines and load/force measuring equipment to have a minimum accuracy of ±2%. This is necessary to fall within the range of accuracy laid down in most of the product standards. However some standards require an accuracy of ±1%. Standards are generally limited to new products. However, the majority of thorough examinations the tester and examiner will do will be on items which are, or have been, in service. The Code of Practice for the Safe Use of Lifting Equipment lists the defects which can arise in service and which the examiner must consider when deciding whether the item is fit for a further period of service. The acceptance/rejection criterion is given in other publications, such as the manufacturer’s instructions. The Lifting Engineer’s Handbook and product specific units of this course. 3.2

Construction

Whilst not foolproof, if an item complies with a British Standard the tester and examiner can be confident that it is of good construction, adequate strength and made from a suitable material. Indeed as already stated, if it is a BS EN standard, it should not be possible to manufacture an unsafe product which genuinely complies with the standard. If the item is CE marked this is, in effect, a claim by the manufacturer (or whoever placed the item on the market in the EU) that the product complies fully with the requirements of the relevant European Directive. This means that it has been produced to a harmonised standard, or otherwise meets the essential health and safety requirements.


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The examiner can check what the item complies with by reference to the original documentation, often referred to as a ‘birth certificate’. This should contain all relevant information about it including any standard it complies with. Items supplied before the Machinery Directive came into force usually had a test certificate. Items supplied since the Machinery Directive came into force should have an EC Declaration of Conformity and manufacturer’s certificate, or other verification document such as a report of thorough examination. 3.3

Marki ng and Identifi cation

British Standards lay down what marking is necessary and where and how it should be marked to fully identify the item, the WLL or SWL, the grade and to provide traceability to its documentation. The identification should be unique so that it is clearly traceable to all relevant documentation. In some cases standards permit the use of batch numbering for new items. This presents the examiner with something of a problem once they have been in service. For example, if an examination is being carried out on a site that was supplied with 100 shackles from the same batch, how does the examiner ensure that all of them have been checked and are safe? The chances are that at least one will not be found. LEEA Technical Requirements therefore call for an individual identification mark at the point of sale. 3.4

Workin g Load Lim it (WLL), Safe Workin g Load (SWL), Proof Load

The working load limit (WLL) is the maximum load that an item of lifting equipment is designed to raise, lower or suspend under ideal conditions. In some standards and documents the WLL is referred to as the ‘maximum safe working load. The safe working load (SWL) is the maximum load as assessed by a competent person which an item of lifting equipment may raise, lower or suspend under the particular service conditions. The safe working load will normally be the same value as the working load limit but it may be less if conditions are not ideal. However for portable items such as slings, shackles, hand chain blocks and lever hoists, if the conditions are not ideal, rather than de-rate them, it is good practice to achieve this by specifying normally rated items with a higher capacity. This avoids the possibility of confusing a normally rated item with a de-rated item. (See the LEEA Code of Practice for the Safe Use of Lifting Equipment for full definitions and an explanation of these terms). LOLER requires that all lifting equipment be marked with its SWL. Modern standards for general purpose lifting equipment require it to be marked with the WLL because the manufacturer will not know the conditions of use. Older standards specify the SWL. In most cases this is the same value and does not create too much of a problem. In fact the guidance to LOLER (paragraph 188) acknowledges the use of alternative terms including WLL. In practice the capacity can be marked without the prefix SWL. However use of the prefix WLL is also acceptable. It is only in those special cases where equipment is de-rated and the SWL is less than the WLL that re-marking be necessary when the item is put into service. Generally, although not always, this only applies to permanently installed items.


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4.

The cor rect use of metric and imp erial

Although modern lifting equipment standards are based on the metric system, a few older imperial standards remain current. A vast amount of lifting equipment made to and rated in the imperial system also remains in service. Many users wish to have all of their equipment rated in the same units. For these reasons the tester and examiner must be able to convert from one system of units to another. This is also important where test machines are used to apply a force, but the standard refers to units of load. Both imperial and metric systems contain many units and divisions of units. To avoid confusion, not all of them are used in the rating, marking and testing of lifting equipment. Instead, a limited range of units and certain conventions in terms of how they are expressed have been adopted. When dealing with any aspect of lifting equipment it is essential that these units and conventions are understood. When specifying and testing lifting equipment, the units of concern are length, mass and force. Their use, and the conversion from one system to another, will now be considered. 4.1

Why change fro m imp erial to metric ?

The imperial system was formed haphazardly. Originally it was based on nonconstant standards, such as a foot being the length of a man's foot. This meant that wide variations existed. As technology advanced it became necessary to introduce a fixed base standard - a national standard. Even then variations existed between the actual measures and weights used in one country to another. For example, the inch used in America was shorter than the inch used in the UK, albeit the variations were tiny. This only became a problem when international trade expanded, with precision components from different countries of origin being assembled into a final product. Some international standardisation was therefore needed. As with so many attempts at standardisation, there are often two or more methods each vying for superiority. The main competitor to the Imperial system was the metric system. However, as with the imperial system, there were ambiguities in the older metric system as practised from one country to another. To overcome these problems, the SYSTEME INTERNATIONAL D'UNITS (international system of units), known as the SI system, was internationally adopted in 1960. The metric SI system soon gained in popularity. One factor to justify changing is the ease of learning. Not only did the imperial system form haphazardly, but it was also a random system, with no direct relationship between the units. For example: 12 inches = 1 foot, 3 feet = 1 yard, 1760 yards = 1 mile. The metric system, in contrast, is a decimal system with a logical progression of 10 between the units. For example: 10 millimetres = 1 centimetre, 10 centimetres = 1 decimetre, 10 decimetres = 1 metre. The metric system is therefore a simpler system to learn and apply and by the 1970s was adopted for all new British Standards. © Lifting Equipment Engineers Association 2013 – Unit 1.2

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4.2

Expressing metric units

Care is needed when writing, stamping or marking the names of the metric units, particularly if they are being abbreviated where the same letter may be common to more than one unit. Many of the SI units take their names from historical people associated with the unit. An example of this, which is relevant to the tester and examiner, is the unit of force - the Newton. This takes its name from Sir Isaac Newton due to his early work on gravity. Where it is derived from someone’s name, the unit is usually written with a capital letter and the abbreviation for the unit is an upper case letter. For example, the Newton abbreviated as N and the Watt abbreviated as W. This applies wherever the abbreviation appears. If the unit is not derived from someone’s name the unit is always written with a lower case letter which is also used for its abbreviation. For example, the SI unit of mass is the tonne and its abbreviation is a lower case t. An upper case T is used as the abbreviation for the unit of magnetic flux. Therefore a WLL or SWL should always be shown as xxt and never xxT. 4.3

Metric multip les and sub-multiples

The metric system uses standard terms for the multiples and sub-multiples of the various base units as shown in the following table: Factor by which unit is multiplied: 1000000 1000 100 10 1 0.1 0.01 0.001

Prefix

Symbol

Mega kilo hecto deca deci centi milli

M k h da d c m

These terms are applied to show the multiplication or division of the base unit. For example the gram is the base unit of mass in the metric system. Thus it can be seen that 1/10th (0.1) of a gram is known as a decigram and 1000 grams is known as a kilogram. As with the unit names, the symbols for the divisions and multiples also use upper and lower case letters, eg Mega = M and milli = m. This then leads to some unusual capitalization, eg MegaNewton = MN, millimetre = mm, Watt = W, kiloWatt = kW. There are a few exceptions, so some care is needed, but it is important to use this convention to avoid any confusion between the units. 4.4

Length

The base unit of length within the SI metric system is the metre (m). Industry and standards accept the thousandth (ie 3 decimal places) as the only subdivision. This is known as the millimetre (mm). Other multiples or sub-multiples are not used. This is partly to avoid confusion on drawings where the symbol is not commonly shown. If, for any reason, the decimal point is omitted or obscured, the dimension will be identical, eg 1250 mm = 1.250 m and would therefore appear as 1250 or © Lifting Equipment Engineers Association 2013 – Unit 1.2

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1.250. Therefore other subdivisions are not used for reasons of clarity. meaning is obvious by the relative scale of the dimensions.

The

Although there are several units of length within the imperial system, only two are used when discussing lifting equipment. The others are too large. •

For small items the inch (abbreviation = in or ") is used.

•

For larger items the foot (abbreviation = ft or ') is used.

•

Sub-division of the inch is by fractions based on 1/64 or multiples thereof, obtaining a progression of 1/64, 1/32, 3/64, 1/16, 5/64, 3/32 etc.

•

Sub-division of the foot is by the inch and there are 12 inches to 1 foot.

•

Plural of inch = inches, plural of foot = feet.

It is also true that when machining items which are required to fit or run together, decimals of an inch to three or four places are used. However, such items are of little concern when dealing with lifting equipment, so this is not considered here. For precision work and conversion purposes it is often necessary to subdivide the millimetre. These subdivisions are expressed as decimals, for example, the conversion 1 inc h = 25.4 mm . Examples:

4.5

(i)

2 ft 7½ inches = 24 + 7½ = 31½ inches = 31.5 x 25.4 = 800.1 mm

(ii)

27 ft = 27 x 12 = 324 inches = 324 x 25.4 = 8229.6 mm or 8.2296 m

(iii)

152 mm = 152 ÷ 25.4 = 5.98 inches

(iv)

3.048 m = 3048 mm ÷ 25.4 = 120 inches = 10 feet

Mass, for ce, weight and load

4.5.1 Mass

Mass is the amount of matter in a body. The mass of a body remains unchanged irrespective of where it is. The force of gravity acts on a mass and we generally think of this as weight. We all know that everything weighs less on the Moon than on Earth because the force of gravity on the Moon is less. The force of gravity does vary a little on Earth. However for practical purposes, a given mass can be said to weigh the same wherever it is on Earth. The SI basic unit of mass is the gram, but this is much too small for every day use. The kilogram (kg) is used for light measurements, whilst the Megagram is used for heavier ones. This too is inconvenient and would lead to confusion, as there would be at least seven digits for even relatively light loads. The Megagram (1,000,000grams or 1,000kg) therefore has its own name, the tonne. Although these are units of mass, in everyday language we say that a load weighs X kilograms or Y tonnes meaning the force exerted by gravity on a mass of X kilograms or Y tonnes. 1000 kilogr ams (kg) = 1 tonne (t)


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Within the imperial system, the units of weight that are used in association with lifting equipment are the hundredweight (cwt) and ton. In calculation, and when dealing with pressure and stress, a further sub-division is used - the pound (lb). As with the imperial units of length, there is no regular relationship between the units so: 112 lbs = 1 cwt , 20 cwt (2240 lbs) = 1 ton

Just to confuse matters, in North America a unit called the ton (US) or short ton is sometimes used. 1 ton (US) = 2000 pou nds = 0.892 ton s (UK)

Note: Caution is needed when dealing with items of USA origin, such as federal specification shackles found commonly in use in the oil industry. Although now marked in metric units, older equipment was often rated in (US) tons without the ‘US’ being shown.

The relationship between the metric weight and imperial weight is as follows: 1 tonne = 2204 lbs and 1 ton = 2240 lbs, a 1.6% difference. However it has been agreed that for practical purposes of conversion: 1 ton = 1 tonne and therefor e 1 cwt = 50 kg

Note: The metric tonne and the imperial ton both have the same pronunciation. Where confusion may arise, it is normal to say ‘metric tonne’ in conversation.

4.5.2 Force

A force is something that moves, or tries to move, the body on which it acts. Force is actually a combination of the mass of the body and the acceleration of the body. We can easily understand that it takes more power, ie force, to accelerate a car quickly than to accelerate it slowly. Similarly it take more power to accelerate a heavy car (greater mass) at the same rate as a light car. In the metric system the SI unit of force is the Newton (N). This is defined as that force which, when applied to a body having a mass of one kilogram, gives an acceleration of one metre per second, per second. Hence: Force (N) = mass (kg) x acceleratio n (m/s²).

As previously stated, the force of gravity acts on a mass and we generally think of this as weight. Weight is the measure of the particular force due to the action of gravity. Acceleration due to gravity on the earth’s surface is 9.806 m/s². Therefore using the above formula it can be seen that: 1 kg (mass) x 9.806 m/s² (acceleration) = 9.806 N (force). For most practical purposes, the weight of 1 kg = a force of 10N © Lifting Equipment Engineers Association 2013 – Unit 1.2

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The Newton is too small a unit for every day use in the lifting industry, so the kiloNewton (kN) and MegaNewton (MN) are used. Therefor e: and

1 kiloNewt on (kN) = 1,000 N = 100 kg 10 kN = 1,000 kg = 1 tonne

Some lifting equipment is tested using weights but, for various reasons, some is carried out on a test machine. The test machine applies a force, not a weight so it is calibrated in units of force. When metric standards require a load test, this is expressed in units of force. For example a single leg chain sling of 500 kg WLL which is to be proof tested to twice its WLL would be subject to a proof test force of 10 kN. In the imperial system, the old lifting equipment standards refer to loads and proof loads, which are expressed as weights, ie the force due to gravity. The terms ‘weight’ and ‘load’ have the same meaning. Using the above example, a single leg sling of ½ ton SWL which is to be proof load tested to twice its SWL would be subject to a test load of 1 ton. Although what is actually being applied to the sling is a force, not a load, the test machines were usually calibrated in units of load rather than force. 4.6

Practical conversions for use in rating lifti ng equipment

Because many items of lifting equipment have a long life, items manufactured to imperial standards may be found in use alongside equipment to metric standards. To avoid operator error, it may be desirable to have all of the equipment on a site marked in the same system of units. The British Standards Institute offered the following guidance with regard to marking SWL (or WLL) when converting from imperial to metric units: "Safe Working Loads of less than 1000kg should be marked in kilograms to the nearest whole kilogram. SWLs of 1000kg or more should be marked in tonnes. Only one place of decimals should be used except for 1.25t; for integral values of SWL the ‘0’ after the decimal point should be omitted." It must be acknowledged that, despite the advantages of a standardised conversion, this system is not always followed. Webbing slings and roundslings in particular are often marked only in kg and small forgings such as eyebolts where space is limited are often marked in t, eg .25t, as it requires less space than 250kg. The following table gives examples of the conversions; others can then be calculated on the same basis.


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Examples of t he conversions:

1 cwt = 50kg

1 Ton = 1 t

1 Ton 11 cwt = 1.5 t

1 Ton 1 cwt = 1 t

1 Ton 12 cwt = 1.6 t

1 Ton 2 cwt = 1.1 t

1 Ton 13 cwt = 1.6 t

1 Ton 3 cwt = 1.1 t

1 Ton 14 cwt = 1.7 t

1 Ton 4 cwt = 1.2 t

1 Ton 15 cwt = 1.7 t

1 Ton 5 cwt = 1.25 t

1 Ton 16 cwt = 1.8 t

1 Ton 6 cwt = 1.3 t

1 Ton 17 cwt = 1.8 t

1 Ton 7 cwt = 1.3 t

1 Ton 18 cwt = 1.9 t

10 cwt = 500kg

1 Ton 8 cwt = 1.4 t

1 Ton 19 cwt = 1.9 t

12½ cwt = 625kg

1 Ton 9 cwt = 1.4 t

2 Ton = 2 t

15 cwt = 750kg

1 Ton 10 cwt = 1.5 t

2 cwt = 100kg

5 cwt = 250kg

7½ cwt = 375kg

It will be noted from the table that in the case of, say, 1 ton 3 cwt, the exact conversion would be 1.15t. However, as the second decimal place is disregarded, this becomes 1.1 t. Examples:

4.7

(i)

¾ ton = 750 kg.

(ii)

1 ton 5 cwt = 1.25 t.

(iii)

4 ton 17 cwt = 4.8 t.

Conclusion

This section has outlined the units used in association with lifting equipment. It has also addressed their relationships and the conversion factors used when converting from the imperial system to the metric system and vice versa. For the conversion of length a factor is used which gives an exact conversion. However it is normally rounded off to a single millimetre decimal place. For weight an approximate conversion is used, which operates on the safe side, so that at no time would a piece of lifting equipment be overloaded. In everyday life these same approximations can be used to visualise the quantity or length of an item measured in either system even if that system of measurement is unfamiliar. To help prepare students for the examinations, the Assignment to this unit is in the form of a multi-choice paper, similar to that used in the Part 1 Entry Examination. This form of questioning enables a wide scope of coverage in a short period of time. The questions are typical of those that may be asked in the exam although only a limited number on this topic will be included on any exam paper.


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Standards & Codes

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