teqnote - chain grade numbers

TeqNote Teqniqal Systems

THE MEANING OF WELDED LINK CHAIN GRADE NUMBERS

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Consul tants Special izing in Performing Arts Technology and Safety

The chain grade numbers which manufacturers commonly use are actually one tenth of the actual grade

classes. Therefore, our grade 80 is 800, grade 70 is 700, and so on. The markings applied to the chain

product are sometimes abbreviated (8 or 80 for 800, etc.).

Grade 30 (300) (Proof Coil). A general purpose chain of standard commercial quality. Made from low

carbon steel, this chain is frequently used for fabricating tow chains, logging chains and, when

appropriate, tie down or binding chains. Hallmarked every foot or so with manufacturer's symbol and

grade marking: 3, 30, or 300 (or DIN ‘L’). NOT rated for overhead lifting. Until recently, was

commonly used in many stage rigging systems for Trim Chains on Battens.

BBB Anchor Chain. A compact (short) link chain of standard commercial quality, this is essentially a

sub-class of Grade 30. Made from low carbon steel, this chain is used primarily for boat windlasses

when hot galvanized. Hallmarked every foot or so with grade marking: 3B (or DIN ‘L’). NOT rated for

overhead lifting.

Grade 40 (400) (High Test). Strength levels are the same as Grade 43 but the dimensions of the chain

links are smaller using ISO standards. Primarily used for boat windlasses, this grade has become a

standard for that industry. The Grade 40 designation was exclusively used by ACCO Chain until 2005

to designate their High Test grade chain. They now use "43" in keeping with the rest of the industry.

The chain is hallmarked "G4". NOT rated for overhead lifting.

Grade 43 (430) (High Test). This is a higher strength chain used for years in the trucking industry for

tie downs that meet DOT specifications. Made from a high-carbon steel, its strength surpasses proof

coil working load limits, size for size, by a factor of 2 to 1. Hallmarked every foot or so with

manufacturer's symbol and grade marking: 4, 40, 43, or 430 (or DIN ‘M’). NOT rated for overhead

lifting.

Grade 70 (700) (Transport). As its name implies, Transport Chain is used primarily to tie down loads

on over-the-road equipment. The yellow chromate (gold) plating makes it easily recognizable even

from a distance. Made from heat-treated carbon-steel it has about 25% more strength than high test

chains. Hallmarked every foot or so with manufacturer's symbol and grade marking: 7, 70, or 700 (or

DIN ‘T’). NOT rated for overhead lifting.

Side Note:

High Tensile chain is anything much above 500 MPa Ultimate Breaking Strength. This is true HT

and is not the same as ‘high test’. The galvanized versions from the principle manufacturers are G7 or

G70, which has an approximately a tensile strength of 700 MPa, although the galvanizing process can

reduce the strength slightly (the manufacturer should adjust the CAP accordingly, e.g. down by 10%).

Commonly labeled as 'transport' chain in the US.

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Teqniqal Systems Teq Notes: Chain Grades

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More on 'high test' and ‘high tensile’

As above, high test does not mean the same thing as high tensile. The similarity in the abbreviations for

the two terms creates much confusion, particularly in the United States where manufacturers and

resellers exacerbate matters. American outlets referring to 'HT' chain are typically misusing the

engineering abbreviation for High Tensile, and this is incorrect. Moreover, because the chain is 'high

tested', it is sold with a Rated Lifting Capacity (CAP / WLL / SWL) which is calculated from a lower

ratio to the Ultimate Breaking Strength (instead of the international standard of 4:1).

This is misleading yet it does not change the ultimate strength of the steel! A particular size of

American ‘high test’ chain may look to be stronger than the same sized non-American G40 because the

CAP is calculated differently, but in-fact, they are next to identical. The proof certificate using a

different system of numbers does not change the physical properties of the steel.

Just to confuse matters further, G40 / G43 / ‘high test’ is now also being explicitly described by some

American sources as ‘high tensile’. Whether a 400-430 MPa grade steel can be properly categorized as

HT is a matter for engineers and academics to debate. Regardless, it is the numbers which matter – just

try not to get misled!

Grade 80 (800) (Alloy). The first chain specifically designed for safety and approved by OSHA and

other agencies for overhead lifting. Its alloy, heat-treated steel makes it ideal for making lifting slings

and heavy duty tow chains. Hallmarked every foot or so with manufacturer's symbol and grade

marking: 8, 80, or 800. Suitable for overhead lifting.

Grade 10 (100) (Alloy). This new innovation in alloy chain metallurgy provides about 25% higher

working load limits over Grade 80 chain with some limitations reported in lower ambient temperatures.

Hallmarked every foot or so with manufacturer's symbol and grade marking: 10 or 100. Listed as

suitable for overhead lifting.

Capacity Limit Chart

Chain strength is identified by

CAP (Rated Lifting Capacity) in pounds - the higher the CAP, the stronger the chain.

Nominal Chain Size

Grade 30 Proof Coil

(CAP in Lbs) (@ 4:1 DF)

Grade 43 High Test


Grade 70

Transport (CAP in Lbs) (@ 4:1 DF)

Grade 80

Alloy


Grade 100

Alloy


3/16” 800 - - - -

7/32” - - - 2,100 2,700

1/4” 1,300 2,600 3,150 *3,250 -

9/32” N/A N/A N/A 3,500 4,300

5/16” 1,900 3,900 4,700 4,500 -

3/8” 2,650 5,400 6,600 7,100 8,800

7/16” 3,700 7,200 8,750 - -

1/2” 4,500 9,200 11,300 12,000 15,000

5/8” 6,900 13,000 15,800 18,100 22,600

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Nominal Chain Size

Grade 30 Proof Coil


Grade 43 High Test


Grade 70

Transport (CAP in Lbs) (@ 4:1 DF)

Grade 80

Alloy


Grade 100

Alloy


3/4” 10,600 20,200 24,700 28,300 35,300

7/8” - 24,500 - 34,200 -

1" 17,900 34,100 - 47,700 -

1¼” - - - 72,300 -

* Grade 63 chain is specifically engineered to replace Grade 30 chain used for stage rigging:

SECOA STC –or– JR Clancy AlphaChain

TERMINOLOGY

Chain Grade

The grade of a chain refers to the tensile strength class of the chain, but it is NOT necessarily the

tensile strength. Tensile strength (Ultimate Tensile Strength / UTS) is measure of force per unit area

required to deform the material beyond its useful limits (i.e. break it or fracture it). If the tensile

strength is listed in MegaPascals (MPa), then the grade of a chain is approximately equal to the tensile

strength. A Grade 800 chain means that the tensile strength of the material (usually a steel alloy) is at

least 800 MPa (MegaPascals). Force per unit area can take many forms, so the tensile strength might

be expressed in MegaPascals (MPa), Newtons per square millimeter (N/mm2), Pounds force per square

inch (PSI or Lbs/in2). The tensile strength is calculated by multiplying the material grade (use the

three digit representation, i.e. Grade 800, not Grade 80 or Grade 8) times the metric area of the two

cross-sections of a link (see below).

Example:

Area (mm2)

˟ Grade (Newtons/ mm2) = Newtons (metric Ultimate Breaking Strength)

157.08 mm2

˟ 800 (Newtons/ mm2) = 125,664 Newtons

125,664 Newtons ÷ 1000 = 125.66 kN (kiloNewtons) (metric Ultimate Breaking Strength)

or converting to imperial units:

125,664 Newtons ˟ 0.224805 (Lbs / Newton) = 28,250 Lbs (imperial Ultimate Breaking Strength)

Capacity / Working Load Limit / Safe Working Load

Working Load Limit (WLL) is sometimes called Safe Working Load (SWL). Both of these terms are

considered to be obsolete and the correct modern terminology, per ASME B30 Standard, is CAP, which

is sort for ‘Capacity’ or 'Rated Load Capacity'. Lawyers in most countries all have strongly advised

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against the use of the term SAFE in 'SWL'. . The terms ‘SWL’ and ‘Safe Working Load’ are

(should be) no longer used as the word 'safe' implies that a rigging part is 'safe' even when used

within the 'SWL'. This, as we all know, is NOT the case. A piece of rigging equipment can indeed fail

even BELOW its SAFE Working Load if not properly used or if it is damaged.

Common Exceptions (documents that have not been updated to reflect this terminology):

The UK legislation which is The Lifting Operations and Lifting Equipment Regulations

(LOLER '98) under Regulation 7 calls for all lifting equipment to be marked with its Safe

Working Load (SWL) and this should be permanent and legible.

Legacy Markings. You can still find ‘SWL’ on many older types of equipment. Many of the

items that are labeled this way are very heavy duty, so they will remain in-use for a long time.

In Europe CE Standards use the term 'WLL' and Working Load Limit.

OSHA regulations for slings for general industry 1910.184 and 1926.251 (effective July 8th,

2011), is littered throughout with the term ‘Safe Working Load.’

The Crosby Group (by virtue, a world standard) exclusively uses the term WLL (but some

training mentions that SWL, ‘Working Load Limit’ / WLL, and 'Rated Lifting Capacity’/ CAP

all mean the same thing).

The National Association of Chain Manufacturers (NACM) Welded Steel Chain Specifications

manual (April 11, 2010) still uses the term ‘Working Load Limit’ / WLL.

ESTA/ANSI E1.4 – Entertainment Technology – Manual Counterweight Rigging Systems; and

ESTA/ANSI E1.6 – Entertainment Technology – Powered Hoist Systems. use the term

‘Working Load Limit’ / WLL

CAP (Capacity, Working Load Limit / WLL, Safe Working Load / SWL) is NOT the same as Proof

Load nor Ultimate Breaking Strength (Ultimate Tensile Strength / UTS).

The CAP (Capacity, Working Load Limit / WLL, Safe Working Load / SWL) is the maximum load

which should ever be applied to a chain, even when the product is new and when the load is uniformly

applied in a straight line pull only. Side loading (i.e. bending a link over a sharp edge) of chain links

should be avoided.

The CAP (Capacity, Working Load Limit / WLL, Safe Working Load / SWL) is typically a predefined

ratio of the tested Ultimate Breaking Strength of the chain, so providing a safe margin of error. This

ratio is commonly around 4:1 (Ultimate Break Strength to Capacity, or UBS : CAP), except in North

America. In North America the ratio can vary by manufacturer and a lower ratio can be used to make a

chain look better than it really is. Check the ratio of the CAP against the listed Ultimate Breaking

Strength if you are unsure. Ultimate Breaking Strength, when published, is obtained under controlled

laboratory conditions. Listing of the Ultimate Breaking Strength does not mean the CAP should ever

be exceeded.

CAP is the Ultimate Breaking Strength (UBS) divided by the Design Factor (Safety Factor)

CAP = UBS ÷ DF

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Proof Tested (not ‘Proof Coil’)

All quality chain is proof tested; this is where a load is applied to the newly produced chain as a quality

control measure. It is NOT a measure of performance, it is only intended to draw the manufacturer's

attention to any flaws in the chain. The common load applied during Proof Testing is done at twice the

CAP, or half the expected Ultimate Breaking Strength. Information on this proof testing should be

freely available from the manufacturer; if it is not, questions should be raised.

Proof Test Load = 2 ˟ CAP = UBS ÷ 2 (assuming that the UBS : CAP ratio is 4:1)

Design Factor (Safety Factor):

An industry term usually computed by dividing the Ultimate Breaking Strength by the CAP and

generally expressed as a ratio. For example: 3:1 (where the breaking strength is 3 times the CAP), or

4:1 (where the breaking strength is 4 times the CAP).

Commonly published Design Factors for chain are:

4:1 G30, G70, G80, G100

3:1 G40/43

Commonly published Design Factors for wire rope are:

Construction Industry 5:1

Characteristic (live) loads in stage rigging (per PLASA / ESTA / ANSI E1.4 – 2009 Manual

Counterweight Rigging Systems) 8:1

The greater of 5:1 for characteristic (live) loads and 8:1 for static loads (per PLASA / ESTA /

ANSI E1.6-1– 2011r2 Draft – Entertainment Technology - Powered Hoist Systems)

Aircraft Engineers sometimes use Design Factors as low as 2:1.

Structural Engineers sometimes use Design Factors of 3:1 or 5:1. This is very important when

looking at data sheets for any type of fastener, structural members, rods, wire rope, or other

connecting parts. Don’t assume what Design Factor was used to determine the CAP.

Shock Load:

A load resulting from rapid change of movement, such as impacting, jerking or swinging of a static load

is referred to as shock load. Sudden release of tension is another form of shock loading. Shock loads

are generally significantly greater than static loads. Any shock loading must be considered when

selecting the item for use in a system.

The term ‘Payload’:

The word 'payload' is used by many who want to describe the weight of a LOAD in layman’s terms.

This word 'payload' is not used in any standard or technical. In short, it should NOT be used as it will

lead to confusion out in the rigging field.

Payload is the term used to state load capacity for transportation, particularly for container shipments.

It is the term used to describe the net load capacity of a container and is the most common word written

on the door of shipping containers to describe this. Payload can be defined as the Maximum Gross

Weight (MGW) of a container less the Tare, or ‘self weight’, of the container box when it is empty. All

three terms (Payload, MGW, and Tare) are used to state the relevant data on a container door or body.

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Other Info:

The CAP (Rated Lifting Capacity) is what a piece of equipment has been designed to lift in a predefined

mode or configuration. What a piece of equipment will lift in particular service conditions and can vary

through configuration such as with mode factors for webbing slings, for example:

1te (1,000kg) webbing sling when used in straight mode can lift 1te (1000kg) but when used in

choked mode is only suitable for 800kg (reduction of 20% in the UK) but when doubled in a

parallel basket is suitable for 2te (2000kg) and when doubled but with an angle of 90 degrees, as

would be with a sling in basket mode around a box, would be 1.4te (1,400kg)

The CAP of a wire rope sling when used in a basket hitch is only valid when the bend ratio (D/d)

is not worse than 20 or 25:1. If you bend it more tightly you have to assess a reduced (de-rated)

capacity.

To convert the CAP (Rated Lifting Capacity) of various pieces of equipment to a useful number that

applies to your lifting situation, you must determine the appropriate Design Factor for the project AND

determine the Design Factor for the product.

Example:

Checking the product table for ¼” G80 chain shows a CAP of 3,250 pounds with a 4:1 Design

Factor.

It is to be used for a Characteristic (Live) Load in a Motorized Stage Rigging System,

so a Design Factor of 8:1 is required.

The Math:

Find the UBS of the chain: 3,250 ˟ 4 = 13,000 Pounds UBS

Apply the new Design Factor: 13,000 ÷ 8 = 1,625 Pounds working CAP

Physical Link Dimensions

Essential Dimensions of Chain Links

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Listed chain sizes always refer to the link diameter, i.e. the diameter of the rod of steel which forms the

chain link. The Grade of the Chain is always a raised enumeration, not a stamped recess. This keeps it

from filling with debris.

Metric EN and DIN

EN and DIN chain present the same size measurement for the diameter of the link, but vary slightly in

pitch and width. It is important to investigate all dimensions to ensure suitability or compatibility.

EN standards are specified by the European Committee for Standardization (CEN) and reflect a

continental metric specification. The alternative DIN standards originate from the Deutsches Institut

für Normung (German Institute for Standardization) but are found worldwide.

American Sizing

American chain sizing can quickly become confusing, with even the higher profile brands generally

failing to reference standards. Peerless (ACCO) offers a number of chains of the same nominal imperial

size in two standards, one according to their own specifications and the other adhering to an ISO

standard. The ISO versions are shorter (lesser pitch) and tend to be wider. Pay particular attention to

exact dimensions if you are trying to match-up with some other parts or existing equipment.

More information:

“Welded steel Chain Specifications”

From The National Association of Chain Manufacturers (NACM)

http://www.nacm.info/Downloads/NACM_Welded.pdf

http://www.nacm.info/Downloads/NACM_Welded.pdf

teqnote - chain grade numbers

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