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Use of truss-out bamboo scaffold is frequent for works at height like renovation of external walls of buildings,removal of unauthorized building works, installation of air conditioners or cleaning of external walls of buildings,etc. Sometimes these renovation and maintenance workers cannot locate a secure anchorage point to anchorthe safety harness, so they just anchor their harness to insecure structures like guardrails, scaffolds, water pipes,etc. However, such insecure structures usually cannot stand sudden vibration or pulling force. Severe accidentsof falling from height are resulted. This article will introduce the different types and their respective testrequirements of anchor devices under the BS EN 795:1997 standard, including a type of transportable temporaryanchor device.

BS EN795:1997Protection against falls from a height - Anchor devices

- Requirements and testing

Anchor devices are classified into 5 classes under BS EN795:1997 to suit for different needs:

A1 Structural anchorsdesigned to besecured to vertical,horizontal andinclined surfaces(e.g. walls,columns, lintels) Key

1. Structural anchor2. Anchor point

A2 Structural anchorsdesigned to besecured to inclinedroofs

Key1. Structural anchors2. Anchor point

B Transportabletemporary anchordevices

Key2. Anchor point

ExampleExampleClassClass DescriptionDescription

Classification of anchor devicesClassification of anchor devices

Anchor Devices Requirements and Testing

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All anchor devices shall be so designed as to ensure that it is not possible for correctly connected personalprotective equipment to become detached unintentionally. Besides, different elements of an anchordevice shall be such that they cannot appear to be correctly assembled without being positively lockedtogether. All metallic parts of anchor devices shall comply with the corrosion protection of EN 362:1992to ensure they are endurable and safe for use, particularly those that are to be used in outdoorenvironment.

C Anchor devicesemployinghorizontal flexiblelines

Key1. Extremity structural anchor2. Intermediate structural anchor3. Mobile anchor point4. Anchor line

D Anchor devicesemployinghorizontal rigidanchor rails

Key1. Anchor rail2. Mobile anchor point

E Deadweightanchors for use onhorizontal surfaces

Key1. Anchor point

ExampleExampleClassClass DescriptionDescription

General requirements for anchor devicesGeneral requirements for anchor devices


69

Anchor devices shall meet the static strength and dynamic strength tests requirements under the BSEN795:1997 standard to ensure they possess sufficient strength for safe use.

Table 1: Requirements of strength tests

Strength tests for anchor devicesStrength tests for anchor devices

ClassClass Test procedureTest procedureTest description and requirementTest description and requirement

A1 Static strength Apply and maintain for 3 minutes 10kNforce. Observe if the anchor device can holdthe force

According toclause 5.2.1 ofBS EN795

Dynamic strength Secure one end of the test lanyard to theanchor device and the other end to a 100kg mass. Allows the mass falls freely through2.5 m. Observe if the mass is arrested


A2 Static strength Apply and maintain for 3 minutes 10kNforce. Observe if the anchor device can holdthe force


Dynamic strength Attach the anchor device at an angle nogreater than 20° from vertical. Secure oneend of the test lanyard to the anchor deviceand the other end to a 100 kg mass. Allowsthe mass falls freely through 2.5 m. Observeif the mass is arrested


B Static strength Apply and maintain for 3 minutes 10kNforce. Observe if the anchor device can holdthe force


Dynamic strength Secure one end of the test lanyard to theanchor device and the other end to a 100kg mass. Allows the mass falls freely through2.5 m. Observe if the mass is arrested and ifthe device remains stable



70

ClassClass Test procedureTest procedureTest description and requirementTest description and requirement

C Static strength Test to 1.5 times the manufacturer ’spermitted designed force and maintain for3 min. Observe if the anchor device(including anchor line and structuralanchors) can hold the force


Dynamic strength Secure one end of the test lanyard to theanchor device and the other end to a 100kg mass and test to differing system lengthand differing span lengths. Observe if theline tension and deflection vary by no morethan ±20% from that determined by themanufacturer’s method of prediction

According toclause 5.3.4.2of BS EN795

D Static strength Apply and maintain for 3 minutes 10kN force(if the manufacturer’s instructions permittwo or more persons to use the devicesimultaneously, apply 1 kN additional forcefor each additional person). Observe if theanchor device can hold the force


Dynamic strength Secure one end of the test lanyard to theanchor device and the other end to a 100 kgmass. Allows the mass falls freely through2.5 m. Observe if the mass is arrested


E Dynamic strength Attach the deadweight anchor device anda 100 kg mass by means of a wire rope of 8mm diameter and route the wire rope overthe pulleys. Release the drop mass at 2.5 mheight. Observe:

• if the mass is arrested

• if the displacement of the center of massof the deadweight anchor device doesnot exceed 1 m

• if the vertical displacement of the massdoes not exceed 1 m after 3 min

Repeat the test for

• each critical direction in which an arrestforce could be applied

• different type of construction materialand conditions for which the manufacturerclaims suitability



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For works at height without secure fixed anchorage point available for anchoring safety harness,transportable temporary anchorage devices (TTAD), use of transportable temporary anchor device isanother choice for consideration. TTAD commonly available in the market comprises a metallic crossbeam, anchor points, fixed clamp and adjustable clamp (please see diagram 1). To install TTAD, choose arigid structure like a concrete wall that can securely support the device to prevent it from shifting duringuse. Lay the device on ground and tightly fix it by adjusting the adjustable clamp to right position anddistance (please see diagram 2). Anchor devices shall be installed according to the manufacturer’sinstructions and inspected to be safe by competent person before use. Consult professional engineerwhere appropriate. Anchor devices shall also meet the requirements of recognized safety standard suchas Class B anchor device of BS EN795:1997. Anchor device shall be used by one person only.

Use of transportable temporary anchor devicesUse of transportable temporary anchor devices

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Diagram 1 : Transportable temporary anchor device

Diagram 2 : Installation of transportable temporaryanchor device

Adjustable clamp

Cross beam

Anchor point

Fixed clamp

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