Hot Topics in Tower Engineering: Pinwheels and Fall Arrest

Hot Topics in Tower Engineering:

Pinwheels and Fall Arrest

April 12, 2016

Speakers – Kurt Penfold, P.Eng, TrylonMark Fudge, P.Eng, WesTower

Rick Tiller, M.Eng., P.Eng., FEC,TEIMirjana Lukac, P.Eng, Telecon

Moderator – Gordon Lyman, eSystem Training Solutions

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Tower Engineering: Antenna Mounts – Fall Arrest

Canadian Labour Code regarding fall

protection

CSA S37 Structural Standard for structures

and mounts

CSA Z259 Fall Protection standard

Fall protection anchorages and antenna

mounts

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CSA S37

Voluntary Standard (Not a Code / Law)

When S37 referenced as requirement in a

Code it becomes a legal requirement

Scope: Strength, Stability and Serviceability

of the Structure and Components

References many other Standards (S16,

Z259 etc) and Regulations

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CSA S37

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Prior to 1976- No Guidance (Prior Editions:1954 (C22.4), 1960, 1965)

S37-1976, 1981 and 1986 Standards-Appendix-Non Mandatory

• 1986+: Frequency of working at heights injuries and fatalities

increases

• Jurisdiction issues arise (Ontario+Federal) starting late 1980s

• Early 1991 LC takes lead in asking S37 to update the Appendix

• Fatal accident January 24, 1991 (TILT!!)

• Provincial Inquest Sept 1991

• Summer 1992 LC require Appendix in Mandatory Part of S37

• LC to reference section in S37

S37-1994: New Section is in body of Standard

CSA S37 Climbing Facilities

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1996 issue of Labor Canada Code: S37-Latest Issue in entirety in

Section (Division II) that covers towers, antennas and antenna support

structures

• Effective January 1, 1996

CSA S37 Climbing Facilities

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With respect to Occupational Health and Safety and Labor Canada

there is not consistent clarity in the field (Inspections and Accident

Investigation)

Some contractors have requested clarity in the 2000s and have received written notification

Jurisdictional Issue

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Design Criteria Covered by S37: Antenna-supporting structures

From 2009 onward: Owners and Engineers discussion around

appropriate additional design criteria for antenna mounts with antennas

supported some distance from the main mast.

In addition to S37 is there additional criteria for fall protection forces and

if so what are the criteria (what is loading criteria and where is it to be

applied)? LC 12.10 (3)?

Antenna Mounts

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Some such mounts (may or may not

meet S37 requirements)

Antenna Mounts

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Antenna Mounts

Labor Canada 12.10 (3)

Is the intent to define “the anchor point of a fall protection

system” at the extreme end of the primary horizontals of a

mount structure?

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Antenna Mounts

Putting 17.8 kN into perspective …

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CSA Z259.17-16

Selection and use of active fall-protection equipment and systems

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Purpose

Provide criteria and considerations for safe selection and use of active

fall-protection equipment and systems

Provide guidance for the selection and use of fall-protection systems,

which make up a fall-protection program

Reduce risks associated with all active fall-protection systems

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Active Fall Protection

Fall-arrest systems shall:

1. Act as the last option to protect the worker

2. Limit free fall to shortest distance possible

3. Limit arrest forces on worker as follows:

4. Ensure fall is arrested within available clearances

5. Protect against swing falls

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Anchorage Design

and Selection

Selection of anchorage location is a critical element of an effective

active fall-protection system

Anchorage location shall be selected to minimize free-fall distance and

swing-fall distance

Temporary or moveable anchorage shall be used when permanent

anchorage is not available

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Temporary Anchorage Minimum Strength Requirements

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Fall Clearance

Fall-arrest systems shall be planned, designed, and installed to ensure

sufficient fall clearances are maintained

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Swing Fall

Occur when there is lateral movement during a fall and can result in a

worker striking an object during a fall

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Fall Protection

Requirements

Canada Occupational Health and Safety Regulation SOR/86-304

current to March 16, 2016:

Part XII 12.10 Fall-Protection Systems

Clause: (3) - The anchor of fall-protection systems shall be capable of

withstanding a force of 17.8KN

Clause: (4) -A fall-protection system that is used to arrest the fall of a

person shall prevent that person:

a. from being subjected to a peak fall arrest force greater than 8kN

b. from falling freely for more than 1.2m

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Fall Protection

Standards

CAN/CSA Standard Z259 series of Standards for components of

personal fall arrest systems

CAN/CSA Standard Z259.16-15-Design of active fall-protection systems

Establishes safety criteria for anchorages

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Current Problem

Current problem: fall arrest vertical force at the end of the arms of the

pinwheels

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Design Loads

Current Design Loads for Pinwheel Assemblies as per CSA S37-13:

Based On Limit states Design — the conditions of a structure at which

it ceases to fulfill the function for which it was designed.

• Self Weight of Antennas, RRUs and Mount Steel

• Local Environmental Conditions – Wind and Ice

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Environmental Load

Variations

There are significant variations in wind & ice across Canada Wind loads

can range from 320 Pa to over 1000 Pa. Ice can vary from 10 mm to

over 50 mm

Clause 5.4.1 limits the minimum value of q to 320 Pa.

Ice Map Recommends minimum ice thickness of 10 mm

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Environmental Load

Variations

Extreme locations such

as NL result in heavy

duty mount designs

whereas southern

Ontario would have a

lighter duty mount design.

The east coast design

may inherently be

capable of an anchor

load of 17.8 kN

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Increasing Mount

Demands

Existing Pinwheel Mount loading is increasing as new generations of

equipment, larger multiport antennas and large antenna diversity get

installed

The new generation loading is no longer just antennas; it is remote radio

units (RRUs) and other equipment that require more frequent

maintenance by climbers

There are also situations when two or three generations of antenna and

equipment exist because the old has not been removed

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Engineering

Considerations

Do designers have to design mounts for fall arrest loads?

17.8 kN is quoted by Labour Canada. Is this value correct?

Do only primary structural members require fall arrest

capacity?

What are the load factors and combinations for this situation?

Can plastic design be used under this scenario?

How do you show this on site? Signs?

How much if any reserve is in a mount?

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CSA 37-Standard

CAN/CSA37-13: Safety of persons who are required to climb the

tower is as important a consideration as the safety of the structure

Clause 16: Minimum requirements for design, construction and use

of ladders, safety devices, platforms and cages used to provide

safe conditions for persons climbing or working on structures

covered by this Standard

The anchor points of cable-type fall arresting devices shall be

designed for an un-factored load of 12kN

For rail-type fall arresting devices attached to the ladder, the ladder

supports shall be designed for an un-factored loads of 6kN any 6m

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Load Consideration

CAN/CSA37-13: Clouse 16

The 12kN load specified in the first instance is calculated on the

bases of four persons being attached to the line at any time and

includes allowance for impact loads.

The 6kN load in the second instance is calculated on the bases of

two persons being attached to the rail at any time and includes

allowance for impact effect.

Canada Occupational Health and Safety Regulation:

The anchor of fall-protection systems shall be capable of

withstanding a force of 17.8KN

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Pinwheel VarietiesRotatable Pinwheel

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Pinwheel VarietiesPinwheel Platform

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Pinwheel VarietiesWireless Frame

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Vendor Directions

On-going discussions and guidance by main carriers

Carriers are being active to identifying any potential hazards

Criteria established or in the final review:Pinwheel main boom members and their connection points, and connections with the tower to be checked for a force of 17.8kN applied at any point of the boom using factored ultimate capacity, but excluding the T-boom/H-frame at the end of main boom.

Consultants are to identify/verify pinwheel mounts that might not satisfy

the fall arrest force (loading independent of wind and ice loading)

Consultants are to provide engineering solution (reinforcing)

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Reinforcing By

Bracing

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Reinforcing By

Adding Guy Bracing

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Reinforcing By

Shortening Pinwheel

Arms

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Questions?

Speakers – Kurt Penfold, P.Eng, TrylonMark Fudge, P.Eng, WesTowerRick Tiller, M.Eng., P.Eng., FEC,TEIMirjana Lukac, P.Eng, TeleconModerator – Gordon Lyman, eSystem Training Solutions

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