Tower Inspection Requirements and Practices


From anti-virus screening for computers to routine service appointments for cars and even medical checkups from people of all ages: maintenance inspections are a common occurrence for most people, places and things these days.

And communications towers are no exception.

In accordance with the CSA S37 standard, all antenna towers and other antenna-supporting structures should receive detailed inspections during critical stages. These inspections should be completed by a professional engineer or otherwise qualified technician, and should be carried out:

  • During initial construction;
  • At regularly scheduled intervals, including:
    • Every four years or less, for guyed towers, monopoles and shrouded tripoles;
    • Every five years or less, for rooftops; and
    • Every six years or less, for self-supporting structures; and
  • After any modifications to an existing structure.

As noted in S37, the primary purposes of these inspections are to (a) identify materials and quality of work that don’t comply with design drawings and client specifications; and (b) to determine if tower degradation is typical wear and tear or it it’s indicative of a larger issue.

While the S37 standard provides a fair amount of guidance on inspection requirements, companies that want to complete tower inspections must also be aware of the various optional inspection requirements that clients may request, as well as the programs and policies they should have in place to ensure their employees can perform inspections safely. This post provides a brief overview of each of these three topics, as identified and discussed by members of the STAC Engineering Guidelines & Practices Committee.

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Recommended Inspection Items (CSA S37)

As the Canadian standard for “Antennas, towers, and antenna-supporting structures,” the S37 standard is the authority on minimum inspection requirements for communications towers and sites. Specifically, Annex D of the standard provides information about a lengthy list of inspection criteria, including points for how to complete visual and measured inspections of specific tower components, as well as identification of some typical deficiencies.

The following notes provide information about 14 different areas of inspection that the S37 standard touches on. These notes are taken from presentation material developed by Jeanne Piercey of Pier Structural Engineering Corp. (P-SEC) and presented by Jeanne Piercey and Shawn Berry, of Comtech, at the STAC 2018 Conference & Exhibition. (Presentation slides available here. Please review CSA S37, Annex D, for more information.)

Verticality, straightness (alignment), and twist

  • For guyed and self-supporting structures, the out of plumb between any two elevations on the structure shall not exceed 1 in 500.
  • The twist between any two elevations shall not exceed 0.5° in 3 m. The maximum twist over the structure height shall not exceed 5°
  • Potential issues for towers that are out of spec include:
    • Minor misalignment can result in increased tower stresses
    • Excessive misalignment could be an indicator of greater structural issues

Guy Tension

  • Guy tension measurements taken during an inspection are compared to the documented guy tension values that were set during installation (guy initial tension).
  • During an inspection, guy tension measurements are to be taken on a calm day to avoid wind effects and adjusted for field conditions (method, temperature).
  • Potential issues for towers that are out of spec include:
    • Tensions too low can result in excessive tower deflections and bending
    • Tensions too high can result in increased mast compressive forces
    • Excessive guy initial tension discrepancies could be an indicator of greater structural issues

Visual examination of tower members and connections

  • Check for bent, fractured, or missing members, cracks in welds, and bolts that are loose, missing, or short.
  • The straightness of individual members shall be within a tolerance of 1 in 500.
  • Potential issues for towers that are out of spec include:
    • Increased member/connection stresses
    • Member/connection failure

Visual examination of ladders, gratings, and handrails

  • Check for fractured members or welds and loose or missing supports
  • Potential issues for towers that are out of spec include:
    • Compromised climber safety
    • Increased risk for injury or death

Visual examination of guy assemblies

  • Broken strand wires
  • Slippage of guy grips, clips etc.
  • Loose, worn, cracked, bent, or missing hardware
  • Articulation at guy ends and, in particular, at turnbuckles.
  • Turnbuckle adjustment available
    • 300 mm for guys of nominal diameter 13 mm or less
    • 450 mm for guys of nominal diameter greater than 13 mm
    • This requirement is only significant on newly installed guys on new and existing towers. There is no need to regrip a guy to provide the ideal turnbuckle gap (adjustment potential) if the guy tension is acceptable. It can always be regripped later if need be.
    • The take-up device shall be secured against self loosening
  • Corrosion in guy cables and hardware
  • Potential issues for towers that are out of spec include:
    • Out of spec guy tensions
    • Increased risk of guy assembly failure leading to tower failure

Foundations

  • Check concrete and grout for movement, cracking, spalling, deterioration, etc.
  • Check visible steel of anchor shafts, guy anchor plates, base plates, and anchor bolts for bending, fractures, etc.
  • Check for adequate drainage and backfill
  • Check base plates for full bearing
  • Potential issues for towers that are out of spec include:
    • Escalation of concrete cracking/deterioration
    • Reduced capacity/increased stresses for damaged steel members
    • Submerged foundations risk reduced soil resistance in bearing and uplift as well as an increased corrosion possibility
    • Increased risk of foundation/anchor failure

Antennas and antenna mountings

  • Check all visible components of the antenna and mountings for damage e.g. loose or missing bolts, cracked welds, bent, fractured, or missing members, etc.
  • Potential issues for towers that are out of spec include:
    • Reduced antenna efficiency
    • Increased risk of antenna mount failure
    • Can result in tower damage (impact w/ tower mast)
    • Can result in tower failure (impact with guy)

Transmission lines

  • Check for fractured, loose, or missing supports, and connections
  • Missing protective sleeves under wraplock connections, dents, or damage in the lines
  • Lines rubbing against structural members.
  • Potential issues for towers that are out of spec include:
    • Damaged tx lines leading to offline antennas

Grounding

  • Check lightning rod and ground wires on the tower base, guys, transmission lines, and waveguide bridge for electrical continuity and loose or missing connections.
  • Potential issues for towers that are out of spec include:
    • Reduced lightning protection
    • Risk of damaged antennas/electronics
    • Risk of damaged electrical system leading to increase risk of aircraft collision due to obstruction light outage

Insulators

  • Check all insulators in guy assemblies and tower base for cracks, flaws, chipping, leaking, etc., where applicable.
  • Potential issues for towers that are out of spec include:
    • Reduced insulator strength
    • Base or Guy insulator failure leading to tower failure

Electrical installation

  • Check for kinks, loose or missing supports, loose or missing junction box covers and screws, blocked drainage holes, deterioration or cracks, etc.
  • Check lamp fixtures for missing, loose, or broken hardware and fittings, burned out bulbs, etc.
  • Check that obstruction lights are in accordance with Transport Canada requirements.
  • Potential issues for towers that are out of spec include:
    • Reduced aviation visibility
    • Increased risk of aircraft collision

Painting

  • Check that painting is in accordance with Transport Canada specifications with regard to length and positioning of colour bands, and that colours are correct.
  • Check paint for peeling, blistering, flaking, fading, oxidation, and ensure the pattern is still visually effective.
  • Potential issues for towers that are out of spec include:
    • Reduced aviation visibility
    • Increased risk of aircraft collision

Galvanizing and other anti-corrosion treatment

  • Check all galvanized components of the tower (i.e., tower members, connections, ladders, guys and guy hardware, base plates and anchor bolts, waveguide bridge, conduit, etc.) for scratching or scoring, flaking, rusting, peeling, blistering, etc. of the galvanized surfaces. Check all non-galvanized metal surfaces (e.g., antenna and transmission line connections) for corrosion or other surface deterioration.
  • Potential issues for towers that are out of spec include:
    • Reduced corrosion resistance
    • Risk of reduced steel member capacities

Typical Deficiencies

Some of the typical deficiencies that tower inspectors should be particularly aware of/on alert for include:

  • Corrosion
  • Safety
  • Loose bolts
  • Bent members
  • Cracks in Foundation
  • Loose Transmission Lines
  • Grounding
  • Lighting/Paint Conditions
  • Tensions – 95% out of tension
  • Debris/overgrowth of vegetation/Interference

Optional Inspection Items

In addition to the recommended inspection minimums outlined in S37 Annex D, Canadian tower owners also request that inspectors provide additional information about their towers as part of some inspections. The following is a list of some of the optional inspection items that site owners frequently ask inspectors to include in their reports. (Please note that site owners may request additional inspection items not identified in this section.)

Antennas and systems:

  • Antenna and equipment labeling
  • Check MW radome covers are in place and not damaged, check ice guards, if installed are not damaged
  • Antenna Azimuths

Climbing Facilities:

  • Visual examination of safety rail

Corrosion Protection:

  • Identification of potential stray currents from surrounding sources from DC transformer stations or pipelines

Enclosures:

  • Visual Inspection of equipment enclosures, such as shelter mounted items, shelter roof, enclosure floor, gates
  • Condition of access roads, compounds and fences

Guy Wires:

  • Ensure ice breakers are installed on guy wires

Tower light:

  • Note type of lighting system on structure, record the manufacture, model, type and quantity of tower light and other details
  • Verification but also replacement of tower light bulbs

Vegetation:

  • Inspection of tree clearing and grubbing to check the presence of trees, shrubs, branches.
  • Tree clearing or excessive vegetation around the guywire anchors is performed on radius of 12 m;
  • The axis of the guys is cleared 4.5 m on each side;
  • The access road and the compound are free of tree;
  • The presence of trees which may fall and cause damage to the equipment (tower, guys, equipment shelter, electrical lines and others installations);
  • The presence of excessive vegetation around the base of the tower and the guys anchors.

UAV Inspections:

In recent years, tower owners have also sought to utilize unmanned aerial vehicles (UAVs) for certain tower inspection activities, including structural and RF inspections. Some types of inspection that can be completed using UAVs include:

  • Pre and post construction
  • Tower inspection Audit
  • Structural mapping / Asset location
  • Structural Modification
  • Line of sight (new asset installation)
  • New tower build – real-estate review
  • RF site surveys
  • RF Coverage Mapping
  • PIM hunting
  • 2D Radiation Pattern
  • Antenna Pattern
  • 3D Radiation Pattern
  • Interference Hunting
  • Verify Point to Point
  • Verify Polarization

Did we miss something on this list? Please let us know! Email STAC’s program director, Nick Kyonka, at nkyonka@stacouncil.ca to suggest more optional inspection items that should be included in this post.

Safety Programs and Policies

Any tower inspection work completed above 2.4 meters above the ground or the closest safe level must be treated as work-at-height and must abide by all appropriate federal and/or provincial regulations, depending on the site’s jurisdiction.

Companies whose employees conduct tower inspections can also develop additional policies and practices to help further ensure the safety of those employees. Some recommended policies and practices include:

  • Training: Provide employees (including tower inspectors) with the training and re-training required to complete inspections safely, including:
    • Fall Protection/Tower Climbing training;
    • First Aid and Rescue training;
    • RF Awareness training;
    • Underground Access and Confined Space training, as required;
  • PPE Inspections: All personal protective equipment that may be used should be inspected prior to travelling to the site. All climbing and rescue equipment should be inspected and verified annually.
  • Use of JSAs: Each crew should complete a Job-Site Assessment upon arrival on site;
  • Regular Updates: dispatched employees and crews should contact their office upon arriving on site and at regular intervals throughout the day, as determined by management;
  • Health & Safety Event Reporting and Investigations: any incident or near-miss on a site should be thoroughly investigated.
  • Other policies: Other corporate workplace policies that can help ensure the safety of tower inspectors and other employees include alcohol and drug policies, workplace violence and harassment policies and those relating to proper use of company vehicles and other property.