Fall protection systems and ladders on poles and masts: what the design must provide

Ladder and fall protection: two separate questions

A ladder only gives a hold for hands and feet. It does not protect against a fall, even with a cage: the hoops reduce the risk of leaning back but do not stop a fall. A fall protection system consists of an anchor line (rail or cable) and a guided fall arrester on it, to which the worker clips a full body harness. The arrester is a separate product, matched to the line.

Ukrainian work-at-height safety rules require ladders leading to a height above 5 m to have provision for attaching the lanyard of a safety belt, and every ladder to be strong, securely fixed and of sufficient length. For a pole this is simple: if a climb above five metres is planned, the design has to state what the worker clips onto all the way up.

We supply ladders and fall protection systems together with poles and masts when the design provides for them. We make the ladders ourselves. On multisided poles we fit external ladders with a safety cage and without one. Line poles and switchyard portals are also made with no ladders at all: this is a project decision. Lighting poles have no ladders. Floodlight masts are also made without ladders: they are serviced from an aerial lift. For any series of masts the presence of a ladder is agreed with the customer when the order is placed. The type, fixing, loads and number are set by the design, not by a catalogue: they are agreed before the KMD drawings, because the shaft, platforms and hatch depend on the decision. The supply set includes the movable fall-arrest device that travels along the rail or the cable. Means of climbing that do not have to be built into the structure (removable step bolts, removable ladders, belts) are covered in the article Installation of multi-sided poles and masts; here we deal with permanent solutions that become part of the pole.

Means of access on a pole or mast

The table lists six solutions found on multisided poles, telecom towers and floodlight masts. The choice depends on the height, the number of climbs per year, who climbs and what has to be carried up.

Rungs, stringers, end stops and brackets of a fall protection system are supplied as a set; parts of different systems must not be mixed, because the system was tested as a whole.

Rigid rail or flexible cable

Both lines give the same result: the guided arrester follows the person up and down and locks on a sharp jerk. For the shaft, though, they mean different things. A rail passes the fall force to many brackets, a cable pulls it onto two end anchors.

The values below come from the instructions for specific systems that were read, and are given to compare orders of magnitude. For your own system they are taken from its data sheet.

What the design has to provide

Below is a list of decisions put onto the drawing before it is decided which system exactly will be supplied.

• The bottom section. The first metres are dangerous because the arrester does not always manage to stop the fall before the ground; one instruction singles this place out. If the ladder does not start at ground level, stops are fitted on it so that the arrester cannot be attached wrongly and the climber cannot fall while descending.
• Access by outsiders. The entry to the ladder is locked: a hatch with a lock, a guard or an anti-climb device. This is already part of the standard set of telecom towers, which have an anti-vandal hatch.
• Rest platforms. On a caged ladder they are provided at intervals of no more than 10 m, as in the standard set of telecom towers and floodlight masts.
• The top exit. The rail or ladder projects above the platform edge by at least 1000 mm (so in the instructions read), the top rung is not higher than the surface the person steps onto, and an end stop at the top keeps the arrester from falling out of the rail. The projection of the rail above the last bracket without reinforcement is limited to 380 mm in one instruction.
• Clear space under the feet. Stopping a fall needs height below the user; in one instruction for the worst fall it is no less than 2 m. On a platform above a slab or roof this is checked separately.
• A sign at the entry. It states the type of system, the manufacturer, the year of manufacture and the requirement to use a full body harness and a suitable arrester.
• Rescue. Before the system is put into use it is decided how to get down a person hanging on the line. Without a rescue plan a fall protection system protects only half.
• Documents. The instruction for the system is handed to the owner of the pole, not left in the workshop; the inspection log goes with it.

How to fix the system to the shaft

Most mistakes are made in this part, because a bracket looks like a trifle next to a shaft, while the load on it is the force of a falling person.

Load on a bracket and an anchor point

Ukrainian rules require anchor points to reliably withstand the force that arises in a fall, but give no figures. The figures are in the instructions for systems. In the documents read, the design fall load is 6 kN along the rail axis, and it may be distributed over no more than four brackets. The service load is added to it: 1.5 kN at 30 cm in front of the ladder axis and a horizontal component of 0.3 kN at the least favourable point.

The spacing at which the service load is applied differs between two instructions: 2 m in one, 5 m in the other. So the values are taken from the documents of the system that has been chosen. For several users, one instruction adds 1.5 kN for each further person, provided that people stay at least 3 m apart.

More than the bracket is checked: the shaft wall at the fixing, the welds of the seat, the bolts and their locking. The minimum bolt in the instruction read is M12. The class of bolts and the locking are chosen by the articles Fastener strength classes and Bolted connections in steel structures.

The thin wall of a multisided shaft

The wall of a multisided shaft is thin compared with its diameter. A bolt from a bracket that pulls the wall with the force of a fall punches it through or bends it out, and the hole weakens the section where the bending moment is still large. A rail is not fixed to the wall «as is»: a doubler plate, a welded seat, a rib or a diaphragm is put around the bracket to pass the force into the body of the shaft.

Another way is a clamp around the shaft with no holes in the wall. System makers offer clamps for diameters of roughly 200 to 1000 mm. On a tapered wall a clamp has stops, otherwise it slides down, and its tightening is calculated so as not to dent the wall.

There is a practical point too: inside the shaft there is nothing to reach a nut on a bolt, and access is only through the hatch. So where there is no access, welded studs or captive nuts are used.

Section joints, the hatch and taper

A bracket is not placed on a telescopic joint or next to a hatch: there the wall is doubled or weakened. These joints are covered in the article Joints of multisided poles. The ends of rail sections are connected with a gap for temperature, and brackets are placed on both sides of the joint.

The wall of a tapered shaft is not vertical, while the rail has to run vertically, so the brackets come out in different lengths. In the instruction read, the line is vertical sideways and forward may deviate from the vertical within 0–15°; for a shaft this is checked on the drawing, not on site.

Galvanizing, holes and welding

A shaft is galvanized whole, so everything welded to it goes into the bath with it. Bracket seats, studs and doubler plates are welded before galvanizing, not after. A doubler plate creates an overlapped zone where liquid from the preparation baths can get in; so the number of vent holes or weld gaps depends on the plate area. The rules are covered in the article Designing for hot-dip galvanizing.

Holes for bracket bolts and vent holes are drilled before galvanizing: cutting through a finished coating damages the zinc. Box brackets made of tube have holes at both ends, otherwise air and zinc will not pass.

The rail or ladder itself is a separate product: hot-dip galvanized steel, stainless steel or aluminium. Aluminium next to zinc in a damp environment forms a couple that leads to contact corrosion, so the joint is agreed with the system maker and, if needed, isolated with a gasket. An aluminium rail also expands almost twice as much as steel, which shows in the gaps at the joints.

The working surface of the rail on which the arrester slides is kept clean: mortar, cement, zinc drips, paint and dirt interfere. After cutting on site the edges are deburred. If the shaft is painted over the zinc (a duplex system), the question of what is painted and what is not is settled before the shaft goes for galvanizing. Fasteners are hot-dip galvanized or stainless; for threads under zinc see Fastener strength classes.

Wind, ice, weight and lightning protection

DBN V.2.6-198:2014 requires (cl. 5.1.2) provision for inspection, survey and repair, and for that, where needed, walkway ladders, platforms and fittings for fixing temporary and permanent devices. For antenna structures the code adds that brackets and hangers of technological platforms are placed at the nodes of the main shaft structures (cl. 20.22) and that deflections of platform elements do not exceed 1/250 of the span (cl. 20.16).

A caged ladder, platforms and a rail add mass and wind area to the shaft, and ice increases both. They are put into the calculation in the same way as antennas and floodlights, as stated in the article on tall floodlight masts. On PMK masts with a mobile crown there is no ladder, because the fittings are serviced on the ground: Masts with a mobile crown.

A metal ladder and rail conduct current, so their connection to the earthing is considered in the lightning protection part: see Lightning protection of telecom towers. One instruction allows rails to be used as part of a lightning protection system, but that is a decision of the design, not a property of the rail itself.

Maintenance and inspection

The system is checked before use and on a schedule. The owner of the pole appoints a responsible person and a competent person: one who knows the rules in force, the standards and the system. Who carries out the inspection work depends on the owner’s organisation.

In one instruction for a rigid-rail system the line itself is inspected as needed, while the guided arrester is examined at least once a year and after every fall. The periods are taken from the documents of the chosen system and the owner’s regulations.

Inspection of the shaft as a whole (corrosion, joints, welds) is covered in the article Assessing the condition of steel structures.

Common mistakes

• a bracket bolted through a thin wall with no doubler and no check for the fall force: the wall is punched through, the bolt does not break;
• the rail ends level with the platform instead of above it, and the person has nothing to hold on exiting;
• there is no end stop at the top or bottom, and the arrester can be attached wrongly or released from the rail;
• the fall protection line passes through a lockable hatch and breaks for several metres in which the person is not clipped on;
• a bracket sits on a joint between shaft sections or next to a hatch, where the wall is doubled or weakened;
• an aluminium rail with no gaps for thermal expansion and tight against a galvanized shaft;
• the rail or its working surface was coated with zinc or paint already in the workshop, and the arrester will not run on it;
• the ladder is calculated for the weight of a person only, without a fall: the design fall force on a bracket is several times the weight of a person;
• the system is assembled from «similar» parts because the original ones were not available: the system was tested as a set, and a different part cancels that test;
• the sign at the entry is forgotten, and the instruction stays in the workshop.

What to state in KM, KMD and the request

The drawings and the request state what is needed to choose the system and calculate the shaft:

• the height of the pole and the places that have to be reached (platform, hatch, antennas, floodlights);
• the type of access: step bolts, ladder, cage, rail or cable, inside or outside;
• the number of people who may be on the line at the same time;
• the height of rest platforms, the direction and the way of exit at the top;
• the diameter and wall thickness of the shaft at the fixing points and the position of the hatch;
• whether the pole is galvanized and whether it is painted over the zinc;
• requirements for the sign, the documents and rescue.

We fabricate steel structures to the customer’s drawings and also prepare KM and KMD drawings: KM and KMD design, steel fabrication. We supply ladders and fall protection systems together with poles and masts when the design provides for them. Erection is done by our partner construction company. For the general picture on telecom towers see the articles Telecom tower design and Types of telecom towers.

Standards and validity

Guided type fall arresters on a rigid anchor line are covered by EN 353-1:2014+A1:2017 (the current edition, which replaced the 2002 edition), and on a flexible one by EN 353-2:2002. Anchor devices are covered by EN 795:2012: a new edition is being prepared in Europe, but until it is approved the 2012 edition remains current. Requirements for instructions for use, maintenance and periodic examination are set out in EN 365:2004. Fixed ladders are covered by EN ISO 14122-4:2016; it applies to machinery and equipment, so for poles and towers it is applied by analogy.

In Ukraine the Rules of labour protection during work at height, NPAOP 0.00-1.15-07 (order of the State Committee for Industrial Safety No. 62 of 27.03.2007, registered with the Ministry of Justice on 04.06.2007 under No. 573/13840), are in force. From them the article uses the requirements for ladders (cl. 3.6 and 3.7), for anchor points (cl. 4.1.14) and for testing safety belts (cl. 4.2.10). Steel structures are designed to DBN V.2.6-198:2014 «Steel structures. Design standards» (cl. 5.1.2, 20.16, 20.22).

Which current DSTU reproduces EN 353-1, EN 353-2, EN 795, EN 365 and EN ISO 14122-4 is checked in the register of normative documents before they are cited in project documents. The figures from system instructions are given for orientation; a project uses the documents of the chosen system and the current text of the standards.