ADSS Cable Accessories: Suspension & Tension Clamp Guide | 5-Min Expert Spec

■ Choosing the right ADSS cable accessories determines the extent of return on investment that you will enjoy

There are no dielectrics in time ADSS wires; only the messenger wires at the sites of work are made metallic. Any slip of a clamp, jacket creep, or a damper of vibration failing, may cost everything. INMR's in-field survey, 2023, indicates that 68% of the early-life ADSS failures occur due to cables and not the accessories. A 45% out of the unplanned outages among operators who spend an extra 3-4% for the certified ADSS cable accessories and within a 15-year period in contrast with unplanned outages decreased to 12 years cycle replacing the 12 to 25.

■ Key hardware pictured at a glance

Before diving into specs, look at the line-up.

• Suspension clamp (also called "support set" or "intermediate hanger")

• Tension clamp (dead-end, anchor, or strain clamp)

• Down lead clamp (pole entry or building entry)

• Vibration damper (AFL's TRD or Spiral Vibration Damper)

• Arcing/grounding hardware (only on the route with earth-wire-pop poles)

• Junction box and storage loop for cables

These six items are the most basic materials on every ADSS segment. Strike one with certainty, and you make your link quite weak.

■ Suspension clamp: the daily workhorse.

Function: sustains vertical load and permits horizontal movement of the wires in case of heat expansion.

Normal load: 5 to 15 kN (1100 to 3300 lbf) for standard span of 50 and 150 m.

Materials: UV-degradated so GFRP is chosen as the polymer base material + neoprene, and EPDM is also used in the manufacture of marine supports.

Key dimension: the inner diameter (ID) varies within ID – 0.3/+/-0 mm; 12.3 mm clamp mounted to a 12.6 mm jacket will slip, while 12.9 mm clamp will get oval bigger the core.

Test standard: IEC 61284 clause 6.3 (slip-strength test); clamp mating to pull of 1 kN or 10% RTS (whichever is bigger) commence.

■ Tension clamp: the anchor that never moves; pendulum does not swing.

Function: transmits 100% of cable RTS to a pole or a tower.

Load classes: 20 kN, 40 kN, 70 kN, and 100 kN. Pick the class orchestration of classes where ≥ 50% RTS is used. A 44 kN-RST cable would not require the 40 kN sets; that needed will be the 20 kN sets instead.

Construction: the tightly twisted wires known as the "dead-end grips," which form layers of steel rods painted with aluminium (sometimes referred to as "dead-end grips"). The colour coding in each first 150 mm of drum gives the installer a means to identify how many rods unit jacket is concerned with out.

Critical test: IEEE 1232 clause 8.4. "1-hour under constant 85 % RTS" there should be no rod breakage and the maximum slip allowed is 1 mm.

■ Down lead clamp: small part, big headache; this is down in the weeds

A section of cable from the suspension point to the splice box is fixated to each pole through a down lead clamp. Spacing less than 1.2 meters, and the jacket suffers from a wind split; in five years, it could be a problem. In wooden posts, a type of clamp made of stainless steel straps should be used; for concrete posts, one made of plastic wedges specific for ADSS should be used. Price difference: USD 0.45 vs 0.90. Cost of this labor: USD 120 to conduct this work. The replacement of a cracked jacket later.

■ Vibration control: turn this differentiated approach into a simple, clear statement and let the numbers tell your story

Aeolian vibration (5-40 Hz) leaves the cable at risk within 12-18 months on the spans above 80 m. The stockbridge dampers used to work. Nevertheless, they add weight and need a messenger clamp. Weather-resistant TPU in the form of Spiral Vibration Damper (SVD) is the easiest remedy in the case of ADSS. Rule of thumb: 1 SVD allowed at each suspension point when the span is over 100 m or when wind speed is higher than 1.6 m s⁻¹ during 20 days a year. Cost: USD 2.80 per piece, 0% maintenance.

■ Standards checklist for procurement

Cable side: IEC 60794-4-20, IEEE 1222, ITU-T L.83

Hardware side: IEC 61284, IEC 61466, EN 50341-1

Factory tests: 100 % visual, 100 % dimensional, 5 % sampling for slip-load.

■ Typical bill of materials for a 5 km 48-fiber ADSS line

Span length 80 m → 63 spans

• Suspension clamp: 63 pcs

• Tension clamp: 2 × 2 = 4 pcs (each end)

• Down-lead clamp: 8 pcs per km → 40 pcs

• Splice/storage box: 1 box every two km → 3 boxes

• Vibration damper: 63 pcs

■ Environmental add-ons

• Coastal salt fog: designate stainless-steel 316 bolts and nuts as opposed to 304. Price uplift 3%.

• Antarctic (minus -40-degree C): shatterproof polymer be polymer used to ensure independence with -50-degree C impact test. The custom-extruded polypropylene EPDM shatters at -45 °C.

• A high-power electric field with ≤ 25 kV m⁻¹ on a shared pole at 138 kV: track resistant type; only the use of clamps that weather-tested to IEC 60587 will be acceptable. Seek laboratory approval for the 500 h, 4.5 kV, and inclined-plane test report.

• Desert UV: black polymer that is colored with harnessed-manufactured UV master batch; a carbon content of 8% minimum. Grey clamps that undergo UV degradation and crack in 3 years.

■ Procurement workflow (buyer checklist)

1. Create cable datasheet (RTS, OD, weight) and send it to the three accessory manufacturers.

2. Get receipt/print out of IEC 61284 test report within five years-old.

3. Keep 3 samples of each type; whoever pulls tests in-house with an approximate load of 1kN (the hydraulic pull tester and 30 min). However, you are likely to succeed in getting another round of tests done.

4. Confirm lead time; most factories keep 20 kN and 40 kN sets in stock, while 70 kN sets need 3 or 4 weeks.

5. Package into plastic bags rated for UV protection and plywood container for bad weather and weight less than 30 kg which allows for hand unloading.

6. Do not hesitate but demand the warranty for 10 years that is valid for both mechanical and tracking failure. Stronger signal sounding here suggesting a problem if the duration is less.

■ Common mistakes installers make – now, how to avoid these occasions?

Mistake 1: Using suspension clamp instead of tension clamp on the initial pole.

Mistake 2: Old neoprene inserts as a substitute.

Mistake 3: Not bringing the storage slack out the loop.

■ FAQ – commonly asked questions we receive every week

Q1: May I use one set of clamps for 12.1 mm and 12.5 mm OD cable?

A. Negative. Directly to the clamp ±0.2 mm. Buy two sizes or ask factory if dual-range inserts are available.

Q2: How can I tell if a 40 or a 70 kN tension clamp is required?

A. MWT, or maximum working tension, = weight × span²/(8 × sag). Provide a 50% safety factor at the beginning. If MWT > 25 kN, jump to the 70 kN set.

Q3: Vibration dampers are needed? Or else, fix just the short 30 m spans.

A. Typically, it is unnecessary. If we attach such cables to the messenger wire, the risk would be low; it is worth to put one SVD every 200 m for safety purposes.

Q4: What is the life expectancy of an ADSS polymer clamp?

A. Ten years sealed in original UV-preventive pack at temperature below 35 °C. After three years of exposure to sunlight outdoors and unpacked, 30% of the impact strength drops.

Q5: Will the rods alone be enough if I want to reuse the dead-end housing?

A. It is only legally possible if the housing is less than five years old and has zero cracks. Saving USD 4 is not worth losing a 40 m of fiber over a 150 m span.

■ Key take-away; these accessories are not only small on the bill but they play an important role in determining your cable life cycle.

Invoicing the right load classes, ask on time for current certs and install with precision done with the torque chart. Give three steps and the clamps are created with the cable industry with the opportunity to outlive them; if not, the best and cheapest type becomes the most expensive type in your life for your time and budget.

Contact us for more information

James is a technical manager and associate at Zion Communication. 

Specializes in Optical Fiber communications,  FTTH Solutions, 

Fiber optic cables,  ADSS cable, and ODN networks.

james@zion-communication.com

+86 13777460328