In the last article,
James explained the structural design of the ADSS cable.
This time James specifically shared the Aramid Thread (Kevlar) in ADSS, design, and use.
Aramid yarn is a high modulus aramid yarn suitable for ADSS cable. Aramid yarn has special properties such as low density, very high tensile modulus, high resistance to breakage, and low elongation at break; At temperature, it can maintain its inherent stability, very low shrinkage, low deformation, and very high glass transition temperature, in addition to high corrosion resistance, non-conductive, in addition to strong acids and alkalis, Strong resistance to chemicals is an upper cable reinforcement unit material.
Within the aramid yarn, there is an American brand, Kevlar, the most widely used, we use the material of this brand to analyze.
As shown below, the yellow part is Kevlar.
In order to accurately calculate the amount of material required, we need to know some parameters, one is the span, one is the maximum pull, and the other is the Kevlar cross-sectional area.
Please refer to the figure below, in the actual use scenario
We are going to calculate it step by step. Have patience. The formula included here is very complicated.
Aramid yarn details: something like (20 * K49 3000D) This main calculation of the tensile strength.
According to the stress formula, S = Nmax / E * ε,
E (tensile modulus) = 112.4 GPa （K49 1140 Cena）
ε = 0.8%
Generally designed voltage <1% （Stranded tube） UTS;
≤0.8% ， evaluation
Nmax = W * (L2 / 8f + f);
L = span (m); generally 100m, 150m, 200m, 300m, 500m, 600m;
f = cable sag ； generally 12m or 16m.
Nmax = W * (L2 / 8f + f) = 0.7 * （500 * 500/8 * 12 + 12） = 1.83KN
S = Nmax / E * ε = 1.83 / 114 * 0.008 = 2 mm²
Saramid (K49 2840D) = 3160 * 10-4 / 1.45 = 0.2179mm²
N numbers aramid yarn = S / s = 2 / 0.2179 = 9.2
General aramid fiber hinge pitch is 550mm to 650mm, angle = 10-12 °
W = Maximum load (kg / m) = W1 + W2 + W3 = 0.2 + 0 + 0.5 = 0.7kg / m
W1 = 0.15 kg / m (this is the weight of the ADSS cable)
W2 = ρ * [(D + 2d) ²-D²] * 0.7854 / 1000 (kg / m) (This is the weight of ICE)
ρ = 0.9g / cm³, the density of ice.
D = Diameter of ADSS. Usually 8mm-18mm
d = thickness of the ice cover; no ice = 0mm, light ice = 5mm, 10mm; heavy ice = 15mm, 20mm, 30mm;
Let's say the ice is thick is 0 mm, W2 = 0
W3 = Wx = α * Wp * D * L = α * （V² / 1600） * (D + 2d) * L / 9.8 (kg / m)
Let's say that the wind speed is 25 m / s, α = 0.85; D = 15 mm; W3 = 0.5 kg / m
Wp = V² / 1600 （Standard partial pressure formula ， V means wind speed）
α = 1.0 (v ＜ 20m / s); 0.85 (20-29m / s); 0.75 (30-34m / s); 0.7 (＞ 35m / s);
α means Coefficient of the Inequality of Wind Pressure.
Level | phenomenon | Mrs
1 Smoke can indicate the direction of the wind. 0.3 to 1.5
2 The human face feels windy and the leaves move slightly. 1.6 to 3.3
3 The leaves and micro-techniques tremble and the flag unfolds. 3.4 ~ 5.4
4 Dust on the floor and paper can explode, causing tree branches to flap. 5.5 to 7.9
5 The green tree sways, and there are ripples in the inland waters. 8.0 to 10.7
6 Large branches tremble, cables are vocal, and the umbrella is difficult to lift. 10.8 ~ 13.8
7 The whole tree is shaken, and it is inconvenient to walk in the wind. 13.9 ~ 17. l
8 The micro-branch is broken and people feel very resistant to moving on. 17.2 ~ 20.7
9 The grass house was damaged and the branches were broken. 20.8 to 24.4
10 trees can be felled and buildings are destroyed in general. 24.5 to 28.4
11 Rare on land, large trees can be felled and buildings, in general, are severely damaged. 28.5 ~ 32.6
12 There are few on earth, and its destructive power is enormous. 32.7 ~ 36.9
RTS: nominal tensile strength
It refers to the calculated value of the resistance of the bearing section (mainly counting the rotating fiber).
UTS: UES maximum tensile strength> 60% RTS
In the effective life of the cable, it is possible to exceed the design load when the cable is in the maximum tension, which means that the cable may be overloaded for a short time
MAT: maximum allowable working voltage 40% RTS
The MAT is an important basis for the calculation of the voltage drop and tension, and also important evidence to characterize the stress-strain characteristics of the ADSS optical cable. It refers to the design of meteorological conditions under the theoretical calculation of the total load, the cable tension.
Under this stress, the fiber deformation should not be more than 0.05% (rolled) and not more than 0.1% (core pipe) without additional attenuation.
EDS: daily strength （16 ~ 25）% RTS
The annual average stress is sometimes called the daily average stress, it refers to the wind and no ice and the annual average temperature, the theoretical calculation of the load cable tension, can be considered as the ADSS in the long-term operation of the tension average (should) force.
EDS is generally (16 ~ 25)% RTS.
Under this tension, the fiber should not have tension, without additional attenuation, that is, very stable.
EDS is also the fatigue aging parameter of fiber optic cable, according to which the anti-vibration design of fiber optic cable is determined.
After calculating the above formula, we know that there are several keywords:
1. The maximum wind speed in place, 2. The thickness of the ice, without ice is 0, 3. Sag 4. Maximum working tension, 5. Cable weight,
These values are very, very important, but most customers are unfamiliar with these design elements. For each query, simply ask the price.
I'm here to congratulate you first, I can see such boring content, stay here.
It is really too difficult to design this cable, the amount of Kevlar. So we can see the final price, the gap is huge.
We ask the customer who cannot provide the data requirements, we will quote according to the standard design and the result is a 50% price that the customer cannot accept.
How to solve this? How to do it? Customers need to buy fiber optic cable, but they are not professionals, they do not know what they need. This is the key to the problem. You do not know what you want, you only know how much you have, this is Budget.
As shown in the figure above, the data in some cases is calculated and is for reference only.
If you don't know the design of the aramid yarn, we will recommend it based on our experience. After confirming the design with you, we will conduct tests.
Usually, it is a 1-kilometer sample, we have to pay a sample fee. Of course, in the transaction in the future, this part of the cost can be eliminated.
There is also a very good way, that is, you have to be the customer, go to your local market, find the actual sample of the ADSS cable you need, send it to us. This part only needs to send 1-2 meters, we can analyze the structural design. We will then produce or run tests based on this.
Product Director: James Xu
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