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NEVARNI KARABINI ZA LETENJE

PostPosted: Sat Dec 06, 2008 11:15
by ZORZY
Če kdo uporablja takšne karabine mu svetujem, da jih zamenja, če se ima rad. Jas sem jih že. Članek, ki je spodaj pripet, ga lahko preberete na naslednjem linku:

http://www.charly-produkte.de/english/

ZA NAŠO VARNOST GRE!!!

Karabiner breakage: the causes

An increasing number of pilots are discovering cracks in their karabiners as pictured above. Several karabiners have broken whilst launching. Are we dealing here with over-burdening, defective material, or metal fatigue due to high oscillation loading ?
Defective material could not be discovered in the case of the affected karabiners. Intact aluminium karabiners withstand a loading of between 5 – 7 KN even when the gate is open.
They become strongly disfigured due to this strain, but they should be able to withstand a loading of approximately 1,5 KN which arise under normal flight conditions. The karabiners broke however when launching, and without any special strain.
Overloading of an open or closed karabiner causes strong deformation as a result of which the anodised layer cracks open extensively around the breakage point. The anodised layer on the broken karabiners appears to be intact however.
Which leaves us with metal fatigue. On first inspection this would seem unlikely as the working load of the karabiner amounts to only 1/10 of its breakage strength at the most. Such marginal strain to the aluminium does not lead to metal fatigue even when affective for long periods, if this were not so then the whole of the aviation industry would have to be shut down.

We are dealing here with a special case caused by the play of the safety catch arising from construction / manufacturing tolerances. The tensions arising because of the gate play do not increase in a linear manner with additional loading. As the safety catch is not loaded in the area of the gate play, we are dealing here with the static system of a hook, in which case the tensions rise very steeply. Only when the safety catch engages by a loading of 60 to 200 kg (depending on the extent of the gate play and the position of the harness strap) are we dealing with a ring shaped carrying element with slowly rising tensions. In contrast to rock climbing karabiners, paragliding karabiners are permanently subject to oscillation loading. In contrary to most D-shaped rock climbing karabiners, paraglider karabiners have a broad harness support, as a result of which they can be subject to high bending tensions especially in the area of the gate play because of the long lever arm. If the karabiners are bent cold without subsequent heat treatment in the finishing process (this is usually the case with steel karabiners) then additional high tensions in the bends remain due to reset forces. Possibly the torsion forces due to twisted straps should also be added. These factors have obviously not been taken into account by the manufacturers when dimensioning the karabiner.

This fault would have been recognised at the DHV Harness tests if the karabiners had been tested in the same manner as they are burdened in flight : with an open gate. Only now has a material testing institute commissioned by the DHV proven the problems arising from gate play by carrying out oscillation loading tests. Tests have shown that even by oscillation loading as low as between 3 and 30 kg hydraulic fracturing can arise in a normal anodised karabiner as shown in the pictures. Due to the cross section weakening of a fractured karabiner, the safety catch engages during flight , the catch is seated solidly, the bending tensions are reduced and thus the karabiner does not break (hopefully) completely. When due to the fracturing the safety catch no longer engages properly at the next launch the karabiner then fails completely.
It becomes clear that the dimensioning of the karabiner is too marginal, when paraglider aluminium karabiners with an open gate begin to permanently misshapen by a load of between 200 and 300 kg. Paraglider steel karabiners also begin to permanently misshapen by a loading of 280 Kg. The karabiner manufacturers warn for this reason against flights with an open gate obviously unaware that the karabiner is always burdened as if the safety catch were open, due to the gate play. The dimensions of the karabiner would be sufficient if a „gate open“ burden of 5 KN could be withstood without permanent misshaping. The DHV was correct to demand this value in a karabiner test seal on10.04.2003.
How many load changes a karabiner can withstand before a breakage due to metal fatigue arises can only be forecast statistically. As far as critical stress exists, a breakage can occur in a wide range of load changes. With the karabiners presently in use, the risk is obviously low, but it does exist. For this reason, a limitation to the service life will not bring about the safety that pilots desire. In the case of the breakage to an anodised aluminium karabiner in the Czech republic, the karabiner was only in use for approximately two years.
In any case it is not only the karabiners from a particular manufacturer that approach a critical limit as regards breakage due to metal fatigue , rather all circulating paragliding karabiners with a gate play of more than 1mm - possibly also steel karabiners in as far as they were not subject to heat treatment after the bending process. Whether or not the karabiners presently in use should continue to be used will be shown by the oscillation loading tests which all paraglider karabiners must currently undergo.
None of the conventional karabiners currently (September 2003) in circulation fulfil the DHV paraglider karabiner norm recommended by the DHV!
Only with the Safe-in-Lock and the Quick Out karabiner from Finsterwalder is metal fatigue due to usage loading of no importance, because they have NO gate play and currently comply with the DHV stability and demands of security steps against unwanted opening from April 2003!

PostPosted: Sat Dec 06, 2008 12:16
by škrat
če sm prav razumel obstaja zelo velika verjetnost da zadeva poči če je odprt?

PostPosted: Sat Dec 06, 2008 13:40
by Simch
O katerih karabinih se tukaj sploh pogovarjamo? Namreč nisem zasledil modela oz. slike!

LP Simch

PostPosted: Sat Dec 06, 2008 14:37
by ZORZY
Opozorjen sem bil predvsem na karabine, ki so izdelani iz aluminija, saj pri delovanju strižnih sil "napokajo" in obstaja nevarnost, da se zlomijo, kot kaže na sliki. Kupite jeklene karabine. Bom še malo poiskal po netu, pa še kaj napišem glede tega. Jaz sem imel ALU karabine od firme EDEL. pa tudi od Austria alpin se govori. Kot sem že navedel je problem predvsem v materialu - aluminij, ki ni tako vzdržljiv kot jeklo. Jaz sem jih zaradi lastne varnosti zamenjel, saj 50€ ne pomeni nič proti življenju.

PostPosted: Sat Dec 06, 2008 14:48
by Simch
Najbrz si imel v mislih to sliko:

Image

LP Simch

PostPosted: Sat Dec 06, 2008 15:44
by jurem
Zivjo,

ze pred kakimi tremi leti je krozilo podobno opozorilo, ko je v eni sezoni prislo do par zlomov aluminjastih karabinov. Od takrat je stvar kar malo potihnila, zdej je pa verjetno spet prislo do kaksne 'slabe serije'? No kakorkoli, sem ze takrat razmisljal o menjavi (na prejsnem sedezu sem imel aluminjaste karabine), a mi zarad lebone to nekako ni uspelo :roll:

Res je, da ni skoda nekaj evrov za to zrtvovati, po drugi strani je pa tud res, da procentualno gledano pride precej redko do zloma. A Murphy nikoli ne pociva... razen ob nedeljah mogoce?

lp, Jure

PostPosted: Sun Dec 07, 2008 12:20
by Stane
A Murphy nikoli ne pociva... razen ob nedeljah mogoce?

lp, Jure


In to predvsem ob deževnih nedeljah :badgrin: :lol: #-o

PostPosted: Mon Dec 08, 2008 20:40
by igorer
Kolikor je meni poznano je to najbolj problem Ausrtialpin Alu karabinov. Pred leti je bil v eni reviji tud objavljen nek test, kao nevarnih karabinov, a sem že pozabil kje. Mogoče bo "Jons" kaj vedu o tem.

Sicer pa je bilo vedno, da je potrebno alu karabine menjati "kao", na vsaki 2 do 3 let. Pa če mal neskomerializiram, je pa mogoče res potrebno na 5 let.

PostPosted: Tue Dec 09, 2008 1:27
by Jons
Si me pa najdu, he, he. Naj da admin tej temi zraven klicaj in jo postavi na vrh threadov. Enkrat smo se to že pogovarjali. Kratka obnova:

Aluminijaste vponke - NI OK
INOX - OK

Aluminijaste vponke so za INOX zamenjali tudi zmajarji, čeprav so imeli povsem drugačen tip/obliko. Kot je bilo rečeno je razlog utrujenost materiala. Če kdo ne ve kaj to pomeni, si lahko prebere ščepec o prvem potniškem reaktivcu. Za razliko od nerjavnih (INOX) vponk, so aluminijaste tudi bolj občutljive na udarce. Problemi niso samo z Al vponkami Austrialpina, ampak tudi drugih proizvajalcev. V prvi vrsti mora za brezhibnost svoje opreme vsakdo poskrbeti sam. Zato kontrolni pregled ne bo škodoval četudi imaš INOX vponke.

Nekaj informacij z weba:
DHV
DHV pdf 1
DHV pdf 2
Charly
PG forum 1
PG forum 2
PG forum 3

Spomnil bi še na dve stvari, ki sta tudi pomembni (za reševalno padalo). Prva je pozicija prečke pospeševalca ali počivala za noge, ki med neuporabo ponavadi prosto niha (pri odprtih sedežih z rezervo spodaj).
Pod drugo pa svetujem, da pregledaš še pin/šplento/varovalo na koncu ročice reševalnega padala. Če imaš tak sistem, je zelo priporočljiv INOX pin/šplenta/varovalo. Aluminijast se lahko zvije in rezerve ne bo možno izvleči.
Prilagam par slikic pina, da bo vsem jasno za kaj gre.
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Re: NEVARNI KARABINI ZA LETENJE

PostPosted: Mon Jul 21, 2014 11:19
by Češnja
Opazila sem da se kar prodajajo, a pol odsvetuješ?

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