High-quality lanyards in a variety of designs
Lanyard is a special rigging, i.e. designed for safe, durable and reliable static fastening, holding and / or moving weights, a product. Its commonly used synonyms:
• cable (screw) coupler;
• rigging coupling;
• cargo fasteners.
Usually, a lanyard is used for a cable, chain, cable, wire or rope: the device allows you to quickly take out their slack by reducing the length with insufficient tension. If it is excessive, the length of the cable and its tension are similarly changed by manual rotation of the body about its axis - only in the opposite direction. In the process of rotation, the screws located at the ends of the tie are displaced towards the center: the stronger the displacement, the shorter the cable length.
Since the lanyard is a rigging unit fixing serious masses, increased requirements are imposed on their reliability. Thus, the quality of products at all stages of their production (from design to release control!) Is regulated by international standards:
• GOST 9690-71 and OST 5.2314-79 (for ship modifications) - Ukrainian (Soviet) standard;
• DIN 1480 and DIN 1478 - European standard (Germany).
Structural elements and other features
Lanyards are very effective, despite the rudimentary device. The composition of 1 product includes 4 key nodes:
• coupling (stamped closed / open, cast, welded closed / open);
• cylindrical body;
• body (closed or open type);
Obligatory additional accessories - two slings (screws, load-gripping elements) screwed into the threaded holes, and their threads are "twisted" opposite to each other. The ends of the screws are equipped with an eye or a hook: a cable / rope / string, etc. is attached to them.
In addition, the hardware is completed with:
• washers that evenly distribute the load;
• lock nuts (according to GOST 5919 by cold heading method) to prevent spontaneous rotation of the grippers.
The main material going to the rope / wire / chain / rope lanyard is mild steel (usually S235JR, C1021) with a galvanized (anti-corrosion) coating. According to clause 2.11 of GOST 9690-71, the surface of all parts must be treated with compounds (according to GOST 9791-68), ensuring normal operation in both climatic conditions:
The body of the products is in the form of a rectangular frame or ellipse and always with two holes, with threads oppositely oriented relative to each other. Screws are screwed into the holes. If the body of the lanyard is open, both screws can be fixed together with a ring mechanism.
Welded screw ties must be with cleaned welded seams, which are welded with electrodes, whose mechanical properties comply with the requirements of GOST 9467-75, namely, not lower than E 42 A. The surface of high-quality products is clean, without sharp edges (they are necessarily rounded). Visually, there are no defects that reduce the strength characteristics and presentation:
• chips, etc.
Hook, lug and fork shanks are available with two thread orientations;
All industrial (in accordance with GOST and DIN) production of screw ties are classified according to at least four criteria:
• configuration of load-gripping parts and their complete set;
• geometry of the coupling (body);
• material and / or working environment;
• the specificity of the tasks performed (purpose).
For specialists, lanyards are not the same in terms of maximum load (from 200 to 3150 kilograms or more), as well as in such an indirectly determining the strength of the structure as a method of forming a coupling:
• stamping (more reliable, since the macrostructure has no cut fibers, and there are no stress concentrators);
• casting (the structure of the cast metal is coarser, which is why the body breaks faster than the stamped one);
• welding (the lowest load-bearing capacity: in the zone of the welded seam, the strength of the metal is reduced by 20-25%).
In addition, a lanyard for wire rope / rope / chain, etc. is produced in different weights: it indirectly determines the tensile force and strength of the structure. The range of weight of finished products is in the range:
• from several grams (for example, fasteners for tensioning the strings of curtain rods - a weak, several kilograms, tension force is required);
• up to tens of tons - for fastening elements of suspension bridges, ship masts and other massive objects.
Configuration of load gripping parts and their complete set
Depending on the shape of the screws to be screwed in, 6 types of lifting couplings are distinguished:
• "hook-hook" ("hook-hook") - DIN 1480;
• "hook-ring" - DIN 1480;
• "ring-ring" - DIN 1480;
• "fork-fork" - DIN 1478 (the safest, because the possibility of slipping is minimal!).
Both attachments can be the same (fork, ring, or hook) or different screw combinations (for example, hook-and-fork).
Coupling (body) geometry and design
According to the European standard, there are two types of housing / couplings (type of construction):
• open - DIN 1480;
• closed - DIN 1478.
But The standards of GOST 9690-71 establish lanyards of three types:
• with an open stamped clutch (ОШ);
• with an open welded sleeve (OS);
• with a closed welded sleeve (ЗС).
Material and / or working medium
On an industrial scale, turnbuckles are made either from stainless and acid-resistant steel (grade A2 and A4), or from carbon steel with a zinc coating (hot method) or galvanized.
According to the standards of GOST 9690-71, it is appropriate to make lanyards from the following steel grades:
• steel 25 (according to GOST 1050-74) - for a fork, a stamped coupling, an axle with a shoulder, an eyelet and a hook;
• steel 20 (according to GOST 1050-74) - per pipe;
• VSt3sp2 (according to GOST 380-71) - for nuts of welded sleeves.
Specificity of the tasks performed
The industry produces two types of products for the two main rigging tasks (tension retention and lift / lower / travel):
• mounting (DIN 1480) - only for static loads (fixation in a fixed position);
• cargo (DIN 1478) - for dynamic application of force (movement of weights).
They also distinguish between general purposes, designed only for axial (linear) load, a lanyard for a cable, as well as specific modifications strictly for a rope, chains or other objects that need stable tension.
Factory lanyards are produced in several size ranges, differing in body length and / or in the diameter of the shaft of the screwed in screws. The larger the diameter, the higher the permissible working load. For example, an M16 lanyard will withstand a load of up to 1200 kg, and an M10 lanyard - a maximum of 300 kg.
Attention! The design (type of load grip) also affects the permissible load limits:
• "fork-fork" (BB);
• "ear-eyelet" ("ring-ring) (VU);
• "ear-ear" (UU).
For example, one and the same size lanyard for a cable in the "BB" version will withstand a theoretical mass greater than in the "UU" version - 3.6 kilograms versus 3.3 kilograms for the same product with a permissible load of 2 tf (GOST 9690-71).
In standard markings, the numeral indicates the diameter of the threaded hole of the stamped coupling: the larger the value, the higher the bearing capacity of the fastener:
• lanyard m8 - up to 200 kg;
• lanyard m10 - up to 300 kg;
• lanyard m16 - up to 1200 kg;
• м24 - up to 3150kg.
For an open type of coupling, the maximum bearing capacity cannot be higher than 6300 kg. For a closed structure, the carrying capacity can reach a record 20,000 kg (welded counterparts maximum 1500 kg!). The reason for the cardinal difference in load is in the greater safety of closed-type couplings: when the gripper is destroyed, the fragments will not fly apart.
Previously, lanyards were used to connect metal and wooden structures. Today they are used as a regulator of very high tension of ropes, cables and chains, which are in demand in many industries, as well as in everyday life. For example, the lanyard m8 is used for the installation of hinged objects made up of several components. Most often these are:
• antennas and other high-rise structures;
• outdoor advertising (city boards, streamers and other suspended demonstration devices);
• gymnastic apparatus;
• masts and other ship elements.
Other modifications of fasteners are in demand:
• in the aviation industry;
• in the construction of industrial, residential buildings;
• for the construction of bridges;
• in radio engineering and power engineering;
• for fixing passenger / freight elevators;
• when creating cable networks between buildings;
• on ships (sea, river navigation);
• in sports - for tensioning the ropes in the rings, etc.
Attention! The direction of the load is strictly along the axis of the hardware! Other directions of force application are strictly not allowed.