The peculiarity of pipelayers' operation is that during pipeline laying several machines work in combination with a single load object, usually a part of the pipeline lifted above the ground.
The load on the hook of each machine may depend on various technological factors: the shape of the pipeline deflection, the weight of the lifted section, the difference in the suspension value between the neighboring pipelayers in the pipe-laying column in case of curved terrain, etc. In case the pipelayer reaches the state of unstable equilibrium with detachment from the crawler base on the counterweight side, a slight lowering of the hook may result in redistribution of the integral load between adjacent pipelayers and then their further tipping, which is inevitable for cranes working with single objects, will not occur. It is noteworthy that the fewer pipelayers in a column, the more additional load redistribution occurs. The column, as a rule, consists of four to six machines used as a service of truck crane in Moscow and if their number increases, the joint coordination becomes worse.
In order to achieve high-quality performance of installation and handling operations, pipelayers are equipped with the following accessories:
- rigging devices and universal rope slings to carry out work with uninsulated pipes, piece loads and pipe sections;
- rigging devices and universal rope slings for handling uninsulated pipes, piece loads and pipe sections;
- elastic grippers or towels for moving, lifting and trenching individual pipes, insulated pipes and pipe sections;
- automatic pincer grippers for moving, lifting, jointing sections and uninsulated pipes during installation and welding works;
- trolley hangers for moving, laying and lifting in a combined way (simultaneous insulation of the whole pipeline or only its joints, if pipes with pre-fabricated insulation are used);
- traverses with end grip for unloading and loading uninsulated and insulated pipes from pipe carriers and for stacking at pipe welding bases.
