When laying pipelines in flooded and swampy areas, pipeline ballasting is often used. Several methods can be used for this purpose. Each of them has certain characteristics, so you should familiarize yourself with the features of the application before starting work.
Tasks
Installation of the main pipeline in wetlands and in flooded areas requires compliance with certain conditions. This is explained by the fact that the constant influence of waves leads to some displacement of the pipes. Moreover, in some cases, the flow can cause significant damage to the pipe. So, analyzing the causes of the failure of gravity lines, experts came to the conclusion: most accidents were caused by the loss of pipe stability.
This problem can be solved by ballasting pipelines. During these works, the main pipeline is fixed and weighted with special devices. As a result, the pipe is given negative buoyancy.
Pipeline ballasting methods
There are 3 ballasting methods, each of which has its own means of solving the problem and differs in installation methods.
In order to impart negative buoyancy to pipes, products are used that are able to increase the weight of the pipeline due to its own. This category includes:
- frame and frameless devices filled with soil;
- saddle weights, annular, covering.
For increased protection against mechanical damage and corrosion, a continuous concrete coating can be used.
Another possible option for pipeline ballasting is the use of anchor devices. Of the features of the action is that increasing the stability of the pipeline is due to the strength properties of the soil.
Types of Weighting
In the list of products that can give the pipeline negative buoyancy, several products should be noted:
- UBO. This abbreviation means weighting concrete concrete type. Such a product is 2 blocks of reinforced concrete, which are fastened together by power belts. Most often, such products are used when laying an oil and gas pipeline in difficult climatic conditions. You can mount the UBO one at a distance equidistant or group them in several pieces.
- Slaughter. This version of the weighting agents is a variation of the previous version, but differs in modification (the letter “m” indicates this). The design in this case is equipped with grooves and a metal rod, with which this device is mounted on a pipe. UBOM should be used when installing a closed loop or when mass securing cargo.
- 1UBKm. This weighting agent has a wedge-shaped structure. The design is presented in the form of two cylindrical surfaces that intersect each other. The radius of the structure slightly exceeds the diameter of the main pipe. This method of pipeline ballasting takes place on the territory of permafrost, wetlands and floodplains.
- UKT. These weighting agents are presented in the form of two half rings. They cover the pipe and are connected by means of nuts and studs.
- UBP. The belt concrete weighting compound is two blocks interconnected by a power belt.
Concrete coating
This option is a concrete monolithic coating of the pipe along its entire length. This layer is applied by shotcreting. With its help, it is possible to both give negative buoyancy to pipes, and to protect it from the effects of water.
To increase the bulk density, aggregate in the form of barium sulfate is added to the concrete. To achieve high strength values, the coating is applied at the factory. At the site during installation, only pipe joints are covered.
When choosing this method of weighting should pay attention to the type of material used.
Anchor Devices
Another way to ballast subsea pipelines is to use various anchor devices. Their installation in the summer is carried out after laying the pipes, and in the winter during the development of the soil.
Anchors can have a different structure, and therefore the method of installation is different. This list includes anchors:
- drop down;
- screw;
- freezing;
- fired;
- injectable;
- explosive.
Ways to install weighting
Specialized equipment is used to deliver ballasting elements and fix pipelines. The choice of a particular device depends on the size of the weights, their type and working conditions. In this case, the following may be involved:
- pipe layers;
- amphibious cranes;
- marsh excavators;
- helicopters.
Ballast calculation
The calculation of the pipeline ballasting must be carried out at the planning stage. This takes into account a number of terrain features and operating conditions:
- The calculation of negative buoyancy depends on the pressure of the water flow and its speed. If along the path of laying the pipeline these indicators can change, at the planning stage, measurements are taken at several sections.
- It is necessary to make calculations at the maximum rate of water flow.
When selecting a weighting agent, it is also important to consider the type of device, the material used for its manufacture and density. During installation, you should clearly adhere to the step size for securing the load. Strict observance of the rules is necessary for the reason that incorrect calculations can cause damage to the pipe.