Polyethylene (PE) belongs to the group of semi-crystalline thermoplastics (polyolefin). It is marked by a high degree of flexibility and ductility also at low temperatures [HDD-415] [HDD-416].

PE is resistant to acids, alkalis and weak solvents. It is not resistant to oxidising acids and halogens. Further information in this respect is contained in the Addendum to DIN 8075 [HDD-417].

For PE-pipes, which are used in HDD, the following standards apply:

PVC-U (polyvinylchloride free of plasticizer or unplasticised) belongs to the thermoplastic group. It is a polymer of vinyl chloride, which is made of ethylene (crude oil or natural gas) and chlorine (of NaCl) and to which thermal stabilizers and lubricants are added for pipe production [HDD-429]. Besides the hardness and form stability, a characteristic property of PVC-U is the high degree of resistance to acids, alkalis, alcohols, oils, fats, aliphatic …

The restrained joint of PVC-U pipes can be achieved by means of a socket, weld or glued connection (see (Type and design of the joints)). The latter variant is not used for HDD applications, because professionally completed glued connections require around 12 hours to harden completely and to be able to reliably bear longitudinal forces resulting from the pulling-in of the pipe [HDD-465].

The restrained joint of PVC-U jacking pipes is achieved by means of a special, rigid or flexible plugin socket joint, in which a mechanism prevents the joint from being pulled apart.

The restrained joint in its rigid variant can be of two types, for example, with the manufacturer CertainTeed [HDD-469] (see (Restrained socket or spigot joints)):

• Joining of both plug-in ends with a coupling, where a milled groove each in the outer wall at the plug-in …

For creating welded joints with PVC-U pipes, heated tool or butt fusion welding is used (Figure 254a and b). The welding process principally resembles that of PE-pipes (see (Heated tool or butt fusion welding)), however, there are essential differences regarding welding temperature, jointing pressure and duration of the single steps [HDD-472].

(Image: Creation of a pipe joint for PVC-U-pipes (12’’, SDR-18, type Fusible C900™) by means of heated element …

The restrained joint of PVC-U pipes can be achieved by means of a socket, weld or glued connection (see (Type and design of the joints)). The latter variant is not used for HDD applications, because professionally completed glued connections require around 12 hours to harden completely and to be able to reliably bear longitudinal forces resulting from the pulling-in of the pipe [HDD-465].

Due to the high abrasion and corrosion resistance (cf. Annex 1 of DIN 8061 [HDD-458]) of PVC-U, special measures to protect the pipe surfaces during pulling-in, such as jacketing, are not necessary.

Figure 255a and b show a special development based on multiple installation in the form of group installation (see Section 2.2.3 in Volume 1 [HDD-1]). Here, special PVCU host pipes with thrust-restrained joints (plug-in joint with socket and spigot end), which allows a 150 m (164 yards) long pipe string to be pulled-in by HDD, are used. Three or four PVC-U cable casing pipes, which during jointing the pipe sections are connected by means of a special …

PVC-U (polyvinylchloride free of plasticizer or unplasticised) belongs to the thermoplastic group. It is a polymer of vinyl chloride, which is made of ethylene (crude oil or natural gas) and chlorine (of NaCl) and to which thermal stabilizers and lubricants are added for pipe production [HDD-429]. Besides the hardness and form stability, a characteristic property of PVC-U is the high degree of resistance to acids, alkalis, alcohols, oils, fats, aliphatic …

According to DIN EN 14457 [HDD-294] and/or DIN EN 805 [HDD-296], a pipe is a “component of uniform bore, normally straight in axis, having e.g. socket, spigot or flanged ends.”

The pipes that are pulled into the usually expanded borehole when using HDD (pulling-in process, see (Method of operation and sequence)), can be classified among the category of jacking pipes.

In the following discussion, jacking pipes will be understood to be prefabricated …

Developed from directional and deep drilling technology, HDD as a steerable drilling method is ideal for the trenchless installation of pipelines. Utilities and communications providers make use of the numerous advantages of this technology, as it provides a customized variant for almost every problem within the scope of its possibilities. However, it is precisely these variants that make it necessary to systematically cover the full range of HDD technology. The book provides valuable guidance and decision support on the topics of equipment, steering and locating techniques, project preparation and planning, structural calculations for the state of construction and operation including: pullback force, buoyancy and ballasting, safety against buckling, pipe stresses, abutment and bedding. Special process developments such as Meeting-in-the-Middle technique, PTT "Push and Pull Technology", COMBI DRILLING method and hybrid systems are described in detail as well as drilling fluids, dry horizontal directional drilling and pipe materials and joints.

Process: Grouted-in-place process for potable water piping

Title: Renovation of a DN 100 potable water pipe with the Cempipe process

Location: Entrance to a small town, open area

Limiting conditions:

• System: Potable water pipe
• Material: Steel
• Cross section: Circular cross section
• Nominal size: DN 100
• Depth position: 2.0 - 2.5 m
• Rehabilitation section: 105 m
• Damage: Incrustation, manganese and iron deposits

Site equipment

Site equipment includes traffic safety, provision and preparation of storage surfaces for equipment and material as well as the provision of power and water supplies.

Water stoppage

During rehabilitation, the water supply is turned off. It can be turned on again approximately 12 h after the rehabilitation work has been completed.

Cleaning the piping

Before rehabilitation, the potable water piping is cleaned. For instance, the cleaning can be carried out by a steel spring scraper.

Digging the excavations

For the rehabilitation of the potable water piping with the CemPipe method, it is necessary to excavate at the start and end of the piping to be rehabilitated (starting and end excavation). As the construction …

Renovation of a DN 100 drinking water pipeline using the Cempipe method (Lining with a rigidly anchored inner plastics layer).

Cleaning is one of the most important measures for maintaining and ensuring a long-lasting efficiency of drain and sewer systems [ [EN752:2017]]. Cleaning measures can either be implemented proactively or reactively.

Proactive cleaning serves to mitigate problems before they occur by implementing the following principal objectives [ [EN14654-1:2005]]:

• Securing a defined status (safe and correct operation) of drains and sewers by eliminating debris, …

In addition to the principal objectives listed in this chapter, the development of the cleaning plan may include other objectives, as e.g.:

• Reduction of operating costs;
• Minimisation of public disturbance and citizen complaints;
• Compliance with technical and legal requirements;
• Improved quality control and documentation of cleaning works by the staff/service providers;
• Acquisition of information for future cleaning planning.

The determination …