Chart Hdd Applications

stricter placement tolerances, as is the case in many municipal applications. Chart 1-1 lists the distribution by industry of HDD applications.

As a result of the growth of HDD, the marketplace is providing a wide range of HDD units and support equipment. HDD rigs range from mini-rigs that are usually used for the installation of smaller pipe and conduits (2 inches) to maxi-rigs that are capable of installing 48-inch pipelines. The length of pipe that can be installed by HDD is determined by many factors, such as rig size, soil conditions, and carrier pipe diameter. Installations over 6000 feet have been successfully completed1. Current HDD equipment can operate in a wide range of soil conditions, from extremely soft soils to full-face rock formations with unconfined compressive strengths of 40,000 psi.

An industry survey2 was conducted in order to gain a better understanding of this multi-billion dollar business, which is relatively unfamiliar to many in the construction sector (see Appendix D). According to the survey there are 17 manufacturers of HDD rigs and accessories and several hundred dedicated horizontal directional drilling contractors in North America. The survey results indicated that 60 percent of the contractors surveyed were relatively small companies with annual revenues of up to seven million dollars. Nearly 90 percent of the contractors surveyed stated that they were involved in the utility industry, with 74 percent in the municipal market and 63 percent in the pipeline industry. Environmental applications of directional

4 Chapter 1 â–  Introduction to Horizontal Directional Drilling drilling are relatively new, as only 28 percent of the contractors indicated that they had experience with the installation of horizontal wells and 17 percent in projects involving horizontal sampling. Most HDD contractors can be described as non-specialty contractors, with 41 percent involved in both the utility market and the pipeline industry and 35 percent involved in three or more different applications. Forty-nine contractors responded to the survey. They owned a total of 185 HDD rigs, with 38 percent classified as mini-size rigs, 33 percent as mid-size rigs, and 29 percent as maxi-size rigs. Seventy-three percent of the mini and mid-size rigs were manufactured by three companies, Vermeer Manufacturing Company, Charles Machine Works, Inc. ("Ditch Witch"), and American Augers, Inc. In the maxi-size category 47 percent were custom-built, 40 percent produced by American Augers, Inc., and the balance manufactured by others.

The survey2 also revealed that during the 1995-96 construction season, 72 percent of all the products installed had an outside diameter (O.D.) of 4 inches or smaller. Products with O.D. between 6 and 12 inches made up 16 percent of the products installed, and those above 12 inches constituted 12 percent. In terms of pipe material, high-density polyethylene (HDPE) was the most common product, accounting for 62 percent of all pipes installed. In addition, HDPE accounted for 75 percent of all pipes installed with 4-inch or smaller diameter. Steel was the most common material used in the installation of12 inches and larger products, accounting for 92 percent of all pipes in this category. Polyvinyl-chloride (PVC) pipes are mainly used in the small diameter range (up to 4 inches).

The survey2 also indicated that HDD projects are normally of short duration and relatively low dollar values. Fifty-one percent of all projects reported in the survey reported durations of 14 days or less, and 47 percent of the projects reported a monetary value less than $70,000. The most common type of contract used in the HDD industry is unit rate; however, all types of contracts ranging from lump sum to target price are also utilized, depending on the project complexity. Appendix 1 contains the full survey report.

Pipeline

The oil, gas, and petrochemical industries are an important market for the HDD industry. During the 1970s and early 1980s, HDD had been used primarily in the oil and gas industries, either for exploration, production, or pipeline installation. This sector of the HDD industry mainly consists of 6-inch and larger diameter pipelines. Because of the HDD lengths and pipeline diameters normally associated with pipeline HDD applications, larger HDD rigs are often required. Figure 1-1 is a picture of a typical HDD rig used in a pipeline HDD application.

Pipeline Construction Swamp
FIGURE 1-1 HDD Pipeline Application

For pipeline construction, major water crossings, swamps, and environmentally sensitive areas pose significant challenges and permitting issues. Even though there has been widespread historical use of open trenching as a means of crossing these obstacles, today's stringent environmental regulations pose one of the most significant challenges facing the pipeline industry. Environmental regulations, especially in North America, require a thorough assessment of alternate methods of crossing environmentally sensitive areas. In many cases, HDD is specified as the preferred method of crossing these obstacles. In order to cross these environmentally sensitive obstacles with other methods, the engineer has to prove that HDD is not a viable method of construction. Moreover, most of these environmental regulations do not consider increased construction cost as a reason for not using HDD as the preferred crossing method.

Largely due to the popularity of HDD construction, there has been an increase in the number of qualified and experienced HDD contractors and improvements in HDD equipment and technology. In many instances this has significantly lowered the cost of HDD construction. For "routine" HDD crossings of water bodies and environmentally sensitive areas, it is not uncommon for the HDD construction cost to be lower than traditional open trenching costs. This has resulted in an increase

TABLE 1-1 Contractors Involved in Pipeline HDD and Years of Experience

Experience

Pipeline HDD

Not involved

37%

Involved

63%

5 years or more

53%

2 - 4 years

4%

2 years or less

8%

0 years

35%

in HDD construction in the pipeline industry. Table 1-1 lists the percentage of contractors involved in pipeline HDD according to a survey2.

For pipeline construction HDD has the following advantages over traditional open trench methods:

  1. Water bodies, wetlands, and their sensitive environments are not damaged.
  2. Since there is no excavation in the sensitive areas, there is no silt buildup or erosion. It is also not necessary to take special measures to protect marine and plant life.
  3. The workspace is much smaller, resulting in the removal of much less earth material than would be excavated using normal open-cut methods.
  4. The crossing can be performed at almost any time without needing to take into account such factors as as fish spawning seasons or high water flows.

Table 1-2 lists some of the key factors for pipeline HDD construction. Utilities

The installation of utility products in urban areas and across rivers and highways has become the largest sector of the HDD industry. Utility companies now use HDD extensively for the installation of power, natural gas, water, sewer, and telecommunications. Municipal applications are still underutilized ; however, they are the most promising future market for HDD applications. Recent advancements in equipment and tracking systems make the use of HDD cost-efficient for projects that involve larger products and stricter placement tolerances, as is the case in many municipal applications. As an increasing number of municipal engineers become aware of the technology and its advantages, this market is expected to grow rapidly over the next five years. Figure 1-2 is a typical HDD layout in a municipal environment, and Figure 1-3 is a typical HDD rig used in a utility application.

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Responses

  • ALCIDE
    How hdd rig size is determined?
    3 years ago

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