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Mechanically Attached Pipe Fittings

More Cost-Effective Pipe Fabrication Through Standardization


Following the end of the Cold War, the Navy sought to lower the cost of maintenance while maintaining fleet material readiness. Repair of shipboard piping systems offered potential cost savings. A typical ship contains miles of pipe and thousands of joints carrying everything from fuel to steam. Shipboard pipe is joined by various methods such as welding and brazing. When pipe and fittings are installed in Navy ships, they must be tested for quality and integrity to ensure performance and to protect the health and safety of the ship and her personnel. As new pipe-joining technologies emerge, they must be thoroughly tested and approved before being used in U.S. Navy ships. Sometimes, this testing process can delay the introduction of promising technologies for years and preclude the realization of substantial savings.

In the 1980s, a new pipe-fitting technology, the mechanically attached fitting (MAF), was developed, promising substantial improvements over other existing pipe-joining technologies such as welding and brazing. Several different types of MAFs were available from several different manufacturers. These included axially swaged, shape memory alloy (SMA), swage marine, bite-type, flared, and elastic strain pre-load (ESP) fittings. Many MAFs offered easy fabrication, high reliability, and lower installed cost. Within the Naval Sea Systems Command’s (NAVSEA) Auxiliary Equipment Division, the life-cycle manager for pipe-fitting components recognized an opportunity to save money and improve performance.

The Problem

The Navy needed proof that MAFs could provide the same or better integrity than brazing or welding before authorizing their use in the fleet. Testing standards were needed to provide that proof. The Navy initially began testing, approving, and procuring various MAFs for the Navy using the test procedures provided by the individual manufacturers. Different fitting types were subjected to different tests and test requirements. The test procedures were informal, sometimes inconsistent, and not standardized.

Some MAF manufacturers were not happy when their fittings were tested under different tests than those used for their competitors; they wanted a level playing field. In addition, procurement decisions potentially were subject to protests because of the differing test methods and acceptance criteria. Also, because the Navy tested different fittings using different tests, it had no way to ensure it would get the best fitting at the best price for a given application. The Navy needed a universal test standard.

The Solution

The Navy had a choice; it could write a military product specification(s) for one or more of the already approved MAF types or it could write a universal performance standard for testing that would apply to all current and future MAF products. By selecting and specifying a preferred MAF technology, the Navy could end the testing controversy and be assured of an acceptable MAF solution to its pipe fitting requirements.

Developing a universal test standard would be a more difficult task because it would need to address all of the differing MAF technologies and would require reaching consensus on acceptable test procedures among all the MAF manufacturers.

Developing new military specifications for MAFs, while offering an easier solution, had the potential of limiting competition, proliferating military documents, and possibly discouraging innovation. The Navy’s MAF life-cycle manager chose to work with industry to develop a nongovernment performance standard for MAF testing, an approach advocated by the industry. This approach prevailed because increasing competition, stimulating innovation, and helping drive down unit costs outweighed the added effort to reach consensus on an NGS.

The life-cycle manager led the effort to develop a single non-government MAF test standard. He worked with industry to accelerate NGS development and to speed adoption of this important new technology.

The Approach

An NGS subcommittee with jurisdiction over MAFs already existed within ASTM (F25.13 on Piping Systems, part of Committee F25 on Shipbuilding), but it had been relatively inactive. The Navy, working with its industry partners, revitalized the committee to reach consensus on a common standard.

Committee members included the key MAF manufacturers with the U.S. Coast Guard and the Navy representing the user community. The Navy conducted aggressive market research to evaluate the range and capabilities of available products and worked diligently to evaluate, approve, and track MAF designs for Navy applications. The goal was to produce a standard acceptable to the Navy and build industry consensus on testing. The result was a flexible but stringent commercial performance standard, ASTM Standard F 1387, Specification for Performance of Mechanically Attached Fittings, which addressed all potential MAF designs. These efforts enabled the Navy to adopt and use many MAF designs early and successfully with substantial savings. By 1993, the Navy had used many approved MAFs with excellent results and saved millions of dollars in the first few years.

One-Time Investment Cost
The ASTM standard F 1387 development took three years and resulted in a single ASTM standard plus a supplement for certain unique Navy requirements. The Navy representative devoted about half his time during this period to conducting market research, evaluating tests, coordinating with interested parties, and expediting the consensus process.

Other government employees were involved to a lesser degree, including the U.S. Coast Guard committee member and various Navy engineers who coordinated on technical issues such as pipe structural strength and fire-related requirements. Table 1 shows the one-time investments costs.

The participating MAF manufacturers each brought their own test procedures and requirements to the committee for consideration. The Navy had a consultant perform a study of commercial pipe-joint testing practices, procedures, and requirements used in the United States and overseas. This study established a baseline and helped the committee develop a complete and robust standard. The Navy also funded a study by the Massachusetts Institute of Technology (MIT) to determine the minimum number of MAF design types, quantities, and sizes that must be tested to approve or qualify a manufacturer’s family of MAFs for Navy use.

Recurring Costs
Developing an NGS performance standard rather than a military product specification increased competition in MAFs, which resulted in more stock numbers in the Navy system. A military specification might have resulted in about 100 different stock numbers. The ASTM performance-based standard motivated manufacturers to produce additional new products to meet the requirements, resulting in about four times more stock numbers in the system. Maintaining a stock number takes an estimated $100 per year. Developing a military specification would have cost $10,000 per year to maintain 100 stock numbers, while the NGS approach costs about $40,000 per year to maintain 400 stock numbers; a $30,000 difference in annual recurring cost, or $300,000 during a 10-year period.

It also costs the Navy two to three person-weeks per year to maintain a document, whether it is military or NGS. A military specification must be kept current and periodically validated. An adopted NGS also must be maintained, and the Navy’s cost is incurred through its participation in the NGS consensus process. For MAFs, the costs of maintenance for a military specification or NGS are considered equal. Table 2 shows a comparison of recurring costs between an NGS and a military specification.

Cost Savings/Avoidance
One-Time Cost Savings
During the development of ASTM Standard F 1387, the manufacturers funded and conducted about $1 million worth of MAF testing to prove concepts and validate tests. The Navy would have needed to fund similar tests if it had chosen to develop a military specification. The NGS route resulted in considerable savings for the Navy.

Each MAF requires six to 12 months to complete qualification testing. By expediting the development of the ASTM standard and engaging industry in validation, the Navy brought the new technology to the fleet faster, better, cheaper, and with greater choice of products. Savings were available to the Navy an estimated three years earlier through development of an NGS rather than a military standard. The Navy was able to leverage the industry resources rather than conducting the research, testing, and validating using its own resources. Table 3 shows the Navy’s one-time cost savings of an NGS.

Recurring Cost Savings
Several different cost studies show that the use of MAFs saves up to 50 percent of the installed cost compared with the use of welded or brazed fittings. Table 4 shows that the actual savings per installed unit vary significantly, depending on the type of system, the fitting, labor rates, and other factors. Although the material cost of an MAF is higher than the same configuration welded fitting, the labor cost savings more than offset the increased material cost, resulting in a lower total installed cost.

About a third of the Navy’s approximately 300 ships spend time in repair or overhaul each year. The Navy installs an estimated 2,500 MAFs per year on these ships using Ship Intermediate Maintenance Activity (SIMA) or ships crew. In addition, shipyards install an estimated 40,000 MAFs each year in ship overhauls and new ship construction.

Table 5 shows an average recurring cost savings with NGSs rather than military standard.

Table 6 shows one-time and recurring costs and savings using NGSs rather than military standards.

Lessons Learned

New, emerging, and changing technologies are important opportunities for performance-based standardization. Using performance-based NGS may provide better results than developing and using military specifications. Standardization can yield dramatic results—simple items, such as pipe fittings, can provide opportunities for huge savings. Individual initiatives in standardization can make major differences. As the Navy continues to qualify new MAFs and adds new applications for MAFs, the recurring savings and cost avoidance continues to grow. //

Copyright 2001, ASTM

This article is excerpted from a standardization case study published by the Department of Defense upon the completion of MILSpec Reform. All case studies are available on the Internet (click on Library, then click on Standardization Case Studies).