Water conservation is a pressing global issue. It has been estimated that worldwide water losses from leaking or broken pipes could be as high as 60 percent, including about a third of the world’s drinking water. The World Bank has put the cost of these losses at some $14 billion a year. In the U.S. alone, leaking pipes lose an estimated 7 billion gallons of drinking water a day.

At the micro level, a water system with slowly leaking flanges or seeping corroded fittings can lose millions of gallons of water, plus the energy investment in treating and distributing it. To gain a better understanding of what the water industry considers most important in sealing products and practices, a series of interviews were conducted.

The survey pool consisted of 11 organizations representing municipal engineers involved with water and wastewater systems. Also included were engineering firms that design treatment plants and transport and distribution systems.

The geographic distribution was weighted toward the western portion of the country, which has been experiencing severe water shortages. The interviews covered concerns about leaks, the state of equipment and pipe fittings and the loss of senior experts to retirement.

Questions about trials

Some of the engineers interviewed were relatively happy with currently available sealing products, while others expressed a desire for better performance and longer service life. Some had conducted their own test programs under controlled conditions to vet vendors’ claims. Most were reluctant to try new products in active municipal water systems.

Determining where in a system to perform product trials is a challenge. The consequences of failure must be low, since shutting off the water to repair a leak caused by a trial is not an option. Other factors working against such trials are the decreasing experience levels and increasing workloads of workers in municipal water systems.

Responses varied when interviewees were asked what types of flange sealing products they were using in their systems. The top four cited were glass-reinforced epoxy (GRE) with elastomeric seals (37 percent), rubber sheet gaskets with and without electrical isolation kits (33 percent), molded push-on gaskets (16 percent) and compressed fiber sheet gaskets (10 percent).

The participants were largely satisfied with current sealing technology but still interested in new products. However, the progression from interest to trial to use is far from assured. Unlike many process industries such as chemicals and refining, the municipal water industry is not concerned with high temperatures and pressures and toxic media. However, the consequences of failures remain severe and are more publicly visible, and that helps explain the industry’s resistance to trying new products.

This puts the onus on sealing manufacturers to present a compelling case for their offerings, including test data, field case studies and references. Any group includes those who are cautious and risk-sensitive, and others who are early adopters of technology. In the water industry the latter are few and far between, even though more than half in the survey indicated willingness to consider a new product.

Sealing issues

The interviews also yielded insights to the industry’s principal concerns about sealing. The first was installation, defined as proper gasket seating (compression), bolt torque required to attain and maintain an effective seal, matching bolt type and strength to flange type and strength, and contractor skill. The yield and ultimate tensile strengths of ductile iron pipe flanges are lower than for forged ASME B16.5 flanges. Installers of gaskets in the former are not comfortable with the high torques cited for forged flanges, yet gasket suppliers often do not differentiate between the allowable bolt torques of these materials.

The second concern was flange condition. Respondents cited the need for gaskets able to accommodate misaligned flange faces and withstand field conditions. Gaskets also must compensate for scratches and other damage to flanges inflicted in pipeline construction and installation. The surface conditions of even well-aligned DIP flanges pose the inherent issue of face serrations, which are deeper than those of a B16.5 raised-face flange. This raises a question of whether isolating gaskets made of GRE or metal carrier plates with elastomeric sealing elements can seal properly.

Remaining concerns about gasket performance included electrical isolation, NSF-61 and chemical resistance. Electrical isolation mitigates the effects of destructive galvanic corrosion between dissimilar metals, as in mating a DIP flange and stainless steel valves. Electrically insulating gaskets kits typically consist of a gasket, bolt sleeves and washers made of high-impedance, nonconductive materials.

NSF-61 requires that sealing and other materials used in potable water systems be certified for safe contact with drinking water. NSF-61 gasket materials are now available for use in these systems. Concerns about chemical resistance focused on chloramines and hydrogen sulfide, which can degrade certain types of elastomers in gasket materials.

Toward solutions

These and other concerns have been addressed by sealing manufacturers and application engineers. Isolating gaskets kits are available to thwart galvanic corrosion. Installation can be improved with classroom and field training coupled with proper procedures and quality checks. And flange condition, NSF-61 and chemical compatibility can be solved by adherence to sealing best practices and use of proven gasket designs.

Thorough assessment of the application and equipment service conditions will point the way to the right product and guidance for its proper installation.

About the authors

Jim Drago, P.E., is senior manager, market intelligence, with Garlock Sealing Technologies, a maker of fluid sealing products for process industries based in Palmyra, N.Y. Angelica Wiume is global industry leader for water and construction with GPT, a maker of critical-service flange systems, spring-energized jacketed seals and electrical flange isolation kits based in Wheat Ridge, Colo.