Mark Hopkins

It is becoming a common occurrence for Hughes Associates, Inc. (HAI) engineers to receive phone calls from clients and building owners expressing concerns about corrosion or leaks in their automatic fire sprinkler systems. Corrosion problems may range from visible staining of piping and surrounding construction elements to more dire consequences such as clogging of pipes, prevention of valve operation, inadvertent sprinkler operations, or pinhole leaks.

HAI engineers provide consulting services to help our clients understand corrosion issues and to develop real solutions to corrosion problems. HAI engineers have been on the forefront of corrosion investigations and can offer a range of services to our clients.

HAI engineers have investigated corrosion in a variety of fire protection systems, including wet pipe, dry pipe, preaction, and deluge sprinkler systems. These systems have included carbon steel, ductile iron, galvanized steel, stainless steel, brass, bronze and copper piping and system components.

The corrosion of fire protection systems can prove costly and have detrimental effects on the reliability and anticipated operational performance of sprinkler systems.

In some cases, the severity and extent of corrosion can impact the ability of a sprinkler system to control or suppress a fire. Corrosion and its products can limit or prevent adequate water flow in sprinkler systems.

Figure 1 – Occluded pipe

Figure 1 shows a partially occluded section of pipe. Looking at this photograph, one can easily understand how this significant build-up of corrosion products would provide an obstruction to water flow.

Figure 2 – Dry pipe valve corrosion

Figure 2, shows corrosion inside a dry pipe valve. In some instances, corrosion in dry pipe valves has proven severe enough to prevent operation of the dry pipe valve during a fire. With the automatic sprinkler system totally impaired by the failure of the dry pipe valve to operate, a severe loss to the facility can result.

A number of misconceptions exist throughout the fire protection industry regarding corrosion. Some of these misconceptions have enabled poor design and installation practices to continue.

One such misconception involves the use of galvanized steel pipe. Many have long believed that steel pipe protected with a galvanized coating would provide superior corrosion performance to ordinary black steel pipe. Because of this belief, designers and authorities having jurisdiction viewed galvanized steel pipe as a panacea when dealing with the possibility of corrosion.

Subsequent, detailed investigation has proven that this belief is false. In fact, the investigation has disclosed that if a contractor incorrectly installs galvanized steel pipe, it can prematurely corrode in less than one (1) year’s time.

Figure 3 – Internal corrosion of galvanized pipe

Figure 3 shows a section of galvanized pipe used in a preaction sprinkler system. This particular system had become partially filled with water. Under normal circumstances the pipes in this system should have only contained pressurized air and should have remained completely dry.

The accumulation of water in the pipe led to an aggressive form of corrosion, known as oxygen cell corrosion. This particular type of corrosion created a number of leaks in a very short period of time.

Each of the nodules (small mounds) shown in Figure 3 indicate potential locations for future pinhole leaks. Following installation, these conditions inside this galvanized steel pipe occurred within approximately one and one-half years of service life.

Figure 4 – Pin hole leak in galvanized pipe

Figure 4 shows a pinhole leak found at another location in a preaction sprinkler system. This hole measured approximately ¼-inch in diameter.

The galvanized pipes identified in this example hardly demonstrate superior corrosion performance. They, most certainly, would not represent an acceptable measure for reducing or slowing the process of corrosion.

HAI engineers routinely work with metallurgical and water testing laboratories to implement a three-pronged approach to investigate the extent, severity, and root cause of corrosion in fire protection systems.

A typical project will involve an examination of the sprinkler system, analysis of the water supply and system water, and a metallurgical examination. A pipe push camera (boroscope) facilitates internal pipe examinations. This scope provides live video from within pipes to allow for instantaneous viewing of corrosion and other abnormalities. While performing this internal examination, the technicians simultaneously save the video to allow for analysis and review with clients at a later time.

HAI engineers take samples from inside the piping. They also take samples of the water supplying the automatic sprinkler system. Working with carefully selected laboratories, HAI engineers determine any factors that may influence corrosion at a particular facility, based on the laboratory findings following a metallurgical analysis and an analysis of the water supply and water taken from within the piping.

HAI engineers then use the findings from these investigations to develop solutions for remediation.

There is no singular solution for all corrosion problems since corrosion can occur for a number of reasons and corrosion rates can vary based on a variety of physical conditions and parameters. As a result, measures to mitigate corrosion vary depending upon the extent and severity of damage, system installation configurations, equipment and material selections, and risk tolerances of building owners and end users.

Figure 5 – Nodules found in copper pipe.

In some cases, corrosion damage has been considered significant enough to warrant complete system replacement, either due to the extent of physical damage or assumed risk. One common example based on physical damage would be a sprinkler system with a history of pinhole leaks coupled with evidence of system wide pitting damage indicative of future pinholes, such as shown in Figure 5. Risk based decisions have been made to replace systems due to zero tolerance for leaks in facilities, such as, mission critical data centers and museums containing culturally significant, high value, rare or irreplaceable collections. In such cases, a water loss would be considered catastrophic or would be considered to have significant impact on mission or business continuity.

Figure 6 – General Corrosion

In other instances, corrosion has been observed to be minor. Figure 6 shows the interior conditions of a section of Schedule 40 pipe that has been in service for approximately 27 years and shows only minor wall loss due to general (uniform) corrosion. In cases such as this, HAI has helped owners in the development of an appropriate maintenance program to minimize future corrosion, which will ultimately increase the longevity of the systems.

In general, the conditions in most sprinkler systems are often between these extremes. HAI engineers develop practical, cost effective solutions intended to have the least impact on facilities. Where localized corrosion damage has been observed, risk tolerances are high, or in cases where corrosion has been discovered in its early stages, remedial measures have included system alterations and adjustments to minimize corrosion and, in some cases, targeted replacement of severely damaged piping and components. HAI engineers develop remediation options based on information collected through individual investigations; therefore, recommendations vary on a case by case basis.

The knowledge gained from the extensive field investigations becomes incorporated into the standard design practices. This knowledge also enables HAI staff to provide consulting services to assist in conducting conditions assessments, due diligence surveys of existing systems, development of remediation options, development of design drawings and specifications to minimize corrosion in both new and existing systems, and the development of corrosion investigation and design protocols.

Please call us to discuss how we can help you solve your specific corrosion problems.

Hughes Associates, Inc. (HAI) is pleased to announce the opening of our Shanghai office.

Founded in 1980, HAI is a global company offering fire protection engineering, environmental, and security consulting services.

Hughes Associates Shanghai is centrally located at the following address:

            Hughes Associates Shanghai 
            Xuanrun International Building 
            Suite 819 
            1100 Wuzhong Road 
            Shanghai, China 201103
            Tel: 86-(0)21-3470-1796
            Fax: 86-(0)21-3470-1798

HAI Shanghai is positioned to meet the growing demands of our China based clients. Any inquiries should be made to Scott Chong (schong@haifire.com), Managing Director Asia Pacific or Kyuback Choi (kbchoi@haifire.com), General Manager Shanghai.