Fire fighting system – cleaning the rust stop the corrosion.

What is a fire fighting system

In this article we will limit ourselves to water-filled fire suppression systems. There are systems that use gas such as halon or other agents to suppress the fire. Merus is a watertreatment company and we address corrosion in water-based systems.

A fire fighting system covers usually an entire area. Be it a factory, a shopping mall or even an entire city. Depending on the size of the fire suppression system, there are one or more fire extinguishing centers, each with a separate supply line leading into the system. Often, these centers also have one or more large watertank installed as a buffer. This is to ensure that there is right from the start enough water to fight the fire. Powerful high-pressure pumps are located next to the tanks, so that if necessary, sufficient extinguishing water can be supplied. From these central points, pipes distribute water in spur lines to the fire fighting equipment in the affected areas. In an office or residential building, the pipes lead to the fire sprinkler system. In factories to the fire sprinklers, on ships or offshore platforms to the extinguishing guns. Or simply to the hydrants on the street, as seen in the photo above. Firefighters can connect their hoses to such hydrants to have enough water in case of fire.

The risk of fire is higher in refineries, chemical plants or offshore platforms. The same applies to efforts to ensure a perfectly functioning fire extinguishing system.

Corrosion in Fire Fighting system

In the so-called wet systems, to which most large fire extinguishing systems belong, the water in the pipes is always under pressure. The reason for this is that sufficient water is immediately available in the event of a fire. However, because the water is not moving most of the time, this system is prone to corrosion.
When some valves are opened and pipes are flushed during maintenance work, the water often comes out dark brown. The reason for this is the loose rust on the pipe walls, which is carried along and turns the water brown.This is a strong indication that there is corrosion in the pipes.
The higher the level of corrosion, the greater the risk that in the event of a fire the dissolved rust will clog the system’s spray nozzles, preventing sufficient water from flowing. Ergo, the fire is not extinguished quickly enough or not at all.

Trial Merus ring on a fire fighting system

Typically, at least one Merus ring is installed on each supply line to the fire suppression system. These can be very supply lines of over 20″ or more. We install them before the shut-off valve, tanks and pumps. Such a pipe system is never absolutely watertight. This means that there will always be some water leaking from the system. To compensate for this, there are small pumps distributed throughout the system. These keep the pressure at the design pressure through, for example, a 1″ pipe.

The aim of such a test is to remove the existing corrosion and to protect the system from further corrosion by flushing out the rust.
The typical course after an installation.
Immediately after installation, a sample was taken at a shut-off valve as far away from the inlet as possible. This was done at slow speed so that the water was mostly clear.
A few days later, a second sample was taken at the same location and under the same conditions. This time the water was dark brown. After only a short time, a thin layer of rusty particles was visible in the sample container. The customer could hardly believe how much rust was in the system and how an aluminum ring a few hundred yards upstream could dissolve all the rust in that short time.
The system was cleaned by flushing water at several points in the system until it was clean. This was repated four times until no more brown water came out.

We have done this many times since. It has been shown that this test is one of the most amazing and fastest ways to show the customer how efficiently Merus technology works.

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