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Fiber Restistant Fiberglass Pipe

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Posted / Last update: 01-09-1996
Publication: Petroleum Equipment & Technology Archive
Issued: September 1996
Author: Curran Sullivan D. , PE

Unprotected FRP pipe performance
Fuel Contribution Index: Unprotected FRP pipe made with epoxy resin systems will be consumed when exposed to fire. However, the piping is self-extinguishing when the flame is removed. Under continuous fire exposure and with water flowing through the pipe, the unprotected pipe tends to degrade at a given level and then maintains that performance level. The movement of fluid inside the pipe remains cool (i.e., FRP pipe is a low conductor of heat) and gives an extinguishing effect to the structural wall of the pipe. As a result, the FRP Fuel Contribution Index is zero, and there are certain applications where unprotected FRP pipe may be used for fire main systems.

Flame Spread and Smoke Development Indices: The Flame Spread Index differs for the various resins used in the manufacture of FRP pipe. In addition, additives may be used to retard flame spread. For example, one epoxy resin pipe Flame Spread Index is 40 and the Smoke Index is 755. Flame retardant additives can be added to the resin and will reduce the Flame Spread to less than 25, which is optimum for building code applications. However, smoke generation is another consideration that may limit the pipe application in occupied building areas.

Coated FRP pipe performance
Coatings have been developed that will reduce the rate at which fire exposure will affect FRP pipe. One product is PPG Fire Retardant Latex 42-7 Paint, which can be applied to the installed piping system. This is known as an intumescent coating. Intumescent is defined in Webster’s Dictionary as “swelling and charring when exposed to flame.” What happens to the coating is consistent with Webster’s definition for intumescent. When exposed to fire, the coating will blister and form a heat shield to reduce the rate at which fire will affect the pipe.

The table to the left shows that coating the same epoxy resin pipe referred to in the first example will reduce the Flame Spread and Smoke Developed Indexes significantly.

Dispenser sump applications
One place that coated FRP piping can be used is with dispenser sumps. The evolution of sumps located under petroleum fueling dispensers has become a concern for fire jurisdictions.

The Uniform Fire Code and the National Fire Protection Association (NFPA) codes reflect the old practice of filling pits “with a noncombustible inert material” to suitably protect low melting point materials and protect against the ignition of vapors. However, fire marshals recognize that filling a dispenser sump defeats the ease of cleanup required for pollution control purposes, and they are looking for an alternate means of protection. If a clean sump with adequate ventilation is not a vapor ignition source, then one way to protect the FRP piping would be with an intumescent coating.

Insulated FRP pipe
Insulating material advancements make it practical to insulate the entire surface of the pipe and fitting system. This is typically done with a thick intumescent coating such as Pitt-Charr© or its equivalent. This coating system has proven to be successful in enduring jet fire exposure, in both wet and dry conditions, consistent with Norwegian Fire Research Laboratory test requirements conducted by Southwest Research Institute. Intumescent coatings are typically applied by spray coating. This is an effective method to protect large surfaces but not small diameter pipe.

Furthermore, in the case of a fire, once intumescing occurs it must remain on the pipe when the pipe is impacted by the water hose streams used to fight the fire. As a result, a new development incorporates the intumescent coating into the filament winding process. The filament winding process provides an intumescent coating that is of consistent thickness and a smoother texture. It is also void-free and cannot be removed inadvertently. The end result is a FRP pipe capable of maintaining the serviceability of the piping in a fire for a minimum of three hours under flow conditions.

Currently available in diameters up to 40 inches, with an operating pressure rating of 150 psi at 200 degrees F, intumescent piping has achieved acceptance in the marine industry. This is because it combines the corrosion resistance historically provided by stainless steel and copper-nickel materials with the light weight, which is so important in marine construction.

 

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