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The fire water supply and fire extinguishing system pipelines mainly follow the following standards:

Chinese National Standard (GB) :

GB 50974-2014"Technical Code for Fire Water Supply and Fire Hydrant System": This is the core code for domestic fire water supply systems, which makes mandatory regulations on pipe material selection, design pressure, installation, testing, acceptance, etc. It stipulates the basic performance requirements for fire protection pipelines (such as pressure-bearing capacity, corrosion resistance, interface form, etc.) and allows the use of other national standard products that meet its requirements.

Specific pipe product standards:

• Galvanized steel pipes (welded steel pipes): GB/T 3091-2015 "Welded Steel Pipes for Low-pressure Fluid Conveyance" (usually hot-dip galvanized steel pipes are selected). The most widely used standard.

• Galvanized steel pipe (seamless steel pipe): GB/T 8163-2018 "Seamless Steel Pipes for Conveying Fluids" (usually treated with hot-dip galvanizing).

• Ductile iron pipe: GB/T 13295-2019 "Ductile Iron Pipes, Fittings and Accessories for Water and Gas Pipelines". It is often used in buried pipelines.

• Stainless steel pipes: GB/T 19228.2-2011 "Stainless Steel Compression fittings - Part 2: Thin-walled stainless steel pipes for connection", GB/T 12771-2019 "Stainless Steel Welded Pipes for Fluid Conveyance", etc.

• Copper tubes: GB/T 18033-2017 "Seamless Copper Water Pipes and Copper Gas Pipes".

• Chlorinated polyvinyl chloride (PVC-C): GB/T 18993.2-2003 "Chlorinated Polyvinyl chloride (PVC-C) Piping systems for cold and hot water - Part 2: Pipes" (For wet systems only and subject to specific conditions).

International/Foreign common standards:

ISO: Relevant standards of the International Organization for Standardization.

ASTM (USA): such as ASTM A53 (galvanized steel pipes), ASTM A106 (seamless steel pipes), ASTM A795 (welded black steel pipes and galvanized steel pipes for fire protection), etc. In some projects (such as foreign-funded or foreign-related projects), it may be necessary to refer to.

DIN (Germany): A German industrial standard that is sometimes referred to.

EN (European Union): For example, EN 10312 applies to stainless steel pipes.

BS (UK): Such as BS 1387 steel pipe.

Based on the above standards and safety requirements, fire protection pipes must possess the following key characteristics:

1.High pressure-bearing capacity: (This is the most fundamental and important requirement.)

• It must be capable of withstanding the maximum pressure of the system during normal operation (working pressure), the moment the fire pump starts (water hammer pressure), and during the system pressure test (usually 1.5 times the working pressure and ≥1.4MPa).

• The selection of pipe material and wall thickness must be strictly calculated to ensure that it does not crack or deform severely under the most unfavorable working conditions.

2.Excellent corrosion resistance

Internal corrosion:

Corrosion that may be caused by long-term static storage or fire-fighting water use. It is necessary to ensure that the inner wall of the pipe does not form scale or rust, to avoid a reduction in the flow area and a decrease in the pressure-bearing capacity.

External corrosion:

• Exposed or indoor installation: It needs to adapt to air humidity, possible chemical environments, etc.

• Buried underground: It needs to be able to resist soil corrosion and stray current corrosion. Generally, it is required that the outer wall have a reliable anti-corrosion coating (such as epoxy coal tar asphalt, PE coating, etc.), and when galvanized pipes are buried underground, caution should be exercised or additional anti-corrosion measures should be added.

• Humid/salt spray environments, such as seaports and coastal areas, have higher requirements for stainless steel pipes or reinforced anti-corrosion galvanized pipes.

The common practice is: for indoor exposed installation or ceiling installation, hot-dip galvanized steel pipes (with inner or outer galvanization) are mostly used, while for underground installation, ductile iron pipes with enhanced anti-corrosion treatment (or welded steel pipes) are mostly adopted. Stainless steel and copper pipes themselves have excellent corrosion resistance, but they are relatively expensive.

Reliable sealing performance and interface strength:

The connection methods of pipes (threaded, grooved, flange, welded, crimped, etc.) must ensure that they do not leak or come apart under high pressure and water hammer impact. The interface strength should be close to or equivalent to the strength of the pipe itself.

Grooved connection (clamp type) is widely used due to its convenience, reliability and the ability to allow a certain degree of deflection (but fire-fighting certified products must be selected). Flange connections are also commonly used in large-diameter pipes, pump rooms, and water tank outlets, etc.

Smaller flow resistance (smooth inner wall) :

• The inner wall should be as smooth and flat as possible (the inner wall of galvanized steel pipes after hot-dip galvanizing is smoother than that of black iron pipes, the inner cement layer of ductile iron pipes is also smoother, and stainless steel pipes and copper pipes are smooth by themselves), to reduce head loss (along-the-way resistance), and ensure that the fire-fighting water volume and water pressure meet the fire-fighting requirements.

• Avoid a significant increase in resistance after rusting and scaling on the inner wall.

Good strength and rigidity:

• Maintain shape stability under pressure and prevent excessive deformation.

• It can maintain structural integrity under the action of external forces such as installation, earthquakes and soil settlement. Grooved connections have certain advantages in this aspect (allowing for small-angle deflection).

Fire resistance performance:

Although the flow inside the pipe is a mixture of water or foam, as a supporting component or exposed object in a fire environment, the material of the pipe itself should have sufficient fire resistance. Metal pipes naturally meet this requirement.

Restricted plastic pipes: Plastic pipes such as PVC-C can only be used in the water distribution network of wet systems, and there are strict restrictions on the ambient temperature, location (such as inside the ceiling), installation method, etc. (such as not being able to pass through fire compartments, requiring fire protection, etc.), and they are strictly prohibited from being used in the section of the pipeline from the main outlet pipe of the water pump to the front of the wet alarm valve, which may be in a high-pressure and water-free state at any time.

Long service life:

Fire protection systems are usually designed to have a long service life (several decades). As a core component, the materials and anti-corrosion measures of pipelines must ensure long-term reliability and reduce the frequency of maintenance and replacement.

Easy to process and install:

The materials should be easy to cut, bend (such as small-diameter pipes), connect and meet the installation requirements of complex building structures. This is also one of the reasons for the popularity of grooved connections.

Safe and non-toxic (for water supply) :

The pipe materials and internal coatings for transporting water sources for both domestic and fire protection purposes should be safe and non-toxic, and meet the drinking water standards (some plastic pipes have such requirements).

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The core of fire protection pipes lies in: at extremely critical moments (when a fire breaks out), it is necessary to reliably deliver sufficient pressure and flow of fire-fighting medium (water or foam mixture) to the fire point. This determines that it must strictly comply with national standards (especially GB 50974) and relevant pipe product standards, and possess characteristics such as high strength, high pressure resistance, corrosion resistance (both inside and outside), low resistance, reliable interfaces, fire resistance (or limited use of flammable materials), and long service life.

The selection of pipe materials (such as galvanized steel pipes, ductile iron pipes, stainless steel pipes, etc.) needs to comprehensively consider the system design pressure, usage environment (indoor/buried/harsh environment), cost, installation convenience and the specific requirements of the specifications. Galvanized steel pipes (especially hot-dip galvanized ones) remain the most widely used type of pipe in fire protection systems due to their comprehensive performance and economy.

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