Ductile Iron Pipe Classes Explained: Your Essential Guide to K vs. C

Selecting a suitable class of ductile iron pipe can be challenging for professional engineers. There are many different options available that are widely used in water supplies, wastewater management processes, and industrial applications. It’s significantly crucial to choose the most appropriate class depending on your project needs and budget.

Generally speaking, there are two classes of ductile iron pipes, each divided into more detailed groups. C and K classes are these two practical families mainly classified by working pressure and wall thickness in order.

The most popular classes in these two groups are K7, K8, K9, C25, C30, and C40, and each offers unique properties, prices, applications, and benefits. Experts and engineers should choose one based on project demands and budget. Today’s Yasmin Trading blog discusses these ductile iron pipe classes in more detail. It provides you with all the information you require to make the best decision.

K Class Vs. C Class Ductile Iron Pipes

In the first place, you need to understand the significant differences between the C class and the K class. It helps you select the suitable ductile iron pipe class. According to McWane Ductile, Here are some general differences explained between C and K classes before dicing in more detail.

• ISO 2531 was upgraded regarding C class in 2009. On the other hand, the K class follows the same international standard but was published in 2003.
• The K class is categorized based on the pipe’s wall thickness. Yet, C classes are defined according to the allowed working pressure.
• Comparing the nominal pressure ratio, this number is lower for the C class than the K class.
• The most popular products for the K class are K7, K8, and K9. We have C25, C30, and C40 for the C-class family.

Considering all these features and differences, it is important to make the final decision wisely. Each class offers unique applications and properties used in projects with different purposes.

Different K and C Classes of Ductile Iron Pipes

As explained below, the K and C class ductile iron pipes are widely used in different industries. Due to their high durability and resistance, their primary focus and application is water distribution systems. Different types of ductile iron pipe are classified into these two groups.

K7 Class in Ductile Iron Pipe classes

As mentioned, class K is divided into different groups by numbers. The number 7 in this type of ductile iron pipe indicates the internal pressure withstanding capacity. The following table discusses some technical properties of the K7 ductile iron pipe.

Pressure Rating	7 bar
Tensile Strength	Min. 420 MPa
Elongation at Break	Min. 10%
Modulus of Elasticity	1.7 x 10^10 Kg/M^2
Hardness	Max. 230 BHN
Standard Sizes	DN 80 mm to DN 2000 mm
External Coating Options	Red/Blue Epoxy, Black Bitumen, Zn & Zn-AI Coatings
Internal Coating Options	Cement Lining, Sulphate Resisting Cement
Joint Methods	T type, Mechanical joint, Self-anchor

Applications of K7 Class

Experts prefer to use the K class in water distribution systems. In fact, this type of ductile iron pipe is the best for municipal water supply, industrial applications, or infrastructure projects. It is considerably corrosion-resistant, which makes it a proper choice for such challenging environments.

K8 Class in Ductile Iron Pipe classes

The K8 class of ductile iron pipes is widely used in various infrastructure projects. Their long lifespan, high durability, and minimal maintenance requirements are only some of their unique features.

Tensile Strength	Min. 414 MPa
Yield Strength	42,000 psi
Elongation at Break	Min. 10%
Pressure Class	100 psi

These pipes are also lined with an internal coating to extend their lifespan and improve their corrosion resistance.

Applications of K8 Class

There are many different applications for the K8 class of ductile iron pipes. Engineers use them in water distribution systems, sewage conveyance, fire hydrant systems, buried pipelines, irrigation systems, and other industrial applications.

K9 Class in Ductile Iron Pipes

Tensile Strength	Min. 420 MPa
Yield Strength	43,500 psi
Elongation at Break	Min. 10%

These K9 ductile iron pipes are also easy to bend, making the installation process more manageable than usual. They provide experts with a high level of fire-resistant properties and good seismic resistance, ensuring long-term reliability.

Applications of K9 Class

Like the K8 class in ductile iron pipes, the K9 class is also used in water management systems and is the most prevalent application. These types of pipes are similar to the K8 class but with slightly different characteristics.

K12 Class in Ductile Iron Pipes

The last popular selection of K-class ductile iron pipes is K12. Due to their toughness, ductility, and corrosion resistance, they are used in specific and somewhat complex projects.

Wall Thickness	7 mm
Nominal Diameter	80mm to 1000mm
Rubber	SBR, NBR, EPDM
Zinc Coating	Min. 130gsm
Bitumen Coating	Min. 70μm
Pressure Rating	-10°C to 80°C
Effective Length	6m / 5.7m

Moreover, polyethylene encasement is used in K12 class ductile iron pipes to enhance its resistance in corrosive environments.

Applications of K12 Class

Besides applying K12 pipes in water distribution systems, they are used in long-distance water transmission. Generally speaking, these pipes are used in various industries, such as chemical, oil, and gas.

C20 Class in Ductile Iron Pipes

Class C ductile iron pipes are designed to handle higher working pressure. Different industrial applications are determined for the C20 class of pipes. A summary of technical parameters regarding this class of ductile iron pipes is provided.

Pressure Rating	100 psi
Tensile Strength	20,000 psi
External Coating Options	Zinc Primer Plus Bitumen, Epoxy Painting
Rubber	SBR, NBR
Bitumen Coating	Min. 70 μm
Zinc Coating	Min. 130 g/m²

These pipes also have an internal coating to prevent rust formation and increase longevity.

Applications of C20 Class

The C20 class ductile iron pipes are utilized in water supply projects, drainage, sewage, irrigation, and water pipelines. They also benefit agricultural networks due to their high-pressure endurance level.

C25 Class in Ductile Iron Pipes

These pipes have many properties in common with other C classes but with minor distinctions.

Pressure Rating	100 psi
Tensile Strength	25,000 psi

These pipes always provide experts with the best water distribution, irrigation, or industrial use solutions.

Applications of C25 Class

They offer many different industrial advantages, such as cooling water, process fluids, and chemical transport. The C25 class also plays a vital role in water management systems, just like other classes. Whether the project concerns fire hydrants or irrigation systems, these pipes guarantee a long-lasting performance.

C30 Class in Ductile Iron Pipes

Tensile strength is the most significant difference between this selection and other C classes. The table below provides more technical data.

Pressure Rating	100 psi
Tensile Strength	30,000 psi

These pips, as can other available selections, can withstand pressure and load effectively.

Applications of C30 Class

They have the same applications and usage as other C classes. However, their mechanical properties make them suitable for use as industrial pipelines.

C40 Class in Ductile Iron Pipes

As explained, these pipes are manufactured with the same pressure rating in the C class but with different tensile strengths.

Pressure Rating	100 psi
Tensile Strength	40,000 psi

Applications of C40 Class

They have similar applications to other C-class ductile iron pipes. However, experts prefer to use C40 pipes when higher tensile strength is needed in a specific project.