Forged Steel vs. Cast Steel: A Deep Dive for Trunnion Mounted Fully Welded Ball Valves

Forged steel is the better choice if you need long-term strength, consistent sealing, and pressure resistance in a trunnion mounted fully welded ball valve. Cast steel makes more sense when the system runs at lower pressures, requires complex body shapes, or prioritizes cost over durability.

The Forging Process: Superior Strength and Grain Structure

Forged steel is created by heating solid metal and shaping it under controlled pressure. This compresses the material’s grain structure, making it denser and stronger.

In a fully welded body ball valve, this matters more than in standard valves. Forging ensures structural continuity, which helps maintain seat alignment and prevents deformation under high torque or thermal cycling. That’s critical in trunnion-mounted designs where the ball is supported at both ends.

Forged bodies also resist cracking, vibration fatigue, and mechanical stress far better than cast alternatives. This is one reason forged valves are commonly used in critical energy infrastructure where reliability is essential.

The Casting Process: Design Flexibility and Cost

Cast steel is made by melting metal and pouring it into a mold. The result is a near-net shape that requires less machining and allows for complex geometries.

This process is often used for large-diameter or uniquely shaped valve bodies. For example, a carbon steel fully welded ball valve designed for moderate flow control may be produced via casting to reduce fabrication time and cost.

Cast steel is often chosen when:

• The valve body has intricate or non-standard geometry
• The system operates at moderate pressure and low cycle frequency
• Project timelines or budgets require faster, lower-cost production

However, castings can introduce micro-voids, porosity, or inclusions that compromise sealing performance over time. While modern quality control minimizes these risks, cast steel remains less mechanically robust compared to forged materials.

Why Forged Steel is Preferred for High-Pressure Trunnion Valves

Reliable sealing under load

Trunnion designs rely on stable, balanced pressure to hold the ball in place. Forged steel maintains the structural integrity needed to support this seal, even during temperature fluctuations or pressure spikes.

Minimal risk of internal defects

Unlike casting, forging eliminates internal cavities and inconsistent density. That’s why a forged steel trunnion mounted fully welded ball valve provides higher assurance against leaks, blowouts, and deformation.

Withstands pressure cycling and vibration

Oil and gas pipelines, LNG systems, and refineries put valves under constant thermal and mechanical stress. Forged steel holds up where cast bodies might wear down, shift, or crack.

Certification-backed performance

PANS manufactures forged valves in compliance with API and TUV standards to ensure consistent performance in the most demanding conditions. For EPC contractors managing long-distance pipelines or buried systems, this ensures confidence from installation through to inspection.

Comparison: Forged vs. Cast for Trunnion Mounted Fully Welded Ball Valves

Feature	Forged Steel Valve	Cast Steel Valve
Sealing performance	Maintains seat alignment under load	Can shift under pressure or thermal cycling
Material density	High; compact grain structure	Moderate; may contain porosity or voids
Mechanical durability	Withstands pressure surges and frequent use	Suitable for steady, lower-pressure conditions
Design complexity	Better for simpler shapes	Allows more complex or large geometries
Certifications	Often meets API and TUV requirements	May not be approved for high-pressure service
Best use cases	Oil and gas, LNG, buried pipelines, critical systems	HVAC, water, and cost-sensitive general applications

When Is a Cast Body Acceptable?

Cast steel is a reasonable choice when:

• The operating pressure is low to moderate
• Valve geometry is complex or oversized
• Tight budget constraints exist
• The valve won’t face frequent actuation or thermal cycling

A stainless steel fully welded ball valve produced via casting can serve reliably in municipal water systems, HVAC loops, or food-grade applications, especially when surface finish or corrosion resistance is more important than raw strength.

But in pipelines where access is limited and failure is costly, cast steel still introduces more risk than forged material.

Conclusion: Specifying Forged Steel for Maximum Reliability

When it comes to sealing integrity, fatigue resistance, and safety in trunnion-mounted configurations, forged steel is the clear winner. A forged steel trunnion mounted fully welded ball valve offers superior structure, fewer defects, and greater resistance to stress over time, making it ideal for buried or high-pressure systems.

At PANS, we manufacture both carbon steel fully welded ball valves and stainless steel fully welded ball valves using forged materials that meet CE, API, and TUV standards. Our fully welded solutions are engineered to help engineering and procurement teams reduce failure risk and increase system uptime.

You can explore more about how casting and forging affect performance across valve types in our detailed guide on cast steel vs. forged steel valves.

Or contact the PANS team to discuss your specs directly.