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Quality Customized High-Temperature Strength Corrosion Resistant Fatigue Resistant Pre-valve Cover Bolt for Steam Turbine factory
Quality Customized High-Temperature Strength Corrosion Resistant Fatigue Resistant Pre-valve Cover Bolt for Steam Turbine factory

Customized High-Temperature Strength Corrosion Resistant Fatigue Resistant Pre-valve Cover Bolt for Steam Turbine

Tags

steam turbine components

steam turbine spare parts

steam turbine spares
Product Summary
Customized pre-valve cover bolt for steam turbines, made from martensitic heat-resistant stainless steel for high-temperature strength up to 580°C, excellent corrosion resistance, and reliable performance under thermal cycling and start-stop conditions.

Product Details

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High-Temperature Strength Pre-valve Cover Bolt

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Corrosion Resistant Steam Turbine Bolt

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Fatigue Resistant Valve Cover Fastener
High-Temperature Strength: Creep Resistance And Relaxation Resistance
Corrosion Resistance: Resists Steam Oxidation And Intergranular Corrosion
Fatigue Resistance: Good Thermal Fatigue Resistance And Impact Toughness
Thermal Expansion: Matched With Valve Body Materials
Material: Martensitic Heat-resistant Stainless Steel
Operating Temperature: Up To 580℃
Product Description
Customized Pre-valve Cover Bolt for Steam Turbine
The pre-valve cover bolt serves as a critical "safety lock" inside the intermediate-pressure main steam valve. Operating long-term in an environment of high-temperature reheat steam, it must withstand massive compressive clamping force between the valve cover and valve body, as well as drastic temperature fluctuations during unit start-up and shutdown. Improper material selection may cause minor issues such as preload relaxation and steam leakage, or severe failures including bolt fracture and ejection of the valve cover.
Critical Performance Requirements
  • High-Temperature Strength: Creep Resistance and Relaxation Resistance The steam temperature inside the pre-valve generally exceeds 500℃. Ordinary carbon steel bolts rapidly soften at this temperature and undergo creep deformation, accompanied by preload decay. Consequently, the bolt material must deliver sufficient high-temperature rupture strength and stress relaxation resistance, maintaining stable clamping force during prolonged hot operation and preventing seal failure induced by stress relaxation.
  • Corrosion Resistance: Steam Oxidation Protection High-temperature superheated steam imposes strong oxidation on metals. If the bolt has inadequate corrosion resistance, oxide scale will form on its surface, resulting in thread seizing and creating huge difficulties for subsequent maintenance. Martensitic stainless steel containing alloying elements such as chromium, nickel and molybdenum can form a dense oxide film on the surface, effectively resisting steam corrosion and intergranular corrosion and greatly extending bolt service life.
  • Fatigue Resistance and Impact Toughness At every unit start-up and shutdown, the pre-valve cover bolt undergoes thermal cycling from ambient temperature to high temperature and back to ambient temperature, together with impact loads generated during valve operation. The material must feature good thermal fatigue resistance and impact toughness. Otherwise, cracks tend to initiate at thread roots under alternating stress, eventually leading to fatigue fracture.
  • Matched Thermal Expansion: Consistent Thermal Deformation The linear expansion coefficients of the bolt, valve cover and valve body must be matched. A large discrepancy in thermal expansion between the bolt and flange will lead to excessive preload that crushes the gasket or insufficient preload causing leakage under hot conditions. Premium heat-resistant alloy steel has thermal expansion characteristics close to those of steam turbine valve body materials, maintaining a reasonable stress level across the full temperature range and ensuring reliable sealing.
Our Product Adaptation Advantages
To meet the severe operating conditions of pre-valve cover bolts, we adopt martensitic heat-resistant stainless steel. It features outstanding high-temperature strength and excellent intergranular corrosion resistance, with an applicable temperature up to 580℃, fully covering reheat steam working conditions. Boasting high thread accuracy and sufficient toughness margin, it retains stable preload under thermal shocks from frequent start-stop cycles. It is an ideal option to guarantee long-term sealing reliability of the pre-valve.

Mr. Tom Hu

General Manager

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