Forged steel low-temperature stop valve

The forged steel low-temperature stop valve is a high-performance shut-off valve specially designed for harsh low-temperature conditions. Its main components are made of high-quality forged steel, featuring a dense structure, high strength, and excellent pressure-bearing performance. It is particularly suitable for the transportation and storage systems of deep-cold media such as liquefied natural gas (LNG), liquid oxygen, liquid nitrogen, liquid argon, and ethylene. The applicable temperature can reach as low as -196℃ (-320°F). This valve is designed and manufactured strictly in accordance with international authoritative standards such as API 602 (compact steel gate valve), MSS-SP-118, and BS 6364 (low-temperature valves). Its inspection and testing are carried out in accordance with the API 598 standard to ensure the reliability and safety of the product. 

The core challenge for applications in low temperatures - preventing the loss of cold energy and the intrusion of external heat leading to abnormal vaporization of the internal medium - is the most distinctive structural feature of this valve, which is the adoption of an elongated valve cover design. The slender valve neck elevates the packing chamber and the operating mechanism to a position far away from the low-temperature fluid, placing them in an area close to the ambient temperature. This effectively prevents the packing from freezing, maintains operational flexibility, and significantly reduces the heat transfer from the environment to the valve. According to the customer's connection and maintenance requirements, the valve offers two reliable valve cover designs: a bolted connection with an elastic graphite wrapped gasket sealing type valve cover (using 316 stainless steel with a flexible graphite wrapped gasket for easy disassembly and maintenance) and a threaded connection with a fully welded sealing type valve cover (fully welded, providing permanent sealing and eliminating leakage). 

In addition, the valve offers options for full-diameter (full bore) or reduced-diameter flow channels. The connection end can be selected as a socket-weld end that complies with ASME B16.11 or a (NPT) threaded end that complies with ANSI/ASME B1.20.1. It can also be customized according to customer requirements for special extended lengths, special low-temperature tests, and PTFE packing, demonstrating a high degree of customization capability. Its exposed stem support type (OS&Y) design makes the valve's open state clearly visible.

1. A specially designed extended-neck valve cover structure for extreme low temperatures 

The valve adopts a long-stem type valve cover, which is a key design for low-temperature valves. The long-neck structure forms an effective "cold bridge" interruption zone, significantly reducing the conduction of environmental heat to the low-temperature medium inside the valve body. This not only protects the packing box and the upper part of the valve stem from the effects of deep cold, avoids the freezing and jamming of the operating components, ensures that the valve can still be flexibly opened and closed under ultra-low temperatures, but more importantly, it minimizes heat loss and prevents dangerous overpressure caused by the continuous inflow of heat, ensuring the safety of the system. 

2. Two high-reliability valve cover connection and sealing schemes 

To meet different operating conditions and maintenance requirements, two classic valve cover designs are provided. The bolted valve cover is connected by high-strength bolts and nuts, and is sealed with a high-performance spiral gasket (usually 316 stainless steel with flexible graphite). Its advantage lies in the ease of on-site disassembly and internal maintenance. The welded valve cover is sealed through threaded connection and then fully welded, or directly connected with the valve body by full weld seams, achieving permanent static sealing and completely eliminating the risk of external leakage at this location. It is particularly suitable for scenarios where extreme sealing requirements are imposed or frequent disassembly is not allowed. 

3. Robust and durable forged steel structure and key component design 

The main body of the valve is made of forged steel, which has higher mechanical strength, better density and better low-temperature toughness compared to castings. Key structures include: the self-centering pressure plate and sleeve type packing box design, which ensures uniform force distribution of the packing and facilitates adjustment; the integral upper sealing seat, when the valve is fully open, a new seal is formed between the valve stem and the valve cover, allowing for the replacement of packing under pressure, thereby enhancing maintenance safety; the valve seat may be designed with pressure balance holes (mainly for gate valves and ball valve variants), to balance the pressure and reduce the operating torque. 

4. Comprehensive standard compliance and rigorous low-temperature testing 

From design, materials, manufacturing to testing, the valves follow strict international standards throughout the process. The design complies with API 602 and BS 6364 (specifically for low-temperature valves), ensuring the rationality of the structure. The manufacturing and inspection conform to MSS-SP-118 and API 598, guaranteeing the reliability of the quality. In particular, special low-temperature tests can be conducted according to customer requirements to simulate the sealing performance, operating torque and material toughness of the valves in a cryogenic environment, ensuring their flawless performance in practical applications. 

5. High degree of customization and flexible configuration options 

The product has fully taken into account the diversity of engineering applications and offers a wide range of customization options. Besides the standard socket-welding and threaded connection ends, customers can specify the extended length of the valve cover to adapt to the specific insulation layer thickness. They can also request the adoption of a soft-sealing stop valve structure or PTFE packing to meet the sealing requirements for specific media. This flexible configuration enables this valve to precisely match various complex cryogenic pipeline systems ranging from conventional liquefied gas plants to specialized research facilities.