API 623 is a newer American Petroleum Institute standard for heavy-duty globe valves designed for demanding petroleum industry applications. BS 1873 is an older British standard with less stringent requirements for general industrial use.
Standard Development and Timeline
API 623 was first published in September 2013 and remains the current active version. This relatively new standard incorporates decades of industry experience and addresses the specific needs of modern petroleum facilities.
BS 1873, originally published in July 1952 and released in its second edition in April 1975, has remained largely unchanged for decades. This older standard doesn’t include many design improvements that newer specifications address.
Key Technical Differences
Size Coverage and Pressure Ratings
The main difference between API 623 vs BS 1873 is their scope. BS 1873 covers valves from 2 inches and smaller, extending to larger sizes with lower pressure ratings. API 623 focuses on valves 2 inches and larger, specifically targeting medium and high-pressure applications where reliability is critical.
Wall Thickness Requirements
API 623 mandates significantly thicker valve body walls than BS 1873. For example, most API 623 valve specifications require a minimum wall thickness that exceeds BS 1873 requirements, with only a few exceptions, like 2″ Class 150 or 12″ Class 300 configurations.
This increased wall thickness in API 623 valves provides better pressure-bearing capacity and improved corrosion resistance, making them suitable for harsh refinery environments.
Stem Diameter and Sealing Reliability
API 623 specifies larger stem diameters, particularly for high-pressure applications. For instance, a 6-inch Class 600 valve under API 623 uses a 48mm stem diameter, while the equivalent BS 1873 valve uses only 41.3mm.
The larger stem diameter reduces deformation under high pressure, minimizing leakage risk and improving overall sealing reliability. This larger stem design helps prevent failure in critical petroleum applications.
Flow Direction and Disc Design
API 623 Flow Restrictions
API 623 mandates unidirectional flow from low pressure to high pressure side. The disc design handles pressure from one direction, with the medium pressure helping achieve tight shutoff when closed.
BS 1873 Bidirectional Capability
BS 1873 supports bidirectional flow with different configurations. For low pressure conditions (≤40 MPa), flow moves from low to high pressure. For high pressure applications (>40 MPa), it allows high to low pressure flow with a dual-disc design that opens the smaller disc first to equalize pressure before lifting the main disc.
Bore Diameter and Flow Characteristics
API 623 typically specifies smaller bore diameters compared to BS 1873 for equivalent pressure classes. A 6-inch Class 600 API 623 valve has a 135mm bore diameter, while BS 1873 specifies 152mm.
The reduced bore in API 623 increases flow resistance but provides larger sealing contact area, beneficial for high-pressure sealing applications. However, this results in higher flow resistance and increased operating torque requirements.
Disc Guidance Requirements
API 623 requires complete disc guidance throughout the full stroke range. For pressure ratings of Class 900 and above, the disc must use non-stem guidance methods to prevent binding and ensure proper sealing.
BS 1873 only requires that the disc have some guiding mechanism without specifying the method or stroke requirements. This less specific guidance can lead to improper disc sealing or valve jamming during operation.
Practical Applications
BS 1873 globe valves are well-suited for general industrial applications with moderate pressures and standard operating conditions. They offer cost-effective solutions for water treatment, light chemical processing, and similar applications.
For demanding petroleum industry applications, API 623 globe valves provide the robust design needed for high-pressure, high-temperature, and corrosive service conditions found in refineries and petrochemical plants.
Knowing these differences becomes crucial when selecting appropriate valve standards for specific applications. For a better understanding of API valve standards, engineers can reference detailed specifications that outline proper selection criteria for various industrial environments.
Manufacturing Excellence
At XINTAI Valve Group, we manufacture both API 623 and BS 1873 globe valves to meet diverse industry requirements. Our 25+ years of experience ensures that each valve meets the specific demands of its intended application, whether that’s the robust construction required by API 623 for petroleum service or the versatile design of BS 1873 for general industrial use.
