ISO 15761 is a standard for small-bore steel valves used in the oil and gas industry, covering sizes from DN 15 to DN 100 and pressure classes from Class 150 to Class 2500. It applies to gate valves, globe valves, and check valves.   These valves are not produced in a single step, but through a sequential manufacturing chain. The quality of each stage directly affects the next. Understanding this chain helps identify critical issues more efficiently during valve selection, compliance review, and supplier evaluation.   Complete Manufacturing Process   Step 1: Material Selection   Material determines the applicable service conditions and is the starting point of the entire process. Common materials under ISO 15761 include: ●  Carbon steel for general oil and gas service ●  Low-temperature carbon steel for cryogenic or low-temperature conditions (e.g., LNG applications) ●  Stainless steel for corrosive media If the service contains hydrogen sulfide (H₂S), materials must also comply with NACE MR0175 / ISO 15156 to prevent sulfide stress cracking. This requirement is applied independently of ISO 15761. Incorrect material selection cannot be compensated by subsequent process control.   Step 2: Forging   This step determines the internal quality of the valve body. Forging involves forming heated metal under pressure, resulting in a dense internal structure with a lower probability of defects. It is typically preferred for high-pressure or high-reliability applications. For Class 800 and above, forged bodies are commonly selected in engineering practice to reduce internal defect risks and improve structural reliability, although final selection depends on project specifications.   Step 3: Machining   After forming, precision machining is performed to meet dimensional and sealing requirements. Sealing surface machining is a critical control point. The contact surfaces between the seat and disc must undergo multiple machining and lapping processes to achieve specified flatness and surface roughness, directly affecting shut-off performance. The stem surface must also meet low roughness requirements to ensure long-term packing sealing stability. Excessive roughness accelerates packing wear and may lead to external leakage during operation.   Step 4: Welding (Hardfacing of Sealing Surfaces)   This process is used to enhance sealing surface performance. For wear or corrosion-resistant applications, sealing surfaces are typically overlaid with hard alloys such as Stellite to improve resistance. During welding, heat input and dilution rate must be controlled to prevent excessive mixing of the base material, which would reduce surface hardness. The hardfacing layer is usually required to meet a specified hardness range (e.g., Stellite typically ≥ HRC 35–45). This process must be performed by qualified welders, with welding procedure specifications (WPS), procedure qualification records (PQR...

In applications requiring remote operation or frequent switching, an automatic line blind valve is typically equipped with either electric or hydraulic actuation. The fundamental difference between the two does not lie in whether they can be used, but in their load capacity, response characteristics, environmental adaptability, and system complexity.   1. Electric Actuation (Electric Actuated Line Blind Valve)   Electric actuation uses a motor combined with a reduction gearbox to generate torque, driving the blind plate to complete the switching operation. Selection logic: ● If power supply on site is stable → electric actuation should be prioritized ● If remote control or automation integration (DCS/PLC) is required → electric actuation is more straightforward ● If switching frequency is relatively high → electric actuation allows better control of operation speed   Key features: ● Simple control: can be directly integrated into control systems, enabling remote operation and position feedback ● Compact structure: no additional hydraulic power unit required ● Lower maintenance requirements: routine checks mainly involve the motor and gearbox   Limitations: ● If valve size is large or high thrust is required → electric actuation may have insufficient torque ● If the environment is high-temperature, hazardous (explosive), or dusty → higher electrical protection standards are required (e.g., ATEX) ● If power supply is unstable or frequently interrupted → reliability may decrease   Conclusion:If the application involves standard automation requirements and moderate load conditions, electric actuation is generally the preferred solution.   2. Hydraulic Actuation (Hydraulic Actuated Line Blind Valve)   Hydraulic actuation generates thrust through hydraulic fluid pressure, making it suitable for high-load applications. Selection logic: ●  If valve size is large (e.g., DN300 and above) → hydraulic actuation should be prioritized ●  If high thrust is required or resistance/sticking needs to be overcome → hydraulic actuation is more stable ●  If a hydraulic system is already available on site → integration cost is lower   Key features: ●  High thrust output: suitable for heavy-duty blind plates or high-pressure pipelines ●  Stable operation: provides continuous output with strong resistance to shock loads ●  Good controllability: enables precise control through pressure regulation   Limitations: ●  If no hydraulic power unit is available on site → system complexity increases ●  If ambient temperature variation is significant → hydraulic fluid performance may fluctuate ●  If maintenance is insufficient → leakage issues are more likely to occur   Conclusion:If the application involves high load and high reliabili...

Gate valves and blind valves are both used for pipeline isolation, but they operate on fundamentally different principles.In industrial piping systems, if the objective is true physical isolation (positive isolation), then a blind valve (Blind Valve / Line Blind Valve) is generally more reliable than conventional valves. Instead of relying on seat sealing, it isolates the medium through a solid blind plate, which defines both its application scope and engineering value. The key features of a blind valve can be understood from an engineering perspective as follows:   1. Absolute Physical Isolation   If zero leakage is required, then conventional valves (such as gate valves or ball valves) introduce risk, as their performance depends on sealing integrity. Blind valves follow a different logic: ▶ If a solid plate is inserted, then the flow is completely blocked▶ If the blind plate is correctly positioned, then sealing failure is no longer a concern This makes blind valves more suitable for:         ● Oil & gas pipeline isolation         ● Flammable media (petroleum, LNG, chemicals)         ● High temperature steam systems   Engineering conclusion:If the project requires verifiable isolation, then a blind valve should be prioritized over sealing-dependent industrial valves.   2. Inline Operation Capability   Traditional spade and spacer blinds typically require flange disassembly, which increases operational complexity and introduces safety risks. Blind valves (such as sliding blind valves and swing blind valves) are designed with a different approach: ▶ If frequent switching between operation and maintenance is required, then manual intervention must be minimized▶ If shutdown is not permitted, then switching must be performed under pressurized pipeline conditions (subject to specific design) Therefore:         ● Sliding Blind Valve: suitable for limited space and higher automation requirements         ● Swing Blind Valve: simple structure, suitable for medium to low switching frequency         ● Spectacle Blind Valve: suitable for low-frequency operation and cost-sensitive projects   Engineering conclusion:If maintenance is frequent or shutdown is not feasible, then a blind valve with inline operation capability should be prioritized.   3. Mechanical Reliability   The reliability of a blind valve does not depend on complex sealing systems, but on:         ● Mechanical structural stability         ● Material strength (such as A105, WCB, F22, LF2)         ● Actuation method (manual, gear-operated, or hydraulic) ▶ If the service conditions involve high temperature, high pressure, or corrosive media, then sealing-based valves are more prone to failure▶ If...