Stainless steel industrial-grade valves

Analysis of the Causes of Sticking in ZZYP Gas Control Valves and Corresponding Improvements

1. Introduction Rizhao Iron & Steel Co., Ltd.’s Power Plant Gas Comprehensive Utilization Power Generation Workshop currently operates eight 50 MW blast furnace gas-fired generating units, with a total installed capacity of 400 MW. It is currently the largest blast furnace gas–based cogeneration plant among domestic metallurgical enterprises, supported by eight 220 t/h boilers whose fuel is the surplus blast furnace gas generated during ironmaking. 2. Causes Analysis Based on years of experience in operating these regulating valves and thorough research, we have identified the following primary causes of valve sticking: 2.1 Improper Installation Method Most valves are currently installed vertically, with the valve disc axis perpendicular to the horizontal plane. While this arrangement ensures that the actuator is located at the top of the gas pipeline, the rear bearing of the valve is positioned at the bottom, where moisture and impurities in the gas tend to settle or accumulate over time. This buildup gradually fills the clearance between the bearing and the shaft, leading to corrosion and eventual jamming of the valve shaft. 2.2 Unreasonable Design Structure Repeated disassembly and maintenance have revealed that the clearance between the valve stem bushing and the valve body is often filled with foreign matter such as sludge, water, and rust deposits. Moreover, the original design features an excessively long bushing, causing the front and rear bushings to bear the frictional forces generated by the reciprocating motion of the valve stem. Over time, dust in the gas and rust particles from the pipeline easily enter these clearances, increasing rotational resistance. The accumulated debris eventually fills the gaps, effectively welding the valve stem, bushing, and valve body together and severely restricting the valve’s ability to move freely. 2.3 Gas Corrosion Currently, all blast furnace gas pipelines in domestic steel plants suffer from severe corrosion. The most noticeable manifestation is frequent pitting and cracking of expansion joints, resulting in gas leaks along the pipeline. Corroded valves and pressure-reducing devices also fail to operate properly. The corrosive nature of blast furnace gas poses serious safety risks to both equipment operation and the integrity of the gas pipeline network. Our own gas pipelines likewise exhibit localized corrosion, including gas leakage through perforations and dripping condensate from expansion joint bellows. These conditions clearly have a significant impact on the valves. To analyze the extent of gas corrosion, we collected gas samples from two separate gas pipelines in the power generation workshop for laboratory analysis. Table 1: Composition Analysis of Blast Furnace Gas (%VOL) High-temperature components such as H2, CO, and H2O also exert considerable corrosive effects on steel. Given the high water content in the gas—particularly since the power generation system is typically located at the downstream end of the gas network—the pipeline often contains substantial amounts of condensate. Testing has shown that the pH of condensate in Rizhao Steel’s gas pipelines ranges from approximately 5 to 6, with an electrical conductivity of about 2762 μS/cm. In addition, the condensate contains high concentrations of iron ions, chloride ions, and sulfate ions. Some studies indicate that Cl⁻ and SO₄²⁻ can induce stress corrosion. In terms of corrosion morphology in gas pipelines and associated equipment, non-uniform corrosion predominates, specifically manifesting as: (1) under-deposit corrosion, also known as crevice corrosion; (2) pitting corrosion; (3) localized corrosion; (4) erosion-corrosion; and (5) stress corrosion. The presence of condensate inherently increases the corrosivity of the pipeline, with higher conductivity accelerating the corrosion rate. The combined effect of contamination and corrosive properties in the gas medium is a major contributing factor to valve sticking. 2.4 Improper Operation Since the current blast furnace gas regulating valves do not operate in a closed-loop automatic control mode, their opening degrees are manually set by operators via the DCS. When the load remains relatively stable for extended periods, the valve disc may stay fixed at a particular angle without regular movement, which can also lead to inflexible valve operation. 3. Improvement Measures 3.1 Installation Method The installation method should be changed from vertical to horizontal to prevent impurities, moisture, and contaminants in the gas from settling in the bushing clearance due to gravity. 3.2 Reducing Gas Acidity Given the significant harm caused by acidic gas to the entire gas pipeline system, large valves, expansion joints, and other components, this issue has drawn the attention of senior management. The company has adopted a neutralization strategy by injecting alkaline solution into the gas pipeline at the TRT inlet. Analysis of condensate samples from the power generation gas pipeline indicates a pH value of around 6. 3.3 Improving the Diseased Bushing Design The bushing dimensions should be reduced: the front bushing length should be shortened from 400 mm to 200 mm, and the rear bushing length from 800 mm to 200 mm. In terms of material, stainless steel, as specified in JB/T1759-2010, should be replaced with cast copper alloy, grade ZCuSn10Pb1. Even if minor scaling occurs inside the clearance, the significantly reduced bushing length will cut friction by one-half to three-quarters, making valve operation much smoother. We are also offering this improvement proposal free of charge to the supplier, requesting that future valve spare parts be custom-made according to our specifications. During maintenance inspections, it was also found that the packing gland on the upper part of the valve stem was overly tight, and in some cases, the packing gland screws broke due to excessive torque. When re-machining the packing gland, the clearance should be appropriately increased, and the gap should be thoroughly greased to prevent gas leakage. 3.4 Process Improvements The operating procedures should be revised to require boiler operators to conduct operational tests on all blast furnace gas regulating valves every shift and meticulously record the setpoint and feedback values in designated forms. This will prevent the valve disc from remaining fixed at a single opening degree for prolonged periods, thereby reducing the risk of scaling and seizing of the valve stem. 3.5 Maintenance Strategy Four spare regulating valves should be procured, and a rotating replacement maintenance approach should be implemented. Whenever there is an opportunity to shut down the boiler, the valve exhibiting the most severe sticking, as determined by the operators’ routine testing, should be replaced. The removed valve should then undergo disassembly, inspection, and refurbishment, followed by lubrication and maintenance before being returned to service, thus minimizing downtime. 3.6 Lubrication and Maintenance Monthly lubrication and maintenance should be performed on the packing glands and front and rear bearings of online-operating blast furnace gas regulating valves, with thorough equipment inspections conducted to promptly monitor operating conditions. Instrumentation and control personnel should ensure that the control components (valve positioners) are protected against rain and corrosion, regularly check air supply pressure, inspect all air connection points for blockages or leaks, and verify the quality of compressed air. In addition, the compressed air supply pressure should be appropriately increased to enhance the output force of the actuators. Instrumentation personnel should adjust the pressure regulator upstream of the positioner to maintain a stable pressure of around 0.5 MPa. Each time a major boiler overhaul is scheduled, the pipeline should be cleaned to remove sludge, debris, and other impurities, thereby reducing wear and corrosion. 4. Implementation Results By establishing revised operating procedures and ensuring that operators continuously monitor the status of the regulating valves, we have achieved comprehensive equipment management—a practical attempt at condition-based maintenance. Following these improvements, the frequency of maintenance has decreased, with the average maintenance interval extending from the original 2–3 months to 6–8 months. The workload for maintenance personnel has been significantly reduced, and crucially, the flexibility and reliability of the regulating valves have been ensured, providing robust equipment support for the safe and stable operation of the boilers. This solution can also be extended to other large valves on the gas pipeline network.

Current National Standards Catalog (Valves)

Serial No. Standard Number Standard Name Replaced Standard Number Adoption Status 1 GB/T 8464-1998 Internal-threaded Valves for Plumbing GB 8464-87 GB 8465.1–.8-87 2 GB/T 12220-1989 General-purpose Valves—Marking JB 106-78 MOD ISO 5209-1977 3 GB/T 12221-1989 Flanged Metal Valves—Structural Lengths JB 97–98-75 JB 1686–1688-75 NEQ ISO 5752-1982 4 GB/T 12222-1989 Multi-turn Valves—Connection of Actuating Devices MOD ISO 5210/1~/3-1982 5 GB/T 12223-1989 Partial-turn Valves—Connection of Actuating Devices MOD ISO 5211/1~/3-1982 6 GB/T 12224-1989 Steel Valves—General Requirements 7 GB/T 12225-1989 General-purpose Valves—Technical Specifications for Copper Alloy Castings 8 GB/T 12226-1989 General-purpose Valves—Technical Specifications for Gray Iron Castings 9 GB/T 12227-1989 General-purpose Valves—Technical Specifications for Ductile Iron Castings 10 GB/T 12228-1989 General-purpose Valves—Technical Specifications for Carbon Steel Forgings 11 GB/T 12229-1989 General-purpose Valves—Technical Specifications for Carbon Steel Castings 12 GB/T 12230-1989 General-purpose Valves—Technical Specifications for Austenitic Steel Castings 13 GB/T 12232-1989 General-purpose Valves—Flanged Iron Gate Valves 14 GB/T 12233-1989 General-purpose Valves—Iron Globe and Lift Check Valves 15 GB/T 12234-1989 General-purpose Valves—Flanged and Butt-welded Steel Gate Valves 16 GB/T 12235-1989 General-purpose Valves—Flanged Steel Globe and Lift Check Valves 17 GB/T 12236-1989 General-purpose Valves—Steel Swing Check Valves 18 GB/T 12237-1989 General-purpose Valves—Flanged and Butt-welded Steel Ball Valves 19 GB/T 12238-1989 General-purpose Valves—Flanged and Wafer-connected Butterfly Valves NEQ BS 5155-1984 20 GB/T 12239-1989 General-purpose Valves—Diaphragm Valves 21 GB/T 12240-1989 General-purpose Valves—Iron Plug Valves 22 GB/T 12241-1989 Safety Valves—General Requirements MOD ISO 4126-1984 23 GB/T 12242-1989 Safety Valves—Test Methods for Performance 24 GB/T 12243-1989 Spring-loaded Direct-acting Safety Valves NEQ JIS 8210-1978 25 GB/T 12244-1989 Pressure-reducing Valves—General Requirements 26 GB/T 12245-1989 Pressure-reducing Valves—Test Methods for Performance 27 GB/T 12246-1989 Pilot-operated Pressure-reducing Valves 28 GB/T 12247-1989 Steam Traps—Classification MOD ISO 6704-1982 29 GB/T 12248-1989 Steam Traps—Terminology NEQ ISO 6552-1980 30 GB/T 12249-1989 Steam Traps—Marking NEQ ISO 6553-1980 31 GB/T 12250-1989 Steam Traps—Structural Lengths JB 2762-79 NEQ ISO 6554-1980 32 GB/T 12251-1989 Steam Traps—Test Methods GB 4981-85 NEQ ISO 6948-1981 33 GB/T 13927-1992 General-purpose Valves—Pressure Testing NEQ ISO 5208-1982 34 GB/T 13932-1992 General-purpose Valves—Iron Swing Check Valves 35 GB/T 15185-1994 Iron and Copper Ball Valves 36 GB/T 15188.1-1994 Valve Structural Lengths—Butt-welded Valves JB 96-75 JB 1686-75 37 GB/T 15188.2-1994 Valve Structural Lengths—Wafer-connected Valves 38 GB/T 15188.3-1994 Valve Structural Lengths—Internal-threaded Valves JB 96-75 JB 1686-75 39 GB/T 15188.4-1994 Valve Structural Lengths—External-threaded Valves JB 96-75 JB 1686-75

New Opportunities in the Valve Market, Booming Industry Outlook

China’s valve industry is experiencing robust growth; however, despite the generally favorable industry outlook, certain concerns remain—particularly the fact that domestic valve manufacturers are predominantly low-end, small-scale, family-run operations. This poses a significant constraint and bottleneck for the sector’s future development. Given the relatively late start of China’s valve industry, the country is still in a developmental phase and lags behind advanced international standards. Many critical valve types continue to rely on imports, and numerous valves lack core technologies. Coupled with limitations in automation and control capabilities, China’s high-end valve technology remains at a disadvantage compared with global leaders. Meanwhile, competition in the valve market is intensifying, with some low-end segments already saturated and characterized by oversupply. Consequently, achieving balanced, sustainable development across both high- and low-end segments has become one of the most pressing challenges facing Chinese valve manufacturers. At present, some Chinese valve producers have reached internationally advanced levels. Although the overall performance of China’s valve industry has improved substantially, product quality remains inconsistent; phenomena such as leakage, emission, dripping, and seepage are still common in domestically produced valves. In addition, China’s capability to provide comprehensive valve systems and supporting components still falls short of that of developed countries. Intense market competition and the saturation of low-end segments have created an oversupply situation, making it increasingly difficult for small and medium-sized enterprises to thrive. Even for higher-tech products, competition in the international market is fierce. Today, China can supply a wide range of valves, including heating valves, environmental protection valves, and building-use valves. However, the high-end segment continues to depend heavily on imports—a key area where China must focus its efforts to achieve breakthroughs and truly drive the industry forward. Since last year, the path toward domesticating high-end valves has grown increasingly challenging. Basic components have now become a major bottleneck hindering the upgrade of China’s manufacturing sector toward higher value-added production. During the 12th Five-Year Plan period, the government will further intensify efforts to localize high-end equipment components. The feasibility of import substitution varies significantly across different sub-sectors; in particular, high-end valves urgently require stronger policy guidance and greater support for research and development. The lack of significant progress in the transformation and upgrading of the valve industry stems from multiple factors, one of which relates to past practices. Historically, emphasis has been placed on product development while neglecting market research and industrialization. Specifically, there has been a tendency to prioritize technology over process engineering and to focus on R&D rather than scaling up production. As a result, although our products may appear sophisticated on paper, boasting advanced features and performance metrics, they often fail shortly after being deployed by end-users. Alternatively, even when the products themselves function adequately, their high manufacturing costs render them uncompetitive in the market. Of course, this situation is also partly attributable to policy priorities: for too long, the focus has been on the quantity of research outcomes and patents, with an emphasis on filling gaps and establishing a presence in the market. While these efforts have achieved important milestones, they have not sufficiently prioritized translating innovations into commercially viable, large-scale industrial applications.

The Petrochemical Industry Drives the Industrial Valves and Actuators Market

The global industrial valves and actuators market for the oil and gas industry is the largest revenue driver. Consequently, the exploration of new oil and gas fields—coupled with increased investment—and the expansion of refineries and pipelines in key growth regions are likely to have a significant impact on market prospects. The market will also benefit from rising demand for automation and infrastructure modernization. According to Frost & Sullivan’s strategic analysis of the global industrial valves and actuators market, the market generated USD 1.837 billion in revenue in 2012 (compared with USD 1.765 billion in the 2011 base year), and is projected to reach USD 2.210 billion by 2016. Niranjan Paul, Associate Research Analyst for Industrial Automation and Process Control at Frost & Sullivan, notes: “Currently, major oil exploration activities are concentrated in Africa, South America, the Middle East, and Russia. These regions therefore represent a focal point for industrial valves and actuators manufacturers and offer sustained growth opportunities.” In the Middle East, Iraq is emerging as a key market for major oil companies. The country is also expected to spend nearly USD 27.0 billion on new power generation and transmission–distribution projects between 2012 and 2017. These trends underscore Iraq’s growing importance as a market for industrial valves and actuators. However, political uncertainty in North Africa and the Middle East is impacting the oil and gas industry. Moreover, sanctions imposed on Iran and Syria—key markets for oil, gas, and power-generation sectors—could restrain revenue growth for industrial valves and actuators manufacturers. In more developed regions such as North America and Europe, environmental legislation plays a pivotal role in shaping market dynamics. Here, stringent regulations may exert cross-industry effects across end-user sectors. Paul explains: “In the oil and gas sector, regulations aimed at reducing air pollution seek to curb emissions of volatile organic compounds (VOCs) that contribute to smog formation; accordingly, the design of process equipment—including valves and actuators—will help achieve reductions in plant emissions.” Even as leading industrial valves and actuators manufacturers capitalize on growth opportunities, their profit margins are under pressure due to price sensitivity across end-user industries. As a result, companies are compelled to adopt aggressive pricing strategies. “The market may see increasing demand for customized solutions tailored to specific end-user applications,” Paul adds. “Market participants must not only meet this demand but also address other critical customer needs, such as high-quality after-sales service and shorter delivery times.” The strategic analysis of the global industrial valves and actuators market is part of Frost & Sullivan’s Growth Partnership Services program for industrial automation and process control. Frost & Sullivan’s research offerings include the European control valve market, the North American control valve market, the Southeast Asia and Australia–New Zealand industrial control valve market, and the Middle East industrial valves and actuators market. All research services provide detailed market opportunity assessments and industry trend analyses, supported by extensive interviews with market participants, and are available through subscription.