FGD pumps are core equipment in flue gas desulfurization systems in industrial sectors such as thermal power plants and steel smelters. Their operational reliability directly impacts desulfurization efficiency and environmental compliance.Against the backdrop of increasingly stringent environmental policies and increasing demands for industrial production continuity, desulfurization pump quality control has expanded from simply ensuring equipment performance to managing stability throughout its entire lifecycle. This article systematically explores the key technical points and implementation strategies for flue gas desulfurization pump quality control from four perspectives: materials science, manufacturing processes, testing technology, and operational compatibility.
Ⅰ. Balancing Corrosion Resistance and Mechanical Properties in Material Selection
FGD pumps operate in environments characterized by strong corrosiveness (chloride ion concentrations in slurry can reach over 50,000 mg/L), high abrasiveness (solids content 15%-30%), and temperature fluctuations (operating temperatures between 40 and 80°C). These factors place stringent demands on the comprehensive performance of materials used in flow path components. Traditional materials such as ordinary cast iron or carbon steel are susceptible to pitting corrosion in chloride environments. While 304 stainless steel offers good corrosion resistance, it lacks wear resistance. Therefore, modern desulfurization pumps commonly utilize composite linings made of duplex stainless steel (such as 2205 and 2507) or ultra-high molecular weight polyethylene (UHMWPE).
The primary step in quality control is incoming material inspection: duplex stainless steel undergoes intergranular corrosion testing (ASTM A262 Practice E), ferrite content testing (ensuring 40%-60% to prevent embrittlement), and impact energy testing (≥47J at room temperature). For plastic lining materials, the bond strength with the substrate (shear strength ≥5MPa) and thermal expansion coefficient compatibility must be verified to prevent delamination during operation. A power plant once purchased 2205 duplex stainless steel with a chromium content 2% below the standard. This resulted in extensive intergranular corrosion on the pump casing after six months of operation. Spectroscopic analysis ultimately traced the cause to excessive impurities during the raw material smelting process, highlighting the importance of precise material composition control.
II. Manufacturing Process Precision Control and Defect Prevention
Critical manufacturing steps for desulfurization pumps include impeller casting, pump body welding, and rotor dynamic balancing. Any process deviation can cause localized stress concentration or flow path distortion. As a core flow-passing component, the impeller's blade profile accuracy directly impacts hydraulic efficiency and cavitation performance. The design requires a blade inlet edge thickness tolerance of ≤0.1mm and an outlet angle deviation of ≤±0.5°. The casting process utilizes a silica sol precision casting process, and X-ray flaw detection (GB/T 5677) is performed to detect internal defects such as shrinkage cavities and slag inclusions (allowable equivalent defect diameter ≤Φ1mm).
The quality of pump body welding is directly related to structural strength. The pressure-bearing welds between the volute and inlet and outlet flanges require a combined process of argon arc welding (ATG) for priming and manual metal arc welding for filling. The interpass temperature is strictly controlled (≤150°C) to prevent thermal cracking. After welding is completed, 100% ultrasonic flaw detection (UT, according to JB/T 4730 Level I) and penetrant testing (PT, detecting surface microcracks) must be performed. Finite element analysis should also be used to verify the distribution of weld residual stress (stress in key areas ≤ 70% of the material's yield strength). A manufacturer experienced delayed cracking and leakage during operation due to insufficient preheating temperature at the pump body's girth weld. This issue was effectively resolved by increasing the preheat temperature to 200-250°C and extending the holding time, combined with post-heat dehydrogenation treatment (200-300°C for 2 hours).
III. Multi-dimensional Verification of the Full-Process Inspection System
Quality control of desulfurization pumps requires a three-tiered inspection network encompassing materials, components, and the entire unit. In addition to the aforementioned chemical composition and mechanical property tests, the material stage also requires metallographic analysis of key components (for example, the austenite/ferrite ratio of duplex stainless steel should be 50:50 ± 10%). Component inspection focuses on dimensional accuracy (for example, the clearance between the impeller and the pump casing should be controlled within 0.5-1.0mm, with a deviation of ≤±0.1mm) and functional simulation (for example, a pressure leak test on the sealing surface, maintaining a pressure of 1.5 times the design value for 30 minutes without leakage). Complete machine testing includes performance curve verification (flow-head and flow-efficiency curves with a deviation of ≤±3% from the design value), vibration testing (effective value of bearing seat vibration velocity ≤4.5mm/s, per ISO 10816), and 24-hour continuous operation assessment (monitoring bearing temperature rise rate ≤2°C/h, temperature rise ≤35°C). Of particular note, the special operating conditions of desulfurization systems require the addition of slurry wear tests (exposing the impeller to a simulated slurry containing 30% quartz sand and operating at 1500 rpm for 500 hours, measuring blade wear with a requirement of ≤0.5 mm on one side) and chloride ion stress corrosion tests (applying 1.5 times the operating pressure in a 3.5% NaCl solution and observing for 72 hours for no crack growth). A renowned international pump manufacturer, by introducing digital twin technology to simulate fluid dynamics and stress distribution under various operating conditions in a virtual environment, shortened prototype verification cycles by 30% and reduced field failure rates by 42%.
IV. Dynamic Quality Control for Operational and Maintenance Adaptability
Quality control of desulfurization pumps should not be limited to factory conditions but should also consider performance degradation and adaptability to operating conditions over long-term operation. It is recommended to establish a closed-loop mechanism of "equipment archives + online monitoring + regular evaluation." The equipment archive records full lifecycle information, including material batches, welding parameters, and test data. The online monitoring system collects parameters such as vibration (accelerometer), temperature (infrared thermometer), and pressure (differential pressure transmitter) in real time, using machine learning algorithms to identify early failure characteristics (for example, the frequency characteristic of bearing inner ring damage is 2-3 times the rotational frequency). A disassembly inspection is performed every 2000 hours of operation, focusing on evaluating impeller wear uniformity (wear gradient difference ≤ 0.2mm), seal aging (rubber hardness change ≤ 10%), and bolt preload loss (torque loss ≤ 15%).
A large steel company has demonstrated that by correlating desulfurization pump operation and maintenance data with manufacturing process parameters, potential failure modes can be predicted 3-6 months in advance. For example, an abnormally high impeller wear rate can be traced back to a high sulfur content in the raw material, resulting in reduced wear resistance. This allows for targeted adjustments to material selection and process parameters for subsequent batches. This "manufacturing-use-feedback" quality improvement spiral has significantly extended the equipment's service life (mean time between failures increased from 8,000 hours to 15,000 hours).
Conclusion
Quality control of flue gas desulfurization pumps is a systematic project involving materials science, mechanical manufacturing, testing technology, and operations and maintenance management. Only by strictly controlling material properties, optimizing manufacturing processes, improving testing systems, and strengthening operational and maintenance adaptability can we ensure the equipment's long-term stable operation under extreme operating conditions. With the continuous upgrading of environmental protection standards and the development of industrial intelligence, quality control of desulfurization pumps will further evolve towards digitalization and predictiveness. By integrating big data analysis with advanced manufacturing technologies, we will achieve a transition from "reactive maintenance" to "proactive prevention," providing solid equipment support for the green and low-carbon transformation of the industrial sector.
