Standards for reducers serve as the core basis for their design, production, inspection and installation. Globally, there are three major systems: Chinese National Standards (GB), American National Standards (ASME/ANSI), and International Standards (ISO). In addition, there are industry-specific standards (e.g., petrochemical, power industry). A detailed interpretation of key standards is as follows: I. Chinese National Standards (GB/T Core System) 1. Basic General Standards GB/T 12459-2017 Steel butt-welding pipe fittings — Types and parameters Core content: Specifies the types, nominal diameters (DN15~DN1200), nominal pressures (PN0.25~PN42.0), radius of curvature, wall thickness schedules and dimensional tolerances of steel butt-welding reducers (concentric / eccentric).…

The wall thickness classification of reducers is mainly designed to meet pressure resistance requirements. There are three mainstream systems worldwide: metric (tied to PN), American standard (Sch series), and plastic (SDR series). These systems differ significantly in classification logic, marking methods and applicable scenarios, as detailed below: I. American Standard Wall Thickness Schedules (Sch Series, ASME B36.10/B36.19) This is the most widely used wall thickness system for industrial metal reducers, marked as Sch + number. The higher the number, the thicker the wall thickness, corresponding to American standard pressure classes (Class). 1. Key Rules For the same nominal size, a…

A pressure vessel refers to a sealed device that contains gas or liquid and bears a certain pressure. As an indispensable key equipment in industrial production, it is widely used in petroleum, chemical, energy, pharmaceutical, food and other industries. Since pressure vessels usually store high-pressure, high-temperature, flammable, explosive or toxic media inside, the consequences would be disastrous in the event of rupture. Therefore, countries around the world have extremely strict laws and regulations governing the design, manufacture, use and inspection of pressure vessels. 1. Definition and Classification Criteria Basic Characteristics Working Pressure (p): greater than or equal to 0.1 MPa…

The manufacture, inspection and acceptance of pressure vessels constitute a systematic engineering process, which must be carried out in strict accordance with national standards (such as GB 150) and special equipment safety technical specifications (such as TSG 21). The following is an analysis of the whole process of pressure vessels from raw material incoming inspection to final delivery: Phase 1: Manufacturing Process The manufacture of pressure vessels generally follows the process route below: 1. Raw Material Preparation and Acceptance Material selection: Select standard-compliant steel plates, forgings, steel pipes, etc., according to design drawing requirements. Re-inspection: After raw materials enter the…

The chemical analysis methods for iron, steel and alloys are well‑established and are generally carried out in accordance with the national standard GB/T 223 series (Methods for chemical analysis of iron, steel and alloys). This standard series includes dozens of specific analytical procedures, with different determination methods for various elements such as carbon, sulfur, manganese, silicon, phosphorus, chromium, nickel, molybdenum, etc. The following is a systematic classification and interpretation of the core content of chemical analysis methods for iron, steel and alloys: I. Main Classification of Analytical Methods Based on different measurement principles, they are mainly divided into two categories:…

A tensile test, also known as a tension test, is the most fundamental and important testing method for evaluating the mechanical properties of materials. In simple terms, a standard metal bar (specimen) is clamped in a testing machine and pulled axially at both ends until it fractures. During this process, the applied force and corresponding elongation are recorded to determine whether the material is strong and ductile. For pressure vessel steels (such as Q345R, 304 stainless steel), tensile testing is a mandatory inspection item to verify that the material meets the design requirements for strength and toughness. 1. Test Principle…

Room Temperature Test Method generally refers to a set of standard operating procedures for testing material properties under normal laboratory ambient temperature. In materials science and engineering (especially metallic materials), when we mention “room temperature test”, in most cases it specifically refers to the tensile test conducted in accordance with GB/T 228.1-2010 Metallic materials — Tensile testing — Part 1: Method of test at room temperature. The following is a detailed interpretation of the room temperature test method: 1. What is “Room Temperature”? (Definition) In standards, “room temperature” is not a fixed value but a specified range. Standard range: Generally…

Charpy Pendulum Impact Test, commonly referred to as impact test for short, is a mechanical property test used to determine a material’s ability to resist fracture under high-speed impact loading. If a tensile test measures how strong a material is when pulled slowly, an impact test evaluates how durable a material is when struck suddenly. For critical structural components such as pressure vessels, bridges and ships, the impact test is the most critical method to determine whether a material will undergo brittle fracture. 1. Test Principle: Similar to Chopping Wood Imagine holding an axe (pendulum), lifting it high, then striking…

I. Sampling Locations (Critical! Sampling positions vary significantly by product form) Sampling location directly affects test results; therefore, strict provisions apply to different material forms in relevant standards. 1. Steel Plates (Most Common) In accordance with GB/T 2975 Steel and steel products — Location and preparation of test pieces for mechanical property testing (1) Tensile Specimens Rolling direction: Transverse (perpendicular to rolling direction). Thickness direction: Thickness ≤ 25 mm: Full-thickness sampling (full-thickness plate specimen). Thickness > 25 mm: Sampling at 1/4 thickness (due to different properties between surface and core). (2) Charpy Impact Specimens Rolling direction: Transverse. Thickness direction: Thickness…

When stainless steels (such as 304 and 316L) are exposed to specific environments, grain boundaries are preferentially corroded, causing sudden fracture of the material without obvious deformation. This phenomenon is known as intergranular corrosion (IGC). To evaluate the intergranular corrosion resistance of stainless steels, the national standard specifies several test methods, among which the GB/T 4334 series is the most widely used. The following is a systematic explanation of the test methods for intergranular corrosion of stainless steels. I. Mechanism of Intergranular Corrosion (Brief Principle) Intergranular corrosion mainly occurs when stainless steel is heated and held in the temperature range…

Spark Source Atomic Emission Spectrometry (Spark OES) is an analytical technique that uses high-voltage electric sparks to excite the sample surface and cause atoms to emit light. The chemical composition of the material is determined by analyzing the wavelength and intensity of the emitted light. In simple terms: by striking a spark on metal and observing the color and brightness of the spark, we can identify the type of steel. It is the most common and fastest analytical method used in iron and steel metallurgy, machinery manufacturing, and raw material acceptance for pressure vessels. 1. Working Principle: From “Spark” to…

The Elevated Temperature Tensile Test is a test that applies tension to metallic materials at a specified temperature above room temperature to determine their mechanical properties. For equipment operating at high temperatures for long periods, such as boilers, pressure vessels, steam turbines, and aero-engines, the elevated temperature tensile test is the most important basis for determining the allowable stress of materials. The following is a systematic analysis of the elevated temperature tensile test: 1. Why Conduct Elevated Temperature Tensile Testing? The properties of metallic materials at high temperatures differ significantly from those at room temperature: Decreased strength: As temperature rises,…