Basic knowledge of chemical engineering!

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1. The five key steps in equipment inspection are: listen, feel, check, observe, and smell.
2. The “four understandings and three abilities” in equipment management: understand the principles, understand the structure, understand the performance, and understand the process flow； Know how to operate, maintain, and troubleshoot. 3. The five main types of valves used in chemical pipelines are: gate valves, globe valves, ball valves, check valves, and butterfly valves. Other common valves include: plug valves, safety valves, steam traps, diaphragm valves, lined valves, pressure relief valves, damping valves, etc. 4. Basic structure of pressure vessels: cylinder body, head, flanges, supports, nozzles, manholes, level gauges, sight glasses, etc. Common types include horizontal storage and transport pressure vessels, and vertical pressure vessels (towers). 5. Chemical piping fittings include: elbows, tees, reducers, union joints, flange covers, blind plates, reduced tees, pipe caps, etc. 6. Common elbow types include: 90°, 45°, 60°, 180°. The elbow radius is in a multiple relationship, generally being 1 or 1.5 times the nominal diameter DN. 7. The materials used to make gaskets include special cardboard, rubber sheets, asbestos sheets, soft metal sheets, low-carbon steel, polytetrafluoroethylene, expanded graphite, and sealant fluids, among others. 8. The dynamic balance accuracy grade for the impellers of ordinary pumps, the rotors of standard motors, and the impellers of fans is: G6.3. 9. The safety accessories for pressure-bearing special equipment include: safety valves, rupture discs, level gauges, thermometers, and data acquisition and processing devices. 10. What are the categories of regular inspections for pressure vessels? How is its inspection cycle specified? There are three types: 1) External inspection, once a year ； 2) Internal inspection: at least once every 6 years for systems with a safety status level of 1 or 2, and at least once every 3 years for those with a safety status level of 3 ； 3) Dielectric strength test: For fixed containers, it must be conducted at least once every 2 internal and external inspections ； For mobile units, at least once every six years. 11. Which department should be informed in writing before the installation of special equipment? The departments responsible for the supervision and management of special equipment safety in municipalities directly under the Central Government or cities with districts: 12. Serious violations related to special equipment include: 1) Designing special equipment without a license ； 2) Use of special equipment without a license ； 3) Unlicensed installation, modification, and repair of special equipment ； 4) Operation of special equipment without a license ； 5) No periodic inspection for special equipment. 13. The safety valve of an in-use boiler shall be calibrated at least once a year. 14. Names and codes for pipeline flange sealing surfaces: In accordance with national standards, the names and codes for flange sealing surfaces are as follows: Flat surface: FF ； Convex surface: RF ； Rough and smooth surfaces: MF ； Tenon and mortise surface: TG ； Ring connection surface: RJ15; types of steel include steel plates, steel pipes, shaped steel, etc. Steel plates: Steel plates are divided into three categories: thin steel plates, medium-thickness steel plates, and thick steel plates. Steel pipes: Steel pipes are classified into three types: welded steel pipes, seamless steel pipes, and spiral pipes. 16. What are the types of section steels? Such as round steel, square steel, hexagonal steel, flat steel, angle steel (equilateral, unequal), channel steel and I-beam, H-beam, etc. 17. What is the relationship between absolute pressure, gauge pressure, vacuum degree, and atmospheric pressure? Absolute pressure = Gauge pressure + Atmospheric pressure ； Vacuum degree = atmospheric pressure - absolute pressure. 18. 1 MPa = (103) KPa = (106) Pa. 19. For φ108×4 steel pipes, the nominal diameter is generally: 100 mm, with a thickness of 4 mm. 20. The main performance parameters of centrifugal pumps include: flow rate, head, rotational speed, efficiency, etc. 21. The performance indicators of lubricating oil include: viscosity, flash point, freezing point, acid value, mechanical impurities, ash content, oiliness (lubricity), extreme pressure capacity, water content, etc. 22. Common methods for denoting steel grades: Q235BF – where Q represents the yield strength of the steel; it is the first letter of the pinyin character for “yield”. 235 denotes the yield strength in MPa. B indicates the quality grade, with common grades being A, B, C, D. F stands for boiling steel (b for semi-killed steel, z for killed steel, tz for specially killed steel). 23. Gray cast iron: HT150 – where HT is the code for gray cast iron ； 150—Tensile strength 24; the first characters of the valve model indicate the type of valve: Z J L Q D G X H A Y SZ—Gate valve ； J—Stop valve ； L—throttle valve ； Q—Ball valve ； D—Butterfly valve ； G—Diaphragm valve ； X — Ball valve ； A—Safety valve ； S—Drain valve ； Y—Pressure relief valve ； H—Check valve/foot valve 25. The Arabic numerals following the initial letter of the valve model indicate the connection type: 1, 2, 4, 6, 7, 8, 9. 1—Internal thread ； 2—External thread ； 4—Flange ； 6—Welding ； 7—Clamped joint ； 8—Clamp ； 9—What materials do the codes for the sleeve 26, the sealing surfaces of the valve core and valve seat, or the lining materials represent respectively: T X N H B H D Y Q C J PT—copper alloy ； X—Rubber ； N—Nylon plastic ； H—alloy steel ； B—Babbitt alloy ； D—Nitrided steel ； Y—Hard steel ； Q—Lead lining ； C—Enameled ； J—Rubber lining ； P—Boronized steel 27. Please state the meaning of each letter and digit in the following valve designation? Q21H-40P-25: Ball valve, manually operated, external threaded, straight-through type; the valve trim is made of alloy steel, while the valve body is made of 1Cr18Ni9Ti. The working pressure is 4.0 Mpa, and the nominal diameter is 25.
J41H-25P-100: Globe valve, flanged connection, manually operated; the valve trim is made of alloy steel, and the valve body material is 1Cr18Ni9Ti. The working pressure is 2.5 Mpa, and the nominal diameter is 100. J41B-25-50: Globe valve, flanged connection; the valve core is made of tin-based bearing alloy, with a working pressure of 2.5 Mpa and a nominal diameter of 50. G41CJ-6-100: Diaphragm valve, flanged connection; the valve core is made of carbon steel lined with rubber, with a pressure of 0.6 Mpa and a nominal diameter of 100. Z744W-2.5-600: Gate valve, hydraulic operation, flanged connection, double gate plates; the sealing material is fabricated directly from the valve body. Its operating pressure is 0.25 Mpa, and the nominal diameter is 600. D341X-10-300: Butterfly valve, worm gear drive, flanged connection, single gate plate; the valve core is sealed with rubber. Its operating pressure is 1.0 Mpa, and the nominal diameter is 300. 28. Seal surface type: convex surface, concave surface, convex tenon surface, groove surface, fully flat surface, annular connection surface; code: RFFMMTGFFRJ. 29. There are two main systems for flange standards: the European pipe flange system and the American flange system. European pipe flange system (DIN, GB, JB, HG20592): Nominal pressures: 0.1, 0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 25.0, 32.0, 40.0, Mpa ； Nominal diameter: 15~600mm ； Types of flange structures: plain weld plate type, plain weld loose flange ring type, flared loose flange type, butt weld flared loose flange type, butt weld loose flange ring type, butt weld type, threaded neck connection type, integral type, and flange cover ； Flange sealing surfaces include: flat surface, concave surface, ribbed surface, tenon-and-socket surface, rubber ring connection surface, lens surface, and diaphragm welding surface ； American flange system: ASME ANSI B16.5 “Steel Pipe Flanges and Flanged Fittings” (including ANSI, GB, HG20615) ； Nominal pressure: 150psi (2.0Mpa), 300psi (5.0Mpa), 400psi (6.8Mpa), 600psi (10.0Mpa), 900psi (15.0Mpa), 1500psi (25.0Mpa), 2500psi (42.0Mpa) ； Nominal diameter: 6~4000mm ； Types of flange structures: strip welding, socket welding, threaded connection, loose flange, butt welding, and flange cover ； Flange sealing surfaces: concave surface, male-female surface, tenon-and-socket surface, metal ring joint surface. 30. The **standard system** for steel pipe flanges in China is the GB standard. 1) Nominal pressure: 0.25 Mpa to 42.0 Mpa. Series 1: PN1.0, PN1.6, PN2.0, PN5.0, PN10.0, PN15.0, PN25.0, PN42 (main series) ； Series 2: PN0.25, PN0.6, PN2.5, PN4.0. Among these, the flange sizes of the 6 grades PN0.25, PN0.6, PN1.0, PN1.6, PN2.5, and PN4.0 belong to the European flange system represented by German flanges, while the others belong to the American flange system represented by American flanges. In GB standards, the maximum nominal pressure rating for flanges belonging to the European flange system is 4 MPa, while for those belonging to the American flange system it is 42 MPa. 2) Nominal diameter: 10mm~4000mm. 31. Structural types of flanges: ① Integral flanges: threaded flanges, welding flanges, butt-weld flanges, slip-on flanges with neck, socket-weld flanges with neck, and plate-type slip-on flanges ； Flange cover (blind flange) ； ② Unit flanges: slip flanges, weld-ring slip flanges with neck, weld-ring slip plate flanges, butt-weld ring slip plate flanges, plate-type flipped slip flanges ； 32. Flange sealing surfaces: flat, concave, convex-concave, tongue-and-groove, ring joint. 33. Commonly used materials for bolts: For non-critical pipelines such as general water lines and compressed air lines, 35A# carbon steel bolts are typically used ； Pipelines for flammable, explosive, and toxic media are mostly made of 35CrMoA/30CrMo material ； Usage of flange bolts for high-temperature pipelines: 510℃-----21CrMoV; 550℃-----20CrMoV, 21CrMoV; 570℃-----20CrMoVTiB, 20CrMoVnBTiB; 600℃-----2Cr12WMoVNbB; 650℃-----GH213, 234. What is the general pattern regarding the relationship between size and length when obtaining pipeline flange connection bolts from the warehouse? What size socket wrench is used for M16 bolts? For example, in the case of M16: when the pressure rating is PN≤2.5 MPa, the length is 5 times the diameter; thus, M16X80 is used ； When the pressure rating PN is greater than 2.5 MPa, the length is 5 times the diameter plus 10; in this case, M16x90 should be used. For example, in the case of M20: when the pressure rating is PN≤2.5 MPa, the length is 5 times the diameter; thus, M20X100 is used ； When the pressure rating PN is greater than 2.5 MPa, the length is 5 times the diameter plus 10; in this case, M20x110 should be used. Note: [This does not apply to pressure levels of 6.0 MPa or higher; however, the values can still be used as a reference.] For bolts of a certain specification, corresponding ring wrenches should be used. Generally, for bolts with a nominal size of X1.5, such as M16 bolts, the ring wrench size is calculated as 16*1.5=24 ； For M20 bolts, a slip joint wrench of size 20*1.5, which corresponds to grade 30, is used. When using a monkey wrench, try to select the size that is closest to the required one. 35. What are the common gaskets? Non-metallic gaskets: such as asbestos gaskets, synthetic resin gaskets, rubber gaskets, asbestos-free rubber gaskets, flexible graphite metal composite gaskets, and polytetrafluoroethylene gaskets. Semi-metallic gaskets: such as wound gaskets, wave-shaped gaskets, metal-wound gaskets, metal-toothed composite gaskets, and metal-clad gaskets. Metal gasket. For example: copper, aluminum, iron, steel, metal flat washers. 36. What are the common types of metal wound gaskets? There are four types of common metal wound gaskets: the basic type ； Gasket with inner and outer rings ； With inner ring ； With an outer ring. 37. For the D1222 model of wound gaskets, what do the digits in various positions of the model number represent? Such as the D1222 model of wound gaskets: D: Wound gasket with inner and outer reinforcement rings. First digit: Material of the outer ring: 1 – Low-carbon steel (20#). Second digit: Embedded material of the main body: 2 – 0Cr18Ni9 (304). Third digit: Outer covering material of the main body: 2 – Flexible graphite strip. Fourth digit: Material of the inner ring: 2 – 0Cr18Ni9 (304). Detailed explanation: First digit: Material of the outer ring; 0: No outer ring ； 1: Low-carbon steel (20#) ； 2: 0Cr18Ni9 (304) ； 3: 0Cr17Ni12Mo2 (316) ； 4: 0Cr17Ni14Mo2 (316L); the second digit indicates the embedded material of the main material. 2: 0Cr18Ni9 (304) ； 3: 0Cr17Ni12Mo2 (316) ； 4: 00Cr17Ni14Mo2 (316L); third digit: the coating material for the main material; 1: special asbestos paper ； 2: Flexible graphite strip ； 3: Polytetrafluoroethylene ； 4: Special non-asbestos board; fourth digit: material of the inner ring – 0: no inner ring ； 1: Low-carbon steel (20#) ； 2: 0Cr18Ni9 (304) ； 3: 0Cr17Ni12Mo2 (316) ； 4:00Cr17Ni14Mo2 (316L) 38. What are the components in reciprocating compressors that wear out most easily? Valve discs, springs, gaskets, copper sleeves, crankshafts, bearing shells, piston rings, pistons, cylinder liners, packing, support rings, etc. 39. Bearing grades are arranged from low to high. Is grade B a low grade or the highest grade? G, E, D, C, B. For B, which is grade 40, does the perimeter of the V-belt refer to the outer perimeter or both the outer and inner perimeters? What is the angle of the V-belt in degrees? Inner perimeter, angle of 40±1 degrees. What are the common faults and their causes in rolling bearings? 1) Bearing overheating: (1) Insufficient lubricant supply or incorrect lubricant type (2) Presence of foreign debris (3) Incorrect installation ； 2) Abnormal sound: (1) Spalling or damage to the bearing raceways; (2) Loose brackets; (3) Severe lack of oil in the bearings; (4) Pitting on the raceways and steel balls ； 3) Poor transmission flexibility: (1) Loose or faulty seals and other accessories attached to the bearings; (2) Bearings stuck due to oil or dirt; (3) Improper fit between the inner and outer rings of the bearings and the bearing housing – either too loose or too tight. 42. Large motors cannot be started continuously; what is the maximum number of times this can be done? It cannot exceed three times. The interval between each of the three times should be 30 minutes, and after three times, the interval should be 4 hours. If the vehicle cannot be brought to a stop while parking, do not press the start button again; instead, contact an electrician promptly. 43. What are special equipment? Special equipment refers to eight major categories of devices and facilities that pose a significant risk to personal and property safety, including boilers, pressure vessels (including gas cylinders), pressure pipelines, elevators, lifting machinery, passenger cableways, large-scale amusement facilities, and specialized motor vehicles used within premises (factories), as well as other special equipment designated by laws and administrative regulations as falling under the scope of this law. 44. What is a fixed-pressure vessel? Fixed pressure vessels refer to enclosed devices that hold gases or liquids and are subjected to a certain pressure; their scope is defined as (1) a maximum operating pressure of 0.1 MPa (gauge pressure) or greater ； (2) Volume greater than or equal to 30 L and inner diameter (for non-circular cross-sections, it refers to the largest geometric dimension of the internal boundary) ； (3) The medium contained is a gas, a liquefied gas, or a liquid with a maximum operating temperature higher than or equal to its standard boiling point. 45. What is the classification of pressure vessels and the determination of pressure grades? Based on the principle of their function in the production process, pressure vessels are classified into reaction pressure vessels, heat exchange pressure vessels, separation pressure vessels, and storage pressure vessels. The specific classification is as follows: 1) Reaction pressure vessel (code R). 2) Heat exchange pressure vessels (code E); 3) Separation pressure vessels (code S); 4) Storage pressure vessels (code C, with spherical tanks coded as B). Based on the design pressure (P) of the pressure vessels, they are classified into four pressure categories: low pressure, medium pressure, high pressure, and ultra-high pressure. The specific classifications are as follows: 1) Low-pressure vessels: P = 0.1–1.6 Mpa ； 2) Medium-pressure vessel P=1.6～10Mpa ； 3) High-pressure vessel P=10～100Mpa ； 4) Ultra-high pressure vessels with P > 100 Mpa. 46. What is a pressure pipeline? It refers to tubular devices that use a certain pressure to transport gases or liquids; such devices are defined as those with a maximum operating pressure of 0.1 MPa (gauge pressure) or more, where the medium is a gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, and has a maximum operating temperature equal to or higher than its standard boiling point, and whose nominal diameter is 50 mm or more. Except for pipes with a nominal diameter of less than 150 mm and a maximum operating pressure of less than 1.6 MPa (gauge pressure), as well as the pipes that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. Pressure pipelines are classified into: 1) Long-distance pipelines (GA category), 2) Utility pipelines (GB category), 3) Industrial pipelines (GC category). 1) GA category (Long-distance pipelines): Long-distance (oil and gas) pipelines refer to those used for transporting oil and gas as commodity fluids between production sites, storage facilities, and users; they are divided into GA1 and GA2 grades. 　　 1) GA1 grade – Long-distance pipelines that meet one of the following conditions are classified as GA1 grade: ① Long-distance gas pipelines with a design pressure of 4.0 MPa or higher (gauge pressure, the same below); ② Long-distance oil pipelines with a design pressure of 6.3 MPa or higher. 　　 2) GA2 level – Long-distance pipelines other than those of GA1 level. (2) GB category (public pipelines) Public pipelines refer to gas and heat pipelines used for public services or domestic purposes within cities or towns, and are classified into GB1 grade and GB2 grade. 　　 1) GB1 grade — Gas pipelines. 　　 2) GB2 grade — Thermal pipelines. (3). GC category (industrial pipelines): Industrial pipelines refer to the process pipelines, utility pipelines, and other auxiliary pipelines owned by enterprises and institutions and used for transporting process media. They are classified into GC1 grade, CC2 grade, and GCD grade. 1) GC1 grade – Process pipelines that meet one of the following conditions are classified as GC1 grade: ① Process pipelines that transport media with an acute toxicity level of Category 1 as specified in the “Catalogue of Hazardous Chemicals”, gas media with acute toxicity of Category 2, or liquid media with acute toxicity of Category 2 whose operating temperature is higher than their standard boiling point; ② Process pipelines that transport flammable gases of Classes A and B or flammable liquids of Class A (including liquefied hydrocarbons), and whose design pressure is 4.0 MPa or greater; ③ Process pipelines that transport fluid media, with a design pressure of 10.0 MPa or greater, or with a design pressure of 4.0 MPa or greater and an operating temperature of 400°C or higher. 2) GC2 grade – Industrial pipelines that meet one of the following conditions are classified as GC2 grade: ① Process pipelines other than those of GC1 grade; ② Refrigeration pipelines. 3) GCD grade – Power pipelines.