Processo di produzione della valvola

Manufacturing process and processing process flow of valvola

At first glance, the valve has few parts, simple structure and general accuracy. It is a simple component in the machinery industry, but the requirements for the core sealing part of the valve are particularly high. The valve manufacturing process is complex and technically difficult. What process characteristics do we need to pay attention to?

Manufacturing materials of valves

Due to the wide variety and specifications of valves, such as valvola a saracinesca, Valvola a globo, valvola di non ritorno, valvola a sfera, valvola a farfalla and hydraulic control valve; Industrial valves include solenoid valves, regulating valves, pressure reducing valves, high-temperature and high-pressure valves, low-temperature valves and other special valves, which are used in various fields of the national economy. Their application occasions vary greatly, such as high-temperature and high-pressure, low-temperature and deep cold, flammable and explosive, highly toxic, strongly corrosive media and other working conditions, which put forward harsh requirements for the material of the valve.
In addition to cast iron, carbon steel and alloy structural steel, CrNi stainless steel, CrMoAl nitriding steel, CrMoV heat resistant steel, CrMnN acid resistant steel, precipitation hardening steel, duplex stainless steel, low temperature steel, titanium alloy, Monel alloy, Inconel alloy, Hastelloy alloy and g0crw cemented carbide are also widely used. The casting, welding and processing properties of these high alloy materials are very poor, which brings great difficulty to the manufacturing process. In addition, most of these materials are valuable materials with high alloy, high strength and high hardness. There are many difficulties in material selection, material preparation and procurement. Some materials are difficult to purchase and supply due to their small use.

Structure of casting blank

Most of the valve blanks are thin shell castings with complex structure, which requires not only good appearance quality, but also dense internal quality and good metallographic structure, without defects such as pores, shrinkage cavities, sand inclusions and cracks. Therefore, the casting process is complex and the heat treatment technology is difficult. In the machinery industry, the casting of pressure bearing thin shell castings of valves is much more complex and difficult than that of other mechanical components.

Machining process of valve

Due to the poor cutting performance of most high-strength, high hardness and high corrosion-resistant materials, such as high alloy stainless steel and acid resistant steel, which have the disadvantages of high toughness, high strength, poor heat dissipation, large chip viscosity and strong work hardening tendency, it is difficult to achieve the required dimensional accuracy and finish, which brings some difficulties to the machining tools, processes and equipment. In addition, the valve sealing surface has high requirements for machining accuracy, matching angle, finish and matching sealing pair, which brings great difficulty to machining.

Process arrangement of valve parts

The number of main parts of the valve is small, the structure is relatively simple, the machining accuracy of most dimensions is not high, and the outside is rough, which gives people the impression that it belongs to simple machinery. In fact, the heart sealing part of the valve is unique. The “three degrees” (flatness, smoothness and hardness) of the sealing surface are very high, and the coincidence of the sealing pair composed of two sealing surfaces must reach zero to zero, so as to meet the zero leakage of the air tightness test. This rough benchmark to ensure the zero to zero requirements of the heart is a major process difficulty in valve processing.

Valve test and inspection

Valve is an important opening, closing and regulating element of pressure pipeline, and the service conditions of pressure pipeline are very different, high temperature and high pressure, low temperature and deep cold, flammable and explosive, highly toxic and corrosive. However, the test and inspection conditions of valve manufacturing can not meet the same requirements of working conditions. Various international and domestic valve test standards stipulate that the test is carried out with gas or water as the medium under the condition close to normal temperature. There is a fundamental hidden danger, that is, the valve products that pass the normal factory test may be difficult to meet the use requirements due to problems such as material selection, casting quality and seal damage under harsh actual working conditions, and major quality accidents will occur. No wonder some old valve experts who have worked all their lives are more cautious and worried as they get older.

Manufacturing process of Valve

Step 1: valve body manufacturing

Valve body (casting, sealing surface surfacing)
Casting procurement (according to standard) ➱ incoming inspection (according to standard) ➱ surfacing groove ➱ ultrasonic flaw detection (according to drawing) ➱ surfacing and post weld heat treatment ➱ finishing ➱ grinding sealing surface ➱ hardness inspection and dye detection of sealing surface.

Step 2: valve trim manufacturing process

A. Internals requiring surfacing sealing surface, such as valve disc, valve seat, etc
Raw material procurement (according to standard) ➱ incoming inspection (according to standard) ➱ making blank (round steel or forging, according to the process requirements of the drawing) ➱ rough machining ultrasonic flaw detection surface (when required by the drawing) ➱ rough machining surfacing groove ➱ surfacing and post weld heat treatment ➱ finishing each department ➱ grinding sealing surface ➱ sealing surface hardness inspection and dye detection.
B. Valve stem
Raw material procurement (according to standards) ➱ incoming inspection (according to standards) ➱ blank making (round steel or forging, according to the process requirements of the drawing) ➱ rough machining of surfacing groove ➱ surfacing and post weld heat treatment ➱ finishing of each part ➱ grinding of outer circle ➱ valve stem surface treatment (nitriding, quenching, chemical coating) ➱ final treatment (polishing, grinding, etc.) ➱ grinding of sealing surface ➱ hardness inspection and dye flaw detection of sealing surface.
C. Internals without surfacing sealing surface, etc
Raw material procurement (according to standard) ➱ incoming inspection (according to standard) ➱ making blank (round steel or forging, according to the process requirements of the drawing) ➱ rough machining ultrasonic flaw detection surface (when required by the drawing) ➱ finishing all parts.

Step 3: Fastener manufacturing

Fastener manufacturing standard dl439-1991.
Raw material procurement (according to standard) ➱ incoming inspection (according to standard) ➱ making blank (round steel or forging, according to drawing process requirements) and sampling for necessary inspection ➱ rough machining ➱ finish machining ➱ spectral inspection.

Step 4: final assembly

Receiving parts ➱ cleaning and cleaning ➱ rough assembly (according to the drawing) ➱ hydrostatic test (according to the drawing and process) ➱ after passing the test, disassemble and wipe ➱ final assembly ➱ and electrical assembly or actuator commissioning (for electric valves) ➱ paint packaging ➱ shipping.

Step 5: valve production and inspection process

• 1. Raw materials of various specifications purchased by the company.
• 2. Use the spectrum analyzer to test the material of raw materials, and print the test report of raw materials for backup.
• 3. Cut raw materials with blanking machine.
• 4. The inspector shall inspect the cutting diameter and length of raw materials.
• 5. The forging workshop carries out forging forming treatment for raw materials.
• 6. The inspector shall inspect various dimensions of the formed blank.
• 7. The worker is cutting off the scrap edge of the blank.
• 8. The sanding worker shall carry out sand blasting on the surface of the blank.
• 9. The inspector shall inspect the surface treatment after sand blasting.
• 10. Workers carry out rough machining.
• 11. Valve body sealing thread processing – employees conduct processing self inspection, and inspectors conduct post-processing inspection on products.
• 12. Valve body connection thread processing.
• 13. Medium hole machining.
• 14. The inspector shall conduct general inspection.
• 15. Qualified semi-finished products are sent to the semi-finished product warehouse.
• 16. Semi finished products shall be electroplated.
• 17. Inspection of electroplating surface treatment of semi-finished products.
• 18. Inspection of various accessories (ball, valve stem, sealing valve seat).
• 19. Product assembly in the final assembly workshop – assembly line inspectors inspect the products.
• 20. After pressure test and drying, the assembled product enters the next process.
• 21. Product packaging in the final assembly workshop — the inspectors of the packaging line inspect the tightness, appearance and torque of the products. Unqualified products must not be packaged.
• 22. Qualified products are bagged and sent to the finished product warehouse.
• 23. All inspection records will be classified and stored in the computer for query at any time.
• 24. Qualified products are sent to domestic and foreign countries through containers.

Inspection for Finished Products

• A: Dimension Measurement
• B: Outer & Inner Surface Inspection
• C: Chemical Composition: Chemical Analysis; Portable Spectrometer
• D: Mechanical Properties: Flattening, Flaring, Hardness; Tensile Strength
• E: Non-destructive Test: Eddy Current Test; Ultrasonic Testing;
• F: Corrosion Test: Intergranular Corrosion Test; Pit Corrosion Test
• G: Hydrostatic Test
• H: Grain Size Test

• Galleria delle attrezzature
• Ambiente

MATERIAL REFERENCE LIST
MATERIAL	PIPES	WROUGHT FITTINGS	FORGING	PLATE	CASTING	TRADE NAME
Stainless steel&Super Stainless	A312 TP304	A403 WP304	A182 F304	A240 gr. 304	A351 CF8	304
	A312 TP304L	A403 WP304L	A182 F304L	A240 gr. 304L	A351 CF3	304L
	A312 TP310S	A403 WP310S	A182 F310S	A240 gr. 310S	A351 CK20	310
	A312 TP316	A403 WP316	A182 F316	A240 gr. 316	A351 CF8M	316
	A312 TP316L	A403 WP316L	A182 F316L	A240 gr. 316L	A351 CF3M	316L
	A312 TP316Ti	A403 WP316Ti	A182 F316Ti	A240 gr. 316Ti		316Ti
	A312 TP317L	A403 WP317L	A182 F317L	A240 gr. 317L	A351 CG8M	317
	A312 TP321	A403 WP321	A182 F321	A240 gr. 321		321
	A312 TP347	A403 WP347	A182 F347	A240 gr. 347	A351 CF8C	347
	A312 S31254	A403 S31254	A182 F44	A240 S31254	A351 CK3MCuN	254 SMO
Duplex steel	A790 S31803	A815 S31803	A182 F51	A240 S31803	A890 Gr.4A	SAF2205
	A790 S32304	A815 S32304		A240 S33304		SAF2304
	A790 S32750	A815 S32750	A182 F53	A240 S32750	A890 Gr 5A	SAF2507
	A790 S32760	A815 S32760	A182 F55	A240 S32760	A890 Gr 6A
Special alloy	B677/674 N08904	B366 WP904L	B459 N08904	B649 N08904		904L
	B729/464 N08020	B366 WP20CB	B462 N08020	B463 N08020	A351 CN7M	Alloy 20
	B161 N02200	B366  WPN	B564 N02200	B162 N02208		Nickel 200
	B161 N02201	B366  WPNL	B160 N02201	B162 N02201		Nickel 201
	B165 N04400	B366  WPNC	B564 N04400	B127 N04400	A494 M35-1	Monel 400
	B407 N08800	B366  WPNIC	B564 N08800	B409 N08800		Incoly 800
	B423 N08825	B366  WPNICMC	B564 N08825	B424 N08825	A494 CU5MCuC	Incoly 825
	B167 N06600	B366  WPNCI	B564 N06600	B168 N06600	A494 CY40	Inconel 600
	B444 N06625	B366  WPNCMC	B564 N06625	B443 N06625	A494 CW6MC	Inconel 625
	B622 N10276	B366 WPHC276	B564 N10276	B575 N10276		Hastelloy C276
	B622 N06455	B366  WPHC4	B564 N06455	B575 N06455	A494 CW2M	Hastelloy C4
	B622 N06022	B366  WPHC22	B564 N06022	B575 N06022	A494 CX2MW	Hastelloy C22
	B622 N10665	B366  WPN\HB-2	B564 N10665	B333 N10665	A494 N7M	Hastelloy B2
Carbon steel	A106 Gr.B	S234 WPB	A105/N	A515 Gr65	A216 WCB
Low temp. service	A333 Gr.3	A420 WPL3	A350 LF3	A516 Gr.70	A352 gr. LC3
	A333 Gr.6	A420 WPL6	A350 LF2	A516 Gr.65	A352 gr. LCB
High temp. service (Chrome-Moly Alloy)	A335 P1	A234 WP1	A182 F1	A204 gr B	A217 gr.B
	A335 P5	A234 WP5	A182 F5	A387 gr.5	A217 gr. C5
	A335 P9	A234 WP9	A182 F9	A387 gr.9	A217 gr.C12
	A335 P11	A234 WP11	A 182 F11	A387 gr.11	A217 gr.WC6
	A335 P22	A234 WP22	A182 F22	A387 gr.22	A217 gr.WC9
	A335 P91	A234 WP91	A182 F91	A387 gr.91	A217 gr.WC12
Line pipe material (High Yield)	API 5L B	A234 WPB	A105/N
	API 5L X42	A860 WPHY42	A694 F42
	API 5L X46	A860 WPHY46	A694 F46
	API 5L X52	A860 WPHY52	A694 F52
	API 5L X60	A860 WPHY60	A694 F60
	API 5L X65	A860 WPHY65	A694 F65
	API 5L X70	A860 WPH70	A694 F70

Comments:

• The list is for reference only. Pls make a final confirming before order.
• If your material is not in this list, pls contact Yaang without any hesitate.