Some standard content:
Mechanical Industry Standard of the People's Republic of China
Reduced Diameter Forged Steel Valves
1 Subject Content and Scope of Application
JB/T 7746:95
Replaces 1600390
This standard specifies the structural type, technical requirements, test methods, inspection rules, marking and supply requirements of reduced diameter forged steel valves. This standard applies to gate valves, stop valves, throttle valves and lift check valves made of carbon steel, stainless steel and alloy steel with nominal pressure PN14.0MPa and nominal diameter DN10~50mm with internal thread, socket welding and butt welding connection; it also applies to gate valves, stop valves, throttle valves and lift check valves with nominal pressure PN2.5.4.0, 10.025.0MPa and nominal diameter DN10~50mm with internal thread, socket welding, butt welding and flange connection.
, cited standards
GB1220
GB1221
GB3077
GB 5796
GB7306
Steel pressure vessels
Basic dimensions (diameter 1~600mm)
Ordinary thread
Ordinary thread:
Tolerance and fit (diameter 1~355mm)
Stud b1.25d
Stainless steel rod
Heat-resistant steel rod
Technical conditions for alloy structural steel
Trapezoidal thread
Pipe thread with thread seal
GB 9113.1~~9113.26
Integral steel pipe flange
GB9125
GB9131
GB12220
GB12221
GB12224
GB 12228
Steel pipe flange
Steel pipe flange
Technical conditions
Pressure-temperature grade
General valve mark
Structural length of flange-connected metal valves
Steel valves
General valves
GB/T 12252
General requirements
Technical conditions for carbon steel forgings
General valves
GB/T 15188.1
JB/T 1751
I13/ 5300
ZBJ16 006
3Structural type
Supply requirements
Structural length of valve
Butt-welding valve
Valve structural requirements Socket welding connection and pipe end dimensions General valve materials
Testing and inspection of valves
The valve structural types and names of main parts are shown in Figures 1 to 4. Designers are allowed to design valves with other structures under the condition that they meet the technical requirements of this standard. Approved by the Ministry of Machinery Industry of the People's Republic of China on June 20, 1995 476 Implemented on January 1, 1996 JB/T 7746-95 1 Valve body 2--Valve seat, 3--Gate: 4··Valve stem; 5--Gasket: 6--Valve cover: 7-Bolt; 8 Packing: 9 Packing sleeve 10 Packing pressure plate; 11 Joint bolt: 12 Valve cup nut; 13-Handwheel: 11--Leg: 15·Locking nut Figure Gate valve JB/T 7746---95
1 Valve body; 2 Valve seat; 3 Gate plate; 4- Valve stem 5- Gasket; 6. Valve cover ·· Bolt ·· Packing pad Packing 10-- Packing sleeve: 11-Pressing sleeve nut: 12-Nameplate; 13. Handwheel: 11 Locking nut Figure 2 Gate valve
Throttle valve disc
JB/T 7746-95
Bonnet; 6 Bolt; - Packing: 8 Headless rivet; 9 Packing sleeve: 1--- Body; 2 Disc; 3 Stem, - Plate, 10-- Packing pressure plate: 11-- Joint bolt: 12- Stem nut: 13-- Nameplate: 11 Figure 3 Stop valve, throttle valve
Handwheel: 15- Locking nut
1 Valve body; 2 Disc; 3 Spring; Gasket; 5 Valve cover: 6. Rivets: 7 plates; 3 bolts Figure 4 Lifting check valve
4 Technical requirements
4.1 Pressure and temperature grade
JB/T 7746--95
4.1.1 The pressure and temperature grade of the valve with nominal pressure PN14.0MPa shall be in accordance with the provisions of Appendix A (supplementary parts), 4.1.2 The pressure-temperature grade of the valve with nominal pressure PN2.5, 4.0, 10.25.0MPa shall be in accordance with the provisions of (B9131. 4.2 Valve body connection end
4.2.1 The internal thread connection shall adopt the tapered pipe thread specified in G137306 4.2.2
The structural length of the valve with internal thread and socket welding connection shall comply with the provisions of Table 1 or the requirements of the order contract. Table 1
Connection type
Nominal pressure
Structural length
Nominal diameter
All threaded connection
Short series Short series!
Note: The deviation of the structural length is ±1.6m
Stop valve
Throttle valve
Stop valve
Socket welding connection
10.0.14.0
Long series Short series Long series
Short series
The end size of the socket welding connection shall comply with the provisions of JB/T1751, 110
4.2.4 The size of the butt welding end shall comply with the provisions of GB12224, and the welding requirements shall comply with the provisions of GB150. 4.2.5 The structural length of the butt welding connection valve shall comply with the provisions of B/T15188.1 or according to the requirements of the order contract. 4.2.6 The form and size of the end face sealing surface of the flange connection shall comply with the provisions of GB9113.1~9113.26. 28.0
Throttling valve
Positive return valve
4.2.7 The end flange and the valve body can be integrally forged or welded. The corrosion resistance of the flange material must be at least equal to that of the valve body material. The welding requirements shall comply with the provisions of GB150, and the welder shall pass the examination as required by the relevant departments. 4.2.8 The welding of the end flange and the valve body is not allowed to adopt the socket welding structure. The integral centering ring (lining ring) used for the convenience of welding must be removed after welding. The final thickness of the welded part shall not be less than the valve body wall thickness listed in Table 2. 4.2.9 The structural length of flange-connected valves shall comply with the provisions of GB12221 or the requirements of the order contract. 4.2.10 The surface roughness of the end flange surface shall comply with the requirements of GB9125. If there are more stringent requirements for the surface roughness of the flange surface, it shall be stated in the order contract.
4.2.11 For all austenitic stainless steel valves, the end flange and valve body must be solution treated after welding. 4.3 Valve rest and valve cover
4.3.1 The minimum valve body thickness at any point except the end connection shall not be less than the value listed in Table 2, 480
Nominal pressure PV
2.5.4.0,10.0,14.0
JB/T 7746—95
Minimum wall
4.3.2 The minimum bonnet wall thickness at any point below the stuffing box shall not be less than the value listed in Table 2. 4.4 Connection between valve body and bonnet
4.4.1 The valve body and bonnet can be connected by flange, thread and welding or welding. 40
4.4.2 The flange is connected by studs or bolts. The studs shall comply with the provisions of G13898. The bolts shall be hexagonal head bolts with a platform, and the number shall not be less than 4.
4.4.3 The basic thread dimensions of bolts and nuts shall comply with the provisions of GI3196, and the tolerances shall comply with the provisions of GB197. 4.4.4 When flange connection is adopted, the valve body and bonnet shall be designed so that the gasket cannot move during assembly, and the gasket shall not be over-compressed after assembly.
4.4.5 When the valve body and the closure are welded, the welding requirements shall comply with the provisions of GB150, and the welding results shall pass the examinations stipulated by the relevant departments. 4.5 Parts
4.5.1 Valve stem
The valve stem shall be made of a whole material, and it is not allowed to be welded by two or more parts: the valve stem shall have a conical upper sealing surface, which coincides with the upper sealing surface of the valve cover when the valve is fully opened to achieve the purpose of sealing; the thread of the valve stem shall be a trapezoidal thread, and its size shall comply with GB5796 or Appendix B (supplementary parts): the valve stem diameter shall not be less than the value listed in Table 3; the surface roughness of the part of the valve stem that contacts the packing shall be R≤0.8un, and if there are special requirements, they shall be indicated in the order contract. Table 3
Nominal diameter DN
Nominal pressure PN
2.5,4.0,10.0.14.0
4.5.2 Gate
The gate is a solid wedge structure:
Minimum stem diameter
The gate should have a guide structure to minimize the wear of the sealing surface between the gate and the valve seat; when designing, it should be ensured that the gate does not block the channel when the valve is fully open; 40
The width of the gate seal pair should be considered when designing. The center of the gate seal surface must be higher than the center of the valve body seal surface. When the seal pair is worn, the gate closing position drops, and the gate and The valve body sealing surface should still be completely consistent, and the gate wear allowance should not be less than 2.311m, as shown in Figure:
If the gate sealing surface needs to be surface-welded, the cladding layer should not be less than →}1.6nm after cladding. The corrosion resistance of the gate base material should be at least equal to the corrosion resistance of the valve body material. 4.5.3 Valve seat www.bzxz.net
Gate sealing surface position
(new valve)
New valve seat
JB/T 7746--- 95
Worn valve seat
Center line of body sealing surface
(after wear)
If it is necessary to perform surface welding on the valve seat sealing surface, the welding layer shall not be less than 1.6mm after processing + the corrosion resistance of the valve seat base material shall be at least equal to the corrosion resistance of the valve body material: the designer shall determine the hardness difference between the sealing pairs based on the selected materials; b.
The minimum diameter of the valve seat shall not be less than the values listed in Table 4, Table 4
Nominal pressure PN
2.5, 1.0, 10.0, 14.0
Nominal diameter of the valve seat
Minimum diameter of the valve seat||t t||If the valve disc sealing surface needs to be surface welded, the weld layer shall not be less than 1.6mm after processing. The corrosion resistance of the valve disc base material shall be at least equal to the corrosion resistance of the valve body material: the valve disc sealing surface of the stop valve and check valve can be in the form of a cone or a plane, and the valve disc sealing surface of the throttle valve adopts a conical structure: b. The valve disc of the lift check valve should have sufficient guide surface. The ratio of the guide length to the diameter shall not be less than C.84.6 Connection between the valve stem and the gate plate
The valve stem and the gate plate should be connected with a T-slot
The connection strength between the valve stem and the gate plate should be greater than the tensile strength of the root of the valve stem thread. 4.6.2
4.7 Connection between stem and disc
The stem and valve are connected by I-shaped grooves, split rings, rolling and other connection methods. It is necessary to ensure that the connection part can rotate flexibly during operation: 4.8 Screwing of stem and stem screw
4.8.1 The screwing length of stem and stem nut should be greater than 1.5 times the major diameter of stem thread for upper thread type and greater than 1.3 times the major diameter of stem thread for lower thread type
4.8.2 When the newly manufactured valve is closed, the threaded part of the stem of the upper threaded gate valve should protrude 3-7mm from the stem nut. The distance between the bottom surface of the wheel of the upper threaded gate valve and the stop valve (throttle valve) and the top surface of the stem nut shall not be less than 5mm; the distance between the bottom surface of the lower wheel of the lower threaded cut-off valve (throttle valve) and the top surface of the gland nut shall not be less than 10mm. 4.8.3 The thread of the valve stem nut is a trapezoidal thread. Its size is in accordance with (135796 or Appendix B (supplementary): 4.9 Connection between valve seat and valve body
JB/T 7746.--95
4.9.1 The valve seat and valve body are connected by thread, expansion joint, welding and other forms, and can also be directly processed or clad on the valve body. The male welding layer after processing shall not be less than 2mm.
4.9.2 The thread size of the threaded valve seat shall be in accordance with G1196. 4.9.3 When assembling the valve seat, it is forbidden to use sealants. However, light lubricating oil is allowed. 4.10 Bolted packing positive cover assembly. The bolted packing gland can be a whole or composed of a pressure plate and a pressure sleeve. The pressure plate and the pressure sleeve should be able to automatically align 4. 10.1
There should be a shoulder on the top of the gland to prevent the gland from entering the stuffing box and affecting the packing adjustment. The gland plate has two holes for mounting bolts and slots are not allowed. Threaded gland assembly
Threaded glands include gland screws and glands. 4.11. 1
4.11.2 The corrosion resistance of the gland nut shall be at least the same as that of the valve cover. 4.17.3 The thread size of the gland nut shall comply with the provisions of G13196. 4.12 Packing and stuffing box
4.12.1 The packing must be suitable for steam and petroleum media within the design pressure-temperature rating range, and the packing must contain a preservative. 4.12.2 The minimum depth of the stuffing box shall comply with the provisions of Table 5: 4.12.3 After the packing gland is tightened, the remaining adjustment length of the packing gland should be greater than 25 of the minimum depth listed in Table 5. Table 5
Nominal pressure V
2.3,4.0,10.0,14, 0
Stem type
Upper thread type
Lower thread type
Nominal diameter
Minimum depth of stuffing box
4.12.4 The surface roughness Rα of the stuffing box should be 3.2urm. If there are more stringent requirements for the surface roughness of the stuffing box, it should be stated in the order contract.
4.13 The handwheel is a spoke structure and should be of sufficient size for easy closing. Turn the handwheel clockwise to close. There should be an arrow indicating the closing direction and the word "close" on the rim, or a double-directional arrow and the words "open" and "close". 4.14 Materials
4.14.1 The valve body, valve cover and gland nut must be in accordance with GB 1220, GB1221, GB3077 or GB12228. The above materials must meet the requirements of the pressure-temperature grade of this standard. 4.14.2 Stem nut
. The valve stem nut should be made of materials with high wear resistance, corrosion resistance and a minimum melting point of 945 (4.14.3 Valve cover heat plate
The valve cover gasket can be made of stainless steel wound graphite or asbestos, soft iron, polytetrafluoroethylene or steel pads according to different pressures, working temperatures and applicable media. The metal part of the gasket exposed to the working environment should be made of metal with a corrosion resistance at least equal to the corrosion resistance of the shell. 4.14.4 The handwheel should be made of carbon steel, malleable cast iron or ductile iron. Gray cast iron is not allowed. 4.14.5 In addition to selecting the materials of the main parts according to the order requirements, they can also be selected according to JB/T5300. 5 Test method
The test of the valve shall be in accordance with the provisions of Z13J16006. 183
6 Inspection rules
6.1 Factory inspection
JB/T7746.95
6.1.1 The valve must pass the factory inspection and be accompanied by a certificate of conformity before it can leave the factory. 6.1.2 Factory inspection shall be in accordance with the provisions of ZBJ16006. If any item fails during the factory inspection, the product shall be deemed unqualified and shall be repaired. If it still fails after repair, it shall be scrapped. 6.1.3
Forging defects found through testing or inspection are allowed to be repaired according to the corresponding material standards. 6.1.4
6.2 Type test
Type inspection should be carried out in any of the following situations: new product trial production and finalization appraisal:
every two years in continuous production;
when there are major changes in structure, process and materials; when the product is resumed after a long period of suspension;
when there is a big difference between the factory inspection result and the last type inspection; when the national quality supervision agency proposes a requirement for type inspection. 6.2.2 Type inspection adopts random sampling of valves that have been inspected and qualified by the production and quality inspection departments and are in stock or supplied to users but have not been used. The minimum number of valves for sampling for each specification is 30, and the number of sampling is 3. When the user takes samples, the number of sampling is not limited, and the number of sampling is still 3. When conducting quality assessment on the entire series, the sampling department may select 2 to 3 typical specifications from the series for testing according to the situation. The number of units for each specification to be tested and the number of units to be sampled are still 30 and 3. 6.2.3 The contents of type inspection shall be in accordance with the provisions of Table 6.|tt||Type inspection items
Valve body and valve cover
Opening and closing parts
Shell test
Seal test
Technical requirements
4.3 of this standard
4.5 of this standard
4.14 of this standard
ZBJ16006
ZB J16 006
Test method
Conventional basic test
Conventional tools
Related material standards
Z3 J16 006
ZB J16 006
6.2.4 If any unqualified products are found in the type inspection, the same batch of products for sampling shall be re-sampled for inspection. If it is still unqualified, production should be stopped, reasons should be analyzed, and measures should be taken until it is qualified before production can be continued. 7 Marking
Valve marking shall comply with the provisions of GB12220.
8 Supply
Valve supply requirements shall comply with the provisions of GB/T12252. 184 In the type inspection, if there is any failure, the same batch of sampled products should be re-sampled for inspection. If it is still unqualified, production should be stopped, the cause should be analyzed, and measures should be taken until it is qualified before production can be continued. 7 Marking
Valve marking shall comply with the provisions of GB12220.
8 Supply
Valve supply requirements shall comply with the provisions of GB/T12252. 18
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