Gate valve fastener, packing and gasket material selection fastener production process

Gate valve fastener, packing and gasket material selection fastener production process

Raw materials for gate valve fasteners, packing materials, gasket materials and selection, fasteners mainly include bolts, multi-head bolts and nuts. Fasteners directly bear forces in gate valves, which are of great significance to avoid the loss of media. Therefore, the raw materials selected must ensure sufficient strength and fracture toughness at the application temperature.
1. Raw materials for fasteners
Fasteners mainly include bolts, multi-head bolts and nuts. Fasteners directly bear forces in gate valves, which are of great significance to avoid the loss of media. Therefore, the raw materials selected must ensure sufficient strength and fracture toughness at the application temperature.
When selecting fastener materials according to medium pressure and temperature, they can be selected according to Table 5-1.
Nominal diameter Pg(Mpa) medium temperature (℃) 300350400425450530 bolt

Heat treatment process is required when carbon steel materials are used. When the tightening parts have special corrosion resistance standards, Cr17Ni2, 2Cr13, 1Cr18Ni9 and other stainless acid resistant steel can be selected.
Two, filler raw materials
On the valve body, the packing is used to fill the indoor space of the single flow valve packing chamber to avoid media leakage through the valve seat and the single flow valve packing chamber indoor space.
1. The demand for fillers
1) Good corrosion resistance, packing and medium contact, must be able to resist the corrosion of the medium.
2) Compact structure, packing does not leak under the influence of medium and working temperature.
3) Low friction resistance to reduce the friction torque between seat and packing.
2, the type of packing
Packing can be divided into soft plastic packing and hard packing two kinds:
1) Soft plastic filler: it is made of green planting material, namely, linen, cotton, linen, etc., or by mineral, namely glass fiber cotton, or by glass fiber cotton with iron wire and outside coated flake graphite rope woven, and ground into the forming filler, and the new opportunities of flexible graphite filler raw materials in recent years. Green plant material packing is more cost-effective, mainly used for low pressure valves within 100℃; Mineral packing is suitable for 450-500℃ gate valve. In recent years, the construction of plastic O-ring as filler is gradually popularized, but the medium temperature is generally controlled within 60℃. The packing in the high temperature and high pressure valve is also made of pure asbestos and flake graphite powder.
2) Hard packing: packing made of metal materials or metal mixed with asbestos, high purity graphite and polytetrafluoroethylene pressing calcination and forming packing, metal packing application is less.
3, the selection of stuffing
The selection of filler should be based on the medium, temperature and pressure to select, common raw materials have the following points:
1) Oil to asbestos cloth, can be selected according to Table 5-2.
2) Plastic asbestos cloth: can be selected according to Table 5-3.
3) High purity graphite asbestos cloth: asbestos cloth coated into flake graphite, the temperature can be used above 450℃, the working pressure can reach 16Mpa, generally suitable for high pressure steam. Recently and gradually the use of pressure adult font filler, lap speed placement, compact structure.
4) polytetrafluoroethylene: This is a more widely used filler at this stage. Especially available on the corrosive medium, but the temperature can not be more than 200℃. Generally, it is made of suppressor or round rod car, as shown in Figure 5-1 below.
Name model appearance
Size (aperture or square circumference)
Available limit pressure kgf/cm
Available limit temperature (℃)
Used for water steam, gas, petroleum products Y5.6.8.10.13
16.19.22.25 N3.5.6.8.10.13
16.19.22.25YS350F, Y, N3.5.6.8.10.13
16.19.22.25.45350YS250F, Y, N3.5.6.8.10.13.
16.19.22.2545250
Note: Appearance number F indicates square, through-core or one to double braid; Y indicates that it is round, with a twisted mandrel in the middle and one to two layers of braid outside; N means twisted.
Name model
Specifications (straight formula or square circumference)
Available limit pressure kgf/cm
Available limit temperature (℃)
Main purpose plastics
asbestos
Packing XS4503.4.5.6.8.10.13.16.19.22.25.2860450 XS35045350XS25045250 to steam, oil products
Screw type: head machine rubbing machine; There will be a die two punch machine, two die four punch machine, three die three punch machine, four die four punch machine, five die five punch machine, six die six punch machine, and each kind of according to the size of a series, such as a die two punch into: 0# machine, minute machine, 2 extension, two and a half machine, three extension these…
Key equipment for manufacturing fasteners:
1, screw class: head machine rubbing machine; There will be a die two punching machine, two die four punching machine, three die three punching machine, four die four punching machine, five die five punching machine, six die six punching machine, and each one is divided into a series according to the size, such as a die two punching into: 0# machine, minute machine, 2 extension, two and a half machine, three extension;
2, nuts: nuts cold extrusion forming machine automatic tapping machine;
3. Gasket type: high-speed punch;
4, teeth: wire rolling machine;
5, pin class: CNC lathe CNC lathe CNC grinding machine;
6, turning parts: CNC grinding machine; Processing center;
According to the processing technology, fasteners can be divided into hot forging and cold forging, that is, hot pier and cold pier (extrusion processing).
According to cold extrusion (cold top forging) experiment, it is determined that:
Generally, the raw materials for external hexagon head bolts should ensure that the pressure is at least 1/20(l [relative height of a sample] test · grid, and for high cold nuts, cold extruded hexagon screws and French bolts, we must ensure that the pressure deviation test 11311 reaches the standard.
Specification of raw materials for cold and hot upsetting process
The hardness of the standard material of cold pier is slightly lower, and the plasticity is better, which is conducive to the plasticity deformation when the cold pier is produced and processed and rolled. Low carbon steel or low carbon environmental protection, medium carbon carbon steel need to be annealed, quenching hardness < HRB88 is the best. The formation of lost carbon and oxide layer should be prevented during quenching.
The appearance of standard raw materials in hot heading process is better. Heating temperature can not appear coarse crystal condition, otherwise the oxidation layer directly affect the appearance of the product quality.
Fastener production and processing steps: disk element – quenching – pickling passivation – drawing wire – head – rolling teeth – heat treatment process – electroplating process – external packaging This is a bolt integration process.
Disk unit: refers to the cable you bought back
Quenching: Increases the hardness of the cable. (This process is critical, and is now used in a continuous high temperature de-stress annealing furnace)
Pickling passivation: is to wash off the rust, residue on the surface of the cable
Pull the wire: Pull the wire out of the aperture you need to make the bolt
Head: The head of the bolt is extruded by cold extrusion forming. (If it is more than M20 bolts, it needs to be red, that is, you need to warm up and then hit the head, but that kind of bolt surface is not very beautiful, because of the oxide layer)
Tooth forging: refers to the required tooth spacing and screw
Heat treatment process: This process is particularly important to clarify bolt performance levels
Electroplating process: The surface of the metal is treated to the desired surface hue