Precautions for assembly of brass pipe fittings

Precautions for assembly of pipe joints:

(1) The perpendicularity of the end surface of the steel pipe to the axis is less than 0.50.

(2) Deburring the end face, chamfering 0.2×450.

(3) Apply proper amount of grease to the threaded part and the contact cone.

(4) Install the ferrule and nut, and pay attention to the direction.

(5) Grasp the steel pipe and make the end face against the joint body step.

(6) Draw a mark and tighten the nut.

(7) Make sure that the steel pipe does not follow the turn, screw 1.3~1.5 turns.

(8) Remove the nut and check the cutting situation of the ferrule.

(9) When reassembling after pre-installation, feel the tightening torque suddenly increase from the hand, and then tighten 600~900.

In summary, the leak-proofness of the ferrule type pipe joint is inseparable from the manufacturing quality (especially the design of the ferrule and the internal quality of the ferrule) and the precision of the steel pipe. The assembly quality is inseparable, and requires good cooperation between the manufacturer and the user. Selection of progressive stainless steel double-edged ferrules: EO stainless steel ferrules are single-edged and the material is 316 (0Cr10Ni17Mo2Ti). Because of the large amount of Cr and Ni, the diffusion of infiltration elements is strongly prevented during chemical heat treatment, making the surface infiltration concentration too high , High hardness and high brittleness, containing the dispersion strengthening element Ti, making the surface hardness of the ferrule further improved. Therefore, the hardened layer of Eo stainless steel ferrule (Φ16) is only 11um.

In addition, the high concentration of infiltrating elements reacts with Cr and Ni to form a compound, which greatly reduces the solid solution amount of the matrix alloy elements and falls below the passivation point. Therefore, the corrosion resistance of the Eo stainless steel ferrule is poor, and it can be corroded during storage. Due to the special surface treatment of the thread of the Eo nut, the joint body will have less loss when the tightening torque is transmitted to the ferrule during assembly. The special wear-reducing surface layer and shallow hardened layer design allow the ferrule to smoothly cut into the steel pipe. Ordinary single-edged stainless steel ferrule, material 1Cr18Ni9Ti (304) cyanide treatment, the thread part is not surface-treated, because the friction coefficient of stainless steel to stainless steel is 1.0, so the tightening torque cannot be effectively transmitted to the ferrule.

The surface hardness of the ferrule cannot be high, and the material and processing technology cannot be guaranteed. Only the depth of the hardened layer is reduced to avoid false cutting of the ferrule. (021-57590225) The national standard recommends that the steel 1Cr17Ni2 used for ferrules is a dual-phase steel. The fluctuations in the ferrite and austenite content have a greater impact on the mechanical properties, and the double-phase ratio is directly affected by the material processing temperature, and the material has "4750C "Brittleness, due to the toughness of the passivation film before nickel heat treatment, the heat treatment process is not good. Material 430 (0Cr18) made of stainless steel ferrule, 0Cr18 is a single-phase steel, so the heat treatment process is better, through a reasonable heat treatment process, the surface can be easily penetrated into the element concentration, the hardness of the layer, the depth of the layer, adjusted to a reasonable Level. The yield limit of the three materials is: 430 is 28.1Kg/mm2. 304 is 27Kg/mm2. 316 is 25Kg/mm2. 430 has a higher yield limit, so the ferrule has a stronger ability to resist yielding and over-tightening. If the yield limit is high, the elastic limit is also high. When the ferrule is tightened, the prepared elastic energy is also high, which improves the ferrule absorber tube. Road vibration energy, ability to counteract thermal expansion and contraction deformation.

The advantages of pre-installed card sleeve joints:

Because the pre-assembled body is made of alloy tool steel and is used in the hardened state, the friction coefficient between the ferrule and the cone, the body and the nut is much smaller than that of austenitic stainless steel to austenitic stainless steel. In this way, the tightening torque can be directly applied to the cutting of the ferrule with a small loss. The tightening torque of the pre-assembled body assembly can be well matched with the number of tightening turns, and it is impossible to tighten if the tightening is less than one turn. Dynamic situation. When directly assembled with the body, only some anti-bite and anti-friction measures, such as special surface treatment of threads, are used.