Some tips on buying gasket products

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At present, gaskets will also be widely used in many industries. Regardless of their small size, they can play a very important role. So how do we choose when we need a gasket?
1. The type and scope of gaskets should conform to the design documents and current effective standards of the country and related industries. Changes in gasket materials and usage standards must be approved.

2. There are many factors that affect the selection of gaskets. Generally, on the premise of ensuring safe operation, you can try to choose a gasket that is cheap, easy to manufacture, easy to install and replace.

3. The thickness of the gasket depends on the specific situation. Generally speaking, if the sealing surface is well treated and the pressure is not too high, a thin gasket should be used. However, when the internal pressure is high, the washer is too thin, which is not conducive to the extension of the bolt, and the rebound of the washer is too small to achieve the required amount of recovery, which may cause leakage. Therefore, when the pressure is higher, a thicker gasket should be selected.
4. In order to ensure the interchangeability of gaskets, the specifications and materials should be unified as much as possible when selecting models. When considering meeting the requirements for use, specifications and materials should be combined as much as possible, and unnecessary problems should be avoided.

5. It is not allowed to use edgeless high-strength gaskets under the conditions of medium gas and high pressure, and corrugated gaskets are also not allowed to be used on serpentine and grooved flanges.

6. Special requirements should be paid attention to. If a certain medium does not allow mixing of fine fibers, fiber gaskets should not be used. If some parts will vibrate violently, you need to choose a gasket with strong vibration resistance, resilience and durability.

7. The gaskets connected to the valve and flange at the bottom of the liquefied balloon tank should be spiral wound gaskets with metal protective rings.

8. When using gaskets, they should be used in a fully annealed state, and softer materials should be used as much as possible. The hardness of the gasket should be lower than the flange sealing surface.

9. The replacement principle of gaskets on imported equipment is to replace the types and materials as they are. When the gasket form or material needs to be replaced due to special reasons, approval is required.

Decho is a professional supplier on gasket products, if you need any , pls contact us by email [email protected]

What should I pay attention to when using gaskets with flange connections?

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What should I pay attention to when using gaskets with flange connections?

Definition of gasket:

The gasket is made of paper, rubber sheet or copper sheet. It is a material placed between two planes to strengthen the seal. It is a sealing element arranged between static sealing surfaces to prevent fluid leakage. When the flange sealing surface is matched with the gasket, the following points should be noted:

1. Thread of flange

Thread is the main direction of flange surface roughness, such as: multi-direction, recording spiral, serration and other surface finish patterns should be as close as possible to the center line of the gasket to be consistent, such as round flanges. The surface texture should be processed into concentric circles or recording spirals to avoid straight lines passing through the flange surface. If there is a straight line across the sealing surface, it will become a direct leakage path. If the gasket needs to be used in conjunction with the flange, then you need to pay attention to this point.

2. Waviness of flange

The waviness is the deviation from the overall flatness. Under normal circumstances, there is no need to consider the waviness problem, but there are two situations that require special attention, because excessive waviness is also a difficult problem to solve.

3. Roughness of flange

Roughness refers to the average value of unevenness calculated from the center of the flange surface, in units of tenths of inches (or meters). For serrated flange surfaces, the typical roughness is 125-500 microinches, while for non-serrated flange surfaces, the roughness is 125-250 microinches. For flanges that are too rough, it is usually impossible to seal the gasket, so you can only choose the softest possible gasket; on the other hand, it is difficult to seal the surface of the flange with a high degree of polishing. This kind of flange should also be avoided because of the sealing The surface needs to have enough “bite marks” to provide enough friction to prevent the gasket from being blown out or extruded or excessive creep.

Decho is a professional supplier on flange and gasket products , if you need any , pls contact us by email [email protected]

What are the advantages of spiral wound gaskets?

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The six advantages of metal spiral wound gaskets are specifically introduced as follows:

1. The metal spiral wound gasket has good compressibility and elasticity.
2. The metal spiral wound gasket has proper plasticity. After compression, it can adapt to uneven sealing surfaces, fill gaps in the sealing surfaces, and ensure good sealing performance when the system temperature and pressure alternate.
3. Metal spiral wound gaskets have good mechanical properties, tensile strength and elongation. The structural density of metal spiral wound gaskets can be determined according to different locking force requirements. The inner and outer steel rings are used to control compression. The surface accuracy of the flange sealing surface contacted by the spiral wound gasket is not high. It is also suitable for occasions where the load is uneven, the joint force is easy to relax, the temperature and pressure will change regularly, and where there is impact or vibration.
4. It has good corrosion resistance, will not be damaged in some extreme media, and will not produce large expansion and contraction.
5. Spiral wound gaskets will not soften at high temperatures, but will shrink at low temperatures.
6. With sufficient strength, the metal wound gasket will not be crushed under the action of external force, nor will it explode under high pressure.

Decho is a professional supplier on spiral wound gaskets . If you need this product, pls contact us by email [email protected]

What is a nut?

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A nut is a nut, a part that is screwed together to fix it with a bolt or screw. According to different materials, the components used in the manufacturing machinery of nuts are divided into several main types such as carbon steel, stainless steel, and non-ferrous metals (such as copper).

The locknut consists of two parts, each part has a staggered cam. Since the inclination angle of the inner wedge design is greater than the angle of the bolt and nut, this combination is tightly bitten into a whole. When vibration occurs, it can prevent the protruding parts of the loose nut from staggering and generating lifting tension, thereby achieving the combined anti-loosening effect.

Embedded nuts are brass nuts made of various embossed wires. The embedded knurled brass nuts we usually contact are all processed by precision automatic lathes.

The main method of operation for embedded knurled copper nuts is injection molding. After heating, it is embedded in plastic parts or directly injection molded. If injection molding is used, the melting point of the nut needs to be higher than 200°C, so that the embedded nut is melted by heat. After inserting the plastic part, the temperature rises rapidly.

After injection molding, the plastic body rapidly cools and crystallizes. If the temperature of the embedded nut is still high, you can pour it into the place where the copper nut contacts the plastic part and starts to loosen or crack. Therefore, copper nuts can be used instead of carbon steel nuts in the injection molding of embedded nuts.

There are two methods to form the external die knurling of the embedded copper nut. One is to use copper raw materials to draw patterns and then produce them on upper equipment. Usually, the figure drawn in this way is straight, the other is to use a round copper material. In the production process, the round copper material is directly embossed. This processing method can produce some non-standard size knurled copper nuts. The embossing shape of the embedded copper nut can be selected by the user, such as mesh or various scroll patterns.

Tianjin Decho is a professional supplier on nuts products . If you need any for your project , pls contact us by email [email protected]

How to judge the strength of hexagon socket bolts?

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Cylinder head hexagon socket screws, also known as hexagon socket bolts, cup head screws and hexagon socket screws, have different names, but they have the same meaning. Commonly used hexagon socket screws also have 4.8, 8.8, 10.9 and 12.9. Also called hexagon socket bolt, the head is hexagonal and cylindrical. According to the material, there are stainless steel and iron.

Iron is classified according to the strength grade of hexagon socket bolts. There are 4.8 grade hexagon socket screws, 8.8 grade hexagon socket screws, 10.9 grade hexagon socket screws and 12.9 grade hexagon socket screws. Hexagon socket bolts of grade 8.8-12.9 are called high-strength hexagon socket bolts.

In the process of steel structure construction, high-strength hexagon socket bolts are often used. What is a high-strength hexagon socket bolt? It should have high-strength friction and pretension. However, for convenience, people often omit “friction” and “pretension”. There are two misunderstandings:

Misunderstanding 1: Bolts with a material grade exceeding 8.8 are equivalent to “high strength”

Compared with ordinary bolts, the core of high-strength hexagon socket bolts is not the strength of the material itself, but the form of stress. The so-called stress form is the shear resistance when preload and static friction are applied.

The high strength mentioned in the bolt standards of the United States and the United Kingdom is only 8.8 and 10.9, while ordinary bolts have not only 4.6, 5.6, but also 8.8, 10.9, etc., so you cannot rely on materials to determine whether it is a high-strength hexagon socket bolt.

Misunderstanding 2: The bearing capacity of high-strength hexagon socket bolts is higher than that of ordinary bolts

The strength of high-strength hexagon socket bolts is not determined by its carrying capacity, but by high rigidity, high safety performance and strong destructive resistance.

High-strength hexagon socket bolts mainly have the characteristics of small elasto-plastic deformation in terms of high strength and high joint stiffness. Therefore, under a certain combined load, the use of high-strength bolts cannot reduce the number of bolts, but the deformation is small and the stiffness is large, so it is very suitable for occasions that require high stiffness.

Decho is a professional supplier on hexagon socket bolts products , if you need any , pls feel free to contact us by email [email protected]

What is the working principle of the nut?

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A nut is a nut, a part that is screwed together to fix it with a bolt or screw. The materials are divided into carbon steel, stainless steel, non-ferrous metals (such as copper), etc.

Nuts are parts that tightly connect mechanical equipment. Through the internal thread, nuts and bolts of the same specification can be connected together. The working principle of the nut is to self-lock through the friction between the nut and the bolt. However, the reliability of this self-locking will be reduced under dynamic load. In some important occasions, we will take some anti-loosening measures to ensure the reliability of the nut lock. One of the anti-loose measures is to use anti-loose nuts.

There are also three types of lock nuts:

1) Use two same nuts to tighten the same bolt, and increase the tightening torque between the two nuts to make the bolt connection reliable.
2) Special lock nuts need to be used together with lock washers. The special lock nut is not a hexagonal nut, but a round nut in the middle.
3) Drill threaded holes from the outer surface of the nut to the inner thread surface for screwing in small-diameter countersunk screws. The purpose is to tighten the centripetal force to prevent the lock nut from loosening.

There is a small piece of copper inlaid on the lock nuts with better quality currently on the market. The copper piece matches the thread of the lock nut on the inner surface of the nut to prevent the radial jack screw from directly contacting the locking thread and damaging fasten the screw nut. This kind of locknut has gradually begun to be applied to the shaft end locking of rotating parts, such as anti-loosening of the bearing at the mounting end of a ball screw.

TJ DECHO is a professional supplier on nut products , if you need any , pls feel free to contact us by email [email protected]

What are the anti-corrosion treatment methods for hexagon head bolts?

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When using hexagon head bolts, anti-corrosion treatment is a very important requirement. Depending on the corrosion conditions, different treatment methods can be used.

1) Oxidation

Since it hardly has the ability to prevent rust due to blackening, it will quickly rust without oil. The torque preload consistency of the blackened square column template is also poor. If improvement is needed, grease can be applied to the internal thread during assembly and then tightened.

2) Sherardizing

Sherardizing is a solid metallurgical thermal diffusion coating of zinc powder. Its uniformity is good, and a uniform layer can be obtained in the threads and blind holes of hexagon head bolts. Its processing process is pollution-free and environmentally friendly.

3) Electro-galvanized

Hydrogen embrittlement is prone to occur in the electrogalvanizing process, and the consistency is poor. Connect and assemble with a square column template with a height of 500. When butting and assembling hexagon head bolts, please pay attention to the consistency of the socket interface. You can take an auxiliary bracket, open the auxiliary bracket, and clamp the auxiliary bracket to the wooden side of the junction of the two square column templates according to the marked position, and tighten it on the other side of the same height to mark the position. First place a single piece of toggle clamp horizontally on the auxiliary support. Place the elbow up so that the end of the second clip passes through the curved space of the clip head, and then place it horizontally on the auxiliary support. In order to improve the torque-pre-tightening force consistency, the method of coating lubricating substances after plating can also be used to improve and increase the torque of the hexagon head bolts.

4) Cadmium plating

The corrosion resistance of cadmium coating is very good, especially in the ocean atmosphere, its corrosion resistance is better than other surface treatments. The waste liquid treatment in the cadmium electroplating process is expensive, and the price is about 15-20 times that of electro-galvanized zinc. Therefore, it is not suitable for hexagonal head bolts in general industries, but suitable for fasteners for oil drilling platforms and HNA aircraft.

5) Chrome plating

The chromium coating is very stable in the atmosphere, is not easy to change color and lose luster, has high hardness and good wear resistance. Chrome plating on hexagon head bolts is usually used for decoration.

Decho is a professional supplier on all kinds of bolts and nuts products . If you need any for your project , pls contact us by email [email protected]

How should the bolts be maintained?

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Bolt fasteners have become a very important part of the mechanical field, which means that we usually need to pay attention to the maintenance and maintenance of bolts, so that they can play the greatest role in the mechanical field. If they are not standardized in use, they will reduce Its service life. For the maintenance of bolts, we should do the following

1. When heating the standard parts, it should be noted that they should be stacked reasonably. If there is a deviation, the standard parts will be slightly oxidized in the quenching oil, and there will be a phenomenon of discoloration when the tempering is delayed. , If you use ether to soak it again, oily impurities are very likely to appear.
2. Standard parts are generally cleaned with silicon-hydrochloric acid cleaning agents after quenching. They must be cleaned first and then rinsed. Be careful when rinsing them, and thoroughly check the rinsing tank to avoid leaving other substances. In the above, and the water used for rinsing must be changed frequently, otherwise the products produced may have quality problems.
3. When the standard parts are about to be heat-treated, they must be cleaned thoroughly, especially the alkaline substances remaining on the surface of the standard parts. If the impurities cannot be completely removed, the standard will be removed at high temperature. The part is burned, and when it is tempered again, it will make the standard part a waste.
4. If the quenching oil cannot be replaced in time when it is in use, it will cause pollution residues and black stripes on its appearance, which will cause its appearance to be very unsightly.

Decho is a professional supplier on bolts and nuts products . If you need any , pls contact us by email [email protected]

What is the correct installation method for stainless steel flanges?

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What is the correct installation method for stainless steel flanges?

1. the stainless steel flange should have sufficient strength and not deform when tightened. The flange sealing surface should be flat and clean, and the oil stains and rust spots should be carefully cleaned up when installing the stainless steel flange.

2.the gasket should have good oil resistance and anti-aging properties, as well as good elasticity and mechanical strength. When installing stainless steel flanges, seal gaskets of different cross-sections and sizes should be selected according to the shape of the connection, and placed correctly.

3. the fastening force of the stainless steel flange should be uniform, and the compression of the rubber gasket should be controlled at about 1/3. In addition, stainless steel flanges are used according to normal methods and principles in actual use. Stainless steel flanges ensure quality and value in use, and are used and installed in accordance with normal use standards. There are no certain quality and performance issues. The stainless steel flange is not a simple mechanical part in the usual sense. The stainless steel flange is a mechanical product carrier that contains abundant technical connotations, which is used in many equipment processing. Hydraulic oil stainless steel flange is a disc-shaped part, the most common in pipeline engineering, stainless steel flanges are used in pairs. Any connecting parts that are bolted on two planes and blocked at the same time are generally called ” “Flange”, such as the connection of ventilation pipes, this type of part can be called “flange type parts”. But this kind of connection is only a part of the equipment, such as the connection between the flange and the water pump, it is not good to call the water pump “method” “Blue parts”. Smaller ones, such as valves, can be called “flange parts”. In pipeline engineering, stainless steel flanges are mainly used for pipeline connection. In the pipelines that need to be connected, a variety of flanges are installed, low-pressure pipelines can use wire flanges, and welding flanges for pressures of more than 4 kg. Add sealing points between the flanges, and then fasten them with bolts. Flanges with different pressures have different thicknesses and use different bolts. Water pumps and valves, when connected to pipelines, are also made of parts of these equipment The corresponding flange shape is also called flange connection.

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Weldability and its test evaluation for carbon steel material

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Carbon steel weldability and its test evaluation

1. Welding:

A process in which two objects are combined between atoms to form an inseparable whole by heating or pressing, with or without filling materials.

2. Weldability:

refers to the ability of homogeneous or dissimilar materials to be welded to form a complete joint and meet the expected use requirements under the conditions of the manufacturing process.

3. The four major factors that affect weldability are:

material, design, process and service environment.

4. The principles for assessing weldability mainly include:

①Assess the tendency of welding joints to produce technological defects, and provide a basis for formulating reasonable welding procedures;

②Assess whether the welded joints can meet the requirements of structural serviceability; design new welding test methods to meet the following requirements The stated principles: comparability, pertinence, reproducibility and economy.

5. Carbon equivalent:

The content of alloying elements in steel is converted and superimposed according to the equivalent of several carbon content, which is used as a parameter index to roughly evaluate the cold crack tendency of steel.

6. Oblique Y-shaped groove butt joint crack test:

The purpose is mainly to identify the cold crack tendency of the first layer of low-alloy high-strength steel welds and HAZ, and it can also be used to develop welding procedures.
1) Preparation of the test piece, the thickness of the welded steel plate δ=9-38mm. The grooves of the butt joints are processed by mechanical methods, and the two ends of the test plate are welded within a range of 60mm, and the two-sided welding is adopted. Take care to prevent corner deformation and incomplete penetration. Ensure that there is a gap of 2mm at the weld of the sample to be welded in the middle.
2) Test conditions: The electrode selected for the test weld matches the base metal. The electrode used should be strictly dried. The diameter of the electrode is 4mm, the welding current (170±10) A, the welding voltage (24±2) V, and the welding speed ( 150±10) mm/min. The test welds can be welded at various temperatures, and the test welds are welded only one line without filling the groove. After welding, let it stand and cool down for 24 hours, and then take samples and conduct crack detection.
3) Detection and calculation of crack rate. Use the naked eye or hold a 5-10 times magnifying glass to detect whether there are cracks on the surface and section of the weld and heat-affected zone. It is generally believed that when the surface crack rate of low-alloy steel “Xiaotieyan” test is less than 20%, cracks generally do not occur.

7. Latch test:

purpose, mainly to evaluate the hydrogen-induced delayed cracking tendency of steel. With other equipment, it can also measure reheat crack sensitivity and laminar sensitivity.
1) For the preparation of the test piece, take the welded steel processing or cylindrical bolt test bar, take samples along the rolling direction and indicate the position of the bolt in the thickness direction. There is a ring or spiral gap near the upper end of the test bar. Insert the pin test rod into the corresponding hole of the bottom plate so that the notched end is flush with the surface of the bottom plate. For plug test rods with annular notches, the distance a between the notch and the end surface should be such that the penetration depth of the weld bead is tangent to or intersects with the cross-sectional plane of the notch root, but the penetration of the notch root circumference shall not exceed 20%. For low alloy steel, the a value is 2mm when the welding heat input is E=15KJ/cm.
2) In the test process, according to the selected welding method and strictly controlled process parameters, a layer of surfacing weld bead is melted on the bottom plate, the center line of the weld bead passes through the center of the sample, and the penetration depth should be such that the tip of the notch is located in the heat affected zone In the coarse-grained region, the weld bead length L is about 100-150mm. When welding, the cooling time value t8/5 value of 800-500℃ should be measured. When welding is not preheated, load it when it is cooled to 100-150℃ after welding; when preheating before welding, it should be 50- higher than the preheating temperature. Load at 70°C. The load should be applied within 1 min and before cooling to 100°C or 50-70°C higher than the preheating temperature. If there is post-heat, load it before post-heat. When the test bar is loaded, the bolt may break within the duration of the load, and record the load time.

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