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Causes of Oil Leakage in Hydraulic System Pipelines
Date : 2021-12-10
There are many types of pipelines used in the hydraulic system. According to the working pressure and installation position of the hydraulic system, steel pipes (seamless hydraulic tube ) , copper pipes, rubber pipes, nylon pipes and plastic pipes are selected. Once these pipelines are damaged and leaking oil, it will pollute the environment and affect the normal function of the system, or endanger safety in severe cases. This article analyzes and summarizes the causes of oil leakage in hydraulic pipelines and the corresponding countermeasures.
Analysis of the cause of oil leakage:
1. Poor quality of piping
When repairing or replacing hydraulic pipelines, if inferior pipelines are installed in the hydraulic system, oil leakage will occur due to their low pressure-bearing capacity and short service life. The poor quality of hard tubing is mainly manifested by uneven wall thickness, which reduces the load-bearing capacity; inferior hoses are mainly caused by poor rubber quality, insufficient steel wire layer tension, and uneven weaving, resulting in insufficient load-bearing capacity. Under the impact of pressure oil, It is easy to cause pipeline damage and oil leakage.
![\"hydraulic](\"https://www.eastern-steels.com/attached/image/20211210/20211210102552465246.png\" "\\"hydraulic")
2. The pipeline installation does not meet the requirements
a. Poorly bent pipeline
In the process of assembling the hard pipe, the pipe should be bent according to the specified bending radius, otherwise the pipe will have different bending internal stresses and gradually leak under the action of oil pressure. If the bending radius of the rigid pipe is too small, the outer pipe wall of the pipe will become thinner, and the inner pipe wall will have wrinkles, so that the pipe has a great internal stress at the bend, and the strength is greatly reduced. The road is prone to transverse cracks and oil leakage; if a large ellipse occurs in the bending part of the hard pipe, longitudinal cracks and oil leakage are likely to occur when the oil pressure in the pipe fluctuates.
When the hose is installed, if the bending radius does not meet the requirements or the hose is twisted, it will cause damage to the hose and oil leakage.
b. The installation and fixation of the pipeline does not meet the requirements
Common improper installation and fixation include:
(1) When installing oil pipes, regardless of whether the length, angle, and thread of the pipes are suitable for assembly, the pipes are deformed and installation stress is generated. At the same time, it is easy to damage the pipes and reduce their strength;
(2) When installing the oil pipe, do not pay attention to fixing it. When the bolts are tightened, the pipe will rotate together, causing the pipe to twist or collide with other parts and cause friction, which will shorten the service life of the pipe;
(3) Sometimes the pipe clamps are too loose, which increases the friction and vibration between the pipe and the clamp; sometimes they are too tight, causing the pipe surface (especially aluminum pipe) to be clamped and deformed; these conditions will damage the pipe and cause damage to the pipe. Oil spill
(4) The tightening torque of the pipeline joint is severely exceeded, causing the bell mouth of the joint to be broken, the thread is strained, and the tripping leads to a serious oil leakage accident.
3. Fatigue damage or aging of hydraulic pipeline
The observation and analysis of a large number of hard hydraulic pipeline fractures show that the rupture of the hard pipeline is a kind of fatigue failure, so there must be an alternating load on the pipeline. When the hydraulic system is working, the hydraulic pipeline has to withstand higher pressure, coupled with the combined effect of alternating stress caused by pressure instability, vibration stress caused by equipment vibration, assembly stress, etc., so that the hard tube is in the material defect. , Stress concentration occurs at the corrosion point or damage, and the pipeline is fatigued and fractured and oil leaks. For rubber pipelines, they will age, harden and crack from places with high temperature, high pressure, bends, and serious distortions, and finally the pipeline will burst and leak oil. Long Ben hydraulic steel pipe
4. Hydraulic oil pollution and pipeline surface pollution
When the hydraulic oil is contaminated, the oil pipe will be worn and corroded, and the rupture of the pipeline will be accelerated and the oil will leak. Moreover, this kind of damage is not easy to be found, and the damage is more serious.
Since the hydraulic system is easily contaminated, hydraulic oil containing solid contaminants is similar to the abrasive used for grinding metal processing surfaces, increasing the friction between the oil and the inner wall of the pipeline. Moreover, the hardness of solid pollutant particles is usually much higher than the hardness of the inner wall material of the catheter, which accelerates the abrasion of the inner wall of the catheter and even scratches the inner wall. Especially when the flow rate of the liquid is high and unstable (fast flow rate and large pressure pulsation), the material on the inner wall of the catheter will be impacted and peeled off.
When the hydraulic oil contains water, it will promote the hydraulic oil to form an emulsion, reduce the lubrication and anti-corrosion effect of the hydraulic oil, and accelerate the wear and corrosion of the inner wall of the pipeline. When the hydraulic oil contains a lot of air bubbles, the air bubbles in the high-pressure pipeline are compressed, and the surrounding oil flows to the space originally occupied by the air bubbles at high speed, causing strong hydraulic shock. Under the impact of the high-pressure liquid mixture, the inner wall of the pipeline is affected. Corroded and peeled off. These conditions will eventually rupture the pipeline and cause oil leakage.
In addition, the outer surface of the pipeline is often stained with moisture, sludge and dust. If the protective layer is damaged, it is easy to corrode, resulting in a decrease in strength, until blasting oil occurs from high temperature, high pressure, bending, and serious distortion.
Material of hydraulic pipe: Ordinary carbon steel pipe is used more in large hydraulic systems, and most of stainless steel is used in special pipelines. The hydraulic pipe is relatively less used. The most common is carbon steel pipe.
How to maintain the hydraulic system pipeline?
Date : 2021-12-14
1. Check the quality of the pipeline carefully, and strictly prohibit the use of unqualified pipelines
When repairing, the newly replaced pipeline should be carefully checked by the manufacturer, date, batch number, specified service life, and whether there are any defects. The pipeline that does not meet the requirements must not be used. When in use, always check the pipeline for wear and corrosion; in the process of use, once the rubber hose is found to be severely cracked, hardened or bubbling, it should be replaced immediately.
![\"hydraulic](\"https://www.eastern-steels.com/attached/image/20211210/20211210105160046004.png\" "\\"hydraulic")
2. Install the pipeline correctly, and it is strictly forbidden to assemble in violation of regulations
1) Correct assembly of hose lines
When installing the hose to tighten the threads, be careful not to twist the hose, you can draw a colored line on the hose for observation; when the hose is installed in a straight line, there should be a length allowance of about 30% to meet the needs of oil temperature, tension and vibration ; The bending radius of the hose bend should be greater than 9 times the outer diameter of the hose, and the distance from the bend to the pipe joint should be at least 6 times the outer diameter of the hose; rubber hoses are best not to be used in an environment with high temperature and corrosive gas; There are many hoses in the system, which should be fixed by installing pipe clamps or separated by rubber plates.
2) Correct installation of hard pipe (hydraulic steel tube)
The installation of hard pipes and pipes should be horizontal and vertical to minimize turns and avoid crossing; the radius of the turns should be greater than 3 to 5 times the outer diameter of the tubing; long pipes should be fixed firmly with standard pipe clamps to prevent vibration and collision; The distance between the clamps should meet the regulations. For pipelines with high vibration, the clamps should be equipped with vibration damping pads; when connecting the pipelines to the mechanical parts, first fix the auxiliary parts joints, and then fix the pipelines to prevent the pipelines from being affected. Twisted, must not be installed forcibly.
3. Properly use and maintain, and it is strictly forbidden to pollute the hydraulic system
In daily maintenance work, it is not allowed to step on, pull or press the pipeline at will, and it is not allowed to hit the pipeline with metal tools to prevent mechanical damage; hydraulic machinery or hydraulic equipment parked in the open should be covered with cloth to prevent damage. Dust, rain and snow work, water removal, drying and rust removal should be carried out in time after rain and snow; oil and dust on the surface of the pipeline should be frequently wiped to prevent pipeline corrosion; when adding oil and disassembling parts, be careful Pollution gates to prevent debris and moisture from being brought into the system. In addition, be sure to prevent harmful solvents and liquids from being spilled on the catheter.
4. Other
For pipelines with large changes in the oil temperature and ambient temperature on the equipment, thermal expansion compensation should be considered during installation to reduce the impact of thermal stress; in order to ensure the safe operation of the pipeline and extend the service life, The rubber tube should be insulated and cooled, such as wrapping the insulation layer and introducing heat dissipation air, etc. are effective measures; on the premise of meeting the system performance requirements, consider installing a suitable accumulator in a place that is prone to hydraulic shock Or vibration absorber, and try to use hydraulic components with buffer devices to reduce hydraulic pulsation and prevent hydraulic shock.
Eastern Steel Manufacturing Co.,Ltd is a leading manufacturer and distributor of carbon seamless steel pipe(seamless line pipe/seamless boiler tube/seamless galvanized pipe/hydraulic steel tube), welded steel pipe, OCTG products and fittings. We supply first-step processing, semi-finished parts and finished parts to help our clients meet fabrication requirements beyond their capacity or to improve operations by moving forward the pre-production processing.
Import and export of seamless pipes in China
Date : 2021-12-21
1. Generally, the import volume of seamless steel pipes is very large. The main importing countries are Germany and Japan. European countries such as Romania, Russia, Switzerland, France, Spain, Czech Republic, Yugoslavia, Hungary and other countries have imports. There are also a small amount of imports from South American countries such as Argentina and Mexico.
2. According to the different requirements of our country\'s users, there are more than 100 kinds of imported seamless pipe specifications, and the common specifications are 159.22mm, 159.5mm, and 159.18mm. 114.38mm, 114.310mm, 114.313mm. The length is generally 5-8m or 4-7m. Mainly hot-rolled carbon structure, steel grades are ST35, ST45 and ST65. The smallest imported size is 305mm and the largest is 478.13mm.
3. A small number of seamless pipes with smaller diameters and thin walls have been imported from France and Spain, such as 183mm, 223mm, 26.93mm, etc. Carry out the general rules of the Mannesmann steel pipe factory in Germany.
4. For seamless pipes imported from Hungary and Japan, often refer to DIN2448 and DIN1629.
5. In the case of import claims, the quality problems of imported seamless pipes mainly include: divergence of chemical composition, splitting in flattening test, low tensile strength, severe rust and pits, etc.
2) Market supply and demand
The data shows that China\'s seamless steel pipe production decreased year by year from 2014 to 2018. In 2018, China\'s seamless steel pipe production was 24.83 million tons, a year-on-year decrease of 4.87%. It rebounded in 2019. In 2019, China\'s seamless steel pipe production was 27.98 million tons. A year-on-year increase of 12.69%.
From 2014 to 2018, the demand for seamless steel pipes in China has decreased year by year. In 2018, the demand for seamless steel pipes in China was 20.86 million tons, a year-on-year decrease
5.94%, a rebound in 2019, China\'s seamless steel pipe demand in 2019 was 23.77 million tons, an increase of 13.93% year-on-year.
3) Import and export trade
The export volume of China\'s seamless steel pipes is greater than the number of imports. From 2014-2017, the number of China\'s seamless steel pipe exports decreased year by year, and began to pick up in 2018. In 2018, China\'s seamless steel pipe exports were 4.16 million tons, an increase of 1.60% year-on-year; in 2019, China had no The export volume of seam steel pipes was 4.35 million tons, a year-on-year increase of 4.48%.
China’s seamless steel pipe imports increased year by year from 2016 to 2018. In 2018, China’s seamless steel pipe imports amounted to 200,000 tons, an increase of 9.65% year-on-year. In 2019, there was a decline. In 2019, China’s seamless steel pipe imports were 140,000 tons. A year-on-year decrease of 29.32%.
From 2016 to 2019, China\'s seamless steel pipe export value increased year by year. In 2018, China\'s seamless steel pipe export value was 5,444.5 million U.S. dollars, an increase of 22.65% over the same period last year; China\'s seamless steel pipe export value was 562,124 U.S. dollars in 2019, an increase of 3.44% year-on-year.
In 2018, China\'s seamless steel pipe imports amounted to US$96,166, a year-on-year increase of 5.92%; China\'s seamless steel pipe imports in 2019 were 694.43 million yuan, a year-on-year decrease of 27.79%.
Seamless steel pipe production process
Date : 2021-12-28
The production methods of seamless steel pipes are roughly divided into cross-rolling method (Mennesmann method) and extrusion method. The cross-rolling method (Mennesmann method) is to first pierce the tube blank with a cross-rolling roller, and then extend it with a rolling mill. This method has a fast production speed, but has high requirements on the workability of the tube blank, and is mainly suitable for the production of carbon steel and low-alloy steel pipes.
![\"Seamless](\"https://www.eastern-steels.com/attached/image/20211215/2021121515220372372.png\" "\\"Seamless")
The extrusion method is to use a piercing machine to pierce a tube blank or a steel ingot, and then use an extruder to extrude into a steel tube. This method is less efficient than the cross-rolling method and is suitable for the production of high-strength alloy steel tubes.
Both the cross-rolling method and the extrusion method must first heat the tube billet or steel ingot, and the produced steel tube is called a hot-rolled tube. Steel pipes produced by hot working methods can sometimes be cold worked as needed. There are two methods of cold working: one is the cold drawing method, which is to draw the steel pipe through a pipe drawing die to make the steel tube gradually thinner and elongated; the other method is the cold rolling method, which is the invention of the Mennesmann brothers The hot rolling mill is used in cold working methods. The cold processing of seamless steel pipes can improve the dimensional accuracy and processing finish of the steel pipe, and improve the mechanical properties of the material.
Production process of seamless steel pipe (hot rolled steel pipe)
The seamlessness of steel pipes is mainly accomplished by tension reduction, which is a continuous rolling process of hollow base material without mandrel. Under the condition of ensuring the welding quality of the mother pipe, the welded pipe tension reducing process is to heat the welded pipe as a whole to above 950 degrees Celsius, and then roll it into various outer diameters and walls by a tension reducer (the tension reducer has 24 passes) For thick finished pipes, the hot-rolled steel pipes produced by this process are essentially different from ordinary high-frequency welded pipes. After being heated by the heating furnace, the metallographic structure and mechanical properties of the weld seam and the parent body can be completely consistent. In addition, through multiple passes The secondary tension reducer rolling and automatic control make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the pipe body) better than similar seamless pipes. In the fluid pipes produced in developed countries in the world, a large number of welded pipe seamless technology has been adopted in boiler pipes. With the development of society, the situation of domestic hot-rolled welded pipes gradually replacing seamless pipes has taken shape.
The necessity of pickling seamless steel pipes
Date : 2022-01-05
First of all, we must understand what is pickling: the method of using acid solution to remove oxide scale and rust on the surface of steel is called pickling. Acids for pickling include sulfuric acid, hydrochloric acid, phosphoric acid and mixed acids.
![\"seamless](\"https://www.eastern-steels.com/attached/image/20211230/20211230152210041004.jpg\" "\\"seamless")
The pickling process is to remove the surface oxide scale, and then go through lubrication treatment (carbon steel-phosphorous saponification, stainless steel-butter lime, copper and aluminum pipe-oiling), using the old process-copper plating), and then deep drawing processing. If the seamless steel pipe is not pickled, there may be oxides and oil stains on the surface, and the nuclear energy of the phosphating liquid cannot remove them, and the quality of phosphating will be reduced. Moreover, in the manufacturing process of seamless steel pipes, after many processes, if you are not careful, it will leave scars on the surface of seamless steel pipes, which will reduce the corrosion resistance of parts and directly affect the service life.
Pickling passivation of seamless steel pipes is a chemical reaction to remove rust on the surface of seamless steel pipes. Pickling and passivation of stainless steel can remove all kinds of dirt, such as oil stains, rust, oxide scale, welding spots, etc. After pickling and passivation of seamless steel pipes, the surface becomes uniform silver white, which greatly improves the corrosion resistance of stainless steel and is suitable for various models. Stainless steel parts, plates and equipment. It is simple to operate, easy to use, economical and practical. At the same time, it is added with high-efficiency corrosion inhibitors and fog inhibitors to prevent metal corrosion, hydrogen embrittlement, and acid fog. It is suitable for small and complex workpieces, and is not suitable for pasting. It is superior to similar products in the market.
What are the uses of large diameter seamless steel pipes?
Date : 2022-01-12
1. In our daily life, large-diameter seamless steel pipes are a very common channel, mainly used in sewers and water pipes. Our tap water is transported to each of our homes through large-diameter seamless steel pipes. Our life Water is inseparable from large-diameter seamless steel pipes. And the water pipe will also use large-diameter seamless steel pipe, so that we have a steady stream of water resources.
![\"large](\"https://www.eastern-steels.com/attached/image/20220112/20220112101140384038.png\" "\\"large")
2. Large-diameter seamless steel pipes have great contributions to agriculture and heavy industry. In agriculture, this steel pipe is mainly used for irrigation, providing water for agricultural irrigation and reducing farmers\' labor. The heavy industry needs to transport some oil, and the large-diameter seamless steel pipe has good sealing performance to ensure that the fuel does not leak, and it is a good transportation pipeline.
3. Large-diameter seamless steel pipes have good load-carrying capacity. In our big cities, in addition to being used in our daily life, large-diameter seamless steel pipes are also widely used in our cities, such as , There are frequent bridges in our city, such as bridges across the sea, bridges are basically constructed with large-diameter seamless steel pipes, which are the main body of these large buildings. With large-diameter seamless steel pipes, our Cities are built better and stronger.
4. With the development of science and technology, South-to-North water transfer and gas transportation have become simple things, and these are inseparable from large-diameter seamless steel pipes. Large-diameter seamless steel pipes are mainly used for gas transportation, and various For the transportation of natural gas and other gases, when the gas and water supply in a certain place is insufficient, transportation pipelines are needed at this time, and large-diameter seamless steel pipes are such a transportation pipeline.
Tips: Line pipes are used to transport the oil, steam, and water extracted from the ground to petroleum and natural gas industrial enterprises through line pipes. Line pipes include carbon seamless line pipes and welded steel pipes. The pipe ends have flat ends, threaded ends and socket ends; its connection The method is end welding, coupling connection, socket connection and so on.
Features of Mild steel (low carbon steel)
Date : 2022-01-12
Mild Steel (Mild steel seamless pipe) is carbon steel with a carbon content of less than 0.25%. It is also called mild steel because of its low strength, low hardness and softness. It includes most ordinary carbon structural steel and some high-quality carbon structural steel, most of which are used for engineering structural parts without heat treatment, and some are used for mechanical parts requiring wear resistance after carburizing and other heat treatment.
![\"mild](\"https://www.eastern-steels.com/attached/image/20220112/20220112110556335633.png\" "\\"mild")
Features of Mild steel (low carbon steel):
The annealed structure of low carbon steel is ferrite and a small amount of pearlite, its strength and hardness are low, and its plasticity and toughness are good. Therefore, its cold formability is good, and cold forming can be carried out by methods such as hemming, bending, and stamping. This steel also has good weldability. Low carbon steel generally refers to steel with a carbon content between 0.10 and 0.25%. This type of steel has low hardness and good plasticity, which is convenient for cold plastic deformation forming process, welding and cutting, and is often used in the manufacture of chains, rivets, bolts, shafts, etc. Low carbon steel with very low carbon content has low hardness and poor machinability, and normalizing treatment can improve its machinability.
Mild steel has a large aging tendency, both quenching aging tendency and deformation aging tendency. When the steel is rapidly cooled from a high temperature, the carbon and nitrogen in the ferrite are in a supersaturated state, and it can also slowly form iron carbonitride at room temperature, so the strength and hardness of the steel increase, while the ductility and toughness decrease. This phenomenon is called quench aging. Low carbon steel will age even if it is not quenched and air cooled.
Mild steel produces a large number of dislocations after deformation, and the carbon and nitrogen atoms in the ferrite interact elastically with the dislocations, and the carbon and nitrogen atoms gather around the dislocation line. This combination of carbon, nitrogen atoms and dislocation lines is called the old Coriolis air mass (Korpal air mass). It will increase the strength and hardness of the steel while reducing the ductility and toughness, a phenomenon called deformation aging.
Deformation aging is more harmful to the plasticity and toughness of low carbon steel than quenching aging, and there are two obvious upper and lower yield points on the tensile curve of low carbon steel. From the appearance of the upper yield point until the end of the yield extension, a surface wrinkle band formed by uneven deformation on the surface of the sample, called the Ludes band. Many stamping parts are often scrapped because of this. There are two ways to prevent it. A high pre-deformation method, the pre-deformed steel will also produce Lüders strips during stamping after being placed for a period of time, so the pre-deformed steel should not be placed for too long before stamping. The other is to add aluminum or titanium to the steel to form a stable compound with nitrogen to prevent the deformation and aging caused by the formation of Coriolis aerosols.
How to distinguish floating rust and rust of seamless steel pipe?
Date : 2022-01-18
Seamless steel pipes have a hollow section and are used in large quantities as pipelines for conveying fluids, such as pipelines for conveying oil, natural gas, gas, water and certain solid materials. Compared with solid steel such as round steel, steel pipe is lighter in weight when the bending and torsion strength is the same, and it is a kind of economical cross-section steel. It is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction.Save materials and processing man-hours.