March 29, 2024

Anti-corrosion effect of silicone polymer modified cement mortar lining on inner wall of steel pipe

1Good anti-corrosion effect The thermal power plant of Shanghai Jinshan Petrochemical Complex is the water source for the use of Hangzhou Bay seawater as cooling water. The seawater quality elements here are roughly pH: 7.1 ~ 8.3, ion content (5700 ~ 8760) x16, The dissolved oxygen concentration is 3.59

1Good anti-corrosion effect The thermal power plant of Shanghai Jinshan Petrochemical Complex is the water source for the use of Hangzhou Bay seawater as cooling water. The seawater quality elements here are roughly pH: 7.1 ~ 8.3, ion content (5700 ~ 8760) x16, The dissolved oxygen has a mass concentration of 3.59 ~ 9.35, a high carbon dioxide content, and an annual corrosion amount of 0.73 mm. The sea creatures have many shellfish and melon seeds, and have typical seawater intake corrosion and easy growth of marine organisms. Characteristics. In this regard, both the water intake and the circulating water pipes in the 27.5MW phase I built in the 1970s and the 22.5MW power plant built in the 1980s have adopted corresponding anti-corrosion technologies and measures to prevent sea life growth. This paper intends to explain the anti-corrosion effect of silicone polymer modified cement mortar lining on the inner wall of steel pipe by analyzing the situation occurred in the first phase of the engineering facility overhaul in 1991 and the current detection potential of the metallographic laboratory of the thermal power plant.

1800mm ordinary steel pipe, a total length of 3480m, while laying DN900mm and other steel pipes of different caliber. During the construction, only the inner and outer walls of the 2xDN 1800mm steel pipe were provided with anti-corrosion measures, and the inner wall was lined with 10mm thick polyacetic acid. Ethylene and coupling water-repellent agent are blended into the anti-corrosion lining of cement mortar. After the outer wall is derusted, it is coated with cold bottom petroleum asphalt bottom layer and rubber petroleum asphalt surface layer, and the potentiometric cathodic protection technology is adopted for the pipeline. The above linings are not used for DN900mm and other steel pipes. After overhauling, it proved that the steel pipe lining with polymer cement mortar has good corrosion resistance, while the DN900mm pipe is blocked and corroded. Moreover, the DN 1800mm pipeline has been tested to show that its potential value is normal, and there is no obvious sea creature reproduction, and it still maintains a good operating state. The original intention of adopting this measure in construction is to meet the needs of completing the DN 1800mm steel pipe lining cement mortar on time. It only recognizes that the polymer cement mortar will have a longer life than the ordinary cement mortar itself, and the operation shows that this type of mortar has good performance. Antiseptic effect.

2 What is the difference between the anti-corrosion mechanism and the anti-corrosion mechanism of polymer cement mortar and ordinary cement mortar? The mechanism of ordinary cement mortar after being eroded by seawater is: CaO CaCl2 and Mg(OH)2 in cement mortar, loosely dissolved with CaCl2 After the formation of the crystallites of the water fossils, MgCl2 expands and becomes a loose precipitate which is gradually washed away by the water flow. This kind of process is very fast. It is not necessary for ordinary cement mortar lining to lose the anti-corrosion effect on steel pipes. For example, the first phase of Shanggang No. 5 Plant and Qinshan Nuclear Power Plant belongs to this type of shedding.

In the polymer modified cement mortar, due to the addition of water-soluble polymer, the precipitation of Ca(OH)2 is effectively prevented, and the displacement reaction of chloride and sulfate in seawater is inhibited; The gas permeability of the mortar layer and the water resistance of the surface of the mortar layer; the combination of the polymer and the silicone will produce another "anti-corrosion layer", and the mortar particles in the cement mortar layer are protected by the interpenetrating network of the polymerized latex, water-soluble The polymer interacts with the mortar to form a "dry film" layer. Under the long-term immersion and water pressure of seawater, the "dry film" gradually dissolves to form a glue body, the glue body floats to the lining skin layer, and the skin layer absorbs water. After the minerals, a soft layer of about 1.5 mm thick was gradually formed. The soft layer is in contact with seawater in a black film with a fibrous, slippery object. This layer of soft body and its black film is called the "anti-corrosion layer". The formation of a certain thick "anti-corrosion layer" is very meaningful. It prevents the re-action between the polymer cement mortar and the seawater, and the inner wall of the steel pipe protected by the 8.5 mm thick polymer cement mortar layer of the Jinshan seawater pipe is precipitated. The Ca(OH)2 solution is passivated to form a white passivation surface. This tightly bonded interface, like the combination of reinforced concrete, causes the overall potential of the steel tube to drop, and the steel tube itself establishes a cathodic protection system. The actual measured steel pipe potential data of the power plant indicates that this analysis is correct. This layer of “anti-corrosion layer” was proved by the analysis of the physical and chemical room of Shanghai Water Supply Company. In addition, it has certain elasticity and gas permeability, which can overcome the sudden sudden change of pressure in the pipeline, absorb the energy between the lining and the pipe wall to prevent the cracking of the polymer modified cement, called "elastic bonding". . The compressive strength of the protected 8.5mm polymer cement mortar layer can reach 60MPa, and the expansion coefficient of the cement mortar and steel is very close, which reduces the effect of temperature stress difference. The operation practice shows that the dry shrinkage cracks and micro-gap in the construction are under the action of “self-sufficiency” after long-term water supply, and the overall texture is good, which is also the advantage of this mortar layer. From the chemical mechanism, this layer of anti-corrosion slippery body has the function of adsorbing chloride ions, which has obvious functions of inhibiting microbial reproduction, so that the marine organisms attached to the tube wall can not get nutrients, preventing the sea creatures from staying on the tube wall. And breeding, the effect of chlorine ions in the absence of a chlorination device is achieved, thereby preventing sea creatures from blocking the pipeline and ensuring smooth water flow.

3 Application Examples The 6th International Conference on Polymer Mortar and Polymer Concrete held at Tongji University in Shanghai in 1994 showed that foreign countries have studied the physical and chemical properties of polymer mortar and obtained certain experimental data. And developed the corresponding technical standards. The lining project of seawater circulating water pipeline of Jinshan Petrochemical Thermal Power Plant in China can be regarded as a large-scale experiment. It conforms to the German DIN4030 and D2614 standards. The seawater steel pipeline lining must use polymer K mortar lining. The US Petroleum Industry APIR-10E standard states that seawater steel pipelines must be lined with modified mortar or polymer mortar. Due to the physical and chemical properties of polymer cement mortar, it has also been applied to the outer surface of concrete to prevent seawater from eroding concrete.

Nowadays, this polymer cement mortar has been applied in coastal projects in China. For example, in 1997, the DN1600~DN2200mm steel pipe sewage project in Tuen Mun, Hong Kong, with a total length of 5600m. The British side identified the Jinshan project example technology and adopted Chinese modification. The cement mortar formula is executed according to the American AWWA602 standard. The thickness of the lining is 28mm. The British guarantees the service life of 100 years for the Hong Kong authorities. In April 1998, the Hong Kong Lane Bay water supply pipe DN1400~DN1800mm, with a total length of 1600m, is lined with polymer cement mortar. The thickness is 25 ~ 31mm; in June 1998, Qinshan Nuclear Power Plant Phase III diversion pipe DN2 730~DN150mm, the Shanghai Electric Power Construction and Repairing Factory is responsible for a total of 8 000m steel pipe lining, using polymer cement mortar lining thickness of 20~30mm, now It has been completed and has been applauded by the US BECHTEL contractor, the US quality inspection department MODER's Beijing office and the Canadian investor; recently, the polymer cement mortar lining scheme was adopted in the DN 1200mm 14km pipeline of the Shanghai Baosteel Yangtze River Phase III diversion project. .

4 Construction process Polymer cement mortar lining construction is completed by a combination of feeder, screw pump and shot miller. The spraying work can be prefabricated or constructed on site. Large-diameter steel pipes are generally embedded with underground pipes. After cleaning the inner wall, the lining work can be carried out without anti-rust treatment. The inner surface is sprayed at a speed of about 50 m2/h, and is simultaneously polished after spraying. The lining with a thickness of 20~30rmn can be designed to be sprayed 2 to 3 times. The curing process is based on the maintenance regulations of ordinary cement mortar. Generally, the strength requirement can be reached in about 7 days.

The value of the lining material is 525 cinnamate cement, the yellow sand with a particle size of 0.4~4mm, the tricalcium aluminate and the ST and SM admixture are stirred at a weight ratio of 1:2:0.3:0.01, and the density is 2.5. Since the injection acceleration is 250m/s2, the pressing force is large and the density is 篼. Compared with the centrifuge operation, the machine has less investment, easy operation, quick personnel training and less construction space. When the pipeline is lining several kilometers long, the inner wall can be remotely controlled by an infrared probe, the construction quality is guaranteed, and the crack repair is facilitated. An example of this kind of polymer cement mortar is easy to take and investing in outdoor overhead steam pipeline operation accidents Xu Kun Yang Ming (Northeast Electric Power Design Institute of State Power Corporation, Changchun City, 130021) Heating steam pipe laid by overhead support of a thermal power plant, due to welding quality Poor, not implemented according to the relevant regulations during installation, the guide bracket has no guide groove; more serious is that the strength calculation is not carried out at the time of design, the system configuration is unreasonable, and the non-reinforced three-way components are used. The rupture of the bellows compensator caused by the investment after the operation caused serious accidents. After the calculation of the thermal pipeline stress analysis calculation program, the piping layout was re-modified, and the investment operation has been performed so far.

Steam pipeline overhead bracket bellows compensator tearing heat pipe stress analysis calculation program strength calculation 1 accident situation A heating power plant heating steam pipeline is laid with overhead brackets, and a steam pipeline rupture accident has occurred. The heat network pipe rack is arranged on the west side of the road. The bracket is a double-shaped door bracket. The steam and hot water main pipe are arranged on the bottom layer, and the steam and hot water branch pipes are arranged on the upper layer. The bellows compensator is arranged on both sides of the bracket at 6 and 9 points. See the form.

The steam pipe network was first started in November 1994. During the first steam supply operation, the bellows compensator on the steam pipe between the supports 8 and 9 broke. When the accident occurred, the pipe erected at the corrugated pipe with the sound, and the bellows was torn into two sections, one section turned northward by 180. After the 10kV cable was broken, it fell on the top of the west side of the house, and the other section Turning south 180., tearing open the A-point welding joint and falling on the road, this road is just a free market, but fortunately, there is no injury, but the accident is serious.

2 Basic condition of pipeline 2.1 Steam parameter ~1.3MPa, temperature is 250T. When an accident occurs, the steam pressure is 0.61MPa and the temperature is 196:.

2.2 Steam pipe size 7mm spiral seam electric welded steel pipe is arranged horizontally along the direction of the mother pipe after it is connected upwards from the 630mmx 8mm mother pipe by 2.73m. The total length of the pipe section is 55.2m, the length of the south section is 17.6m, the length of the north section is 376m. 2.3 The bellows 150/1.6 is the inner bellows; the material is lCrl8Ni9Ti, and the chemical analysis result: C is 0.1%. Cr is 18%, Ni is 9%, Ti is 0.5%. The installation length is 750mm, and there are 3 limit screws. One of the bolts is not wearing a nut, and the other two nuts are only screwed 2~3. There is no product certificate and quality certificate. 2.4 Welded joints There are undercuts in the welded joints, the grains in the heat-affected zone are coarse, and voids appear on the grain boundaries.

2.5 Pipe bracket The guide bracket is open, and the brackets 4 and 7 are installed without two guide slots. The setting of the bellows guide bracket is not set according to the relevant specifications of the product manual.

2.6 Three-way three-way welding on the mother tube, not a reinforced type, the corner of the A point is actually a three-way form, no hot extrusion elbow is installed.

3 Stress Analysis Calculate the stress calculation using the thermal pipeline stress analysis calculation program. This low, the capital investment listed in the budget is several thousand yuan / m2, so it is of considerable use value in the future use of coastal power plant pipelines and seawater buildings. For example, a project will use a polymer liner with a thickness of 30mm in DN3600mmx32mm and L=2x800m steel pipes. The total cost is about 1 million yuan, which can greatly reduce other anti-corrosion costs. At the same time, the 30mm thick polymer lining will undoubtedly strengthen the steel pipe. The strength and stability of the steel pipe wall thickness can also reduce the speed of thinning.

(This article was supported by the metallographic laboratory of the thermal power plant of Shanghai Jinshan Petrochemical Complex and related construction units.)

Derrick 313 Pwp Shaker Screen

Replacement PWP Screens for Derrick 313 Shakers


SJ-Derrick 313 PWP Shaker Screen is designed for the replacement screen of Derrick 313M shale shaker. There is an operating handle on one side of the screen and a triangle breach in the center of the opposite side. Thanks to he machine assembled backside seal rubber, even the strip appears a small broken part, the other parts will be steady on back panel still. The most obvious advantage of  PWP screen is better resistant to oil. And mesh sizes are commonly available from API 40 to API 270.

Technical Parameter

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Adaptable Shale Shaker Model

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Derrick 313 PWP  Shaker Screen

Remarks:

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Derrick 313 PWP  Shaker Screen


Derrick 313 Pwp Shaker Screen

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