1 Introduction
The large pull rod double wave compensator is generally installed on the large-diameter pipeline and directly installed in the steel structure support. It is large in size, large in quality and expensive. Once damaged, it is not only difficult to construct, but also leads to high maintenance costs. Generally speaking, this kind of large compensator is widely used in the gas pipeline and flue gas pipeline of the metallurgical system. Due to the quality of the compensator and environmental conditions, the compensator is the most vulnerable component to leakage due to erosion, wear and fatigue aging, which will cause potential safety hazards and economic losses, Generally, the overall replacement is carried out or the plugging rod is used for temporary plugging. However, one of the two schemes has huge production loss and spare parts cost, and the other has short maintenance time, which cannot fundamentally solve the problem. In order to minimize the loss and repair the leakage point of the original compensator without changing the mechanical properties of the original design, so as to repair the original compensator without dismantling or stopping production, we have summarized a scheme to wrap a new compensation structure on the outside of the leakage compensator, which can perfectly solve this problem.
2 Scheme introduction
2.1 Cause analysis
After being used for a long time, the corrugated compensator is constantly expanding and changing, and the corrugated compensator is damaged by fatigue; The medium in the pipe continuously washes and abrades the corrugated pipe, and the chemical substances contained therein, such as chloride ion, sulfur, phosphorus, etc., erode the stainless steel of the corrugated pipe, resulting in cracks and perforation, which not only brings safety hazards to production but also affects normal production activities.
2.2 Difficulties Analysis
2.2.1 Huge economic losses
In this case, the traditional treatment is to stop production and replace the new compensator, but such a large corrugated compensator is expensive and there is more than one compensator on the pipeline; Secondly, if the whole line is to be replaced, it will cause immeasurable losses, which is obviously not allowed economically.
2.2.2 Difficult construction
Due to the large dead weight and moving parts of this large corrugated compensator, this kind of large compensator is often installed high above the ground, and is often directly installed inside the steel structure support, and many other medium pipelines are often laid on the same support at the same time. Therefore, the overall replacement must be carried out on the surrounding pipelines, pipe supports, etc., which is very difficult and takes a long time.
2.2.3 Difficult welding
Because the corrugated compensator is located at a high altitude, with large air volume and narrow operation space, the interface welding is quite difficult, especially the welding of stainless steel corrugated.
2.3 Scheme selection and formulation
According to the characteristics of the large rod double wave compensator of the object this time, after continuous research and analysis, the following scheme is formulated: add a layer of newly made compensator outside the original leakage compensator to repair the compensator without changing the original function, as shown in Figure 1.
2.3.1 Construction preparation
(1) Construction personnel preparation. Before construction, all personnel shall be trained in safety protection, high-altitude operation, welding technology and other technical aspects. At the same time, we will organize everyone to focus on the technical disclosure and construction scheme of this construction task, and sign the real name system.
(2) Machine preparation. According to the construction scheme, the construction equipment demand table shall be prepared and checked and confirmed before entering the site. The person in charge shall issue the equipment entry permit before entering the construction site. The tools and instruments shall be placed reasonably on site to meet the construction and safety requirements. During the construction process, the equipment shall be operated by specific personnel and machines, and rechecked before use to ensure the correct use of machines and tools, and confirm the validity of special equipment.
(3) Prefabricated parts processing. The components required for this project shall be prefabricated in advance: 1) according to the maximum diameter and length of the original compensator ripple, determine the size of the outer steel plate and roll it into two groups, and divide it into 2~3 pieces; 2) Prefabricate two corrugated pipes according to the compensation amount of the original compensator and the outer diameter of the original pipe, and divide them into 2~3 pieces for installation; 3) Prefabricate four annular end plates according to the diameter of the outer steel plate, of which the inner annular plates (two) are made into serrations; 4) The size of corrugated connecting pipe shall be determined according to the corrugated size of the new compensator and the size of the outer steel plate. Four connecting pipes shall be prefabricated and divided into 2~3 pieces.
(4) Scaffold erection. The height of the construction site is 3-6m. In order to facilitate the construction, the scaffold shall be erected in advance and the hoist bolt point shall be welded.
2.3.2 Transformation of large tie rod
Since the minimum clearance between the original pull rod position and the compensator ripple is only about 10mm, it is impossible to directly wrap the steel plate, so it is necessary to first change the position of the large pull rod to increase the construction space.
(1) Determine the position of the new tie rod: firstly, determine the corrugated width of the compensator and the width of the short pipe according to the original design compensation amount, and then determine the transverse position of the tie rod end plate; The middle position of the existing two tie rods is set as the longitudinal position of the new tie rod; The height of the new tie rod is set to be twice the height of the original tie rod.
(2) At this position, first weld 200mm wide stiffening ring plate around the pipe to reinforce the original pipe. Weld new tie rod end plate and stiffening plate on the stiffening plate.
(3) After installing and fastening the new pull rod, remove the original pull rod and cut the end plate of the original pull rod.
2.3.3 Wrapped steel plate of original corrugated compensator
(1) Positioning and setting out shall be carried out on the pipeline according to the pre calculated size. Ring plates shall be installed on both sides of the original compensator. The inner circle of the connecting ring plate shall be serrated and fixed with the pipeline by spot welding. On the one hand, the serrated annular plate plays a supporting and positioning role when installing the outer steel plate, and on the other hand, it can effectively reduce the friction between the annular plate and the pipeline after the structural construction is completed, without affecting the performance of the original structure.
(2) The wrapped steel pipe is installed in 2 or 3 pieces. Three groups of temporary chain blocks are set on the upper part of the pipe to assist the installation. First, spot weld and fix, and then weld uniformly. The welding method is manual welding and full welding. In order to ensure the welding quality and overall dimensions, the joint of the outer steel plate shall be welded at the same time.
(3) According to the size of the bellows, install the end ring plate, long and short connecting pipes. After welding, install the compensator. The connection between the compensator and the steel plate and the connection of the compensator ripple itself are welded by TIG welding. First spot weld and then weld uniformly.
(4) After the corrugated welding of the compensator is completed, the reinforcement shall be installed and welded.
2.4 Construction management
On the basis of technical disclosure and scheme disclosure, the construction workers are responsible for holding the site construction disclosure meeting and supervising and guiding the site construction in the whole process. During the construction process, before the start of each process, the constructors and technicians check the completion of the previous process.
2.5 Quality management
The quality inspector shall supervise the whole process, carry out construction in strict accordance with the established scheme, and inspect each process in combination with the national standards and company standards to ensure the installation and welding quality. In order to ensure the welding quality, all welding personnel shall work with certificates, especially before welding the compensator, the wind shelter shall be erected.
Technical requirements for welding of steel plate, short pipe and other components: manual full welding shall be adopted. Symmetrical spot welding shall be used for fixing during welding, and then full welding shall be carried out. The selection of welding rod according to the material of welding object can refer to the national standard. If there is no national standard, the welding process shall be evaluated and determined. The welding requirements shall meet the requirements of the Specification for Welding of Building Steel Structures (JGJ81-2002) and the acceptance standards for construction quality of steel structures.
Technical requirements for welding of stainless steel parts (corrugated pipes): TIG welding is adopted and special corrugated compensator welding gun is used for welding. It is required to use concentrated arc energy and high temperature; The heat affected area of welding is small and the deformation is small. Special welding tools with small weld defects, many welding materials and high welding quality. During welding, it is required to be windproof and dustproof. Before welding, a windproof shed shall be erected to keep it clean. Large particles of dust are not allowed in the air. The welding personnel must be trained and obtain the corresponding welding qualification, and work with certificates.
2.6 Safety management
Strictly implement the safety supervision procedures, organize the preparation of hazard identification and risk control procedures before construction, strictly implement the safety disclosure procedures, and conduct safety examinations for construction personnel; The construction shall be carried out in strict accordance with the established plan, and the safety officer shall supervise on site. Gas detector shall be worn during construction, and special personnel shall be assigned for inspection. Four short pipes shall be welded on the wrapped steel plate coiled pipe in advance and valves shall be installed. Before welding, nitrogen shall be applied to the opening, diluted, and then welded. After welding for a period of time, nitrogen shall be applied to dilute, and then welding shall be carried out until the welding is completed to avoid potential safety hazards caused by gas accumulation.
3 Effect inspection
Through the implementation of this scheme, the compensator repair has been successfully completed.
4 Conclusion
After construction by the above methods, the expected effect can be achieved successfully and the construction task can be successfully completed. After the construction is completed, a new layer of compensator is added outside the original compensator. The overall structure and performance of the pipeline remain unchanged, eliminating the risk of large-scale leakage of the original compensator; Avoid shutdown caused by overall equipment replacement, and reduce production loss; At the same time, the safety and service life of the compensator are increased.
