Background
In the operation process of the thermal power plant unit, for accurately reflecting the quality condition of steam, the damage to equipment caused by insufficient steam purity is prevented, the working medium is ensured to meet the design requirement, a plurality of steam sampling devices are required to be designed and installed on the alloy steel pipeline of the thermal power plant, the state of the working medium is monitored in real time, and the safe operation of the unit is ensured.
Fig. 1 is a schematic view showing a conventional steam sampling tube. An austenitic stainless steel steam sampling pipe 4 penetrates into the interior of the pipeline through the openings of a ferrite alloy steel connecting pipe seat 2 and a ferrite steel pipeline 1, the pipe orifice at the upper part of the connecting pipe seat 2 and the upper part of the sampling pipe 4 are welded by adopting a Ni-based welding material to form a dissimilar steel welding seam 3, and the pipe orifice at the lower part of the connecting pipe seat 2 and the opening of the pipeline 1 are welded by adopting the same material welding material to form a same steel welding seam 5; the sampling tube 4 and the opening of the tube opening are in interference fit structure. The steam sampling tube has the following defects and disadvantages: the steam sampling tube 4 and the alloy steel connecting tube seat 2 are respectively an austenite matrix and a ferrite matrix, belong to dissimilar steel connection, have large difference in chemical composition and thermal expansion coefficient between the two, and the fusion interface between the welding seam 3 and the connecting tube seat 2 is easy to crack; in addition, in the operation process of the unit, under the action of steam and the action of the difference of the thermal expansion coefficients, the interference fit between the steam sampling tube 4 and the opening of the pipe orifice 1 is changed into clearance fit, so that the steam sampling tube vibrates under the action of the steam, stress concentration is formed at the root of the welding seam 3, and the fusion interface of the welding seam 3 and the pipe connecting seat 2 is cracked and falls off under the action of alternating stress.
Disclosure of Invention
The invention aims to overcome the defects of the steam sampling pipe structure and provide a steam sampling pipe device for a high-temperature and high-pressure steam pipeline of a thermal power plant, which has the advantages of simple structure, material saving, safety and reliability.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a steam sampling pipe device for a high-temperature and high-pressure steam pipeline of a thermal power plant is characterized in that a cylindrical hole and a circular boss 1-2 which are communicated with each other are formed in the side wall of an alloy steel pipeline 1 adopted by the high-temperature and high-pressure steam pipeline of the thermal power plant from outside to inside, and a cylindrical internal thread 1-1 is formed in the inner wall of the cylindrical hole; the alloy steel steam sampling tube 2 comprises a steam sampling tube connecting tube 2-1, an upper large-diameter cylindrical body 2-2 with a single V-shaped groove at the bottom, a middle small-diameter cylindrical body 2-3 with an external thread, a conical body 2-4 with the lower part contacting with the circular boss 1-2 of the alloy steel pipeline in a contact manner, and a cylindrical body 2-5 with a steam sampling hole 3, which are connected in sequence; the upper large-diameter columnar body 2-2 with the single V-shaped groove at the bottom of the alloy steel steam sampling pipe 2 is positioned at the upper part of the columnar hole on the side wall of the alloy steel pipeline 1 and is welded and connected at the single V-shaped groove by adopting the same type of steel fillet weld 4 matched with the materials of the alloy steel pipeline 1 and the alloy steel steam sampling pipe 2; the middle small-diameter columnar body 2-3 provided with the external thread of the alloy steel steam sampling pipe 2 is positioned in the columnar hole in the side wall of the alloy steel pipeline 1, and the external thread of the middle small-diameter columnar body is matched with the internal thread 1-1 of the columnar hole of the alloy steel pipeline 1; the conical body 2-4 of the alloy steel steam sampling pipe 2 is in contact with the circular boss 1-2 of the alloy steel pipeline in a butting manner to form a fixed fulcrum; the cylindrical body 2-5 at the lower part of the alloy steel steam sampling pipe 2 extends into the alloy steel pipeline 1; the top of the alloy steel steam sampling pipe 2 is provided with a steam sampling pipe connecting pipe 2-1 which is in smooth transition, and the steam sampling pipe connecting pipe 2-1 is connected with a steam sampling pipe system.
The alloy steel steam sampling pipe 2 is screwed in through the matching of external threads of the outer periphery of the middle small-diameter cylindrical body 2-3 and internal threads 1-1 of the cylindrical hole of the alloy steel pipeline 1, and the lower conical body 2-4 of the alloy steel steam sampling pipe 2 is in firm contact with the circular boss 1-2 of the alloy steel pipeline 1 in the circumferential direction by means of axial load between thread pairs.
Preferably, the large-diameter cylindrical body 2-2 at the upper part of the alloy steel steam sampling pipe 2 and the cylindrical hole of the alloy steel pipeline 1 adopt a straddle type installation mode.
Preferably, the same type of steel fillet weld 4 is of a full penetration structure.
Preferably, the internal thread 1-1 of the columnar hole of the alloy steel pipeline 1 is a fine internal thread, and the external thread of the outer peripheral ring of the middle small-diameter columnar body 2-3 of the corresponding alloy steel steam sampling pipe 2 is also a matched fine internal thread, so that the matching is tighter.
Preferably, the aperture of the circular boss 1-2 of the columnar hole of the alloy steel pipeline 1 is 4-8 mm smaller than that of the thread 1-1 in the columnar hole of the alloy steel pipeline 1.
Preferably, the alloy steel steam sampling pipe 2 enables the lower conical body 2-4 of the alloy steel steam sampling pipe 2 to be in circumferential firm contact with the circular boss 1-2 of the alloy steel pipeline 1 through axial load between the thread pairs.
Preferably, the number of the steam sampling holes 3 is 4-6, and the diameter of each sampling hole is 1.5-2 mm.
Compared with the prior art, the invention has the advantages that:
1. the alloy steel pipeline and the alloy steel steam sampling pipe are welded and connected by the same material, the welding line between the steam sampling pipe and the alloy steel pipeline is of a full penetration welding structure, components have no composition difference, the thermal expansion coefficients are consistent, and a weak interface existing in a dissimilar steel welding joint is eliminated.
2. The alloy steel steam sampling pipe is firmly fixed by three points of the upper part of the alloy steel pipeline connected with the same steel fillet weld, the middle thread and the lower cone, has high rigidity, cannot vibrate under the action of high-pressure steam, radically eliminates the mechanical factors of steam sampling pipe cracking or weld cracking, and ensures the safety and reliability of the steam sampling pipe.
3. Processing internal threads on the inner wall of the opening of the alloy steel pipeline, and matching with external threads on the outer periphery of a small-diameter cylindrical body in the middle of the steam sampling pipe; the axial load between the thread pairs can not generate additional stress on the fillet weld between the steam sampling pipe and the alloy steel pipeline, and the reliability of the same type of steel fillet weld is improved.
4. Compared with the steam sampling tube device with the traditional design, the steam sampling tube device does not need a tube socket, saves materials and reduces the number of welding seams of the steam sampling tube device.
5. The steam sampling tube device is simple in installation process, high in reliability and convenient to maintain.
Detailed Description
In order that the invention may be more readily understood, reference will now be made in detail to the following description taken in conjunction with the accompanying drawings and specific examples:
as shown in fig. 2 and 3, in the steam sampling tube device for the high-temperature and high-pressure steam pipeline of the thermal power plant, a cylindrical hole and a circular boss 1-2 which are communicated with each other are formed on the side wall of an alloy steel pipeline 1 adopted by the high-temperature and high-pressure steam pipeline of the thermal power plant from outside to inside, and a cylindrical internal thread 1-1 is formed on the inner wall of the cylindrical hole; the alloy steel steam sampling tube 2 comprises a steam sampling tube connecting tube 2-1, an upper large-diameter cylindrical body 2-2 with a single V-shaped groove at the bottom, a middle small-diameter cylindrical body 2-3 with an external thread, a conical body 2-4 with the lower part contacting with the circular boss 1-2 of the alloy steel pipeline in a contact manner, and a cylindrical body 2-5 with a steam sampling hole 3, which are connected in sequence.
The upper large-diameter columnar body 2-2 with the single V-shaped groove at the bottom of the alloy steel steam sampling pipe 2 is positioned at the upper part of the columnar hole on the side wall of the alloy steel pipeline 1 and is welded and connected at the single V-shaped groove by adopting the same type of steel fillet weld 4 matched with the materials of the alloy steel pipeline 1 and the alloy steel steam sampling pipe 2; the middle small-diameter columnar body 2-3 provided with the external thread of the alloy steel steam sampling pipe 2 is positioned in the columnar hole in the side wall of the alloy steel pipeline 1, and the external thread of the middle small-diameter columnar body is matched with the internal thread 1-1 of the columnar hole of the alloy steel pipeline 1; the conical body 2-4 of the alloy steel steam sampling pipe 2 is in contact with the circular boss 1-2 of the alloy steel pipeline in a butting manner to form a fixed fulcrum; the lower part of the alloy steel steam sampling pipe 2 is provided with a cylindrical body 2-5 with a steam sampling hole 3 and extends into the alloy steel pipeline 1; the top of the alloy steel steam sampling pipe 2 is provided with a steam sampling pipe connecting pipe 2-1 which is in smooth transition, and the steam sampling pipe connecting pipe 2-1 is connected with a steam sampling pipe system.
Fig. 3 is a schematic structural view of a cylindrical internal thread 1-1 and a cylindrical boss 1-2 at the bottom of the cylindrical internal thread of the inner wall of the alloy steel pipeline provided by the invention. The cylindrical internal thread 1-1 of the inner wall of the alloy steel pipeline is matched with the external thread 2-3 of the middle small-diameter cylindrical body of the alloy steel steam sampling pipe and is used as a fixed point in the installation process of the alloy steel steam sampling pipe; the round boss 1-2 at the bottom of the alloy steel pipeline 1 is matched with the inclined plane of the lower conical body 2-4 of the steam sampling pipe of the alloy steel pipeline to serve as another fixing point. The aperture of the through hole with the circular boss 1-2 at the bottom of the alloy steel pipeline 1 is 4-6 mm smaller than the aperture of the columnar hole of the alloy steel pipeline 1.
The implementation case is as follows: the original opening on the alloy steel pipeline 1 is a through-diameter hole, the upper part of the original opening of the alloy steel pipeline 1 is firstly reamed before installation, a round boss with the thickness of more than 3mm is reserved at the bottom of a new opening, the reaming is coaxial with the inner wall of the upper pipe orifice of the alloy steel steam sampling pipe 2, and the deviation between the diameter of the upper opening of the new reaming and the diameter of the upper pipe orifice of the alloy steel steam sampling pipe 2 is less than 1 mm; and (3) processing a fine internal thread on the inner wall of the alloy steel pipeline 1 in the reaming process by using a tapping machine, wherein the small-diameter columnar fine external thread in the middle of the alloy steel steam sampling pipe 2 is matched with the processing specification of the internal thread on the inner wall of the alloy steel pipeline 1 in the reaming process. The alloy steel steam sampling pipe 2 is screwed into the open pore of the alloy steel pipeline 1 through the assembly of the external thread of the middle small-diameter columnar body and the internal thread of the inner wall of the expanded hole of the alloy steel pipeline 1 until the conical body 2-4 of the alloy steel steam sampling pipe 2 is in circumferential firm contact with the circular boss 1-2 of the alloy steel pipeline 1, and meanwhile, the steam sampling hole 3 is ensured to be over against the steam flow direction of the alloy steel pipeline 1. The fillet weld of the alloy steel steam sampling pipe 2 and the alloy steel pipeline 1 is firstly subjected to manual argon tungsten-arc welding bottoming by adopting welding materials of the same material, and then is subjected to filling and capping welding by using manual electric arc welding. The fillet weld welding of the alloy steel steam sampling pipe 2 and the alloy steel pipeline 1 adopts a full penetration structure, and the heat treatment is carried out after the welding according to relevant standards.