CN110726038A - Special handheld online repair purging system for cold insulation structure of LNG pipeline - Google Patents

Abstract

The invention discloses a special purging system for hand-held on-line repair of a cold-insulating structure of an LNG pipeline. The purging system includes a purging tool; the purging tool is communicated with a pipeline through a handle, and the pipeline is communicated with a gas source; the purging tool includes a first purging component and several second purging components; the first purging component The purging assembly includes three hoses connected by a spool and a purging nozzle communicated with the hoses; the second purging assembly includes two hoses connected by a spool and a purging nozzle communicated with the hoses; through the spool , the first purging component and the second purging component are connected to the handle after being communicated in sequence. The present invention can adjust its longitudinal and circumferential control ranges according to the needs of users; the present invention is small in weight, portable in hand, simple in operation, flexible in adjustment, and does not require other auxiliary support tools, providing convenience for online repair; the present invention is not only suitable for horizontal straight The online repair of the cold insulation structure of the pipe section is also suitable for the online repair of the cold insulation structure at special structures such as vertical pipes, confined space pipes, elbows, tees, valves and so on.

Description

A special purging system for hand-held online repair of LNG pipeline cold insulation structure

technical field

The invention relates to a special purging system for hand-held on-line repair of a cold-insulating structure of an LNG pipeline, and belongs to the technical field of low-temperature cryogenics.

Background technique

my country's LNG industry has developed rapidly. Many domestic LNG receiving stations that have been put into operation in the country have suffered damage to the cold layer of LNG pipelines to varying degrees. Some equipment and pipelines have the phenomenon of frost, icing, deformation and cracking, which not only increases energy consumption, but also increases energy consumption. It also increases the corrosion of equipment pipelines and urgently needs to be repaired and replaced. Scientific diagnosis and evaluation of the cold insulation performance of the cold insulation layer of LNG pipelines, and repair of the cold insulation structure on the existing basis, especially the on-line repair technology under the condition of non-stop production is particularly critical.

In the process of online repair of LNG pipeline, after the old cold insulation material is removed, in the natural state, if no operation is performed, a layer of frost will appear on the surface of the exposed pipe within 1 minute, and a layer of frost will form between the exposed pipe and the new cold insulation material. Layer cooling bridge, resulting in cooling loss. What's more, if the frost is too thick, it is not conducive to the installation of new cold insulation materials, resulting in gaps, and the cold insulation effect is not as good as before the repair. Therefore, how to control zero frost on the surface of LNG pipelines during the entire repair process, especially during the interval between the removal of the old cold insulation material and the installation of the new cold insulation material in the inner layer of the pipeline, is a key technical point of online repair of the cold insulation structure.

At present, there is no safe, reliable, economical and suitable control method for large-scale on-line repair of the receiving station site, and there is no special repair device to realize on-line control. For the online repair of LNG pipelines, especially for special parts such as vertical pipes, confined space pipes, elbows, tees, valves, etc., due to their complex structures, online repair of cold insulation structures is more difficult. Therefore, it is particularly important to develop a special repair system that is easy to operate, convenient and applicable.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a special purging system for hand-held on-line repair of LNG pipeline cold insulation structure. In the state of non-stop, nitrogen is used as the gas source, and the pipeline to be repaired is continuously purged, so that the surface of the low-temperature pipeline is uniform during the whole repair process. No frosting, the purpose of "zero freezing" and "zero frosting" in the entire online replacement and repair process is achieved; the purging system of the present invention is not only suitable for It is also suitable for online repair of cold insulation structures at complex and special structures such as pipes and valves.

The special purging system for hand-held on-line repair of LNG pipeline cold insulation structure provided by the present invention includes a purging tool;

The purging tool is communicated with a pipeline through the handle, and the pipeline is communicated with the gas source;

The purging tool includes a first purging assembly and several second purging assemblies;

the first purge assembly includes three hoses connected by a cross and a purge nozzle in communication with the hoses;

the second purging assembly includes two hoses connected by a spool and a purging nozzle in communication with the hoses;

Through the spool, the first purging assembly and the second purging assembly are communicated in sequence and then connected to the handle.

In the above-mentioned dedicated purging system for hand-held online repair, the first purging component and the second purging component and between the adjacent second purging components are connected by a short joint structure, and then connected with all the components. the handle connection.

In the above-mentioned dedicated purging system for hand-held online repair, the pipeline is a hose pipeline.

In the above-mentioned special purging system for hand-held online repair, the hose is a metal hose, which has a certain flexibility, which is convenient for temporarily adjusting the purging distance and the direction of the air outlet, so that it can be compatible with the pipelines to be repaired with different pipe diameters. Use to match.

In the above-mentioned special purging system for hand-held online repair, the handle is provided with a valve for adjusting the amount of purging gas.

In the above-mentioned special purging system for hand-held on-line repair, the gas source is nitrogen gas source, which is used to block the wet air from contacting the pipeline to be repaired in a short time, so as to prevent the air from rapidly condensing on the surface of the LNG pipeline due to excessive moisture. Frost is formed, which further protects the surface of the repaired pipeline and strengthens the purging effect.

In the above-mentioned special purging system for hand-held online repair, the material of the purging nozzle is an organic composite material or an aluminum alloy material;

The purging nozzle is a flat type, and its specifications can be: length 40-60mm, width 30-50mm, thickness 10-20mm, and the bottom is provided with 1-3 air outlets, each row of which includes 5-15 air outlets air outlet.

In the special hand-held purging system for on-line repair of the present invention, the purging components, the short joint structure, the handle, etc. can all be made of stainless steel pipes. The specifications of the stainless steel pipes refer to GB/T4437. high strength.

The hand-held on-line repair special purging system of the present invention can adjust the number of the second purging components according to the length of the pipe section to be repaired, and flexibly adjust the vertical control range of the hand-held purging system.

The hand-held on-line repair special purging system of the invention can adjust the length of the metal hose according to the diameter of the pipe section to be repaired, and flexibly adjust the circumferential control range of the hand-held purging system.

The hand-held on-line repair special-purpose purging system of the invention can be hand-held during operation and use, and can move flexibly in the circumferential and longitudinal directions of the pipeline to be repaired to control the purging range.

The present invention has the following beneficial effects:

1. The hand-held on-line repair special-purpose purging system of the present invention has a good purging effect, and achieves the goals of "zero freezing" and "zero frost" in the process of online replacement and repair, making the online repair technology of cold insulation structure feasible;

2. The present invention is not only applicable to the online repair of the cold insulation structure of the horizontal straight pipe section, but also to the online repair of the cold insulation structure at special structures such as vertical pipes, confined space pipes, elbows, tees, valves, etc.;

3. The present invention can adjust its longitudinal and circumferential control ranges according to user needs;

4. The invention has the advantages of small self-weight, hand-held and portable, simple operation, flexible adjustment, no need for other auxiliary support tools, and provides convenience for online repair;

5. The present invention is not only applicable to LNG pipelines, but also applicable to other low-temperature pipelines and devices, and can be popularized and used in other low-temperature and cryogenic fields.

Description of drawings

Fig. 1 is the overall schematic diagram of the special purging system for hand-held online repair of the present invention;

Fig. 2 is the front view of the purging tool in the hand-held online repair purging system of the present invention;

Fig. 3 is the left side view of the purging tool in the hand-held online repair purging system of the present invention;

4 is a schematic structural diagram of a metal hose in the hand-held online repair and purge system of the present invention;

5 is a schematic structural diagram of the purging nozzle in the hand-held online repair purging system of the present invention;

FIG. 6 is a flow chart of repairing the cold insulation structure of the LNG pipeline by using the hand-held online repair and purge system of the present invention.

The marks in the figure are as follows:

1. Purge tool; 2. Hose; 3. Nitrogen gas source; 4. Pipe section to be repaired (including elbow, tee, valve, etc.); 5. Valve; 6. Second purge component; 7. Short joint structure; 8. Handle; 9. Four 10 metal hose; 11 purge nozzle.

Detailed ways

In the following, the present invention will be clearly and completely described by taking the purging system with the working tube diameter ≤ DN200 series as an example in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the present invention, not All examples.

As shown in FIG. 1 , the special purging system for hand-held online repair of LNG pipeline cold insulation structure provided by the present invention includes a purging tool 1, and the purging tool 1 is connected with a hose 2 through a handle 8, and the hose 2 is connected with nitrogen gas Source 3 is connected. In this embodiment, the purging tool 1 includes a first purging component and a second purging component 6 . As shown in Figures 2 and 3, the first purging assembly includes three metal hoses 10 connected by a spool 9 and a purging nozzle 11 communicated with the metal hoses 10, and the second purging assembly 6 includes a spool. 9 connected to the two metal hoses 10 and the purging nozzle 11 communicated with the metal hose 10 , and then the first purging assembly and the second purging assembly 6 are connected through the short joint structure 7 , and then connected to the handle 8 .

As shown in Figures 1 and 2, a valve 5 is installed on the handle 8, and the amount of purge gas can be adjusted for easy control.

As shown in Figures 1 and 2, the distance between the first purging assembly and the second purging assembly 6 in the purging tool 1 is 200mm; the second purging can be increased or decreased at any time according to the length of the pipe section to be repaired The number of components 6 and short joint structures 7 can flexibly adjust the longitudinal control range of the hand-held purging system.

As shown in Fig. 2 and Fig. 3, the length of the metal hose 10 is 150mm; as shown in Fig. 4, the metal hose 10 has a certain flexibility, which is convenient for temporarily adjusting the purging distance and the air outlet direction, so that it can be compatible with different pipes The diameter of the working steel pipe is matched to use.

As shown in Figure 5, the purging nozzle 11 belongs to the purchased part, and its size is different, the purging section is different, and the area that can be blown is also different. When designing the quantity of the second purging component 6, reference is required.

For the wind parameters of the purging nozzle, please refer to Table 1. The data in the table are the values under 5bar air pressure:

Table 1 Purge nozzle wind parameters

Purge distance A=50 B=100 C=200 D=300 E=400 F=500 L(mm) 80 100 140 180 220 260 W(mm) 45 65 105 145 185 225 S(m/s) 126 105 60 42 37 34

In Table 1, A-F represents the purging distance, L represents the length of the air curtain, W represents the width of the air curtain, and S represents the corresponding wind speed.

The special purging system of the present invention is used to repair the cold insulation structure of the LNG pipeline according to the flow chart shown in FIG. 6 .

1. When carrying out the evaluation of the cold insulation performance of the cold insulation structure of the LNG pipeline to be repaired, the old cold insulation scheme is designed with reference to the anti-condensation cold insulation layer thickness method in GB/T8174-2008 "Test and Evaluation of the Insulation Effect of Equipment and Pipelines". According to the original design parameters of the pipeline collected on site and the operating parameters such as temperature, flow rate, pressure and other operating parameters of the conveying medium in the pipeline to be repaired, as well as the environmental parameters around the pipeline, the measured surface temperature is converted to the surface temperature under the design conditions. It is 25.2 °C, which is about 3 °C lower than the dew point temperature of 28.3 °C under the design conditions, indicating that the cold insulation performance of the cold insulation structure of the pipeline to be repaired has not met the cold insulation design requirements of the pipeline, and the cold insulation structure needs to be repaired.

2. When redesigning the cold insulation for this part, refer to GB/T8175-2008 "Guidelines for Design of Equipment and Pipeline Insulation", and select the cold insulation material and design the thickness of the cold insulation as follows:

1) Selection of cold insulation material: choose rigid polyurethane (PIR for short) as cold insulation material, the thermal conductivity of PIR material is 0.029W/(m*k)@25℃, the density is 50kg/m ³ , and the compressive strength is ≥0.22MPa , the oxygen index is greater than 28.

2) Design of cold insulation thickness: The cold insulation thickness is calculated by the thickness method of anti-condensation and cold insulation layer, as follows:

In the formula: D ₀ - the outer diameter of the pipe, m; D ₁ - the outer diameter of the cold insulation layer, m; λ - the thermal conductivity of the cold insulation material, W/(m*k); t _s - the outer surface temperature of the cold insulation layer, °C ; t _a - ambient temperature, °C; t - medium temperature, °C; δ - thickness of cold insulation layer, m; a _s - heat transfer coefficient between outer surface of cold insulation layer and atmosphere, W/(m ² *K).

The specification of the pipeline to be repaired is Φ108*4, the medium temperature is -196℃, the surface heat dissipation coefficient is 8.141W/(m ² *K), and the dew point temperature under the design condition is 28.3℃. Based on the principle that the temperature is 1.5-3°C higher, the required thickness of the PIR material is calculated to be 110mm.

In particular, for the convenience of construction, the required cold insulation material PIR is prefabricated into a tube shell. The cylindrical tube shell is symmetrically divided into two parts along the center. Each section of PIR is processed into steps along the axial and radial directions. Cold insulation materials larger than 100mm need to be processed in two layers. The design thickness of the cold preservation layer in the above cold preservation scheme is 110 mm, which is divided into two layers, and the thickness of each layer is 55 mm.

3. In the process of dismantling the old cold-insulation structure in this part, when the old cold-insulation structure is dismantled, it should be dismantled in sections, in layers and in sequence; The outer layer of cold insulation structure can be removed more to facilitate the construction of the inner layer of PIR, and each layer of PIR is still connected in a staggered manner.

At the moment of dismantling the old cold insulation structure, the special purging system for online repair provided by the present invention should be activated synchronously to purge the surface of the exposed pipeline to avoid frost on the surface of the pipeline;

In the interval of purging the low temperature pipeline, a new cold insulation structure should be prepared quickly to ensure the installation of the inner layer PIR cold insulation structure in the shortest time;

In the construction process of replacing the new cold insulation layer, moisture-proof layer and protective layer for the parts to be repaired, it is necessary to strictly implement GB50126-2008 "Code for Construction of Industrial Equipment and Pipeline Insulation Engineering".

After the replacement of the upper cold insulation layer is completed, the cold insulation layer of the next section can be removed in sequence, and the expansion joints, moisture-proof layer and protective layer can be processed at the same time. The entire repair process is reasonable and compact.

4. When verifying the cooling effect of the part, according to the evaluation method in step 1, re-check the cooling effect of the repaired cooling structure. The dew point temperature is high at 28.3°C, and the cooling effect is significantly improved.

The special purging system for hand-held online repair of LNG pipeline cold insulation structure provided by the present invention can be applied to low temperature equipment and low temperature pipelines such as LNG stations, especially vertical pipelines, confined space pipelines, elbows, tees, valves and other complex and special During the online repair of the cold insulation structure at the structure, the goal of "zero icing" and "zero frosting" during the online replacement and repair of the cold insulation structure is achieved.

The above is only one of the implementation cases of the present invention, and all modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included within the protection scope of the present invention.

Claims (7)

1. A handheld online repair special purging system for an LNG pipeline cold insulation structure comprises a purging tool;

the purging tool is communicated with a pipeline through a handle, and the pipeline is communicated with a gas source;

the purging tool comprises a first purging component and a plurality of second purging components;

the first purging assembly comprises three hoses connected by a four-way joint and a purging nozzle communicated with the hoses;

the second purging assembly comprises two hoses connected by a four-way joint and a purging nozzle communicated with the hoses;

through the cross joint, the first blowing component and the second blowing component are sequentially communicated and then connected to the handle.

2. The handheld online repair dedicated purge system of claim 1, wherein: the first purging assembly and the second purging assembly and the adjacent second purging assemblies are connected through short joint structures.

3. The handheld online repair dedicated purge system of claim 1 or 2, wherein: the line is a hose line.

4. The handheld online repair dedicated purge system of any of claims 1-3, wherein: the hose is a metal hose.

5. The handheld online repair dedicated purge system of any of claims 1-4, wherein: the handle is provided with a valve.

6. The handheld online repair dedicated purge system of any of claims 1-5, wherein: the gas source is a nitrogen gas source.

7. The handheld online repair dedicated purge system of any of claims 1-6, wherein: the material of the blowing nozzle is an organic composite material or an aluminum alloy material;

the blowing nozzle is flat, 1-3 air outlets are formed in the bottom of the blowing nozzle, and each air outlet comprises 5-15 air outlets.

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