Preface

Learn from the experience of design, procurement and installation of instrument tube valve parts of M310 power station. At the same time, drawing on the design concept of the AP1000 project, the corresponding solution was proposed. And further studied the related programs in autonomy applicability in the project ACP1000.

1 design principle of instrument tube valve parts

1.1 Instrument measurement circuit introduction and instrument tube valve function The typical instrument measurement circuit is shown in Figure 1.

The instrument tube valve component is an important part of the instrument measurement pipeline connection. It is necessary to ensure that the instrument connected to it meets the design function requirements. Its design and installation quality directly affects instrument and measurement channel performance.

1.2 Principles for the establishment of instrument tube valve parts

Classify systems, devices, and components based on the safety features performed by the device. The safety level of the instrumentation and valve components shall be determined by considering the connected process piping, the grade of the equipment and the level of safety functions performed by the connected instrument to determine the different requirements in design, manufacture, materials, inspection and quality assurance. .

The relationship between the safety level of the equipment and the specification level and quality assurance level is shown in Figure 2.

1.3 Main instrument tube valve parts classification

1.3.1 Instrument pressure tube

Because the pressure tube is in direct contact with the process medium. Therefore, the choice of the tube is related to the physicochemical properties and operating conditions of the measured medium. To ensure the integrity of the entire process system and accurate measurement of process media parameters, the pressure pipe is required to have a certain strength and sealing, so the instrument pipe is selected as a cold-worked seamless steel pipe. According to the instrument installation design, the instrument pressure piping mainly includes two types: the nominal pipe (PIPE) and the instrument pipe (TUBE).

1.3.2 Pipe fittings

The standard parts are standard products selected according to the instrument installation design requirements and different pipe diameters according to the instrument's pressure pipe; non-standard parts are based on Q/CNPE. The specified dimensions of J106.25 "Technical Conditions for Instrument Pipe Joints" are manufactured and processed.

Analysis of typical problems in the field of instrument tube valve parts of 2M310 power station

2.1 Pressure pipe and fittings have many specifications

It is easy to lead to design selection errors. Due to the variety of types, the individual fittings are scattered. It increases the difficulty of the work and also affects the construction on site.

2.2 hierarchical division is complicated

At the time of contract execution, due to the variety of manufacturing grades and quality assurance systems, it brought many difficulties to equipment manufacturing and project execution, and it was not conducive to multi-project stocking, and the equipment supplementing cycle was long, which seriously affected the progress of the project.

2.3 pipe material requirements are diverse

There are many types of pipe fittings and various material requirements, resulting in a small amount of purchase of single-variety materials. Difficulties in purchasing and affecting the progress of the project.

2.4 Process interface is not uniform

In the past projects, due to the long procurement cycle of the equipment, the publication schedule of the instrument and valve data sheet was earlier than the design progress of the installation drawing. The procurement often refers to the reference material of the reference power station for bidding, and later, due to the change of the instrument supplier, Process interface modification due to upstream professional changes, instrument selection changes, etc. Causes the instrument tube valve to be modified.

2.5 On-site installation environment and process pipeline changes

Due to the strong subsidiary of the instrument control profession, the nuclear-grade instrumentation pipelines that have been designed are often not fully applicable due to changes in the on-site installation environment. It is necessary to redesign the instrumentation pipeline path according to the site environment and process pipeline changes, resulting in the instrumentation pipeline valve. Changes in the type and quantity of the pieces require on-site additions, modifications, etc.

3 ACP1000 instrument tube valve design improvement

3.1 Design improvement of pressure piping and fittings

3.1.1 Analysis of project design

The design ideas of many M310 projects are not uniform, resulting in different types and sizes of instrumentation pressure pipes in each project. The specific situation analysis is shown in Table 1. In Table 1, 1" = 2.54 cm.

AP1000: The instrument tube before and after the instrument isolation valve is a 3/8” instrument tube.

It can be seen from Table 1 that there are two main types of impulse piping in front of the meter isolation valve in the M310 stack type, namely 3/8” TUBE tube and 1/4 PIPE tube, and the TUBE tube used after the instrument isolation valve. The AP1000 three-generation power station uses TUBE tubes.

Due to the inconsistent type of the instrument's impulse piping, the technical parameters are complex, resulting in a variety of corresponding pipe joints. Take the Fangjiashan project as an example, there are 89 kinds of standard pipe fittings. .

There are many types of instrument pressure piping and fittings, which may lead to incorrect design selection, increase procurement costs, and it is difficult to purchase and reserve spare parts. The on-site supplementary period is long, which affects the construction progress on site.

3.1.2 ACP1000 design improvement program

3.1.2.1 Analysis of the selection of TUBE pipe and PIPE pipe

PIPE pipe has high mechanical strength and is not easy to be bent. The change of direction requires additional matching joints, resulting in a large number of pipe joints. In addition, PIPE pipe joints can only be welded and threaded, which will increase many non-standard pipe joints.

The mechanical strength of the TUBE tube is also large. Because it is easy to form, there is no need to add additional elbows during field bending. Can reduce the pipe joints, easy to lay, due to the saving of a large number of pipe joints. Can reduce the construction cost; in connection with the pipe fittings. The TUBE tube can be welded or directly connected to the ferrule joint. It is very convenient to disassemble and repair. The ferrule joint has been widely used in more severe temperature and pressure environments in other industries in the world. It is a mature technology in the industry and is also widely used in nuclear power plants. The instrument is installed in the design, and the on-site installation is convenient, which has a driving effect on shortening the installation period.

Therefore, the design improvement scheme of the instrument's pressure guiding pipe and pipe fittings is as follows: the uniform source pipe is TUBE pipe, which simplifies the type of pipe joints, not only the design work is more standardized, but also the interface is more simplified, which saves the procurement cost. Shortening the installation schedule has played a catalytic role.

3.1.2.2 Determination of TUBE pipe specifications

As shown in Table 1. In the M310 power station, the instrument piping in the NSSS atlas section uses a 3/8" TUBE tube between the root valve and the instrument isolation valve. The BNI catalogue uses a 1/4 PIPE tube for installation. It is used well in operation. According to the selection analysis of TUBE pipe and PIPE pipe, 3/8" TUBE pipe is adopted uniformly. At the same time, the foreign three-generation nuclear power AP1000 power station is also introduced, which is also the same standard instrument tube as JJJ. Advanced technology is consistent.

For the pipeline between the secondary valve and the instrument, some 3/8OD tubes are selected in the M310 reactor type in the domestic and foreign nuclear power plants, and some 1/4" OD tubes are used, which are all used well. According to the nuclear power field feedback The 3/8" OD tube is large in diameter when it is laid. The bending radius is not easy to meet the requirements. There is no problem with long pipe laying between the root valve and the secondary valve, but for short distances between the secondary valve and the meter. Due to the limited space for laying, there are many bends in the direction of change. Selecting 3/8” OD will bring many difficulties to the construction on site. Therefore, I/4” ODTUBE tube is considered between the root valve and the secondary valve.

In summary, in the autonomous project. The design of the instrument impulse tube. It is proposed to make the following optimization and improvement: the instrument pressure guiding pipe between the root valve and the secondary valve adopts the 3/8" ODTUBE pipe uniformly, and the 1/4" ODTUBE pipe is uniformly used between the secondary valve and the instrument.

The comparison chart before and after the improvement is shown in Figure 3.

After the improvement, the instrument pipeline design is more standardized. The interface has also been simplified, the gauge and type of instrumentation pressure tube have been greatly reduced, and the number of instrument fittings has been reduced accordingly, which not only saves procurement costs. It also reduces the difficulty of on-site construction, and is conducive to the on-site application of the second modification, the urgent need for the instrument's impulse piping and fittings, and the reserve of spare parts, which provides a guarantee for the progress of the project.

3.2 Unified Quality Assurance Level

3.2.1 Analysis of project design plan

Since the instrument pipeline needs to ensure the realization of the function of the instrument control system connected to it, the instrument tube valve parts have very strict requirements in design, manufacture, materials, quality assurance, etc., resulting in a complicated classification of the instrument tube valve parts. Take the M310 project as an example. See Table 2 for details.

Take the 0015/0426/0706/0819 project as an example. The tube valve parts used in the nuclear instrument of the BNI catalogue have a warranty level of Q1: the remaining quality assurance grades are Q3: almost all of the valve parts of the NSSS atlas are used. Q1, the instrument tube valve parts in the RNS sampling room are all Q2, and the design principles are not uniform.

3.2.2 ACP1000 design improvement program

According to the past project experience, even for the design of the tube parts, the design quality is not the same. Manufacturers from the production and processing inspection and quality assurance have always been in accordance with the uniform quality assurance level, that is, according to Q1 implementation, that is, the price is not affected. Instrument isolation valve and non-standard pipe fittings. According to the experience of previous projects, Q2 is arranged in the RNS sampling room. Most of the equipment is process equipment. In the ACP1000 project, this part has been separated from the instrument pipe valve specification. Responsible for the layout of the professional and responsible for design procurement.

In summary, the quality assurance level of the ACP1000 instrumentation valve components is divided into Q1+Q3, and the quality of the pipe valve parts used for the seismic instruments of Class 1E or NC is unified to Q1; the remaining quality assurance grades are all Q3. The unified quality assurance system not only facilitates supplier supply, reduces procurement costs, reduces spare parts storage costs, facilitates procurement and multi-project coordination, etc., is more conducive to the versatility and interchangeability of subsequent projects, and ensures the construction of various projects.

Duration.

3.3 Unified pipe material

3.3.1 analysis of engineering project design

In the past, there were two types of ferrule materials in the M310 project: 316 and 316L. The details are as follows:

0015: The ferrule joint is specified in the pipe valve data sheet as 316. The ferrule plug is 316L:

0401: The ferrule fittings in the pipe valve data sheet are available in 316L and 304L:

0706/0738: RCCM2/3 level ferrule, body and nut are 316L, the ring is not limited. RCCME articles are not required.

A variety of materials resulting in a wide variety. The design is not uniform, which is not conducive to the exchange of group reactors and equipment, and also brings many difficulties to equipment procurement and project execution.

3.3.2 ACP1000 design improvement program

Since the body of the tube member directly contacts the process medium, the selection of the body of the tube member is related to the physical and chemical properties of the medium to be tested, and the operating conditions, especially the tube member that is in contact with the primary circuit medium, and some chemical elements of the tube material are strict. The requirements, especially the control of cobalt content, are relatively strict, and the body of the tube part is also required to have certain strength, sealing and corrosion resistance, so it should be considered comprehensively.

According to previous project implementation experience, 316L is easier to control the cobalt content. Therefore, the body material is 316L. Because of the patented technology involved in the product, the snap ring requires a certain hardness to ensure its tightness and does not contact the medium. Therefore, the material of the snap ring is not made. limit. This unified material not only simplifies the design, reduces the procurement cost, facilitates the procurement operation, and facilitates the multi-project stocking, which is conducive to procurement coordination. [2]

3.4 curing interface

3.4.1 Process Interface

In the reference project, the interface between the process and instrument control of the BNI atlas is strictly in accordance with the enterprise standard document Q-CNPE. J101.9~13 (General technical requirements for the design, manufacture and installation of nozzles on equipment and pipes) are constrained, but the NSSS atlas interface is diversified and the types of interfaces are complicated. Therefore, in the ACP1000 project, it is required to uniformly follow the enterprise standard documents. To constrain the interface, this also reduces the type of tube valve.

3.4.2 Instrument Interface

During the contract signing phase, the instrument supplier is required to solidify the instrument process interface according to the type of instrument, thereby streamlining the type of instrument pipe valve. Make the design work more standardized.

3.5 Adopting 3D design mode

The autonomous design project draws on the advanced experience of the AP1000 and performs three-dimensional design of the instrumentation tube in the PDMS three-dimensional design software.

(1) The three-dimensional design software is relatively intuitive, and any professional changes are directly reflected in the software, and the multi-professional comprehensive and collision check work is carried out before the construction drawing is officially published. It can reduce the modification of the pipe valve parts due to the change of the installation environment on site;

(2) It is possible to directly design the path of the instrument pipeline by using the three-dimensional design software, without secondary design of the pipeline, and avoiding the phenomenon of pipe fitting due to the secondary design;

(3) The three-dimensional design can be used to standardize the component library and grade library of the valve valve parts, reduce the types of pipe valve parts and reduce the selection errors.

4 Conclusion

In the selection and design process of nuclear power instrumentation, on the basis of ensuring the normal performance of the pipe fittings, the speciality of the instrument installation materials in the nuclear power plant should also be fully considered, taking into account the aspects of irradiation, sealing, pressure, special working environment, etc. Requirements. The special design, complete experiment or application of the instrumentation for nuclear power has proved the safety and reliability of the instrumentation fittings for nuclear power. This is one of the key considerations in the selection of nuclear power meter fittings, and it is also the localization of fittings. An important part of the process.