Research on the Application Status of Valves in Petrochemical Devices

1. Technical requirements
1.1 Requirements on valves for large-scale devices
As the equipment becomes large-scale, the size of process pipelines is getting larger and larger. The number of valves is also increasing. Taking a 3.8 million t/a continuous reforming unit as an example, the number and specifications of process valves are shown in Table 1.
 
Table 1 Statistics of 3.8 million t/a continuous reforming process valves 

 
It can be seen from the statistical data of the process valves of the continuous reforming unit (3.8 million t/a) that there are about 6000 process valves in a large continuous reforming unit, and the maximum valve specification reaches DN1400. It should be noted that these data will be different for different projects due to some differences in product schemes and process technologies, but the approximate proportional relationships and trends are basically the same. The application of valves with large sizes has brought a series of challenges to the layout of pipelines, selection, design, manufacturing, installation, maintenance, and use of valves. Among them, the medium in the pipeline (DN1400) has the characteristics of high temperature, toxicity and flammability. Therefore, when the valve is required to be closed, the sealing of the valve must be reliable and bidirectional sealing is required, and the medium is not allowed to leak.
 
Considering the requirements for the working condition system, gate valves are used on the pipelines. However, the large installation size and heavy weight of the gate valves bring many difficulties to the pipeline's layout. However, if butterfly valves with high temperature resistance and reliable sealing performance can be used, the above situation will be better. From the data of comparing the weight and size of gate valves of and butterfly valves the same specification  listed in Table 2, it can be seen that under the same conditions, the structural length, height and weight of the butterfly valve are much smaller than those of the gate valve. Compared with gate valves, butterfly valves have the advantages of saving materials, small installation space, and simple operation. At the same time, their production costs are low, and they are more in line with the requirements for energy saving, emission reduction and investment reduction. With the development trend of large-scale units, valve design, manufacturing, and use departments need to strengthen communication, exchange and technical research, and develop high-performance valves that can meet the requirements for working conditions as well as being easy to operate and economical in investment.
 
Table 2 Parameters of gate valves and butterfly valves

 
1.2 The quality requirements for the valve for the device
With the improvement of the overall manufacturing capacity of the valve industry, the overall quality of valves has made great progress. However, by investigating the recent supply of several large petrochemical projects, there are still some problems with valve quality, which are mainly concentrated in several aspects:
(1) The appearance of castings such as valve bodies and bonnets is poor, and there are defects exceeding standards.
(2) The chemical composition and mechanical properties of purchased parts such as bolts and gaskets do not meet the requirements.
(3) The valve's sealing surface material is inconsistent with the technical files.
(4) Leakages happen on the valve's sealing surface.
(5) Leakages appear at the valve stem packing.
(6) The operating torque is too great, jamming or even not being unable to operate occurs.
(7) Marks and identification information of valves are incomplete and unclear.
(8) Poor packaging causes mechanical damage, corrosion, or foreign matter entering the valve cavity during transportation and storage.
(9) The actual valve does not match the delivery information, and the product’s quality lacks traceability.
The reasons for quality problems of valves include both technical factors and quality management factors. Generally speaking, management factors are the main factor, and most of the quality problems that occur in valves are caused by the inadequate management of the company. Therefore, valve manufacturers need to further improve quality awareness, strengthen quality management throughout the process, and form their own complete quality management system to ensure the provision of high-quality valve products.
     
1.3 Requirements for the use of valves
Features of the new petrochemical system equipment are as follows:
(1) The scale of production is large and the investment is high.
(2) The project is big and the construction period is short.
(3) The purchase price of products is low, and the delivery cycle is short. However, the product’s quality requirements are high.
(4) There are few professional stable personnel.
(5) After the project is put into production, the operation load of the device is great and the operation period is long.
(6) The downtime is short and there is a shortage of professional maintenance personnel.
Analyzing the requirements and characteristics of new petrochemical system devices, valve companies must have rapid response capabilities and a strong sense of active service. Because of the lack of professional valve repair, maintenance personnel and professional technical support in newly-built devices, many kinds of valves used, the provision of professional valve maintenance services has become a new demand, and it has also brought new opportunities to valve manufacturers.
 
In addition, the replacement and maintenance of the valve of the current petrochemical plant after putting into use rely more on the experience in the operation of the device, which lacks scientific, systematic and unified standards. There are risks of production and safety accidents caused by no timely maintenance and replacement. At the same time, there are also excessive maintenance and replacement, causing unnecessary waste. Therefore, if you can provide inspection and evaluation services for valves used, discover potential problems in time, even give early warning, achieve the purpose of planned and focused maintenance and replacement of valves, you can ensure safe production and save costs.
 
Therefore, while providing valves, valve companies extend to testing and maintenance services of valves. The service provided by valve manufacturers will have industrial foundations and technical advantages, and at the same time, it can become the future development trend and new business growth point of the valve manufacturing industry.