Discussion on the Quality Control of Valve Procurement in Refining and Chemical Enterprises
2025-04-09 09:54:43
In the refining and chemical industry, production and safety accidents are often caused by improper valve selection. Therefore, valve procurement should be regarded as a key task both currently and in the future. Relevant personnel must have a quality awareness when purchasing valves, implement quality control throughout the whole process, and ensure that the purchased valves can meet the production requirements of refining and chemical processes.
I. Common Types of Valves in the Refining and Chemical Field
(1) Gate Valve
Gate valves are frequently and widely used in the refining and chemical field. When a gate valve is used reasonably, the flow direction of the liquid remains unchanged. When the gate valve is fully open, the resistance coefficient is extremely small. There is a strong selectivity in terms of the caliber, pressure, and temperature range used in the refining and chemical industry. The installation space of the gate valve is relatively small, and it can be used in many situations. However, the gate valve also has some disadvantages. For example, it is relatively tall, and the opening and closing cannot be completed instantaneously, which takes a long time; during the opening and closing process, the sealing surface is extremely prone to local damage due to erosion; it has a high requirement for the cleanliness of the medium; if it is made of non-metallic corrosion-resistant materials, there are great technical risks during production and high operation requirements. Once the gate valve is opened, the probability of the occurrence of the eddy current phenomenon on the back of the gate plate will increase. And the eddy current is the main cause of the erosion and vibration of the gate. If the relevant personnel do not find this phenomenon in time and do not intervene as soon as possible in the actual work, the long-term eddy current phenomenon on the back of the gate plate will interfere with the function of the gate valve and lead to valve failure. Considering these factors, in refining and chemical production, the performance and functional advantages of gate valves are not significant for regulating the flow rate, and other types of valves can be selected.
At present, when applying gate valves, it is mainly necessary to analyze their application environment and function, and compare the application effects of rising-stem gate valves and non-rising-stem gate valves. If there are corrosive media in the use environment, the rising-stem gate valve has a better effect; in an environment with low pressure and no corrosive media, the regulating function of the non-rising-stem gate valve is remarkable.
(2) Ball Valve
Ball valves are often used in the refining and chemical field. In the environment of high temperature, low temperature or high-viscosity media, ball valves can show superior performance. If the medium contains suspended solid particles, most ball valves on the market can be used in this condition, but the installation and operation standards need to be followed during use. For the more common full-port ball valve, it is more often used when there is a need to regulate the flow rate, and it is relatively rare in other cases. Once this type of valve is used, in case of an emergency in refining and chemical production, the full-port ball valve can be cut off instantaneously. With the steady development of the refining and chemical industry, corresponding specifications have been successively introduced in the industry. When there are strict requirements for sealing and wear resistance, or there is a need for high-pressure cut-off and rapid opening and closing response, ball valves need to be equipped. From the perspective of the medium, for corrosive and lightweight structures, the application effect of ball valves is relatively ideal. In addition, ball valves are also suitable for low-temperature and cryogenic media.
(3) Check Valve
Check valves are suitable for use in clean media conditions. Referring to the existing work specifications, check valves have a high requirement for the cleanliness of the medium. When the nominal diameter (DN) does not exceed 40 mm, a lift check valve should be selected, and it needs to be installed in the designated position to play its due role; if the DN is in the range of 50-400 mm, a swing check valve should be selected. This type of valve has an outstanding application effect and can be applied both on horizontal and vertical pipelines, but the flow direction of the medium should be determined according to the actual situation during specific application; when DN ≥ 450 mm, the buffer check valve has superior performance; when DN is in the range of 100-400 mm, a butterfly check valve is often used. Based on the application experience of check valves in the refining and chemical field, the swing check valve has good bearing capacity. Even under relatively large pressure, it can still be used normally, and this type of check valve can be used in many complex working conditions.
(4) Globe Valve
In some refining and chemical production operations where there are no strict regulations on the fluid resistance, a globe valve can be selected. Even in the face of high-temperature and high-pressure cut-off, using this valve can achieve the expected effect. There are many types of globe valves on the market, and they need to be selected and used according to the situation. For example, if DN ≤ 200 mm and it belongs to the steam pipeline, in order to highlight the role of the globe valve in the entire pipeline, it is necessary to optimize the position of the globe valve, conduct tests, comparisons, and analyses to achieve accurate positioning; for small valves such as sampling valves, needle valves, and instrument valves, or valves for low-vacuum systems and exhaust valves, the application effect of globe valves is also relatively good, but the corresponding operation requirements need to be followed during use. Compared with other types of valves, the globe valve can not only regulate the flow rate but also control the pressure. Therefore, in specific applications, there are not too many requirements for the regulation accuracy. As long as the pipeline diameter is not large, a globe valve can be equipped at a specific position.
(5) Throttle Valve
The structural form of the throttle valve is roughly the same as that of the globe valve, but there are significant differences in its applicable conditions and functions. In addition, there is no throttling element in the throttle valve, and its size is relatively small. When applied, it has good reliability and remarkable energy-saving performance, and external factors rarely affect its application effect. Even so, the throttle valve also has disadvantages, which are manifested as poor control and regulation capabilities, and errors are likely to occur in many situations. Through comprehensive analysis, in the refining and chemical field, if the medium is at low temperature and high pressure, a throttle valve can be equipped. When there are requirements for regulating the flow rate and pressure in actual work, using a throttle valve can achieve the goal. When the medium has poor cleanliness and high viscosity, the use of a throttle valve is strictly prohibited.
(6) Butterfly Valve
The fluid resistance of the butterfly valve is extremely small, and it can be opened and closed flexibly. When applied in the refining and chemical field, its weight, structure, and size determine that it can achieve good application effects. In the refining and chemical industry, if there are requirements for cutting off and throttling design, the butterfly valve is more suitable. However, in terms of large-flow regulation, considering the influence of the sealing material, the butterfly valve is not completely suitable, and in some cases, other valves need to be selected. In the design of liquid media containing suspended solids and large-diameter pipelines, a butterfly valve can be installed at an appropriate position.
(7) Plug Valve
In the refining and chemical field, the plug valve can be preferentially used. It has good sealing performance, has two-way sealing conditions, has flexible opening and closing actions and short time consumption, and has good durability. In refining and chemical production, many harmful materials are often used, and in this case, the advantages of the plug valve are obvious, but its opening and closing torque is relatively large. After long-term use of the plug valve, there is no liquid accumulation in its cavity, and it will not pollute the materials of the intermittent device.
(8) Diaphragm Valve
Diaphragm valves are also relatively common in the refining and chemical field. In specific applications, they can precisely control the movement direction and state of the fluid with the help of rubber membranes or plastic membranes. In actual work, if a diaphragm valve is used, the resistance faced by the fluid is extremely small and can almost be ignored. This feature determines that two-way sealing can be carried out when necessary. When facing low-pressure and suspended viscous fluids, a diaphragm valve should be preferentially equipped, and installing it at a specific position can achieve the purpose of regulation. The diaphragm material has good temperature resistance, creating good temperature conditions for the diaphragm valve.
II. Precautions for Valve Procurement in the Refining and Chemical Field
(1) Clarify the Function and Purpose of the Valve
The refining and chemical field often involves a variety of valves. Although they are small in size, there are a large number of them in the process flow, and they play an important role in control and regulation. When purchasing valves, relevant personnel must be familiar with the specific functions of the valves and clearly understand their purposes. Based on these, they should compare the advantages and disadvantages of various valves and select the best valve type. Before purchasing valves, relevant personnel must communicate with the technical personnel in charge of the refining and chemical devices and the design personnel of the design institute to understand the process flow and the specific requirements for the valves, so as to achieve reasonable selection. There are relatively many types of valves on the market, and different types of valves have differences in functions, application conditions, etc. In order to purchase valves that meet the requirements, relevant personnel must be familiar with the characteristics of various valves and the application process of the valves to ensure that the selected valves meet the site requirements, so that the valves can be highly integrated with other accessories and maintain the normal operation of the relevant devices, pipelines, and equipment.
(2) Determine the End Connection of the Valve
When purchasing valves in the refining and chemical field, relevant personnel also need to pay attention to the connection. Currently, the connection treatment of the valve ends mainly includes threaded connection, flange connection, and welded connection. Comparatively speaking, the first two are more commonly used. In threaded connection, there is a high requirement for the nominal diameter of the valve. Generally, it needs to reach DN ≤ 50 mm. Once the diameter of the selected valve exceeds 50 mm, the installation and sealing difficulties of the connection part will increase simultaneously. Flange connection is relatively convenient for both installation and disassembly, with small workload and simple technology, and this connection method can be used in many situations. The welded connection method has strict regulations on the conditions. Under the standardized welding process and operation, the connection effect is relatively ideal. However, it also has some problems. For example, the technical requirements for valve disassembly and reinstallation are high, which limits the promotion of this connection method to a certain extent. When purchasing valves in the refining and chemical field, attention needs to be paid to the above aspects. Communicate with installation personnel and others to understand the difficulty coefficient and technical requirements of the valve end connection, select valves optimally, and strengthen quality control.
(3) Selection of Valve Materials
When purchasing valves, attention also needs to be paid to the materials. There are many types of valves on the market, and the materials of these valves are different. They are mainly divided into forged steel valves and cast steel valves. Commonly used materials in daily applications mainly include carbon steel, alloy steel, stainless steel, etc. In order to purchase valves that meet the production requirements, when purchasing valves, professional personnel not only need to pay attention to their types, functions, and applicable conditions, but also need to analyze the type of the medium, master the physical and chemical properties of the medium, and be clear about the cleanliness of the medium, etc. Paying attention to these aspects in the early procurement stage can ensure that the valves can play their due role after being put into use and meet the requirements of efficient and safe production in the refining and chemical industry. When selecting the valve materials, the procurement personnel must take the design material list and the detailed requirements of the work order as the preconditions, and make the procurement according to the actual application working conditions and in combination with the relevant system and specification requirements. If necessary, communicate and interface with the demand unit.
(4) Other Aspects
At present, with the steady development of the refining and chemical industry, people have put forward higher requirements for valve procurement. Whether the valves selected and purchased in each link meet the requirements is related to the safety and economy of chemical production. When purchasing valves, in addition to paying attention to the above aspects, the following aspects also need to be analyzed.
Firstly, the valve size. From the perspective of efficient and safe production, the valves used in any refining and chemical design need to be selected based on the type and size of the process pipeline, etc. When purchasing valves, the procurement personnel not only need to consider the function and purpose of the valve itself but also need to analyze the valve size to ensure that the size is completely consistent with the actual requirements.
Secondly, the working pressure and temperature of the valve. At present, although there are many types of valves with the development of technology, each valve has its applicable conditions and basic requirements. In the face of different pressure and temperature conditions, the procurement personnel also need to consider these aspects when selecting valves, clarify the valve materials and pressure ratings, and use these as the basis for procurement.
Thirdly, the pressure loss of the valve. Some valves have local resistance loss during use. Since each valve has its structural characteristics, there is a corresponding resistance under different valve structures. When purchasing valves, it is also necessary to evaluate the allowable range of the valve resistance.
III. Quality Control Measures for Valve Procurement in the Refining and Chemical Field
(1) Do a Good Job in Inspection and Testing Work
1. Valve Inspection
Valves play an irreplaceable role in the refining and chemical field. In order to ensure that the procurement personnel can purchase valves that meet the requirements every time, these personnel must be familiar with the valve inspection standards and technical requirements and select valves with reference to these aspects. The following work needs to be done in the procurement work.
Firstly, valve appearance inspection. When placing orders for standard valves, the principle of framework procurement and the technical requirements for valve framework bidding need to be implemented. When purchasing special valves or valves outside the framework, the procurement personnel need to interface with the supply manufacturer, explain the type, quantity, quality requirements, etc. of the valves they need to meet the customized requirements. When the manufacturer supplies the goods, it needs to provide the valve quality certification documents, and for special valves, it needs to provide the product instruction manual. When inspecting the appearance of the valve, the nameplate, mark, shell, and components of the appearance should be inspected to ensure that the relevant marks on the valve appearance are clear, which is convenient for the relevant personnel to understand the quality and relevant parameters of the valve and determine whether the valve meets the actual requirements. The valve nameplate should include information such as the nominal size, nominal pressure, valve body material, valve stem and sealing surface material, manufacturer's name or trademark, and TS mark. At present, the valve manufacturers on the market are uneven. Some manufacturers use inferior materials when producing valves, or the adopted process does not meet the requirements, and they do not mark the information completely and accurately according to the industry regulations. According to their work experience, the procurement personnel find that for general-purpose valves, the information marked on the shell is relatively complete, mainly including the nominal size, nominal pressure, trademark, material grade, heat number, medium flow direction, etc. Some valves on the market have the characteristic of a small diameter. Due to the limited space on this type of valve, the information cannot be fully marked, and only the key information can be presented. For the information that cannot be marked on the shell, it needs to be marked on the nameplate. The handwheel or handle of the valve also needs to be marked with information, generally the opening and closing direction. In short, when purchasing valves, the procurement personnel must communicate with the manufacturer. Only when the manufacturer marks various aspects of information in strict accordance with these standards can the procurement personnel comprehensively evaluate the valve quality and thus do a good job in valve selection. The ex-factory protection inspection of the valve is particularly important and should be entrusted to a dedicated person. These personnel mainly need to refer to the standards of JB/T 106—2004 and JB/T 7928—2014. However, the protection inspection contents and key points of different types of valves are different, and the relevant personnel need to pay attention to the differences when being responsible for these works. For example, for cast iron, carbon steel, and alloy steel valves, the focus of the protection inspection should be on the protective paint on the outer surface. When selecting these valves, the procurement personnel need to focus on these aspects. If the manufacturer does not implement JB/T 106—2004 and JB/T 7928—2014 for these types of valves and does not carry out corresponding treatments for special links, they should not be applied in the refining and chemical process.
Secondly, scientific testing. In the valve procurement in the refining and chemical field, in order to effectively ensure the valve quality, all kinds of inspection and testing items of the valves should be carried out according to the standards and agreed requirements, and the valves can only be delivered from the factory after passing the inspection. The testing items include but are not limited to pressure tests (including shell and sealing tests), visual inspection, dimension inspection, material chemical composition, material test certificate (PMI) inspection, material mechanical properties, non-destructive inspection, and intergranular corrosion inspection (if required).
2. Taking the Pressure Test as an Example
Firstly, the shell test. Close all the ends of the valve, operate the opening and closing parts to make them enter the open state, fill the inner cavity with the test medium, create an air-free condition, and slowly and uniformly increase the pressure until the test pressure requirement is reached and then stop increasing the pressure. Maintain this pressure condition for a certain period of time. After the time is consistent with the test time requirement, comprehensively inspect the shell and evaluate whether there are quality defects such as damage on the shell.
Secondly, the upper seal test. (The test is carried out to check the sealing performance of the upper seal structure of the valve) Close all the ends of the valve, loosen the packing gland, fill the inner cavity with the test medium to ensure that it is completely filled and there is no air; fully open the valve, continue to increase the pressure, create the test pressure condition and then maintain the pressure. When the pressure holding time meets the test regulations, a dedicated person checks whether there are any abnormalities at the valve stem packing.
Thirdly, the sealing test. Many valves can achieve two-way sealing. To determine the performance of this type of valve, special attention should be paid to the sealing performance. Close all the ends of the valve, open individual opening and closing parts as needed, fill the inner cavity with the test medium, and then increase the pressure until the test pressure is reached. Close the opening and closing parts, relieve the pressure at one end, and maintain the pressure at the other end for the specified test time, and check the leakage situation at the pressure-relieved end. Repeat the above steps to conduct a reversing test and check the leakage situation. For valves with one-way sealing and marked flow direction, keep all the opening and closing parts in the closed state, fill the inlet end with the test medium and discharge the air in it, slowly increase the pressure to reach the test pressure value, maintain the pressure for the specified test time, and check whether there is any leakage at the outlet section.
If the result of any of the above tests is inconsistent with the standard situation, it indicates that the valve has quality problems and needs to be returned to the factory for processing or repurchased.
(2) Establish a Sound Quality Control System for Valve Procurement
During the valve procurement process, in order to ensure quality, many aspects need to be paid attention to. Refining and chemical enterprises need to establish a sound quality control system for valve procurement work. This system should specify the valve procurement process, quality control methods, responsibility division, etc., to ensure that relevant departments and personnel in relevant positions can effectively participate in the quality control of valve procurement according to the requirements of the system. For example, the quality control system for valve procurement should include the key points of quality control for the procurement process and model selection. Relevant personnel must strictly implement these contents in the subsequent procurement process, highlight the role of the institutional system, and provide institutional guidance and constraints for the actual work.
(3) Improve the Professional Ability and Quality Awareness of Procurement Personnel
Procurement personnel are responsible for the valve procurement work, and their professional ability and quality are important factors affecting the quality of purchased valves. In refining and chemical enterprises, according to the requirements for the quality and ability of personnel in valve procurement quality control, training activities should be organized regularly and irregularly. Through various forms of training activities, the professional ability of procurement personnel should be improved, enabling them to purchase valves that meet the requirements from the market according to the actual needs of valves in chemical production and do a good job in the quality control of the entire procurement process.
IV. Conclusion
Valves are key elements in refining and chemical production. To highlight the role of valves, refining and chemical enterprises need to ensure the quality of valves from the source and do a good job in the quality control work in the procurement stage. In the future, in terms of valve procurement, it is necessary to innovate the concepts and methods of quality control and build a scientific working mechanism.
Cited from China Business Update. Author: Ren Binxin
