Compromising on quality when purchasing gate valves commonly leads to early replacement when the gate valve inevitably fails. The solution to decreasing total lifecycle costs, as outlined in our previous article titled 'The Hidden Costs of Gate Valves', is to use high-quality gate valves that last longer and have lower maintenance costs. This two-part guide will help you to recognize what makes a quality product stand out among the many gate valve options on the market. Part 1 covers pre-purchase quality checks, valve body & coating checks, and checks related to the wedge, wedge nut, and wedge guides.
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Before making any purchases, you can confirm if a manufacturer's gate valve meets some basic quality criteria essential to long service lifetimes:
Confirm the gate valve meets or exceeds code and standard requirements by checking:
Does the manufacturer have a proven track record of longevity? Hawle for example, still has gate valves functioning after over 50 years of underground service?
Of the two most commonly used materials, GJS400-15 ductile iron offers double the elongation at break over GJS500-7. The improved ductility of this valve makes it less prone to cracking and improves long-term durability. Gate valves made using GJS400-15 are typically heavier because they use increased wall thickness to compensate for the slightly lower tensile strength.
Steel bolts easily corrode, causing them to 'stick' which complicates bonnet removal during maintenance or potentially causing the bolts to break when put under stress. Galvanized bolts are more resilient to corrosion than plain steel, but stainless steel bolts are the most resilient and are the best option for gate valve longevity.
Visually inspect the gate valve for surface irregularities from the casting process, such as pores or grooves. The internal and external valve surfaces should be smooth, especially along the length of the wedge guides. Ensure that the surfaces of the bonnet flange are machined by running a finger along them. If they are left as-cast and not machined, the bonnet gasket might be squeezed unevenly, resulting in premature failure and leakage.
Tip: Advanced checks
For those that want to be certain their gate valve body is top quality, the following expert inspection checks can be performed:
Conduct testing on the bonding strength and the impact strength of the valve's protective coating. Coating quality is highly dependent on the coating material, coating process used, and surface preparation. As a baseline standard, GSK specifies that coatings must have a minimum bonding strength of 12 N/mm² or greater. For best-case long-term performance, however, Hawle recommends aiming for a bond strength of at least 18 N/mm².
The first part of this guide covers a number of basic, advanced, and expert inspection checks to determine if a gate valve body and wedge components are of high-quality make and will perform well in service. From materials selection to processing methods, and from standards and testing compliance to intelligent design, selecting the right gate valve can make all the difference to your business but improving service life and decreasing lifecycle costs. Read Part 2 of this guide to learn more about the gate valve's spindle and seals and to see a brief recap of the whole inspection process.
There are various types of valves used in different industries, each with its own specific testing requirements. Some common types of valves include gate valves, globe valves, ball valves, butterfly valves, check valves, and pressure relief valves.
Gate valves are commonly used for on/off applications and require testing for proper sealing and operation. Globe valves are used for regulating flow and require testing for proper throttling and sealing. Ball valves are versatile and require testing for proper sealing and operation. Butterfly valves are used for large flow applications and require testing for proper sealing and operation. Check valves are used to prevent backflow and require testing for proper sealing and operation. Pressure relief valves are used to protect equipment from overpressure and require testing for proper set pressure and operation.
Understanding the specific testing requirements for each type of valve is crucial to ensure their proper functioning. For example, gate valves may require a seat leakage test to check for any leaks when the valve is closed, while pressure relief valves may require a pop test to verify that they open at the correct pressure. By following the appropriate testing procedures, engineers can ensure that valves meet the necessary standards and specifications.
Safety should always be a top priority when conducting valve testing. Valves are often subjected to high pressures and temperatures, which can pose significant risks if proper safety measures are not followed. Before conducting any testing, it is important to assess the potential hazards and implement appropriate safety measures.
Some common safety measures include wearing personal protective equipment (PPE), such as gloves, safety glasses, and protective clothing, to protect against potential injuries. Additionally, ensuring that the testing area is properly ventilated can help prevent exposure to harmful gases or fumes. It is also important to have emergency procedures in place in case of any accidents or incidents during testing.
Before conducting valve testing, it is essential to perform equipment checks and maintenance. This includes inspecting the testing equipment for any damage or defects, ensuring that all connections are secure, and verifying that all necessary components are in working order. Regular maintenance of testing equipment is crucial to ensure accurate and reliable results.
Proper setup and calibration of testing equipment is also important to ensure accurate results. This includes calibrating pressure gauges, flow meters, and other measuring devices to ensure they are reading correctly. It is also important to ensure that the testing equipment is properly connected to the valve being tested and that all connections are tight and secure.
There are several methods available for testing valves, each with its own advantages and disadvantages. The choice of testing method depends on various factors, including the type of valve, the specific testing requirements, and the available resources.
One common method of valve testing is visual inspection. This involves visually examining the valve for any visible defects or damage. Visual inspection can be a quick and cost-effective method, but it may not be sufficient for detecting internal defects or issues that are not visible to the naked eye.
Another method is functional testing, which involves operating the valve to ensure that it functions properly. This can include opening and closing the valve, adjusting the flow rate or pressure, and checking for any leaks or abnormal behavior. Functional testing provides a more comprehensive assessment of the valve's performance but may require specialized equipment and expertise.
Pressure testing is another commonly used method for valve testing. This involves subjecting the valve to a specified pressure to check for any leaks or failures. Pressure testing can be conducted using water, air, or other suitable fluids. It provides a quantitative measure of the valve's ability to withstand pressure but may not detect other types of defects, such as internal corrosion or wear.
Other methods of valve testing include leak testing, which involves checking for any leaks in the valve or its components, and actuation testing, which involves testing the valve's ability to open and close properly. Each method has its own advantages and disadvantages, and the choice of method depends on the specific requirements of the valve being tested.
Pressure testing is a commonly used method for evaluating the performance and integrity of valves. It involves subjecting the valve to a specified pressure to check for any leaks or failures. Accurate results are crucial to ensure that valves meet the necessary standards and specifications.
To ensure accurate results in pressure testing, it is important to follow certain tips and best practices. First, it is important to select the appropriate test pressure based on the valve's design and intended application. The test pressure should be sufficient to evaluate the valve's performance but should not exceed its maximum allowable working pressure.
It is also important to ensure that the testing equipment is properly calibrated and maintained. This includes calibrating pressure gauges, flow meters, and other measuring devices to ensure they are reading correctly. Regular maintenance of testing equipment is crucial to ensure accurate and reliable results.
Proper setup and preparation are also important in pressure testing. This includes ensuring that all connections are tight and secure, and that the valve being tested is properly installed and aligned. Any leaks or loose connections can affect the accuracy of the test results.
During the pressure test, it is important to monitor the pressure closely and record any changes or deviations. This can help identify any potential issues or leaks in real-time. It is also important to conduct a thorough visual inspection of the valve and its components before and after the pressure test to check for any visible defects or damage.
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Leak testing is an essential part of valve testing, as even small leaks can have significant consequences in terms of safety, reliability, and efficiency. Leak testing involves checking for any leaks in the valve or its components using various techniques.
One common technique for leak testing is visual inspection. This involves visually examining the valve for any visible signs of leaks, such as dripping or wet spots. Visual inspection can be a quick and effective method for detecting leaks, especially in external components or connections.
Another technique is bubble testing, which involves applying a soapy solution to the valve or its components and looking for any bubbles that indicate a leak. This method is particularly useful for detecting small leaks or leaks in hard-to-reach areas.
Pressure decay testing is another commonly used technique for leak testing. This involves pressurizing the valve and monitoring the pressure over a period of time. Any decrease in pressure indicates a leak. Pressure decay testing can be conducted using air or other suitable fluids.
Other techniques for leak testing include helium leak testing, which involves using helium gas to detect leaks, and ultrasonic testing, which uses sound waves to detect leaks. Each technique has its own advantages and disadvantages, and the choice of technique depends on the specific requirements of the valve being tested.
Once a leak is detected, it is important to fix it promptly to ensure the proper functioning of the valve. This may involve tightening loose connections, replacing damaged seals or gaskets, or repairing any defects or damage. It is important to follow the manufacturer's recommendations and guidelines for repairing leaks to ensure that the valve is restored to its proper working condition.
Valve actuation testing is an important part of valve testing, as it ensures that valves are functioning properly and can open and close as intended. Valve actuation refers to the process of operating the valve to control the flow of fluids through pipes and other passageways.
There are various techniques for testing valve actuation, depending on the type of valve and its intended application. One common technique is manual actuation testing, which involves manually opening and closing the valve using a handwheel or lever. This can help assess the valve's ability to operate smoothly and without any sticking or binding.
Another technique is motorized actuation testing, which involves using a motor or actuator to open and close the valve. This can help evaluate the valve's response time, torque requirements, and overall performance under different operating conditions.
For valves that require precise control, such as control valves used in process industries, it may be necessary to conduct performance testing. This involves measuring various parameters, such as flow rate, pressure drop, and response time, to ensure that the valve is meeting the required specifications.
Valve actuation testing is important to ensure that valves are functioning properly and can perform their intended functions. It helps identify any issues or defects that may affect the valve's performance, such as sticking, binding, or excessive wear. By conducting thorough actuation testing, engineers can ensure that valves meet the necessary standards and specifications.
Calibration and verification are essential in maintaining accurate test results in valve testing. Calibration refers to the process of adjusting and verifying the accuracy of testing equipment, such as pressure gauges, flow meters, and temperature sensors. Verification refers to the process of confirming that the testing equipment is functioning properly and providing accurate results.
Regular calibration of testing equipment is crucial to ensure accurate and reliable test results. Over time, testing equipment may drift or deviate from its original calibration, leading to inaccurate measurements. By calibrating the equipment at regular intervals, engineers can ensure that it is reading correctly and providing accurate results.
Calibration should be performed by qualified personnel using traceable standards and procedures. This ensures that the calibration process is consistent and reliable. It is also important to keep records of all calibration activities, including the date of calibration, the standard used, and the results obtained. This helps maintain a history of calibration activities and provides evidence of compliance with applicable standards and regulations.
In addition to calibration, it is important to verify the performance of testing equipment on an ongoing basis. This can be done through regular checks and inspections to ensure that the equipment is functioning properly and providing accurate results. Any deviations or abnormalities should be investigated and addressed promptly to maintain the integrity of test results.
Regular maintenance of testing equipment is also important in maintaining accurate test results. This includes cleaning, lubricating, and inspecting the equipment for any damage or defects. Any worn or damaged components should be replaced promptly to ensure the proper functioning of the equipment.
Documentation and reporting are essential in valve testing to maintain accurate and detailed records of the testing process. This includes recording all relevant information, such as the date and time of testing, the type of valve tested, the testing method used, and the results obtained.
Accurate documentation is important for several reasons. First, it provides a record of compliance with applicable standards and regulations. This can be useful in demonstrating that valves have been tested and meet the necessary requirements. Second, it provides a reference for future maintenance or troubleshooting activities. By documenting the testing process, engineers can easily refer back to previous test results and identify any trends or patterns.
Best practices for record-keeping in valve testing include using standardized forms or templates to ensure consistency and completeness. This can help ensure that all necessary information is recorded and that nothing is overlooked. It is also important to keep records organized and easily accessible, either in hard copy or electronic format.
In addition to documentation, it is important to report the test results accurately and clearly. This includes summarizing the findings, identifying any issues or defects, and recommending any necessary actions or follow-up activities. The report should be concise but comprehensive, providing all relevant information in a clear and understandable manner.
Valve testing can present various challenges that can affect the accuracy and reliability of test results. It is important to be aware of these challenges and to have strategies in place to overcome them.
One common challenge in valve testing is ensuring representative samples. Valves are often produced in large quantities, and it may not be feasible or practical to test every single valve. Instead, a representative sample is selected for testing. It is important to ensure that the sample accurately represents the population of valves being tested. This can be achieved through proper sampling techniques and statistical analysis.
Another challenge is the complexity of testing procedures and requirements. Valve testing can involve multiple steps and procedures, each with its own specific requirements. It is important to have a clear understanding of the testing procedures and to follow them accurately. This may require specialized training or expertise.
Equipment limitations can also pose challenges in valve testing. Testing equipment may have limitations in terms of pressure range, temperature range, or other factors. It is important to be aware of these limitations and to select the appropriate equipment for the specific testing requirements. If necessary, additional equipment or modifications may be required to overcome these limitations.
Environmental factors can also affect valve testing. Valves are often subjected to extreme conditions, such as high temperatures, corrosive environments, or high vibration levels. It is important to consider these factors and to simulate them as accurately as possible during testing. This may require specialized equipment or test setups.
Finally, time constraints can be a challenge in valve testing. Testing schedules may be tight, and there may be pressure to complete the testing quickly. However, it is important not to rush the testing process and to ensure that all necessary steps and procedures are followed. Cutting corners or skipping steps can compromise the accuracy and reliability of test results.
In conclusion, valve testing is a critical process in ensuring the safety and reliability of valves used in various industries. It involves identifying potential issues, ensuring proper functionality, and maintaining accurate test results. By following best practices and implementing appropriate testing methods, engineers can ensure that valves meet the required standards and perform optimally in their intended applications. Some key best practices for effective valve testing include conducting regular inspections, using calibrated equipment, following standardized testing procedures, and documenting all test results. Additionally, it is important to involve experienced personnel who are knowledgeable about valve testing and can accurately interpret test data. By adhering to these best practices, industries can minimize the risk of valve failure, improve operational efficiency, and enhance overall safety.
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