Piston Check
A piston check is very similar in function to a lift check. The big difference is that the disc is spring loaded, meaning that a spring pushes the disc into a closed position. This closes the disc faster, causing less backflow in the line and reduces the possibility of hammer-stop. However, it can also result in a higher amount of pressure reduction since the flow pressure has to both lift the disc and press the spring-loaded piston upward.
Inline Check
Inline check valves are smaller-bodied check valves that are spring loaded. Most inline check valves are intended for vertical installation, though they can be used in any direction. It has a disc or globe inside of it that is forced by a spring to seat in the inlet, stopping backflow. Flow pressure against the disc or globe in the correct direction causes it to open, and when pressure begins reducing, the spring presses it back into a closed position again. This is great when a check is needed and flow is moving in a downward vertical direction because the check does not rely on gravity or solely on backflow pressure to close.
This style is also known as a silent check. The reason for this is that the spring pressure causes it to close gradually and directly as inflow pressure reduces which results in a quieter close. A silent close means less hammer-stop and less vibration, which means pipes and valves last longer.
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Quality inspections and valve testing are extremely important when it comes to the smooth running of fluid systems. Industrial valves are an integral part of many industrial machines and even the tiniest malfunction can have a ripple effect on the rest of the machine. Therefore, it’s important to carry out the right checks to ensure safety and efficiency.
When it comes to testing valves, there are multiple valve testing procedures used and all of them need to conform to the strict acceptance criteria or performance standards. In this article, we’ll go through the key things you need to know about valve inspection procedures and tests.
What Are the Common Types of Valves?
Valves come in all different shapes and sizes depending on what industry or application they are being used for.
These are the most common types of valves:
Butterfly Valve
Gate Valve
Globe Valve
Gray Iron Valve Body
Gray Iron Valve Cover
Plug Valve
Swing Check Valve
The Importance of Valve Testing
Valves need to conform to certain leakage standards and various other checks are also carried out. Valve testing and inspections should ideally be done every 12 months or so to ensure they are still in the best working condition. However, this will vary depending on the age of the valve, the condition of the valve, and what type of valve is in question.
How Do Valve Leakages Happen?
Valve leakages are a common phenomenon. They can happen for many different reasons. But there are two primary ways a leak can happen in a valve: fugitive emissions from a valve escaping into the atmosphere and leaks escaping through the valve but remaining contained within the piping system.
The first can naturally damage the environment and become a potential safety hazard to people. Valves are considered to be the major reasons for fugitive emissions being lost so quality management and testing of valves are important.
What Are the Common Causes of Valve Leakages?
Valve leakage is a common problem in most industries and it can be caused by a series of factors. But the most common causes of leakages in valves include a valve not being fully closed because the valve seat is being prevented from closing due to dirt, rust, or line debris; there being insufficient actuator travel, or the valve seat being damaged. There are naturally other factors that could cause leakages and testing will check for all of these potential issues.
What Are the Common Reasons for Leaks Into the Atmosphere?
The reasons for potential leaks into the atmosphere could include the gasket between the valve body and valve bonnet being damaged or the stem packing being out of place, worn, or damaged in some way.
What Is Valve Testing?
Valve testing is a process that is used to test and evaluate the health or condition of an operational valve. Naturally, there are many different types of tests and inspections that are performed on valves to ensure they are in the best condition and safe for use.
What Are the Valve Testing Procedures?
A typical testing procedure for a hydrostatic valve might involve the following stages:
What Are the Main Valve Leakage Tests?
Here is a list of the most common types of tests carried out to check for valve leakages and the types of valves associated with them:
Valve Seat Leakage Tests
The valve seat tests procedure involves placing a valve under pressure, then measuring the amount of leakage on the other side of the valve. The test pressures are often determined according to the American Society of Mechanical Engineers (ASME) B16.34.
Back Seat Tests
Valve backseat tests are commonly conducted on valves that have a backseat element, such as the gate and globe valve types. The back seat tests are performed according to the approved test procedure, but they often involve opening the valve while the packing gland is loose or not installed.
Valve Closure Tests
The closure test is a test that is typically conducted on valves that are used in full closed and full open service. These kinds of valves include, but are not limited to, stop valves, globe valves, plug valves, and ball valves.
Shell Leakage Tests
Valve Shell Leakage Test is a test that helps identify the presence of water and other fluids in the valve casing. The test is conducted by pressuring the valve for a specified amount of time, usually one minute or more, and looking for leaks. They are performed on valves like a check, stop, and isolation types.
The Types of Valve Testing Standards
Below is a breakdown of some of the most common valve testing standards:
API 598: Valve Inspection and Test
API 527: Seat Tightness of Pressure Relief Valves
ASME B16.34: Valves – Flanged, Threaded, and Welding End
ASME PTC 25: Pressure Relief Devices
FCI 70-2: Control Valve Seat Leakage
ISA-S75: Hydrostatic Testing of Control Valves
ISO 5208: Industrial Valves, Pressure Testing of Valves
MSS SP61: Hydrostatic Testing of Steel Valves
MSS SP70: Cast Iron Gate Valves, Flanged, and Threaded Ends
MSS SP71: Cast Iron Swing Check Valves, Flanged, and Threaded Ends
MSS SP78: Cast Iron Plug Valves, Flanged, and Threaded End
MSS SP80: Bronze Gate, Globe, Angle, and Check Valves
MSS SP85: Cast Iron Globe and Angle Valves
All of the above documentation can be gained through a third-party quality management company such as HQTS. Our inspectors are ready to perform testing on your valves to ensure only the best products leave your factory which keeps your customers happy and the environment in a better state.
Conclusion: Valve Testing Procedures in Quality Control
The quality control procedure for valves is integral to the success of any manufacturing process. Valves are important in many fields – and even the smallest malfunction can have a detrimental effect on operations. The valve inspection procedure ensures that the valve is free of defects and will meet the defined quality standards
There is a range of valve testing procedures. At HQTS, we have over 25 years of experience in quality management, which includes quality assurance and quality control. We are a global company and can help with valve testing across many regions. Contact us if you want to book your valve test today!
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