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Today, more than ever before, testing is extremely important in the valve industry. The increase in globally sourced products and much-reduced domestic manufacturing has caused everyone in the valve supply chain to request and require more testing.
In order to effectively test a valve, there first must be an established testing procedure, combined with the acceptance criteria or performance standards that the valve is expected to meet or exceed. When it comes to testing standards though, one size does not fit all. There are different standards for industrial valves, pipeline valves, control valves and pressure-relief valves. This article provides you with information about the inspection of valves and valve testing in the manufacturing shop as well as in operational plants.
Valve Shell Test
Shell Test or Body test is performed after successful completion of valve individual components e.g. seat, disc, body, stem, etc. inspection, and assembly. The test is conducted by valve manufacturer or a repair service provider and based on the requirements of API STD 598 or other relevant standard ( Valve Inspection and Testing).
The valve shall be partially open and be able to hold pressure for a certain time. The pressure shall not be less than 1.5 times of maximum working pressure. No leakage is allowed. Leakage check points are body, bonnet, stem, plugs/fittings and flange connections.
Valve Seat Leak Test
The Seat Leakage (Closure Test) is performed after successful completion of the valve shell test (Body Test). One side (valve inlet or outlet) shall be subjected to the hydrostatic pressure and amount of leak shall be measured on the opposite side of the valve.
It means if you are pressurizing valve inlet, then you have to measure the amount of leakage in the outlet. The limited amount of leakage is permissible. In the same manner, you have to test and inspect both sides. Though valves have only one seat or other may have 4 seats as per their respective types. Test pressures are determined according to ASME B16.34.
Valve Back Seat Test
The Valve Back Seat Test is performed in the valve with a backseat feature. This is a feature that allows valve packing being replaced while it is in the service. In this test, the valve shall be fully opened and packing gland shall be loose or not installed. No leakage is permissible in the backseat test. Keep in mind that the test pressure for the backseat is same as the other seat test of the valve.
Pressure Safety Valve Testing
The pressure safety valve is a direct, spring-loaded pressure-relief valve that is opened by the static pressure upstream of the valve and is characterized by a rapid opening or pop action.
When the static inlet pressure reaches the set pressure, it will increase the pressure upstream of the disk and overcome the spring force on the disk. The fluid will then enter the huddling chamber, providing additional opening force. This will cause the disk to lift and provide a full opening at minimal overpressure. The closing pressure will be less than the set pressure and will be reached after the blowdown phase is completed.
Cold Differential Test Pressure (CDTP) Test: In this test, the Safety valve is mounted on a test rig. Adjust Nozzle ring (raise) to -2 notch position (Gas trim Valve). The operator applies the pressure (As per valve specification and data sheet) at the inlet of the valve. A safety relief valve pops or releases pressure when it reaches the desired set pressure. POP Test (to be repeated a minimum of 3 times to identify consistency). A reseating pressure shall be noted and recorded. In the industry, for this type of test, the standard which is widely followed is ASME Sec VIII Div.I. Test passing requirement and acceptance criteria are described as per the size of the valve.
Seat Test: In the seat test, the operator raises the pressure up to 90% of the CDTP and observes the leakage at the outlet of the valve for a particular period of time. Acceptance criteria in bpm or meter cubic feet are described in API-527 standard based on size and testing medium.
PSV Back Seat Test: Safety Relief Valves which contain a balanced bellow to overcome the back pressure which is caused by different outlet aspects. For such valves, it is mandatory to verify bellow integrity. To check the bellow you have to apply approx. 1 to 2 bar pressure at the outlet of the valve and observe leakage from the vent which is situated in the bonnet. No leakage is allowed.
External body or Shell Test: In the shell test for a conventional safety valve you have to apply 100 PSIG / 7 Bar at the outlet of the valve and then observe leakage at different connecting points such as body/bonnet joint, nozzle/body, nozzle ring adjustment lock and the stem opening on top. But for the body test of a balanced type valve, the same pressure is to be applied at both outlet and bonnet vent. Leakage observing points are the same which are mentioned above.
Third-Party Inspection for Valve:
TPI part guides you through all the necessary stages in the production of the valves, from the examination of certification of procurement sources to the final inspection, preservation, and packing, to the dispatch to site.
It is particularly suitable for the inspection of Gate, Globe, Ball and Check valves. The following points are addressed in this article:
- Valve Material Inspection
- Valve Welding Inspection
- Visual and Dimensional Checking
- Valve Low Pressure Air Test
- Valve Hydrostatic Testing
- Post Hydrostatic Testing
- Valve Final Inspection
- Valve Name Plate Checking
- Valve Painting and Coating Checking
- Valve Spare Parts, Loose Items and Accessories control
- Valve Packing, Marking and Shipping Inspection
Valve testing techniques definitely changing over the years and at the same time test procedures have become more concise. To improve the performance of a plant, it is essential for everyone working in this field to ensure that the right techniques with enough knowledge and mandatory safe work procedures are being followed.
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The purpose of this article is to guide Valve Technicians/operators for successful valve testing and inspection and also to make them familiar with the standards used to observe such activities.
Note: Photos used in this article are just for illustration.
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Testing for Heart Valve Problems
Echocardiogram
What is an echocardiogram?
An echocardiogram (echo) is a test that uses high-frequency sound waves (ultrasound) to make pictures of your heart. The test is also called echocardiography.
Why do I need an echocardiogram?
An echocardiogram looks at your heart’s structure and checks how well your heart functions. The test provides information about:
- The size and shape of your heart.
- The size, thickness and movement of your heart’s walls.
- How your heart moves.
- The heart’s pumping strength.
- If the heart valves are working correctly.
- If blood is leaking backward through your heart valves (regurgitation).
- If the heart valves are too narrow (stenosis).
- If there is a tumor or other abnormalities around your heart valves.
Understanding Your Echo Results (PDF)(link opens in new window)
Exercise Stress Test
Why is an exercise test sometimes needed to assess a valve problem?
Also called a stress test or treadmill test, exercise testing can provide valuable information in patients with valvular heart disease, especially in those whose symptoms may be difficult to assess.
Your health care team may use an exercise test in combination with echocardiography, an angiogram and cardiac catheterization.
Exercise testing helps evaluate changes in blood pressure and symptoms, and the heart’s response to a more challenging workload. Because heart valve symptoms can develop slowly, you may not realize you have limited activity over time or attributed the change to “normal aging.” If you have a heart murmur, your health care team will note any changes in the murmur that happen during exercise. Read more about exercise testing.
Chest X-ray
What’s a chest X-ray?
A chest X-ray is a picture of the heart, lungs and bones of the chest. A chest X-ray can show the heart’s overall shape, but it can't show the inside structures of the heart.
Why is it done on someone with a valve condition?
A chest X-ray shows the location, size and shape of the heart, lungs and the blood vessels. This can provide clues to a valve problem that include an enlarged or thickened heart and calcium deposits on the valve. Read more about chest x-ray procedures.
CT Scan
What’s a CT Scan?
The CT scan captures multiple X-ray images to create a cross-sectional image of the heart and lungs. Like an MRI, this test sometimes takes clearer pictures. Unlike MRI imaging, the CT scan uses about the same amount of X-ray as is needed for an angiogram.
Although an echocardiogram, including transesophageal echocardiography and transthoracic echocardiography is now the standard tool for assessing valvular heart disease, there are times when its effectiveness is limited in some patients. A CT scan creates images of the valve anatomy and allows for evaluation of the severity of stenosis and regurgitation. A CT scan also can determine whether there are valvular lesions or nearby tumors affecting the function. Read more about CT scans.
Cardiac Catheterization
How does cardiac catheterization help diagnose valve disease?
Although cardiac catheterization is most often used to look at the blood flowing to the heart muscle, it also can provide important information about narrowed heart valves, leaky heart valves or blood that is not flowing through the heart as it should.
View an illustration of cardiac catheterization.
For valve disease patients, a cardiac catheterization can:
- Measure blood pressure within the heart and oxygen in the blood
- Evaluate heart muscle function for moving blood through each chamber
- Help determine the best course of treatment
Cardiac catheterization is a “minimally invasive” procedure and isn’t necessary for every person who has a cardiac murmur or valve problem, but it can provide additional information when other tests may be inconclusive. Read more about cardiac catheterization.
Cardiac Magnetic Resonance Imaging
Cardiac magnetic resonance imaging (CMR), also called cardiac MRI, is a painless, non-invasive imaging test used to assess the function and structure of the heart. It uses radio waves, magnets and a computer to create detailed pictures of your heart.
CMR has become an optimal technique in assessing people with heart valve disease without the need for radiation. It’s enhanced diagnostic power can:
- Determine the type and severity of valve disease.
- Measure heart function or how much blood the left ventricle can pump out to the body.
People with any type of metal device inside the body should not have an CMR unless the device is certified as MRI safe.
Check with your doctor about the safety of CMR if you:
- Have a stent or artificial heart valve, or if you have had open-heart surgery recently.
- Are pregnant, especially during the first 3 months.
- Have tattoos or permanent (tattooed) makeup. You might feel some mild discomfort or a burning feeling on your skin from the metal in the darker inks of the tattoo.
- Have been told you have kidney problems.
Read more about magnetic resonance imaging.
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