Wenzhou Unique Valve Co., Ltd.
Why Industrial Valves Fail and How to Repair
Apr 20, 2020
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Industrial valves don't last forever. They don't come cheap either. In many cases, repair begins within 3-5 years of use. However, understanding the common causes of valve failure can lengthen the life service of valves.
This article provides information on how to repair faulty valves, the common causes why valves need fixing and the signs that valves are already faulty.
What Makes Valves Last Longer
The lifespan of the valve depends on three factors: the quality of the seal, internal and external environment and the frequency of operation.
If the seal works perfectly, the valve works well, too. Choosing the right seal ensures better performance and maintenance.
On the other hand, factors such as pressure, temperature, as well as the type of media are worth considering. Lastly, the maintenance period is around 3 months if the valve works all the time. Timely maintenance ensures optimum operating conditions.
When to Repair Valves
#1 When there is internal leakage
One of the reasons why there is internal leakage is that the valve cannot have a total shutoff. According to international standards, each valve type has a maximum allowable leakage (MAL). A sign that the valve needs repair is when the leakage is beyond MAL.
#2 When there is external leakage
There are a few culprits of why external leakage is present. In many circumstances, there is improper maintenance. It is also possible that the material of the valve and the media are not compatible. Extreme temperature can also cause external leakage.
#3 When the valve becomes noisy
Water hammer is the term used in industrial applications to describe the sound made by valves. This is an indicator that the valve needs maintenance. This noise is caused by the disc hitting the valve seat.
#4 When the valve is no longer working
Obviously, when the valve is not working anymore, it is high time to salvage or repair it. While many valves can be repaired, some valves are almost impossible to repair.
The Common Causes of Industrial Valve Failures
#1 Improper Valve Size
The wrong valve size calculation can lead to either undersized or oversized valves. It is important to select the valve of correct size because the flow of media depends on the size of the valve. An oversized valve can decrease the pressure, whereas an undersized one can cause bottlenecks.
Solution
Find an online valve sizing calculator. There are different formulas for liquids as well as for gases. If manual calculation is too tedious, an online one will just do the trick.
This would make it easier to find a suitable valve. The Kv value found in the product description is as a point of reference. Also, consider the required flow rate as well as the pressure drop.
#2 Material Incompatibility
The media type, the seat material and the material of the valve body should match. Incompatibility means that the valve is more prone to wear and tear.
Solution
Check the product description for the type of material used for the valve seat and body. What media to use should follow the industry standards. Also, check for valve damage if you suspect there was an improper use of materials. Changing the valve is costly. Replace the parts in contact with the medium with those that can withstand it.
#3 Elastomer Damage
Elastomers are often used as valve seats, gaskets or O-rings. They act as seals. Because those elastomers are elastic, they are the natural choice for sealing applications. They also prevent the metal valve body from contacting with the medium. Elastomers used in industrial applications include nitrile, Aflas, and Teflon.
The wear of elastomers is caused by the natural movement of the fluids. Most often, the cause would be the incompatibility of the elastomer and the media.
Solution
Consider the compatibility of the elastomer and the media. Check the product description for what types of media to use with elastomers. When you make a purchase of the elastomer, check the description of the valve. If the elastomer seal is not compatible with the media, please find others.
Once the elastomer seal has dents, cracks and the likes, replace this component. Also, check if there are wear patterns that follow the media flow, which means that the latter is too abrasive.
#4 Valve Stem Wear
Smaller components such as valve stem packing and gland bolts cause wear and tear to the stem. Furthermore, the constant movement of the valve disc, as well as the contact of the corrosive, also contributes to the wear and tear of the stem.
For the stem packing, the lack of elasticity narrows the sealing clearance, causing the stem wear. This is especially true in the case of the combination of inelastic packing materials and gland bolts.
Solution
For the smaller valve, the only solution is to replace it. After all, it is readily available. However, for larger valves, it is not cost-effective to replace them. The best solution is to upgrade the current valve.
Before you check the stem, check the other smaller components first such as the gland studs, bolts and the stuffing boxes. The next step is to check if the stem needs to be reworked or replaced.
#5 Cavitation
Cavitation often occurs in control valves with liquid media. Two factors that contribute to cavitation are fluid velocity and pressure drop.
Bubbles form when liquid pressure is lower than the vapor pressure in the valve. These bubbles somehow stop the flow of media. When liquid pressure recovers from the normal level, the bubbles collapse, causing damage to the valve.
Solution
Ensure the correct valve is used in the application. If it is a wrong style or size, there is a greater chance of cavitation. Use anti-cavitation valves for water and liquid applications. If the control valves are used, place them in areas where the valve has a lower orientation in relation to the pipes.
#6 Water Hammer
Water hammer is the condition where there are abrupt pressure spikes in the valve. It is one of the most destructive forces that can wreak havoc on the valve body. Three factors create water hammer: how fast the valve closes, how fast the liquid is the moment the valve closes and what the pressure wave along the pipe is.
Other significant factors that contribute to this phenomenon are the thickness of the inner cavity of valves, the strength of the pipe and the pressure of the medium.
Solution
Use a throttling valve to minimize water hammer. Also, utilize a high speed on-off valve such as the butterfly valve. A slow-acting one is also suitable as this reduces pressures caused by water hammer. Instead of manually opening and closing the valve, use a hydraulic actuator to allow faster opening and closing.
#7 Pressure and Temperature Exceeding the Required Parameters
Valves have specific pressure and temperature requirements. If the valve exceeds the range of the temperature and pressure it can withstand, it will be damaged.
Solution
Before installation, check the product requirements to ensure that no pressure and temperature upsurge happen. Routine maintenance and repairs are important. Replace damaged parts due to increased temperature and pressure.
#8 Faulty Actuator
Actuators come in three forms: manual, powered or automatic ones. Actuators manage the entry and exit of media and the flow of media, pressure, and temperature. That is to say, choose the wrong actuator shortens the life of the valve because the valve is easy to wear.
The incorrect use of voltage can trigger overheating. Overheating will not only cause fire, but also totally damage the actuator.
Solution
Strong input from the actuator can actually damage the valve stem and disc when the valve is in the open or closed position. If the medium is slow-moving, choose actuators that suit it. If you want to avoid the loss of pressure, choose an actuator that can easily open or close.
To know whether the valve is damaged or it is just the actuator that is acting weird, turn on the manual override. It the valve seems OK, the actuator is damaged.
If the valve doesn't move, the problem lies with the actuator. Additionally, check the valve stem for any damage. A worn-out valve stem affects how the actuator moves.
Installing sensitive components of the valve should be far from the actuator when there is high pressure or the possibility of high vibrations. This is to protect the sensitive parts from being damaged.
NEMA (National Electrical Manufacturers Association) has set safety ratings of electrical valves.
#9 Incorrect Installation
Some valves are easier to install than others. Sadly, many cases of valve failures come from incorrect valve installation. Take for example the installation of swing check valves. Some people have been installing them in the wrong orientation. To facilitate installation, there are some symbols below.
Solution
Most valves are installed in an upright position unless specified. Make sure that the person installing the valve has enough skills and training to properly perform the task.
#10 The improper operational and set pressure differential
Operational pressure is the amount of actual pressure existing during operation. On the other hand, set pressure is the standard pressure the pipe operator sets for the pipeline system. Problems often occur when the operational pressure approaches to the set pressure.
Solution
Check the integrity of the valve. Pay more attention to the valve disc, seat and stem. Also, check for leakage. Replace the damaged parts if necessary.
Factors such as the material of the valve, the media, seat tightness make a minimum of 10% differential between the operational and set pressures. However, the ideal differential is 20%.
#11 Reverse Flow
Reverse flow refers to the instance that the direction of the medium flow suddenly changes. This, together with water hammer, is two of the most common causes of valve damage.
Solution
Prevention is the key. Installing a silent check valve or any valve that closes fast would greatly improve valve performance.
#12 Debris
Thicker particles cause the seat to wear. These can get stuck in the valves, making the valve remain open or closed. Additionally, when the debris hardens in the valve, it can potentially cause the valve components to break.
Solution
Regular maintenance and valve cleaning are of importance, which can remove debris and prevent the debris to harden and further damage the valves
#13 Incorrect Maintenance and Repair
Incorrect repair and maintenance are not only damaging, but also costly and time-consuming.
Solution
Make sure that the valve orientation is correct. Use the guides in the valve body that can help install the valve correctly. Make sure that directions are followed as to the valve orientation.
Best Practices to Avoid Valve Failures
Like in many cases, prevention is better than cure. Regular maintenance works by highly skilled technicians. Often times, valves issues arise because of human error. To solve this problem, employ skilled and highly trained personnel to install and maintain the valve and piping system.
Clean the valves and make sure that these are devoid of debris. If necessary, install filters to separate the debris from the flow media. Flush the pipes to reduce the debris build-up.
In addition to this, lubricate the valve. The valve is made up of movable smaller components. Lubricating these means less friction, which reduces wear and tear and improves performance.
Check the valve and its parts from time to time. Replace damaged components, which will extend the service life of the valve. Also, make sure the valves are properly installed.
In Summary
Valve replacement is highly costly. That is why it is necessary to get sturdy valves with relevant safety certifications. Always check the valves at the first sign of valve damage, repair what needs to be repaired and replace the damaged parts.
This article provides information on how to repair faulty valves, the common causes why valves need fixing and the signs that valves are already faulty.
What Makes Valves Last Longer
The lifespan of the valve depends on three factors: the quality of the seal, internal and external environment and the frequency of operation.
If the seal works perfectly, the valve works well, too. Choosing the right seal ensures better performance and maintenance.
On the other hand, factors such as pressure, temperature, as well as the type of media are worth considering. Lastly, the maintenance period is around 3 months if the valve works all the time. Timely maintenance ensures optimum operating conditions.
When to Repair Valves
#1 When there is internal leakage
One of the reasons why there is internal leakage is that the valve cannot have a total shutoff. According to international standards, each valve type has a maximum allowable leakage (MAL). A sign that the valve needs repair is when the leakage is beyond MAL.
#2 When there is external leakage
There are a few culprits of why external leakage is present. In many circumstances, there is improper maintenance. It is also possible that the material of the valve and the media are not compatible. Extreme temperature can also cause external leakage.
#3 When the valve becomes noisy
Water hammer is the term used in industrial applications to describe the sound made by valves. This is an indicator that the valve needs maintenance. This noise is caused by the disc hitting the valve seat.
#4 When the valve is no longer working
Obviously, when the valve is not working anymore, it is high time to salvage or repair it. While many valves can be repaired, some valves are almost impossible to repair.
The Common Causes of Industrial Valve Failures
#1 Improper Valve Size
The wrong valve size calculation can lead to either undersized or oversized valves. It is important to select the valve of correct size because the flow of media depends on the size of the valve. An oversized valve can decrease the pressure, whereas an undersized one can cause bottlenecks.
Solution
Find an online valve sizing calculator. There are different formulas for liquids as well as for gases. If manual calculation is too tedious, an online one will just do the trick.
This would make it easier to find a suitable valve. The Kv value found in the product description is as a point of reference. Also, consider the required flow rate as well as the pressure drop.
#2 Material Incompatibility
The media type, the seat material and the material of the valve body should match. Incompatibility means that the valve is more prone to wear and tear.
Solution
Check the product description for the type of material used for the valve seat and body. What media to use should follow the industry standards. Also, check for valve damage if you suspect there was an improper use of materials. Changing the valve is costly. Replace the parts in contact with the medium with those that can withstand it.
#3 Elastomer Damage
Elastomers are often used as valve seats, gaskets or O-rings. They act as seals. Because those elastomers are elastic, they are the natural choice for sealing applications. They also prevent the metal valve body from contacting with the medium. Elastomers used in industrial applications include nitrile, Aflas, and Teflon.
The wear of elastomers is caused by the natural movement of the fluids. Most often, the cause would be the incompatibility of the elastomer and the media.
Solution
Consider the compatibility of the elastomer and the media. Check the product description for what types of media to use with elastomers. When you make a purchase of the elastomer, check the description of the valve. If the elastomer seal is not compatible with the media, please find others.
Once the elastomer seal has dents, cracks and the likes, replace this component. Also, check if there are wear patterns that follow the media flow, which means that the latter is too abrasive.
#4 Valve Stem Wear
Smaller components such as valve stem packing and gland bolts cause wear and tear to the stem. Furthermore, the constant movement of the valve disc, as well as the contact of the corrosive, also contributes to the wear and tear of the stem.
For the stem packing, the lack of elasticity narrows the sealing clearance, causing the stem wear. This is especially true in the case of the combination of inelastic packing materials and gland bolts.
Solution
For the smaller valve, the only solution is to replace it. After all, it is readily available. However, for larger valves, it is not cost-effective to replace them. The best solution is to upgrade the current valve.
Before you check the stem, check the other smaller components first such as the gland studs, bolts and the stuffing boxes. The next step is to check if the stem needs to be reworked or replaced.
#5 Cavitation
Cavitation often occurs in control valves with liquid media. Two factors that contribute to cavitation are fluid velocity and pressure drop.
Bubbles form when liquid pressure is lower than the vapor pressure in the valve. These bubbles somehow stop the flow of media. When liquid pressure recovers from the normal level, the bubbles collapse, causing damage to the valve.
Solution
Ensure the correct valve is used in the application. If it is a wrong style or size, there is a greater chance of cavitation. Use anti-cavitation valves for water and liquid applications. If the control valves are used, place them in areas where the valve has a lower orientation in relation to the pipes.
#6 Water Hammer
Water hammer is the condition where there are abrupt pressure spikes in the valve. It is one of the most destructive forces that can wreak havoc on the valve body. Three factors create water hammer: how fast the valve closes, how fast the liquid is the moment the valve closes and what the pressure wave along the pipe is.
Other significant factors that contribute to this phenomenon are the thickness of the inner cavity of valves, the strength of the pipe and the pressure of the medium.
Solution
Use a throttling valve to minimize water hammer. Also, utilize a high speed on-off valve such as the butterfly valve. A slow-acting one is also suitable as this reduces pressures caused by water hammer. Instead of manually opening and closing the valve, use a hydraulic actuator to allow faster opening and closing.
#7 Pressure and Temperature Exceeding the Required Parameters
Valves have specific pressure and temperature requirements. If the valve exceeds the range of the temperature and pressure it can withstand, it will be damaged.
Solution
Before installation, check the product requirements to ensure that no pressure and temperature upsurge happen. Routine maintenance and repairs are important. Replace damaged parts due to increased temperature and pressure.
#8 Faulty Actuator
Actuators come in three forms: manual, powered or automatic ones. Actuators manage the entry and exit of media and the flow of media, pressure, and temperature. That is to say, choose the wrong actuator shortens the life of the valve because the valve is easy to wear.
The incorrect use of voltage can trigger overheating. Overheating will not only cause fire, but also totally damage the actuator.
Solution
Strong input from the actuator can actually damage the valve stem and disc when the valve is in the open or closed position. If the medium is slow-moving, choose actuators that suit it. If you want to avoid the loss of pressure, choose an actuator that can easily open or close.
To know whether the valve is damaged or it is just the actuator that is acting weird, turn on the manual override. It the valve seems OK, the actuator is damaged.
If the valve doesn't move, the problem lies with the actuator. Additionally, check the valve stem for any damage. A worn-out valve stem affects how the actuator moves.
Installing sensitive components of the valve should be far from the actuator when there is high pressure or the possibility of high vibrations. This is to protect the sensitive parts from being damaged.
NEMA (National Electrical Manufacturers Association) has set safety ratings of electrical valves.
#9 Incorrect Installation
Some valves are easier to install than others. Sadly, many cases of valve failures come from incorrect valve installation. Take for example the installation of swing check valves. Some people have been installing them in the wrong orientation. To facilitate installation, there are some symbols below.
Solution
Most valves are installed in an upright position unless specified. Make sure that the person installing the valve has enough skills and training to properly perform the task.
#10 The improper operational and set pressure differential
Operational pressure is the amount of actual pressure existing during operation. On the other hand, set pressure is the standard pressure the pipe operator sets for the pipeline system. Problems often occur when the operational pressure approaches to the set pressure.
Solution
Check the integrity of the valve. Pay more attention to the valve disc, seat and stem. Also, check for leakage. Replace the damaged parts if necessary.
Factors such as the material of the valve, the media, seat tightness make a minimum of 10% differential between the operational and set pressures. However, the ideal differential is 20%.
#11 Reverse Flow
Reverse flow refers to the instance that the direction of the medium flow suddenly changes. This, together with water hammer, is two of the most common causes of valve damage.
Solution
Prevention is the key. Installing a silent check valve or any valve that closes fast would greatly improve valve performance.
#12 Debris
Thicker particles cause the seat to wear. These can get stuck in the valves, making the valve remain open or closed. Additionally, when the debris hardens in the valve, it can potentially cause the valve components to break.
Solution
Regular maintenance and valve cleaning are of importance, which can remove debris and prevent the debris to harden and further damage the valves
#13 Incorrect Maintenance and Repair
Incorrect repair and maintenance are not only damaging, but also costly and time-consuming.
Solution
Make sure that the valve orientation is correct. Use the guides in the valve body that can help install the valve correctly. Make sure that directions are followed as to the valve orientation.
Best Practices to Avoid Valve Failures
Like in many cases, prevention is better than cure. Regular maintenance works by highly skilled technicians. Often times, valves issues arise because of human error. To solve this problem, employ skilled and highly trained personnel to install and maintain the valve and piping system.
Clean the valves and make sure that these are devoid of debris. If necessary, install filters to separate the debris from the flow media. Flush the pipes to reduce the debris build-up.
In addition to this, lubricate the valve. The valve is made up of movable smaller components. Lubricating these means less friction, which reduces wear and tear and improves performance.
Check the valve and its parts from time to time. Replace damaged components, which will extend the service life of the valve. Also, make sure the valves are properly installed.
In Summary
Valve replacement is highly costly. That is why it is necessary to get sturdy valves with relevant safety certifications. Always check the valves at the first sign of valve damage, repair what needs to be repaired and replace the damaged parts.
