1. What is the difference between Cast iron and Cast steel?
   
   The difference between Cast iron and Cast steel is their carbon content. Cast Iron with carbon content greater than 2.06% is iron; steel with carbon content between 0.02% and 2.06% is steel.
   
2. What is carbon steel? How many categories does it fall into?
   
   An alloy of carbon and iron (when the carbon content is between 0.02% and 2.06%) is called carbon steel. According to the different carbon content, carbon steel is divided into three categories:
   
   A. Low carbon steel-C <0.25%;
   
   B. Medium carbon steel-C = 0.25%-0.60%;
   
   C. High carbon steel-C> 0.60%.
   
   In carbon steel, due to the different sulfur and phosphorus content, it can be divided into:
   
   A. Ordinary carbon steel-P≤0.045%, S≤0.050%;
   
   B. High-quality carbon steel-P≤0.040%, S≤0.040%;
   
   C. High-quality high-quality carbon steel-P≤0.035%, S≤0.030%.
   

In industrial valve systems, strainers are essential components for ensuring smooth fluid flow and protecting downstream equipment. However, when an oil strainer becomes clogged, it can lead to a series of issues, significantly impacting the system's stability and safety.

 

Common Causes of Oil Strainer Blockage

(1) Excessive Impurities

The working medium contains a large amount of particulate matter, such as metal debris, sand, or sediment, which can accumulate over time and block the filter mesh. 

(2) Lack of Regular Maintenance

Failure to clean or replace the filter mesh as required leads to excessive accumulation of impurities, reducing flow capacity. 

(3) Process Issues

Poor oil quality containing high-viscosity substances or solid particles can easily lead to buildup and clogging.

 

Signs of Oil Strainer Blockage

(1) Reduced Flow Rate

A clogged strainer directly causes a noticeable decrease in the flow rate of the medium, along with a drop in outlet pressure. 

(2) Abnormal Equipment Operation

Downstream equipment, such as pumps or valves, may fail to operate properly due to insufficient medium supply, resulting in increased vibration or noise. 

(3) System Alarms

Automated systems may trigger alarms due to abnormal pressure or insufficient flow, indicating potential faults.

 

Dangers of Oil Strainer Blockage

(1) Equipment Damage

A clogged strainer may allow impurities to enter downstream equipment, increasing wear and potentially damaging critical components, such as pump impellers or valve seats. 

(2) Reduced System Efficiency

Restricted flow can significantly decrease the overall efficiency of the system, affecting process timelines and the completion of production tasks. 

(3) Safety Risks

Blockages can cause sudden pressure surges or equipment overload, leading to leaks or even catastrophic incidents like explosions. 

(4) Increased Maintenance Costs

Failure to address strainer blockages promptly may result in cascading failures, substantially increasing the cost of equipment repairs and replacements.

 

How to Address Oil Strainer Blockage?

(1) Regular Maintenance and Cleaning

Develop a reasonable cleaning schedule based on operational needs to ensure the strainer remains unobstructed. 

(2) Monitor System Performance

Install monitoring devices such as flow meters and pressure gauges to track the strainer's performance in real-time and detect potential blockages early. 

(3) Optimize Strainer Selection

Choose the appropriate mesh size, material, and structure based on the characteristics of the medium to ensure the strainer meets operational requirements. 

(4) Improve the Quality of Process Medium

Use higher-purity oils with lower impurity levels to reduce the risk of blockages at the source.

In the industrial valve field, the wafer check valve is an important one-way valve widely used in various fluid pipelines. Due to its compact design and excellent performance, it has become the preferred choice in many operating conditions.

 

Basic Function of the Wafer Check Valve

The primary function of the wafer check valve is to prevent the backflow of the medium in the pipeline. Its internal design includes one or two rotatable valve discs, which are pushed open when the fluid flows in the set direction. Once the fluid flows in the reverse direction, the valve discs close quickly, thus achieving the check function. This automatic closing mechanism requires no external operation and relies entirely on the flow pressure and direction changes of the medium.

 

Various Valve Disc Designs

Wafer check valves commonly feature single-disc, double-disc, and spring-loaded valve disc types. 

(1) Single-Disc: Suitable for low flow rate and low-pressure differential conditions. 

(2) Double-Disc: More stable and reduces water hammer impact. 

(3) Spring-Loaded: Maintains good sealing performance at low flow rates, preventing leakage.

 

Advantages of the Wafer Check Valve

(1) Compact Design

The wafer check valve, with its simple structure, small size, and lightweight, is highly suitable for piping systems with limited space. 

(2) Low Pressure Drop

The resistance to fluid flow through the valve body is minimal, maintaining high flow efficiency, making it ideal for applications sensitive to flow rate and energy consumption. 

(3) Flexible Installation

The wafer-style connection allows for easy installation and removal, and can be used in both horizontal and vertical pipelines. 

(4) High Reliability

The valve disc closes quickly, effectively preventing water hammer and protecting the safety of the pipeline and equipment.

 

Main Application Scenarios of Wafer Check Valves

(1) Water Treatment Systems

Wafer check valves are widely used at the inlet and outlet of water pumps to prevent backflow when the pump is turned off, avoiding equipment damage.

(2) HVAC Systems

In cooling water circulation systems, wafer check valves are used to ensure the water flows in the designed direction, preventing backflow that could reduce energy efficiency.

(3) Chemical and Petroleum Industries

In pipelines transporting corrosive media or high-temperature, high-pressure liquids, wafer check valves provide reliable one-way flow control while preventing system contamination or damage caused by backflow.

(4) Gas Transmission Pipelines

Wafer check valves are suitable for pipelines conveying compressed air, natural gas, and other gases, preventing backflow that could cause pressure fluctuations or safety hazards in the system.

 

Performance in Special Applications

(1) Marine Engineering

Wafer check valves are commonly used in water treatment systems of seawater desalination equipment and offshore platforms. Their corrosion-resistant design (such as the use of super duplex steel) makes them suitable for high-salinity environments.

(2) Energy Industry

In the cooling water systems of nuclear power plants and thermal power plants, wafer check valves are used to prevent backflow that could lead to system instability or equipment failure.

(3) Food and Pharmaceutical Industries

For sanitary applications, full stainless steel materials and high-polishing processes can be selected to meet strict hygiene and cleanliness requirements.

 

Precautions for Use

(1) Correct Selection

Choose the appropriate material for the wafer check valve based on the characteristics of the medium, temperature, pressure, and other parameters. For example, stainless steel is used for corrosive media, while carbon steel is suitable for general water or oil media.

(2) Correct Installation Direction

Ensure that the flow direction during valve installation matches the actual flow direction of the pipeline to avoid affecting the check function.

(3) Regular Inspection and Maintenance

After long-term operation, the sealing elements of the wafer check valve may age or the valve disc may wear. Regular inspection is required to ensure its reliable performance.

In the installation and maintenance of gas systems, selecting the appropriate valve is crucial for both safety and performance. Given the characteristics of gas and its application environments, ball valves and gate valves are widely recommended as ideal choices for gas pipelines due to their excellent sealing performance and ease of operation. However, their specific characteristics, suitable applications, and considerations for installation and maintenance differ. The following provides a detailed analysis of the advantages and disadvantages of these two valves, as well as the gas system scenarios in which they are best suited.

1. Ball Valve: Precise Control and Quick Shut-off

(1) Quick Opening and Closing Operation

The design of the ball valve allows for rapid opening or closing, which is especially crucial for emergency control in gas pipelines. By simply rotating the handle 90 degrees, the gas flow can be quickly cut off, making it highly effective in handling emergencies such as leaks.

(2) Reliable Sealing Performance

The ball valve opens and closes through the rotation of its spherical element. When closed, a tight seal forms between the ball and the valve seat, reducing the risk of gas leakage. This sealing advantage is particularly prominent in high-pressure pipelines, where the ball valve can effectively ensure system safety.

(3) Corrosion Resistance and Broad Applicability

Ball valves used in gas pipelines are often made of materials such as stainless steel and brass, offering strong corrosion resistance and suitability for various gas types, including natural gas and liquefied gas. Whether in outdoor exposed environments or enclosed indoor settings, the materials and design of ball valves ensure their durability and stability.

(4) Low Maintenance Cost

The simple structure of ball valves results in minimal wear and low maintenance requirements, making them suitable for long-term use. Particularly in commercial and industrial pipeline systems, the low-maintenance nature of ball valves can reduce downtime and enhance cost-effectiveness.

These characteristics make ball valves a preferred choice for residential, commercial, and industrial gas distribution systems.

2. Gate Valve: Suitable for Flow Control in Long-Distance Pipelines

The gate valve controls flow through a rising and lowering gate mechanism. Unlike ball valves, gate valves open and close more slowly, making them more suitable for applications where frequent operation is not required.

(1) Suitable for Flow Regulation in Long-Distance Pipelines

When fully open or fully closed, the internal passage of the gate valve is nearly unobstructed, reducing pressure drop within the pipeline. This is particularly important for long-distance gas pipelines, as it helps maintain stable pressure and flow rate over extended distances.

(2) Gradual Opening and Closing to Reduce Pressure Shock

During closure, the gate valve gradually lowers the gate, making it suitable for pipeline systems that require controlled flow variation. This gradual operation effectively reduces the impact of fluid on the valve and pipeline, extending the system's service life.

(3) Versatile Pressure Ratings for Flexible Application

Gate valves are suitable for gas pipelines with various pressure ratings, meeting diverse flow requirements. Whether in low-pressure residential pipelines or high-pressure industrial systems, gate valves can provide relatively stable control.

3. How to Choose the Right Valve?

(1) Quick Switching and Emergency Handling

If a gas pipeline requires rapid opening or emergency shutdown, such as in response to a gas leak or emergency situation, a ball valve is more suitable.

(2) Stable Flow Control and Long-Distance Transportation

If a gas pipeline requires gradual flow control, such as in adjusting pressure variations during long-distance transportation, a gate valve is the better choice.

(3) Characteristics of Different Gases

Select suitable materials based on the corrosiveness and flammability of the specific gas to ensure the durability and safety of the valve.

In industrial pipeline systems, ball valves and other regular valves each have distinct characteristics, making the selection process crucial for different operating conditions.

 

1. Structure and Operating Principle

Ball Valves use a spherical closure element to control fluid flow by rotating 90°. With a straight-through flow path, they offer minimal flow resistance and quick operation.

Conventional Valves include gate valves, globe valves, butterfly valves, and others, each with different closure elements such as a gate, disc, or plate. Most conventional valves regulate flow through linear or rotational stem movement, resulting in a relatively more complex structure.

 

2. Seal Performance Comparison

Ball valves typically use soft seals (such as PTFE) or metal seals, providing excellent zero-leakage performance, making them ideal for applications requiring high sealing integrity.

Conventional valves employ various sealing methods, such as wedge seals in gate valves and conical seals in globe valves. Some conventional valves, like butterfly valves, may experience minor leakage under low-pressure conditions.

 

3. Operation Method and Flow Control

Ball valves enable quick opening and closing with just a 90° turn, making them suitable for applications requiring frequent operation. Conventional valves vary in operation depending on the type. For example, gate valves typically require multiple turns for full operation, making them slower but well-suited for large-diameter, fully open or fully closed control. Globe valves, on the other hand, are more suitable for flow regulation.

 

4. Application Scenarios

Ball valves are widely used in industries such as oil and gas, chemical processing, and water supply and drainage, especially in applications requiring rapid switching and high sealing performance.

Conventional valves are suitable for a broader range of conditions, such as high-temperature and high-pressure pipelines (gate valves), flow regulation (globe valves), and large-diameter, low-pressure transportation (butterfly valves).

 

5. Maintenance and Service Life

Ball valves have a compact structure with minimal wear on the sealing surfaces, resulting in low maintenance costs and a long service life. Conventional valves, such as gate valves, may experience wear on the disc or sealing surfaces due to prolonged friction and corrosion, making maintenance more complex in some cases.

Gate Valve is the most widely used one among all types of valves. Gate Valve, whose disc or wedge moves vertically along the axis of the channel, has the same basic function of other valves, turning on or turning off channels. In the pipeline, it is used as a piece to connect and cut off the media inside. What is worthy to be noted is that an ordinary gate valve usually opens or close pipeline completely. In other words, it can’t be used as a controlling device to restrain the volume of the flow.

Gate valve can is designed to handle a wide range of situations: high temperature and high pressure or low temperature and low pressure. It also has the ability to deal with a handful of different media except those that are vicious, easy to precipitate or with granules.

Gate Valve has the following advantages:

1. small fluid resistance, safe and reliable;

2. small torque when turning it on or off;

3. it can be used in circular network pipelines where the medium flows in both directions. Namely, the flow direction of the medium is not restricted;

4. when it is fully open, gate vale’s sealing surface is less eroded than globe valve;

5. with a simple shape, it’s easy to cast and machining;

6. small face to face dimension.

Gate valves are widely used thanks to their many advantages mentioned above. Generally, the gate valve serves as the first choice to pick a cutting device for pipelines with DN≥50mm. And certain gate valves are still can be found even in some small size pipelines (such as DNV15 ~ 40mm).

Gate Valve also has its disadvantages:

1. relatively bigger space is required to install gate valves for their large size.

2. when open and close, abrasion occurs due to the relative friction between sealing surfaces;

3. gate valve’s two sea faces add difficulties to machining, grinding and maintenance.

4. long opening and closing time.

Gate Valves vary in structures. Generally, they differ from each other according to their seal components. Therefore, gate valves are usually divided into two types: parallel type and wedge type. What’s more, according to the structure of the stem, they also divided into rising stem and non-rising stem.

More tips about valves are coming soon. get more knife gate valve, wellhead gate valve from https://www.dvsvalve.com/

The plug valve, with its simple structure and excellent sealing performance, has a wide range of applications in industrial fields. Its plug design allows for quick and safe opening and closing, making it suitable for numerous operating conditions that require strong sealing, high corrosion resistance, or frequent operation.

1. Applications Requiring High Sealing Performance

The plug valve excels in applications that require high sealing performance due to its unique design. The plug inside the valve body fits tightly, and the sealing material between the plug surface and the valve seat further enhances the sealing effect, effectively preventing leakage of the media. Many plug valves use high-performance sealing materials, such as polytetrafluoroethylene (PTFE), which are resistant to corrosion, making them suitable for transporting high-pressure and highly corrosive media in industries like oil and gas and chemicals.

(1) High Pressure Sealing Requirements in the Oil and Gas Industry

In oil and gas pipelines, the transportation of high-pressure, high-temperature gases or liquids is common, and any leakage could result in serious safety incidents. The plug valve, with its ability to quickly close and provide effective sealing, is an ideal choice for preventing leaks and ensuring the safety of the transportation process.

(2) Transportation of Volatile or Toxic Media

The sealing capability of the plug valve also makes it suitable for transporting volatile or toxic liquids and gases. Especially in fine chemicals and petrochemical production, preventing the leakage of volatile chemicals is a core aspect of safety. The sealing structure of the plug valve is perfectly suited to meet this requirement.

2. Frequent Opening and Closing Operations

The plug valve only requires a 90-degree rotation to open or close, making the operation simple and fast, while reducing mechanical wear. This makes the plug valve suitable for applications with frequent on/off cycles. In chemical plant production processes, valves are often required to open and close frequently to regulate fluid flow. Compared to other valves, the plug valve's opening and closing mechanism is more stable, which helps to extend its service life.

(1) Impact of Frequent Operation on Equipment

In environments where frequent operation is required, improper handling can lead to increased valve wear and a higher probability of leakage. Due to its simple structure and fewer components, the plug valve is less affected by frequent operations, offering significant economic benefits in this regard.

3. Applications with High Corrosion Resistance Requirements

Plug valves are typically made from corrosion-resistant materials, and their interiors are often lined with corrosion-resistant materials such as PTFE or reinforced plastics, allowing them to maintain long-term operation when handling acidic, alkaline, or corrosive solutions. Plug valves are particularly well-suited for the transportation of highly corrosive liquids.

(1) Transporting Corrosive Media in the Chemical Industry

In the chemical industry, the media being transported often have strong corrosive properties. The design of plug valves ensures that they do not fail quickly when in contact with corrosive liquids, effectively reducing the frequency of equipment replacement and saving on maintenance costs.

4. Emergency Systems Requiring Quick Shutoff

The quick open/close design of the plug valve allows it to rapidly shut off the fluid passage in emergency situations, making it an ideal choice for preventing accidents and ensuring the safety of operators. For example, in emergency shutdown systems for natural gas pipelines and chemical plants, the plug valve can achieve a complete closure in an instant, preventing the leakage of hazardous substances and ensuring safety.

(1) Safety Requirements in the Natural Gas and Petrochemical Industries

In the natural gas and petrochemical industries, where high-temperature and high-pressure environments are common, safety is of utmost importance. The plug valve is not only easy to operate but also capable of quickly shutting off in emergencies, thereby protecting the overall safety of the system and reducing potential safety risks.

5. Medium and Low Pressure Fluid Transportation Systems

In medium and low pressure fluid transportation systems, the plug valve is an economical and practical choice. Its simple design reduces installation and maintenance complexity, and in situations where high-precision flow control is not required, the cost-effectiveness of the plug valve stands out. It is commonly found in systems such as water treatment, municipal water supply, and general industrial pipelines.

(1) Municipal Water Supply and General Industrial Applications

In municipal water supply systems, plug valves are widely used for flow control. Compared to more complex control valves, the plug valve features a simple structure and easy installation, making it suitable for fluid control applications that do not require high precision, while also being easier to maintain.

Gate valves are a popular choice in many industries for specific types of applications. Here’s why they are commonly used:

1. Full Flow or Isolation

Gate valves are ideal for situations where a full, unobstructed flow or complete shutoff is required. When fully opened, the gate valve allows fluid to pass through with minimal restriction, which helps to reduce pressure loss. This makes them particularly useful in systems where flow efficiency is critical, such as pipeline systems in oil, gas, and water distribution.

2. Low Pressure Drop

Because the gate in the valve fully retracts, there is little interference with the fluid flow when the valve is open. This results in low pressure drop, which is essential in applications where maintaining high flow efficiency is important, such as in petroleum refining or water treatment plants.

3. Versatility Across Applications

Gate valves can handle a wide range of fluids, including liquids, gases, and even slurry or other more viscous materials. They are also used in a variety of pressure and temperature conditions, making them highly versatile. This versatility is why they are found in industries such as chemical processing, mining, and power generation.

4. Bi-Directional Sealing

Gate valves can provide a tight seal in both directions, meaning they can effectively stop flow from either side of the valve. This feature makes them suitable for applications that require flow isolation from both ends, ensuring safety and operational control, especially in critical systems like offshore platforms and high-pressure pipelines.

5. Durability in Large-Scale Systems

Gate valves are particularly durable when used in large-diameter piping systems. Due to their robust design, they can handle the stresses of large-scale industrial applications, such as those found in hydropower or municipal water systems. Their ability to withstand high-pressure and high-temperature conditions adds to their durability and reliability.

6. Emergency Shutoff

Gate valves are often used as emergency shutoff valves because of their ability to completely block flow when needed. In situations where quick and reliable isolation is required, such as firefighting systems or hazardous material pipelines, gate valves offer peace of mind.

Ball valves are widely used in various industrial sectors due to their simple structure, excellent sealing performance, and ease of operation. However, during long-term use, ball valves may develop leaks. Leaks not only lead to the waste of media but can also disrupt the normal operation of the system and even pose safety risks.

Common Reasons

1. Aging or Damage of Sealing Materials

The sealing performance of a ball valve primarily relies on the tight fit between the valve seat and the ball. These sealing components are typically made from materials such as rubber or polytetrafluoroethylene (PTFE). Over long-term use, the sealing materials may experience aging, deformation, or damage due to medium corrosion, high-temperature and high-pressure environments, or friction, leading to leaks. This issue is particularly common in applications involving high temperatures and highly corrosive media.

2. Wear of the Ball or Seat

The core components of a ball valve are the ball and the seat, which continuously contact and rub against each other during opening and closing. If the medium contains solid particles, or if the ball valve operates for an extended period in high-pressure, high-flow environments, wear can occur on the surfaces of the ball and seat. Worn surfaces struggle to form a tight seal with the sealing components, leading to inadequate sealing and resulting leaks.

3. Seal Failure of the Stem

The operation of a ball valve is facilitated by the stem, which connects to the valve body through the packing gland, providing a sealing function. Due to frequent operation, aging of the packing, or improper installation, the packing gland may experience seal failure, allowing the medium to leak along the stem. This type of leak is classified as external leakage, which can lead to environmental pollution and energy waste.

4. Improper Installation

If a ball valve is not correctly installed or tightened at the flange or threaded connections, gaps may occur, leading to leaks. Additionally, if factors such as thermal expansion and vibration of the pipeline are not considered during installation, the ball valve may experience stress during operation, resulting in leakage at the interface between the valve body and the pipeline.

5. Medium Factors

Certain special media, such as high-temperature, high-pressure fluids, highly corrosive substances, or fluids containing suspended particles, can accelerate the wear and corrosion of ball valves, leading to leaks. For example, acidic media can hasten the corrosion of metal components, while particulate matter may cause wear on the seat and ball, both of which can diminish the sealing performance of the ball valve, ultimately resulting in leakage issues.

How to Prevent and Handle

1. Choose Appropriate Sealing Materials

Selecting the right sealing materials for different operating conditions is crucial. For example, in high-temperature environments, high-temperature resistant sealing materials should be chosen, while chemical-resistant seals are necessary for highly corrosive media. Regular inspection and replacement of seals can also effectively prevent leaks caused by aging or wear.

2. Regular Maintenance and Care

Routine maintenance and regular servicing of ball valves help extend their lifespan and reduce the risk of leaks. The wear of the ball and seat should be regularly checked, and impurities and particles in the medium should be promptly removed to prevent further wear. Additionally, the packing should be inspected to ensure good sealing, and aging packing should be replaced in a timely manner.

3. Proper Installation and Operation

Installation should strictly adhere to the technical specifications of the ball valve, ensuring that flange or threaded connections are tight to avoid leaks caused by thermal expansion, vibration, or stress. Additionally, during operation, frequent opening and closing should be avoided, especially under high-pressure conditions, to reduce wear on the valve.

4. Special Treatment for Media

For applications involving fluids with suspended particles or strong corrosive properties, it is advisable to install a filter upstream of the ball valve to reduce solid particle damage to the valve. Additionally, choosing ball valves made from corrosion-resistant materials can effectively slow down the corrosion process and lower the risk of leakage.

A gate valve is considered better than a ball valve in certain applications due to its design and functional advantages in specific conditions. Here are some key reasons why a gate valve might be preferred over a ball valve:

1. Flow Control

Gate Valve: Designed for full, unobstructed flow when fully open, allowing fluids to pass with minimal resistance. It is ideal for on-off control but not as suitable for throttling or flow regulation, as partial opening can cause vibration and damage to the sealing surfaces.

Ball Valve: While it offers full flow similar to a gate valve when open, it is not generally used for precise flow control either. However, it closes and opens faster than a gate valve, which may not always be ideal for systems that require gradual control of flow.

2. Size Availability

Gate Valve: Typically better for larger diameter applications, as they are available in larger sizes, making them suitable for large pipelines in industries like water treatment, oil, and gas.

Ball Valve: More commonly used in smaller pipe sizes but can also be found in larger sizes. However, large ball valves can become bulky and expensive compared to gate valves.

3. Pressure Drop

Gate Valve: When fully open, the gate valve provides a straight flow path with minimal pressure drop, which is beneficial in applications where maintaining fluid pressure is critical.

Ball Valve: Even though a ball valve offers low resistance to flow when fully open, the pressure drop might be slightly higher due to the internal mechanism of the ball and seat, especially in smaller sizes.

4. Cost Efficiency in Larger Systems

Gate Valve: More economical for large-diameter and high-pressure systems, making it a preferred choice in large-scale applications like water supply systems or oil pipelines.

Ball Valve: Generally more expensive for large diameters, as the ball itself and its seat must be designed to handle high pressures without deforming.

5. Operational Effort

Gate Valve: Requires more time and effort to open and close fully, as the gate needs to travel vertically through the fluid. This can be a disadvantage in situations where fast operation is needed but may be an advantage in preventing water hammer.

Ball Valve: Opens and closes quickly with a 90-degree turn, which is more convenient for applications requiring rapid shutoff. However, this quick action may cause issues like water hammer in some fluid systems.

6. Maintenance and Wear

Gate Valve: Due to its simple design, gate valves are easier to maintain and have a longer lifespan in systems where they are rarely operated. The seating surfaces experience less wear when the valve is either fully open or fully closed.

Ball Valve: The sealing surfaces in ball valves are more prone to wear, especially in high-pressure or abrasive flow conditions. Maintenance can be more complex, particularly with large valves.

7. Suitability for Dirty Fluids

Gate Valve: More suitable for handling fluids containing solids or slurries, as the gate can cut through debris or sediments. It is less prone to clogging in such environments.

Ball Valve: Not ideal for dirty or viscous fluids, as the tight tolerances between the ball and seat can trap particles, leading to damage or failure of the valve over time.