Benefits of Different Pinch Valve Types - AUTOMATIC VALVE

Benefits of Different Pinch Valve Types - AUTOMATIC VALVE

Pinch valves are ideal for various slurry control applications due to their versatility, flexibility, and ability to handle corrosive and abrasive slurries. Pinch valves come in different types, including air-operated, manual, hydraulic, electric, manual override, and solenoid pinch valves. Each of these types has unique features and benefits, making them suitable for different slurry applications. In this blog post, we will explore the benefits of each type of pinch valve so you can decide which one is most suitable for your application. Let's dive in and take a closer look at the advantages of different types of pinch valves.

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I. Air-Operated Pinch Valve

Pinch valves are known for their flexibility, durability, and versatility in handling different slurry applications. Air-operated pinch valves offer several benefits, including precise slurry flow regulation, resistance to abrasion and corrosion, and minimal maintenance. Additionally, there is no contact between the slurry and internal valve components, reducing contamination risks. In this section, we will delve deeper into the advantages of air-operated pinch valves and their features and applications.

Minimal maintenance required due to its simple design

One significant advantage of pneumatic pinch valves is the minimal maintenance required due to their simple design. Since they lack internal moving parts, there is no wear and tear, making maintenance less frequent and costly. The valve operates by compressing the rubber sleeve to control the flow of slurry, requiring minimal adjustment or maintenance. This simplicity ensures efficient slurry flow control while minimizing downtime and maintenance costs.

No contact between the slurry and internal valve components, reducing the risk of contamination

Another benefit of air-operated pinch valves is that there is no contact between the slurry and internal valve components, reducing contamination risks. The valve sleeve compresses the slurry, creating a seal between the inlet and outlet. This minimizes cross-contamination, ensuring slurry purity. The valve's simple design eliminates the need for seals and other internal components that might corrode or contaminate the slurry, providing a reliable solution for slurry control in industries where purity is crucial, such as the food and beverage industry.

Ability to control the slurry flow precisely

Air-operated pinch valves offer precise control over slurry flow, making them ideal for various applications. The rubber sleeve is compressed to regulate the slurry flow through the pipe. The close tolerances between the valve sleeve and the body enable precise flow control. Adjusting the air pressure regulates the compression on the valve sleeve, ensuring consistent slurry flow. This precise flow control reduces production waste and improves process efficiency.

Resistance to abrasion and corrosion

Air-operated pinch valves are resistant to abrasion and corrosion due to their robust design. The rubber sleeve is highly resistant to abrasion from slurry and other abrasive materials, reducing the risk of valve wear and failure. Additionally, the valve body is typically made of materials resistant to corrosion from chemicals and other corrosive substances. This resistance extends the valve's lifespan and ensures reliable performance in harsh environments. The durability of air-operated pinch valves makes them ideal for slurry control applications in mining and chemical industries, where abrasive and corrosive materials are commonly transported.

II. Manual Pinch Valve

Manual pinch valves are operated by hand to regulate slurry flow. These valves are highly versatile, and their simplicity makes them ideal for various industrial applications. Manual pinch valves offer a range of benefits, including adaptability to different flow rates and slurry viscosities, customizable sleeve options, and minimal maintenance requirements. This section will examine the benefits of manual pinch valves and their performance in different applications.

No external power supply required

One of the key benefits of manual pinch valves is that they do not require an external power supply. The valve is operated manually by applying pressure to the valve body or handwheel, compressing the rubber sleeve to regulate slurry flow. This feature makes manual pinch valves ideal for remote locations or areas with limited access to electricity. They can also be used as backup valves in case of power outages, ensuring uninterrupted slurry flow. The absence of an external power supply also makes manual pinch valves a more cost-effective solution for slurry control applications.

Versatility and flexibility in adapting to different flow rates and slurry viscosities

Manual pinch valves offer versatility and flexibility in adapting to different flow rates and slurry viscosities, making them suitable for various applications. The rubber sleeve can be customized to handle different slurry compositions, from low to high concentrations of solids. The simple design allows easy adjustments to adapt to different flow rates and viscosities. Manual pinch valves are available in different sizes and configurations to fit various pipe diameters and fluid flow rates. This versatility makes them an excellent solution for slurry control applications in industries like food and beverage, chemical processing, and mining.

Minimal maintenance required due to its simple design

Manual pinch valves feature a simple design that results in minimal maintenance requirements. The valve consists of a body and a rubber sleeve that can be easily replaced. There are no complex components or external parts needing regular maintenance or repair, reducing downtime and costs. Additionally, manual pinch valves do not require additional lubrication or cleaning, making them a low-maintenance solution for slurry control applications. Their simplicity ensures reliable slurry flow regulation with minimal maintenance, making them a preferred choice in various industries like wastewater treatment, pharmaceuticals, and pulp and paper.

III. Electric Pinch Valve

Electric pinch valves are a popular type of control valve that provides precise and efficient slurry flow regulation. These valves operate via an electric motor that actuates to compress the valve sleeve, controlling the slurry flow through the pipe. Electric pinch valves offer several advantages, including accurate flow control, reduced energy consumption, and remote control capabilities. In this section, we will take a closer look at the benefits of electric pinch valves and their use in various industrial applications.

Precise flow control with minimal manual adjustments

Electric pinch valves offer precise flow control with minimal manual adjustments, making them ideal for automation in various industrial applications. The electric motor allows accurate and repeatable positioning of the valve sleeve, resulting in precise slurry flow control. This feature reduces the chances of over-compressing or under-compressing the sleeve, minimizing errors in flow regulation. Compared to manual pinch valves, electric pinch valves provide greater regulation accuracy, improve process efficiency, and reduce waste. Additionally, electric pinch valves can be easily integrated into process control systems, allowing for remote operation and performance monitoring without on-site personnel.

Customizable sleeve options to handle different slurry types and concentrations

Electric pinch valves offer customizable sleeve options to handle different slurry types and concentrations. The rubber sleeve serves as the primary separation barrier between the slurry and internal valve components. Electric pinch valves can accommodate various sleeve materials, including natural and synthetic rubbers, silicone, and fluoropolymers. Different sleeve durometers and thicknesses can also be used to handle various slurry compositions, including low to high concentrations of solids and corrosive materials. With customizable sleeve options, electric pinch valves provide flexible slurry control solutions for different industrial applications, such as chemical processing, mining, and wastewater treatment.

Selecting the Best Pinch Valve for Your Application

What are the types of pinch valves?

There are two primary types of pinch valves used in the medical and scientific industries: external and internal. Each has benefits and drawbacks, depending on its end-use.

How does a pinch valve work?

The core functionality of a pinch valve is a flexible flow path element compressed by an external plunger or pinch block. Most pinch valves in these industries are actuated using a solenoid, although some manual hand-actuated pinch valves exist and operate like a clamp.

What is the difference between internal and external pinch valves?

Internal Pinch Valve

External Pinch Valve

Minimized Internal Volume

X

X

Low Carryover Volume

X

Maintenance Free

X

Replaceable Flow Path

X

Figure 6: General comparison of features between internal and external pinch valves.

External pinch valves are characterized by tubing that can be easily replaced; internal pinch valves are sealed and maintenance-free. The choice of which valve to purchase for a scientific or medical instrument application depends on several factors. Consideration should be given to the internal volume, carryover volume, maintenance, cycle life, and materials. These factors are discussed in greater detail below.

What factors affect pinch valve performance?

The internal volume of flow path components is a frequent design consideration for the medical and scientific industries. Instrument designers focus on reducing expensive reagents, patient sample sizes, and fluid loss during medical treatments.

The internal volume of a pinch valve, for both external and internal styles, is determined by the inner diameter (ID) and length of the tubing. The ID of pinch valve tubing is generally based on the flow capacity required for a given application. Most medical and scientific applications choose a tubing ID of 1.5 mm or less, equating to a flow of less than 50 mL per minute. If internal volume is a priority, it is important to choose a valve with a total flow restriction that leaves little margin above your pressure drop requirements.

Tubing Inner Diameter (inches / mm)

Volume (µL)

Approximate Water Flow With 1psi Drop (mL/minute)

0.020 inch / 0.5 mm

20

9

0.031 (1/32) inch / 0.8 mm

49

30

0.040 inch / 1.0 mm

81

60

0.062 (1/16) inch / 1.6 mm

195

200

0.125 (1/8) inch / 3.2 mm

792

2,100

Figure 1: Comparison of volume for a 10cm length of tubing of common inner diameters.

When the tubing ID is selected, consideration must be given to tubing length. The tubing and pinch block in internal pinch valves are enclosed in the port head and typically offer a minimized tube length, resulting in the lowest internal volume for a given tubing inner diameter. This advantage is particularly noticeable with 3-way valves because the joining point (Y-connector) for an external pinch valve is located externally to the valve.

What is Carryover Volume?

Carryover volume refers to the amount of fluid volume remaining after a valve switches state. For 2-way “on-off” pinch valves, this is usually not a concern. However, for 3-way pinch valves, the volume carried over can mix with other fluids and is wasted when it is flushed out. Therefore, minimizing this volume is very important. Internal pinch valves offer a major benefit when carryover volume is a consideration because the volume between the pinch point and Y-shaped combination point is minimized.

What is the life cycle of pinch valves?

Design considerations for medical or scientific instruments focus heavily on maintenance requirements and costs. When these factors are a prime concern, the internal pinch valve is the better choice. These valves are typically rated to 5 million or more cycles before replacement. In comparison, external pinch valves typically require tubing replacement every 200,000 to 500,000 cycles, although the solenoid actuators have similar life ratings to that of internal pinch valves.

The difference between internal and external pinch valve tubing life can be explained by examining the properties of common tubing materials. Inexpensive silicone and flexible PVC tubing, normally used in external pinch valves, wear out easily and must be replaced frequently. Elastomeric tubing materials such as EPDM or the fluoroelastomer FKM commonly used in internal pinch valves offer life ratings an order of magnitude better, with slightly higher upfront costs.

Are Pinch Valves useful for Medical Devices?

The stark difference in cycle life (driven by the choice of material) is a key determinant in the selection of a pinch valve for a specific application. External pinch valves are best used in applications where flow path replacement is required, particularly for in-vivo medical applications. For example, dialysis machines frequently replace tubing used to carry blood to eliminate cross-contamination risk. An internal pinch valve, with its maintenance-free design, is a better choice for in-vitro diagnostic applications where a cleaning solution can be used between patient samples.

Fluoro-Elastomer (FKM, FFKM)

EPDM

Silicone (VMQ)

Fluoro-Silicone

Flexible PVC

Tensile Strength

Excellent

Excellent

Fair

Fair

Good

Abrasion Resistance

Good

Good

Poor

Poor

Good

Tear Resistance

Fair

Excellent

Poor

Poor

Good

Figure 5: General Dynamic Properties of Common Pinch Valve Tubing Materials

What material should you get for pinch valve tubing?

A critical consideration in the selection of pinch valves is the materials used in the flow path. External pinch valves feature a single wetted material: the pinch tubing. The available tubing options vary considerably, so the choice of tubing is based on compatibility with biological fluids and organic solvents. It is important to test each application. Tubing connectors need to be selected and separately qualified. Internal pinch valves, with integrated tubing connectors such as hose barbs or threaded fittings, typically have more than one wetted material. These materials are selected for compatibility with a wide variety of applications, making compatibility issues rare.

When should I use a pinch valve?

The selection of internal or external pinch valves for applications such as analytical chemistry, diagnostics, medical equipment, or next-generation sequencing must be carefully examined. In general, internal pinch valves are the best choice when low internal volume, low carryover volume, and long life are important factors. External pinch valves are a great solution for applications where easy tubing replacement is a valued attribute. Both valve types offer clean flow paths, relatively low internal volumes (compared to other types of valves), and excellent compatibility with fluids commonly used in the medical and scientific industries.

Need a Pinch Valve for your application?

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