Types of valves

There are many kinds of valves used in the pharmaceutical industry, each unique feature, and function. The application of a particular type depends on many factors, which affect the quality of the product being processed.

Some common types of valves used in the pharmaceutical industry include the following.

Gate Valves

Gate valves are used as an on/off valve to ultimately allow the fluid to flow or completely shut the fluid flow.

The gate valves use circular or rectangular metallic elements between two rectangular plates, often called the gate. The fluid flows in between the two plates. The position of the metallic gate is controlled through a circular handle. The handle is turned clockwise and anti-clockwise to place the gate in the fluid flow path. As the gate comes in the path of the fluid, flow is blocked. Similarly, when the gate is removed from the fluid flow path, fluid starts to flow.

Due to their internal construction, these valves cannot provide flow regulation and can only be used for shut-off operations. 

In the pharmaceutical industry, they allow or disallow fluid to pass through a machine inlet or a system. For example, machines that require utility supplies for their operation, such as compresses air and steam. 

The main advantage of using a gate valve is that there is no pressure drop in the fluid flow when the valve is open. This feature makes them ideal for use in the fluid source location. 

Globe Valves

Globe valves can be used in applications requiring complete ON/OFF and throttling operations. Its construction design also makes it possible for frequent operation, unlike the gate valves, which cannot be used for these two purposes. 

Its design is based on a disk and seat arrangement. The fluid flows in between the disc and seat. The disc moves up and down against the seat. The fluid flow increases when the disc moves away from the seat. As the disc moves closer to the seat, the path of the fluid flow decreases resulting in decreased fluid flow.

There are three types of globe valves - Angle body, Y-pattern, and T-pattern body. 

In angle body valves, the valve stem is oriented at an angle of 90° to the valve body, and in Y-pattern globe valves, the valve stem is oriented at an angle of 45°. 

Needle Valves

Needle valves are a type of globe valves used in high pressure, high-temperature applications. 

They are beneficial for small-sized diameter lines such as tubing. They are also used in applications requiring precise fluid flow.  

These valves gained their name because of the needle-type disc controlling the fluid flow. The needle-type disc resides against the seat to open or shut down the fluid flow. Since they serve small-sized applications, they require many turns to shut down the fluid flow completely.

Ball Valves

The ball valve uses a ball-shaped plug inside the valve's boy to control the fluid flow. The ball inside the valve has a hole where the fluid passes through it. The ball can be rotated through a handle directly connected to the ball. As the handle moves, the ball also rotates, and the hole also moves away or near the fluid flow path.

They are used in applications requiring complete shutdown or fluid flow opening. They are unsuitable for applications requiring precise fluid flow control or regulatory purposes.

They provide an excellent option when a contamination control feature is required. They provide excellent sealing characteristics and extended life of the operation. 

Butterfly Valves

Butterfly valves are quarter-turn rotational motion valves used as an On/Off valve. These valves are lightweight and compact compared to their counterparts in larger valve sizes. This makes them an ideal cost-effective solution. These valves can be easily installed without any special space requirement. Butterfly valves require low maintenance, as few moving parts are in them. 

There is a circular disc hinged centrally in the valve body in the butterfly valve. The disc is connected to the actuation mechanism through a shaft called Stem. The disc act as a barrier to the fluid flow, and by controlling the rotation of the disc, fluid flow is adjusted. When in the closed position, the disc rests against the seat. The seat acts as a seal and prevents leakage when the valve is completely shut.

Commonly, there are two types of butterfly valves - Wafer-type and Double flanged-type.

Wafer-type: this type of valve is mounted between two flanges with the help of flange bolts. It is necessary to use a seal in between the valve and pipe. The wafer type is used in applications to prevent bi-directional fluid flow or avoid backflow in the fluid system.

Double flanged-type consists of two flanges connected individually to the attached piping network. A sealing mechanism is also required to prevent leakages in the attached system.

Diaphragm Valves

Diaphragm Valves are primarily used in the pharmaceutical industry and provide excellent aseptic and sterile conditions. They can be used for controlling flow and completing On/Off applications. They can also be used in applications that use corrosive chemicals in their process. 

They differ from other valve types in that all the moving parts are separated from the valve body through a diaphragm. The satisfying actuator presses against the diaphragm, which moves relative to the actuator movement. When the actuator presses the diaphragm against the valve body, the fluid path is blocked, effectively blocking the fluid flow. Similarly, if the actuator releases the diaphragm, the fluid way is open, and fluid starts to flow.

Valves Specifications

When selecting valves for a particular application, standard parameters need to be considered before installation. The following are typical specifications that must be considered before choosing and purchasing a valve. These specifications help understand the physical criteria for valves installation.

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Type of Fluid

The pharmaceutical industry uses different types of fluid for its processes. Each juice has specific properties, which cannot be compared to other liquids. 

Valves are designed according to the fluid type. If one kind of valve is used for another type, the valve will not function accurately, resulting in loss of fluid in the system. The valve of a variety of fluid cannot be used for another kind.

Operating pressure

Operating pressure means the pressure with which the fluid flows in the system to which the valve is a part. The valve comes in direct contact with the fluid pressure and must withstand the system pressure. 

If the valve fails to withstand the system pressure, the valve will become faulty. It can also damage the valve's internal components and outer body. 

Operating temperature

In the pharmaceutical industry, different processes require different temperatures, such as dry heat sterilization, where temperature can reach up to 200°C. Like other pharma processes, valves are also employed in these high-temperature applications. 

The valves must withstand high temperatures, and their function must be accurate. Otherwise, the valve's internal or outer parts could melt or deform. This condition makes the valve faulty, with an erratic process.

Nominal sizes

Valve for pharma and other industries comes in various sizes, depending on the attached network or piping size. The valve's operating capacity directly depends on the valve size.

It is necessary to consider valve size before installing it in the system. Undersized or oversized valves can result in loss of fluid and cause damage to the valve body.

Actuators for valves

Valve needs some external force to operate and perform its related functions. Commonly the external force is applied through a separate mechanism or module called Actuators. The actuators activate the valve, and the valve performs its intended function.

Some standard methods that are used to actuate valves include the following. 

Manual Actuators

Manual actuation is the most straightforward activation mechanism and uses human force to activate the valve. Handwheel and Lever are the two most common methods of manual actuation. 

Internal disc, plate, or locking mechanism is connected to the handwheel or Lever. As these are turned or rotated, the internal mechanism also changes its position against the fluid flow path to Open, Shut or regulate the fluid flow.

Pneumatic Actuators

These valves use compressed air for their activation. When the compressed air of required pressure is applied to the valve, the internal mechanism causes the valves to activate. 

Compressed air is usually supplied by solenoid valves, controlled by a control signal. The generation of a control signal is dependent on the specific process requirement, which is being monitored by different process sensors and measurement devices. The main controller or PLC generates the control signal for solenoid valve activation. 

Motorized Actuators

Motorized actuators use a small electric motor to control the valve movement. These actuators provide excellent control over fluid flow and are used in applications that require precision fluid output.

The motorized actuators take input from the central controller or PLC in analog form, i.e., 4 – 20mA or 0 -10 V. The value of the analog input determines the motor's position, which in turn defines the position of the valve. For example, a 4mA signal from the main controller can represent the shut condition, while 20mA represents the open condition.

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About the Author:

Muhammad Asim Niazi has a vast experience of about 11 years in a Pharmaceutical company. During his tenure he worked in their different departments and had been part of many initiatives within the company. He now uses his experience and skill to write interested content for audiences at PharmaSources.com.