Tier 5 DRAG® technology: How to control extreme pressure drops and reduce cavitation

By distributing pressure reduction through a compact multi-turn, multi-path trim, DRAG® technology helps control fluid velocity, reduce cavitation and noise, protect downstream equipment, and deliver reliable performance in your severe-service environments.

For engineers responsible for high-pressure steam, gas, hydrocarbon, power generation, and other critical process applications, selecting the right valve technology can significantly impact safety, reliability, maintenance requirements, and the total cost of ownership. As pressure-drop increases, conventional valve designs can reach their practical limits, creating challenges with valve size, weight, complexity, and long-term performance.

This article is part of IMI's #ChooseTheRightValve series, which helps engineers select the right valve technology for specific process challenges and operating conditions. Rather than focusing solely on valve specifications, the series explores the real-world process problems that engineers face, explains the technologies available to address them, and provides practical guidance on when each solution is likely to deliver the greatest operational value.

Each article examines a different level of valve performance, from standard control applications to the most demanding severe-service duties. By understanding the strengths, limitations and ideal use cases of each technology, engineers can make more informed decisions that improve process stability, extend equipment life, reduce maintenance interventions and minimise operational risk.

In this instalment, we examine Tier 5 DRAG® technology and explain why it has become the preferred solution for some of the industry's most extreme pressure-drop applications. We'll explore where conventional multi-stage trims reach their limits, and how DRAG® technology delivers exceptional pressure reduction in a compact valve package. We then outline the practical benefits it can deliver to plant operators seeking greater reliability, performance, and lifecycle value.

IMI's 100D DRAG® Control Valve is part of the IMI CCI severe-service portfolio and is specifically engineered for applications involving extreme pressure drops, high fluid velocities and demanding operating conditions. Built on almost six decades of proven DRAG® technology, the valve uses a multi-stage, multi-turn trim to provide precise flow control while helping reduce cavitation, erosion and noise. Each 100D valve is engineered to suit the requirements of the specific application, supporting reliable operation, equipment protection and long-term lifecycle performance in high-pressure and high-temperature environments.

In the previous #ChooseTheRightValve article, we explored how Tier 4 multi-stage cage trims help manage high-pressure drops by dividing pressure reduction into multiple controlled stages. For many severe-service applications, this approach delivers excellent control, improved equipment protection and reliable long-term performance.

However, some operating conditions push conventional multi-stage designs to their practical limits. As pressure drops become more extreme, achieving effective velocity control and equipment protection often requires additional pressure-reduction stages. This can result in larger valve bodies, increased weight, higher material requirements and greater installation costs.

For operators facing these challenges, the question is no longer simply how to manage pressure reduction. Rather, you will need to determine how best to achieve exceptional severe-service performance without compromising practicality, maintainability or lifecycle value.

This is where Tier 5 DRAG® technology provides a different approach. Originally developed to solve the most demanding pressure-drop applications, DRAG® technology distributes fluid energy through a highly engineered series of flow paths and pressure-reduction stages contained within a remarkably compact trim design. The result is a solution capable of controlling extreme pressure drops while reducing cavitation, limiting noise, protecting downstream equipment, and maintaining stable process control.

In this article, we explore why conventional multi-stage trims eventually reach their limits, how DRAG® technology overcomes these challenges, and why it remains one of the industry's most proven severe-service control valve technologies nearly six decades after its introduction.

A Tier 5 DRAG® valve is a severe service control valve specifically engineered for extreme pressure-drop applications. It uses a highly sophisticated multi-turn, multi-path trim design that distributes pressure reduction across numerous engineered stages.

This enables the valve to:

DRAG® technology is widely used in power generation, oil and gas, refining, petrochemical and other critical process applications where reliability and performance are essential.

Tier 4 high-pressure-drop control valves are designed to divide pressure reduction into multiple controlled stages. This approach helps manage fluid energy, reduce damaging velocities and mitigate cavitation and noise that can occur within a single-stage trim.

For many applications, this delivers excellent results. However, as pressure drops become more severe, additional stages are often required to maintain acceptable velocity control and equipment protection. At this point, engineers face a practical challenge.

A useful way to evaluate severe service valve technology is to consider the relationship between valve volume and stage capacity. While several trim geometries can achieve multi-stage pressure reduction, they do so with varying space requirements.

Traditional concentric cage designs typically require more physical space as the stage count increases. More stages generally mean larger valve bodies, additional material requirements, increased weight and higher purchase costs. Eventually, adding more stages becomes impractical. The challenge then becomes achieving greater pressure reduction without increasing valve size, cost or complexity.

Tier 5 DRAG® technology was developed specifically to overcome these limitations. Rather than relying on increasingly large concentric cage arrangements, DRAG® trims utilise a compact multi-turn, multi-path design that delivers significantly more pressure-reduction stages within a practical valve package. This enables you to achieve the severe service performance your facility requires without the size and weight penalties associated with conventional multi-stage designs.

IMI's DRAG® technology provides one of the industry's lowest volume-to-stage-capacity ratios, helping you achieve greater pressure reduction while meeting practical installation requirements and ensuring long-term reliability. For applications involving extreme pressure drops, this translates into greater design flexibility and improved installation practicality. All of this is designed to enhance your operational performance.

IMI introduced DRAG® technology in 1967 and has continued to refine and develop the design ever since. Advances in manufacturing have enabled us to produce increasingly sophisticated trim configurations, including EDM-etched discs, stacked punched discs and stacked laser-cut discs. Each manufacturing method offers distinct advantages depending on valve size, capacity and application requirements.

This flexibility enables our engineers to tailor every DRAG® trim to the specific operating conditions of your application. Today, we can provide you with DRAG® trims featuring more than 30 stages of pressure reduction while maintaining practical valve dimensions and customised flow characteristics. The result is a valve specifically engineered around your process requirements rather than forcing your application to conform to a standard design.

Customers typically choose Tier 5 DRAG® technology because it helps solve some of their most challenging operational problems related to severe service control.

The key benefits include:

These benefits make DRAG® technology particularly valuable in high-energy applications where equipment failure or poor control can have significant operational and financial consequences.

The objective of a Tier 5 DRAG® valve is similar to that of a Tier 4 severe-service valve: to manage high-pressure drops, control cavitation, reduce noise, and maintain stable process control. The difference lies in how the technology achieves these outcomes.

Each disc within the DRAG® stack contains a carefully engineered maze-like flow path made up of multiple right-angle turns. As fluid travels through these pathways, pressure is reduced through a series of small, controlled reductions rather than a handful of larger pressure drops. This not only allows for compact valve design but also for the fluid energy to be dissipated gradually. This helps prevent damaging velocity spikes that can compromise reliability, efficiency and equipment life.

One of the major advantages of DRAG® technology is its flexibility.

Our engineers can customise:

This enables us to deliver a trim tailored precisely to the operating conditions, performance objectives and process requirements of your application. The result is more predictable performance, improved controllability and greater confidence in long-term operation.

Stable control is essential in severe service applications. DRAG® trims incorporate pressure-equalising ring (PER) grooves that maintain balanced pressure throughout the trim assembly. This helps prevent binding, vibration and buffeting under both under-plug and over-plug flow configurations. A robust packing arrangement supports reliable sealing under high-pressure and high-temperature operating conditions up to 9,000 psi (600 kg/cm²). When combined, these features help operators maintain reliable control of flow, temperature, pressure, and level in some of the world's most demanding process environments.

Many severe-service applications require precise control over a very wide operating range. Where low-flow precision is required, specialised labyrinth grooves can be incorporated into the disc stack to further restrict annular flow and improve controllability. This enables DRAG® technology to achieve throttling ranges exceeding 100:1. In some applications, this level of precision can even eliminate the need for dedicated start-up valves, reducing system complexity while lowering maintenance and lifecycle costs.

The right severe-service control valve depends on far more than pressure drop alone. Engineers must consider:

In general, Tier 5 DRAG® technology is the preferred solution when a Tier 4 multi-stage cage design would require so many stages that the resulting valve is impractical due to its size, weight, or cost. When you need extreme pressure reduction within a compact, reliable, and highly controllable package, DRAG® technology often provides the optimal balance of performance, practicality, and lifecycle value.

DRAG® technology represents a major milestone in the evolution of severe service valve design. However, innovation continues to push the boundaries of what is possible. There are applications where even conventional DRAG® manufacturing techniques begin to approach their practical limits.

In our next article, we will explore Tier 6 technology, where additive manufacturing enables highly sophisticated 3D-printed trim geometries that guide fluid flow in three dimensions. These advanced designs unlock new possibilities for pressure control, performance optimisation, and application-specific engineering in some of the world's most demanding severe-service environments.

When your application demands extreme pressure reduction, precise control and long-term reliability, Tier 5 DRAG® technology provides a proven solution backed by almost six decades of field experience.

By controlling fluid velocity, reducing cavitation, minimising noise, and delivering exceptional pressure reduction within a compact package, DRAG® remains one of the industry's most trusted severe-service valve technologies.

To learn more, visit: 100D - DRAG® Multi-stage, Multi-turn Control Valve