Double Eccentric vs Triple Offset Butterfly Valve – Detailed Comparison

The butterfly valve is a widely used industrial valve, designed to regulate flow through a pipe system with efficiency and reliability. Among the many types of butterfly valves, two standout variants are the double eccentric butterfly valve and the triple offset butterfly valve. Both types serve critical functions across industries such as oil and gas, chemical processing, water supply, and power generation. This article explores the major differences between the two, examining their working principles, parts, actuator mechanisms, symbols, and typical use cases.

Table of Contents

1. Understanding Butterfly Valves
2. What is a Double Eccentric Butterfly Valve?
3. What is a Triple Offset Butterfly Valve?
4. Butterfly Valve Working Principle
5. Key Differences Between Double Eccentric and Triple Offset
6. Butterfly Valve Diagram & Parts
7. Butterfly Valve Actuator Types
8. Butterfly Valve Uses
9. Material Selection: Stainless Butterfly Valves
10. Butterfly Valve Symbol & HSN Code
11. Delval Butterfly Valve Overview
12. Conclusion
13. FAQs

Understanding Butterfly Valves

A butterfly valve is a type of quarter-turn valve that uses a rotating disc to control the flow of fluids through a pipe. The simplicity of its operation and its compact design make it a preferred option in industrial applications. Over time, butterfly valves have evolved into multiple designs with distinct features and performance capabilities. Among them, the double eccentric and triple offset valves are considered high-performance variants.

What is a Double Eccentric Butterfly Valve?

The double eccentric butterfly valve is also known as a high-performance butterfly valve. It gets its name from the two offset points that shift the shaft away from the center of the disc and body. This design reduces contact between the disc and seat during operation, lowering wear and increasing longevity. These valves are suitable for moderately high-pressure and high-temperature applications.

Key features of double eccentric butterfly valves include:

• Reduced friction during opening and closing
• Longer seal life
• Improved sealing capability under pressure
• Suitable for shut-off and throttling services

What is a Triple Offset Butterfly Valve?

The triple offset butterfly valve goes one step further by adding a third offset in the geometry. This offset introduces a conical profile to the sealing surface, enabling metal-to-metal sealing. These valves are ideal for critical shut-off applications where zero leakage is mandatory. They are widely used in oil & gas, petrochemical, and power industries.

Main characteristics of triple offset valves:

• Metal-to-metal sealing (no elastomer contact)
• High resistance to pressure and temperature
• Zero leakage per API 598 standards
• Durability in aggressive environments

Butterfly Valve Working Principle

The butterfly valve working principle involves the rotation of a disc inside the valve body to open or close the passage. When the disc is turned 90 degrees, it either aligns with the flow (open) or blocks it (closed). The design allows for fast shut-off and throttling, making it an energy-efficient choice.

Key Differences Between Double Eccentric and Triple Offset

Butterfly Valve Diagram & Parts

Understanding the butterfly valve diagram is essential for maintenance and selection. Common butterfly valve parts include:

• Valve Body
• Disc
• Shaft/Stem
• Seat
• Bearing
• Actuator

In triple offset valves, the seat and disc sealing surfaces are angled, forming a cone that ensures non-friction closure and long-term tight sealing.

Butterfly Valve Actuator Types

The butterfly valve actuator can be manual, pneumatic, electric, or hydraulic. Actuators provide automation and are vital for applications that require frequent and remote operation. Triple offset valves often use actuators due to the heavy-duty torque needed to operate the metal seal.

Butterfly Valve Uses

Butterfly valve uses vary by type:

• Double eccentric: Fire protection systems, HVAC, wastewater
• Triple offset: Steam systems, gas pipelines, chemical plants

Both are ideal for compact, lightweight flow control solutions, offering substantial cost and space savings.

Material Selection: Stainless Butterfly Valves

A stainless butterfly valve is preferred in corrosive and sanitary environments. Stainless steel construction ensures high resistance to oxidation, acidity, and microbiological contamination, making it ideal for food processing and marine applications.

Butterfly Valve Symbol & HSN Code

The butterfly valve symbol in diagrams typically shows a circle with a bisecting line, representing the disc. This is universally recognized in P&ID drawings. For billing and classification, use the butterfly valve hsn code: 8481.

Delval Butterfly Valve Overview

The delval butterfly valve brand is known for precision-engineered products. Available in both double eccentric and triple offset styles, Delval offers IS-marked valves that meet global testing standards. Industries across India rely on Delval for trusted performance and easy integration with automation systems.

Conclusion

Both double eccentric and triple offset butterfly valves play critical roles in modern pipeline systems. The right choice depends on pressure class, media characteristics, leakage requirements, and automation needs. For moderate applications, double eccentric valves offer great value. For zero-leakage high-pressure use, triple offset designs are unmatched.

FAQs

Q1: What is the key advantage of a triple offset butterfly valve?

A: It offers zero leakage with metal-to-metal sealing, suitable for high-pressure systems.

Q2: Are double eccentric valves suitable for chemical plants?

A: Yes, especially in systems not requiring metal seals. For harsh chemicals, choose PTFE-seated designs.

Q3: Can both valve types use actuators?

A: Absolutely. Pneumatic and electric actuators are commonly paired with both types for remote control.

Q4: Is stainless steel used in triple offset valves?

A: Yes, stainless butterfly valves are commonly manufactured with 304/316 grades for durability and resistance.