Butterfly Valve Components Explained: Complete Guide with Structure Diagram

Table of Contents

1. What are the Main Components of a Butterfly Valve?

Butterfly Valve Structure Diagram vs Butterfly Valve Cross-sectional view.

Butterfly Valve Parts Name and Main components include:

Body

Disc

Seat

Stem/Shaft

Bushings

O-rings

Actuator / Handle / Gearbox

2. Necessary parameters for each component.

2.1 Butterfly Valve Body

the “load-bearing frame” of the butterfly valve. The valve body withstands the pipe pressure from both ends, maintains the alignment of the valve stem, and ensures that the valve disc rotates smoothly in the center.

A good butterfly valve body is more than just a shell—it needs sufficient strength to resist deformation when bolts are tightened or when the pipe is subjected to pressure shocks.

Butterfly Valve Body types:

Wafer

Lug

Flanged(single and double)

U-section

Body materials:

Cast iron

Ductile iron GGG40/GGG50

WCB

SS304

SS316

2.2 Butterfly Valve Disc

The disc is the valve’s “traffic controller.” Every time flow starts, slows, or stops, the disc makes that decision.

But the disc’s function goes far beyond opening and closing.

Its shape directly affects:

* Flow resistance

* Turbulence

* Pressure drop

* Throttling accuracy

* Sealing contact

A thicker disc increases strength.

A thinner disc reduces pressure drop.

Polished stainless steel discs improve corrosion resistance and reduce fouling.

Rubber-lined discs prevent wear or improve soft-seal performance.

The disc is also the first component to come into contact with the flowing medium, so the structure and material of the disc are crucial.

Disc structure types:

Concentric

Offset

Disc materials:

DI +nickle/nylon

DI + rubber/ptfe lined

CF8

CF8M

DSS

polished SS

aluminum bronze

2.3 Butterfly Valve Seat

The valve seat is the actual contact area where a seal occurs.

When customers ask if a butterfly valve leaks or if the seal is tight, the answer usually depends on the valve seat.

The valve seat is where the valve disc and valve body make face-to-face contact, forming the final sealing barrier.

However, it also bears the friction from each rotation of the valve disc. This means the valve seat needs to possess two diametrically opposed capabilities:

* Sufficiently flexible to achieve a tight seal

* Sufficiently robust to resist wear

Therefore, this balance determines the valve’s lifespan.

seat structure types:

replaceable soft seat(dovetail seat)

Hardback seat

vulcanized seat

metal seat

Seat materials:

EPDM
NBR
VITON
Nature Rubber
Silicone rubber
PU
htK
Hypalon
PTFE
SS+Graphite
SS+Stelite

2.4 Butterfly Valve Stem/Shaft

The valve stem is the “power transmission link” of a valve.
The actuator or handle generates movement, which is precisely transmitted to the torque through the valve stem.
This sounds simple—but in actual operation, it must withstand:
* Repeated rotation
* Starting and stopping forces
* Fluid resistance
* Vibration
* Emergency closing torque
An insufficiently strong valve stem may bend, and a poorly machined valve stem can cause valve disc misalignment.
Even minute deviations in movement can affect the seal.

An insufficiently strong valve stem may bend, and a poorly machined valve stem can cause valve disc misalignment.

Even minute deviations in movement can affect the seal.

Stem structure types:

one-piece shaft

double shaft

Shaft materials:

SS410

SS420

SS431

DSS 1.4462

17-4PH

Monel

3. How to Select the Right Butterfly Valve Components

Just like when a customer inquires about pricing, I ask for their information:

Pressure

Temperature

Media & Applications

Installation

Maintenance

DN (also affects component materials, etc.)

4. FAQ of Butterfly Valves

What are the 4 main parts and butterfly valve parts name?

Generally speaking, a butterfly valve has 4 main parts: valve body, valve seat, valve disc, and valve shaft.

What material is best for a butterfly valve seat?

There is no best, only the most suitable. For example, for use with corrosive media at normal temperature, PTFE can be chosen because it has the best corrosion resistance, but the maximum temperature is only 110 degrees Celsius. If there is slight corrosion but high temperature, stainless steel valve seats can be chosen.

What is the highest pressure of your ZFA centerline butterfly valve?

Our company’s centerline butterfly valves can reach a pressure of up to PN25.

What types of connections can your company provide?

ZFA can provide Wafer, Lug, Single Flanged, Double Flanged, and Grooved.

Can butterfly valve be used for dead-end service?

Wafer butterfly valves should definitely not be used as pipe ends.

Flanged butterfly valves can use either hard-seal seats (eccentric structure) or vulcanized seats.

Lug butterfly valves can use either hard-seal seats (eccentric structure) or hard-backed seats.

Is your leakage class 0?

All butterfly valves in our company meet the API 598 testing standard. The leakage rate of soft-seal butterfly valves is 0%, and for metal-seal valves, 8 drops of liquid are allowed to flow per minute during each liquid test, and 16 bubbles are allowed to escape per minute during the gas test.

5. Services that ZFA can provide

* At ZFA Valve, replaceable Resilient seats are available in EPDM, NBR, and silicone, with pressure ratings up to PN25.

* OEM machining: From valve body and valve plate machining to painting and assembly, we handle all manual labor independently. The materials for the valve body, valve plate, valve stem, and valve seat can be customized, including the type of actuator.

* Pressure testing: We have pressure testing instruments ranging from DN15 to DN2400.

* Technical support before/after purchase: We can design suitable butterfly valves based on the customer’s usage conditions and provide corresponding drawings. We can also assist with installation or usage issues.

* After-sales service period: 18 months.