Butterfly Valve Parts–A Complete Guide

Zhongfa Valve is a professional manufacturer of butterfly valve parts and butterfly valves, established in 2006, providing valves and butterfly valve parts products to more than 20 countries in the world, next, Zhongfa Valve will launch a detailed introduction of butterfly valve parts.


A butterfly valve consists of the following parts, butterfly parts name are valve body, valve Disc, valve shaft, valve seat, sealing surface, and operation actuator, now, we will introduce these butterfly valve parts one by one.


# 1 Butterfly valve parts--Valve body

We discuss the valve body in terms of connection and material

1. Generally speaking, according to the different connection methods, butterfly valves have flange type, wafer type, and lug type, and the approximate styles are shown in the figure. For each type of connection, there are subtle differences according to the different molds, such as for the wafer butterfly valve, Zhongfa Valve has the following common molds.

different shape for the wafer butterfly valve
Flange Type Butterfly Valve (8)
Ductile Iron SS304 Disc Lug Type Butterfly Valves (3)

2. According to the material, the common ones are ductile iron body, carbon steel body, stainless steel body, brass body, and super duplex steel body.

# 2   Butterfly valve parts--Valve Disc

The style of valve disc also varies, pin disc, pinless disc, disc with rubber, Disc with Nylon, Electroplated Disc, and so on, Usually, the valve disc is selected according to the working conditions and medium.


For the pinless disc,  There is a through shaft and double half shaft, disc without a pin will reduce the risk of leakage chances, for the Disc with a pin, it is likely that the pin has worn or rusted after a long time, the media from the pin on the disc that leakage shaft hole. We would like to choose a pinless disc for our client.


# 3  Butterfly valve parts--Valve Spindle

The butterfly valve spindle also called the stem, is used for transmission, is connected to the actuator or handle, the following directly drives the valve plate rotation, in order to achieve the butterfly valve switch or adjustment role.

1. From the material: The spindle material is generally made of stainless steel and carbon steel, and its code is: stainless steel (2cr13, 304, 316, 316L), carbon steel (35, 45, Q235).             

2. From the style: butterfly valve through shaft (left) and butterfly valve double half shaft (right).

a: In terms of price: a double half-shaft is more expensive than a through-shaft.

b: In terms of use: the double half-shaft can do more than DN300, and the through-shaft can do DN800.

c: Fittings versatility: through-shaft fittings can be used on pinned butterfly valves with a low scrap rate. Only double semi-shaft butterfly valves can be used, and the scrap rate is high.

d: Assembly: through-shaft without pin is the basic method in design, simple design, shaft processing, double half-shaft production difficulties, generally divided into the upper shaft, and lower shaft.

# 4  Butterfly valve parts--Valve Seat

The rubber seat of the soft seal butterfly valve can be divided into hard-back rubber seat and soft-back rubber seat, and the seat of the hard seal butterfly valve is mostly propriety seal and multi-level seal

The difference between a hard-backed rubber seat and a soft-backed rubber seat of a butterfly valve: the hard-backed seat is pressed on the valve body with abrasives, which cannot be replaced by itself and requires a special flange for the butterfly valve; the soft-backed seat is made by the model, which can be replaced by itself and can be used with a flange that is not special for butterfly valve.

In terms of rubber seat service life, the service life of the soft back seat is longer than that of the hard back seat, which is a large broadside structure. Valve long-term operation process valve seat shaft end wear. Valve seat shaft end leakage after the hard back seat water seepage directly to the outside of the valve body leakage phenomenon. But the soft back does not appear in this situation.


# 5  Butterfly valve parts--Sealing surface

there are soft sealing and hard sealing, The choice of soft sealing materials:                                       

1、Rubber (including butadiene rubber, EPDM rubber, etc.), mostly used in low-pressure pipelines over oil and water.

2、Plastic (PTFE, nylon, etc.), more for corrosive media in the pipeline.

Operation mode: handle, turbo, electric, pneumatic, hydraulic


Selection of hard seal materials:

1、Copper alloy (for low-pressure valves)

2、Chrome stainless steel (for ordinary high and medium pressure valves)

3、Stellite alloy (for high temperature and high-pressure valves and strong corrosive valves)

4、Nickel-based alloys (for corrosive media)

# 6 Butterfly valve parts--Operation Actuator

Butterfly valves are usually operated in the following, Hand Lever, Worm Gear, Pneumatic Actuator.


Hand levers are usually made of rigid, chemically treated, and powder coated. The hand lever usually contains a handle and an interlocking lever, It is suitable for DN40-DN250.


The worm gear is suitable for large butterfly valves. The worm gearbox usually uses for sizes big than DN250,  there are still two-stage and three-stage turbine boxes. 


Pneumatic actuators are divided into two categories, single-acting and double-acting pneumatic actuators.


Electric actuators can be divided into multi-turn types and part-turn types. Multi-turn type turn more than 360° to open and close the valve while the part-turn type turns normally 90° to fully open and close the valve.

Next, let's take a look at how  to install the butterfly valve parts together  

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