Week 14 challenge

Objective:

The objective of this challenge is to assemble the parts of Butterfly Valve and create a drawing of the assembly with all GD&T details as per ASME Y14.5 standards. To create the 3D model and drafting using Siemens NX software.

Introduction:

Butterfly valve is a type of Quarter-Turn Valve. It is called Quarter-Turn because when operating the valve, the flow controlling disc is rotated by 90° to open or shut the valve. The Butterfly Valve is classified based on the mounting used as lug type, wafer type, flange type. Their simple design and efficient operation make them a popular choice across various industries. The main components of the butterfly valve are the body, stem/shaft, disc and seat (a part that forms a seal with the valve disc to prevent any leakages).

Commonly used material for various main parts of the Butterfly Valve are:

Body: Carbon steel, Cast iron, Stainless Steel and various alloys.
Disc: Stainless Steel, Bronze, Ductile Iron and Specialized alloys.
Seat: Elastomers like EPDM, PTFE(Teflon), NBR, Metal.

Butterfly Valve is most commonly used extensively in the following areas

• Water and waste water treatment
• Oil and Gas industry
• Chemical processing
• Pharmaceutical
• Power generation
• Food and Beverages

Butterfly Valves has its own benefits and drawbacks.

• Pros:
  1. It has a cost effective and easy to manufacture
  2. High flow capacity
  3. Lightweight design
  4. Easy installation and maintenance
  
• Cons:
  1. Throttling capability is limited in partially opened condition
  2. Disc obstruction in the flow path causes pressure drop
  3. Over time the seals are subjected to wear that leads to leakage
  4. Not suitable for high pressure application in all configuration

Types of Butterfly Valves:

Butterfly valves are categorized based on their construction and working principles:

• Concentric (Rubber-lined): The disc is centered within the valve body, with a rubber seat providing a tight seal.

• Eccentric (High-Performance): The stem is offset from the disc's center, reducing seal wear and allowing for higher pressure applications. These include single, double, and triple offset designs. Each offset increases the valve's capabilities in terms of pressure and sealing.

We will have a brief idea of the main parts of the Butterfly Valve below:

1. Butterfly Valve Body
Most commonly used body types are Lug type and flange type body. The body is the most important part that encloses and protects the stem, seal and disc of the valve. For this particular project we are using the lug type butterfly valve.
The lug-style butterfly valve body features protruding "lugs" or ears that extend beyond the valve disc area. These lugs align with corresponding bolt holes in the adjacent pipe flanges. Bolting through these lugs securely sandwiches the valve body between the flanges. This distinct design allows for independent removal, offering significant maintenance advantages. The body itself is typically a robust, circular structure engineered to withstand pipeline pressure and facilitate smooth fluid flow around the rotating disc.

The respective images have been attached, do check for reference.

2. Shaft/Stem
The stem of a lug-type butterfly valve is a high-strength metal alloy, which is precisely engineered to transmit torque from the actuator to the disc. Its design often incorporates features like a keyed or splined connection to ensure secure and accurate disc rotation. Crucially, the stem's robust construction must withstand operational stresses and prevent leakage along the valve's central axis. Proper material selection and surface finishing are vital to resist corrosion and ensure long-term reliability within diverse industrial applications. This critical component facilitates efficient flow control while maintaining structural integrity.

The respective images have been attached, do check for reference.

3. Disc Plate
This is the heart of the butterfly valve, a precisely engineered metallic circular plate that is critical for flow control. It rotates about the central axis within the valve body. When in open condition the disc plate ensures minimal obstruction to the flow, whereas it ensures a tight shut-off when completely closed against the valve seat. The robust construction of the disc ensures that the disc withstands the the operational stresses and fluid pressure. The material selection of the disc plate depends on the application which ensures the compatibility with the media and the temperature.

The respective images have been attached, do check for reference.

4. Retainer Plate
The retainer plate is the part that holds the shaft in place inside the valve body. It also ensure the correct positioning of the shaft/stem along with a tight leakproof seal at the neck of the valve. The robust construction ensures proper operation of the valve by maintaining the alignment of the shaft. It also plays a vital role in the event of maintenance of the valve.

The respective images have been attached, do check for reference.

5. Lever
This is the crucial part that enables the manual flow control in a butterfly valve. The lever is designed for efficient torque application and ergonomic grip. The lever is directly connected to the valve stem/shaft with the help of a key slot and key or splined connection. By rotating the lever, we control the position of the valve disc resulting into controlling or obstructing the flow. This a straightforward and effective mechanism that ensures precise and reliable manual control in various industrial applications.

The respective images have been attached, do check for reference.

6. Nut
The nut retains the lever in its place and hence helps to keep the assembly together. Even in the event of repair work the nut plays a vital role. The size depends on the size of the stem/shaft.

The respective images have been attached, do check for reference.

7. Machine Screws
The Valve Disc Plate need to be mounted on the Shaft/Stem and the Retainer plate need to be mounted on neck of the Butterfly Valve. To do this we need 2 Nos. of M14X2 Round Headed Machine Screw for mounting the Disc Plate and need 3 Nos. of M22X2.5 Round Headed Machine Screw for mounting the retainer plate.

The respective images have been attached, do check for reference.

Operations used when building the above components:

1. Butterfly Valve - Body

• Sketch
• Extrude
• Mirror Feature
• Counterbore Hole
• Boolean Operation - Unite

2. Shaft/Stem

• Sketch
• Revolve
• Extrude
• Chamfer
• Simple Hole
• Boolean Operation - Subtract

3. Disc Plate

• Sketch
• Extrude
• Thread

4. Retainer Plate

• Sketch
• Extrude
• Thread

5. Lever

• Sketch
• Extrude
• Boolean Operation - Unite

6. Nut

• Sketch
• Extrude
• Revolve
• Boolean Operation - Subtract

7. Machine Screws

• Sketch
• Extrude
• Revolve
• Boolean Operation - Unite
• Threads

Assembly of the Butterfly Valve

Creating the assembly is a thoughtful process of sequencing the assembly constraints in the right order and manner. The Body being the main part that will be in direct contact with the external bodies like the pipelines to which the valve is attached. Hence we give a fix constrain to the Valve Body followed by assembly constraints like Touch, Align and Infer Centre.

Once done with the assembly we move forward to the drafting and and application of GD&T constraints to the drafted assembly.

1. As the Butterfly Valve is sandwiched between the external faces of the mounting lugs. To ensure proper fitment without leakage we need provide constrains to both the faces. This is achieved by applying Datum Targets A1, A2 and A3 with a Flatness tolerance to create a Datum A on one side of the mounting lugs and apply a Profile of Surface tolerance to the opposite end mounting lugs.

2. Next we apply Perpendicularity and Position tolerance to two of the mounting lugs on the side which refers to the Datum A. The mounting hole with the Perpendicularity tolerance is designated as Datum B and the one with Position tolerance as Datum C. The third hole is also applied a Position tolerance and labeled as Datum D.

3. For the proper fitment of the Butterfly valve it is important to have the holes in the mounting lugs on both faces of the Valve to be inline with each other. This can be obtained by applying Position tolerance to the holes with respect to the Datums created on the respective opposite holes i.e. Datums B, C and D.

With this we have successfully created the Assembly and applied GD&T to the drawing of the Butterfly Valve.

Operations used to create the Assembly

• Add Component
• Assembly Constraint - Fix, Infer Centre/Axis, Touch, Align

Conclusion
The parts and assembly of the Butterfly Valve was thus created using the Part and Assembly workbench (Application) of Siemens NX 12 Software and the Drawings with GD&T details of the respective parts and assembly was successfully created using the Drafting workbench (Application) of Siemens NX 12 Software.

NOTE: Files of all parts and assembly have been attached in the .zip file.