Week 14 challenge

OBJECTIVE:

• The objective is to design & assemble the components of the butterfly valve using various modeling & assembly features in SIEMENS NX CAD.
• Developing drawing sheets of butterfly valve assembly using various drafting tools.
• Understanding various GD&T symbols and applying the same to the butterfly valve assembly.

INTRODUCTION:

A butterfly valve belongs to a family of QUARTER-TURN valves. A butterfly valve is a flow control device that incorporates a rotational disk to control the flowing media in a process. The disk is always in the passageway, but being relatively thin, it offers little resistance to flow.

In operation, the valve is fully opened or closed when the disc is rotated a quarter turn. When the valve is closed, the disc is turned so that it completely blocks the passageway. And, when the valve is open the disc is rotated a quarter turn/90 deg so that it allows the unrestricted flow of the fluid. The valve may also be opened incrementally to throttle flow. Many different types of valves are used in flow control. They are used for a variety of reasons, such as phase (liquid or gases), pressure, piping restrictions, and solids content. Other valves are chosen for their capability to open and close in a quarter turn.

Early use of butterfly valves focused on water applications, but new designs and component materials have allowed them to be utilized in growing industrial fluid applications. Presently, butterfly valves can be found in almost every chemical plant handling a variety of diverse fluids.

Once the components and assembly are developed, GD&t(geometric dimensioning and tolerance) is applied to each component as well as the assembly. The purpose of GD&T is to describe the engineering intent of parts and assemblies. GD&T can more accurately define the dimensional requirements for a part, allowing over 50% more tolerance zone than coordinate (or linear) dimensioning in some cases. Proper application of GD&T will ensure that the part defined on the drawing has the desired form, fit (within limits), and function with the largest possible tolerances. GD&T can add quality and reduce cost at the same time through producibility.

There are several standards available worldwide that describe the symbols and define the rules used in GD&T. One such standard is the American Society of Mechanical Engineers (ASME) Y14.5. This article is based on that standard, but other standards, such as those from the International Organization for Standardization (ISO), may vary slightly. The Y14.5 standard has the advantage of providing a fairly complete set of standards for GD&T in one document. The ISO standards, in comparison, typically only address a single topic at a time.

DESIGN OF BUTTERFLY VALVE BODY:

• First created the cylinder part of the body in butterfly valve with help of sketch and extrude command in Siemen NX software.

• After extrude the cylinder create ear part of the valve in center of the body then move it in both direction of the valve according in the dimension.

 

• Then create the datum plane either one side of the cylinder.

 

• After that datum plane create the cylinder part by using until select command in extrude option and Boolean option is to unite command.

  

• After all this creating the counter bore part in the cylinder part by using hole command and the Boolean operation is subtract action option is used.

 

• Finally, the hole is provided for the mounting of the body and it is saved in the required folder.

BUTTERFLY VALVE DISC:

• Construction similar to retainer valve design but in sketching the circular structure in retainer in this we develop elliptical.
• Extrude command is used for develop this disc.
• After apply GD&T on this component for constrains the motions.

• First apply datum target on both the circle consider as A1, A2.
• Then provide flatness on the surface and constrain the surface to be a primary datum A.
• Put position and perpendicularity tolerance for both the holes then consider datum B and C.
• After all this we’ve constrain 6 dof.

DESIGN OF BUTTERFLY VALVE SHAFT:

• The stem of the butterfly valve may be a one-piece shaft or a two-piece (split-stem) design. This design consists of a one-piece shaft. The disc/plate, lever, and nut are assembled to this shaft.
• First, create a sketch that is cylindrical in shape along with steps. That sketch must be fully constrained and closed in order to use Revolve command.

  

• Create a rectangular slot in the cylinder , after create the slot develop two holes on the slot for attach the disc plate.

• Create small rectangular slot on the front position of the cylinder for key attachment. That key will lock body and shaft.

 

• Applied GD&T on this part.

DESIGN OF BUTTERFLY VALVE RETAINER:

• The main function of the retainer valve is holding the body in butterfly valve with constant pressure and construction procedure is very simple.
• Create a sketch in circular shape in according to design procedure values and provide 3 holes in the retainer valve for bolt and nut assembly. The retainer valve thickness should be 25mm according to the design procedure.

Butterfly valve lever design:

• The lever is attached at the end of the shaft/stem above the body & retainer. This lever handle is used in a small-sized butterfly valve. Using this we can regulate the flow by opening and closing the disc whenever required.

 

• Create two circular sketches with the appropriate diameters, and specify a suitable distance between them. Also, create a keyway slot in the bigger diameter sketch. Join these two sketches with a line tangent to both the circles.

• After creating the fully constrained sketch, first, extrude the circular regions and then extrude the mid-section with different thickness values.

• Then combine all the features using Unite command. Then create a drawing sheet of the model and apply GD&T to the drawing. 

NUT - BUTTERFLY VALVE:

• It is used to keep the lever and retainer intact with each other as well as the body of the butterfly valve. 
• Create a polygon sketch (6sides) with suitable dimensions. Also, add a circular hole in the sketch so that it can be inserted into the shaft.

  

• For safety handling provide a fillet on the top edge of the nut.

BUTTERFLY VALVE ASSEMBLY:

• After designing every component. we have created the final assembly model using SIEMENS NX CAD.

MODEL VIEWS:

CONCLUSION:

• Learned the significance of GD&T that states how it controls the dimensional variation in parts which leads to less wastage of material, reduces cost, and eliminates inspection of some features, being a language that consists of symbols make it easy for the engineers to communicate with other engineers all over the world.
• Also, learned how to perform stack/gap analysis using different of stack-up analysis such as RSS, MRSS, and, WC.
• Learned modeling, assembly, drafting applications in SIEMENS NX CAD and developed a butterfly valve. Also, applied GD&T to individual components as well as the assembly of the butterfly valve.