APPLICATION OF GD&T ON A BUTTERFLY VALVE ASSEMBLY

OBJECTIVE:

To model different parts of a Butterfly Valve and apply GD&T to all the parts, as well as the assembly.

INTRODUCTION:

A butterfly valve is a valve that isolates or regulates the flow of a fluid. It consists of various parts such as the body, rotating disc, retainer, lever, shaft, screws and nuts. In this project, we will be modelling all the parts and applying GD&T to them individually and to the complete assembly.

OPERATION:

The valve is from a family of valves called quarter-turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn. The "butterfly" is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid.

SOFTWARE USED: NX CAD 12.0

DESCRIPTION:

The various parts of the butterfly valve are as follows,

• Body:

Butterfly valves generally have bodies that fit between two pipe flanges. The most common body designs are lug and wafer. The lug body has protruding lugs that provide bolt holes matching those in the pipe flange. A wafer body does not have protruding lugs. The wafer valve is sandwiched between the pipe flanges, and the flange bolts surround the body.

• Shaft:

The shaft controls the flow through a pipe by use of a single disc mounted on it which creates a variable orifice. It rotates as the fluid passes through the flow passage.The rotary action of the stem initiated from the power of the actuator is transmitted to the disc, allowing the close and open position of the valve.

• Disc:

The flow closure member of a butterfly valve is the disc. Rotating the disc one-quarter turn or 90 Degrees opens and closes the butterfly valve.The disk is always in the passageway, but because it is relatively thin, it offers little resistance to flow.

• Retainer:

The retainer screws into the valve body to hold the seat in place with pressure and make a simple one piece body Valve assembly.

• Lever:

The lever handle operates the valve, but also serves as an indicator for whether the valve is open or closed. When the lever is parallel to the pipe, the valve is open.

• Screw:

The butterfly valve is opened or closed by using a screw.

• Nuts:

They are small washer-shaped circles that thread onto the outside of the valve shaft down to the rim in order to engage the lever with the shaft.

ASSEMBLY:

All the parts of the valve were then assembled using various assembly mates such as Touch, Align, Center-axis align, etc. and GD&T was applied to the whole assembly.

RESULT:

Thus the different parts of a Butterfly Valve were modelled and GD&T was applied to all the parts and to the assembly using NX CAD.