Butterfly valves are specified in MSS SP-67-2022: Butterfly Valves. This standard is devoted to the dimensions, design, testing, and marking requirements for this widely used valve variety.
What Are Butterfly Valves?
Butterfly valves emerged in the 1930s, and the plentiful advantages they grant for water, air, and large pipe diameter applications have allowed these devices to flutter on into widespread usage today. The “butterfly” in a butterfly valve is, of course, not the polymorphic winged insect but a circular disc or plate that serves as the closing device for isolating or regulating the flow of a fluid.
This disc-type element is held in place in the center of a valve by a rod or stem, on which the disc pivots in quarter turns to isolate the fluid. Therefore, once a closed butterfly valve has its disc rotated 90 degrees and is aligned with the direction of flow, it is open, and when that disc is rotated back to a position perpendicular to the direction of flow, it is closed.
This simple and expedited rotation is comparable to that of a ball valve, and it allows for quick shutoff. Butterfly valves, in addition to this desired characteristic, contain a thin profile between flanges, making them lightweight and often less costly than other valves.
What Are the Types of Butterfly Valves?
While butterfly valves are defined by circular discs that rotate on rods or stems, there are different design variations. The basic form, in which the stem travels through the center of the disc, is known as a concentric butterfly valve. A double-offset butterfly valve, on the other hand, has two counterbalance contrasts and the concentric butterfly valve, and its principle balance is the pole found somewhat behind the circle. A triple-offset butterfly valve has three-balance contrast, and it is vital in applications with incredibly tight shut-off. Offset valves always keep the disc off the centerline and are also known as eccentric.
Butterfly valves can also be flangeless (wafer-type), single-flanged (lug-type), and flanged-end valves. These vary structurally and serve different purposes. For example, lug butterfly valves can be inspected, repaired, or cleaned without shutting down the entire system. While wafer butterfly valves do not have this advantage, they are designed to hold a tight seal against dual-directional pressure.
What Is MSS SP-67-2022?
The requirements found in MSS SP-67-2022 deal with the dimensions, design, testing, and marking of butterfly valves. The standard practice covers flanged-end, single-flange (lug-type), and flangeless (wafer-type) valves under NPS (nominal pipe size) 1½ through NPS 72, along with grooved-end and shouldered-end valves. The standard includes these general variations, but MSS SP-67-2022 covers two overarching types of butterfly valves:
- Type I – Valves for tight shut-off
- Type II – Valves permitting seat leakage
Further reference should be made to MSS SP-68-2017 for high pressure valves with offset, or eccentric, design.
What Is the Current Edition of MSS SP-67?
MSS SP-67-2022 is the current edition of the standard practice for butterfly valves, and it revises the 2017 edition and its errata.
MSS SP-67-2022: Butterfly Valves is available on the ANSI Webstore.