Development and Application of Triple Offset Butterfly Valves

Development of Triple Offset Butterfly Valves

Since its inception, the triple offset butterfly valve has undergone a process of self-improvement and continuous development to meet increasingly demanding operating conditions. Even the most basic zero leakage, theoretically achievable by a triple offset butterfly valve, still relies on meticulous design and precision manufacturing in practice. Based on absorbing and summarizing the strengths and weaknesses of other brands' triple offset butterfly valves, Battie Valves Co., Ltd. has launched its own unique Tritec triple offset butterfly valve, with the following features:

1. API Specification

As is widely known, API 609 has become the de facto international standard for valves used in critical industrial pipelines. Tritec designs and manufactures its products strictly in accordance with the latest 1997 version of API 609. Even more valuable is that Tritec's basic design is not limited to API alone; it also conforms to various other standards such as BS5155, ANSI B 16.34, and ASME SEC VIII, ensuring Tritec's applicability across all industrial sectors.

2. Dual safety structure

Tritec strictly adheres to the specifications of API 609. To prevent butterfly plate deformation, valve stem misalignment, and sealing surface seizing caused by fluid pressure and temperature, two independent thrust rings are installed on the upper and lower sides of the butterfly plate, thus ensuring the normal operation of the valve under any working conditions.

Meanwhile, to prevent sudden accidents caused by valve stem breakage or ejection due to unknown reasons, independent valve stem ejection prevention mechanisms are designed at both the inner and outer ends of the lower valve. This also ensures that Tritec's pressure rating can reach up to 2500 psi.

3. Dead zone-free design

During its design process, Tritec specifically considered its application in the control field. It fully utilizes the sealing principle of a triple-eccentric butterfly valve, ensuring that the butterfly plate does not scrape against the valve seat during valve opening and closing. The torque of the valve stem is directly transmitted to the sealing surface through the butterfly plate, meaning there is almost no friction between the butterfly plate and the valve seat. This eliminates the jumping phenomenon commonly seen when opening ordinary valves and eradicates the control failure caused by friction and other unstable factors in the low opening range of the valve, effectively eliminating the dead zone (non-sensing band). This means that Tritec can enter the controllable range almost from 0 degrees of opening to 90 degrees, with a normal control ratio more than twice that of a typical butterfly valve, and a control ratio that can reach over 100:1. This creates excellent conditions for using Tritec as a control valve, especially in large-diameter applications where gate valves are extremely expensive. Furthermore, gate valves cannot achieve zero leakage, and in situations requiring emergency shut-off, a shut-off valve must be installed beside the gate valve. Tritec, however, integrates control and shut-off functions, making its economic benefits extremely considerable.

4. Body valve seat structure

There are two types of seat mounting structures for triple eccentric butterfly valves. Most are mounted on the butterfly plate for convenience, but Tritec uses a body seat structure, mounting the seat on the body. Its advantage is that, compared to butterfly plate seats, it greatly reduces the chance of the seat directly contacting the medium, thereby reducing the degree of seat erosion and extending the seat's service life.

5. Thin-layer valve seat structure

Tritec's valve seats are made of layers of stainless steel and graphite sheets. This structure effectively prevents the influence of tiny solid particles in the medium and the sealing surface from seizing due to thermal expansion. Even if minor damage occurs, there will be no leakage, which is unimaginable for double eccentric butterfly valves or other triple eccentric butterfly valves.

6. Replaceable sealing pairs

Tritec's sealing system is truly unique. Not only can the valve seat be replaced, but also the butterfly plate sealing surface can be replaced because it is independent of the butterfly plate. This means that when the butterfly plate sealing surface is damaged, there is no need to go through the trouble of transporting it back to the manufacturer or disassembling the valve. You only need to replace the butterfly plate sealing surface. This not only greatly reduces maintenance costs, but also significantly reduces maintenance time, intensity, and difficulty.

7. Balanced fixed structure

Based on the sealing surface shape characteristics of triple eccentric butterfly valves, Tritec's sealing pair fixing method adopts an elliptical distribution of bolts, which not only ensures precise positioning but also ensures that each bolt is evenly stressed, eliminating loosening and leakage of the sealing pair caused by uneven stress distribution.

8. Intrinsically refractory structure

Many valves claim to have fire-resistant construction, but a large proportion of them use a dual-seat structure (soft and hard) to reduce leakage, which is actually very dangerous. During a fire, incomplete combustion of the soft-seal seat can cause stress and temperature-induced deformation in the metal support seat, leading to failure of fire resistance. Therefore, Europe and the United States are gradually phasing out these misleading fire-resistant valves. Tritec, because it has zero leakage, does not require a soft seal and is a truly inherently fire-resistant structure, having obtained fire resistance certifications from API 607, API 6FA, and BS 6755 Part 2. This ensures that Tritec can be used in various hazardous areas such as oil and petrochemical industries. The fact that almost all valves used in key parts of the North Sea oil fields in conservative Britain are made by Tritec is the best example.

9. High-sealing packing structure

Traditionally, valve leakage issues have been primarily focused on seat leakage, i.e., internal leakage, while neglecting packing leakage, i.e., external leakage. However, in today's society, where environmental concerns are increasingly emphasized, the harmfulness of external leakage far outweighs that of internal leakage—a fact that is undeniable. Tritec triple eccentric butterfly valves are rotary valves, with their stems rotating only 90°. Compared to gate valves and globe valves, whose stems undergo multiple helical reciprocating motions, this results in significantly less wear on the packing, leading to a much longer service life. Furthermore, Tritec employs the highest standards in its packing seal and other external leakage prevention designs, ensuring a standard sealing performance below 100 ppm when tested according to EPA21 specifications. In fact, in existing Tritec test results, under Lloyd's monitoring, external leakage values ​​have been as low as 7 ppm. These indicators demonstrate that Tritec can effectively handle toxic and hazardous media pipelines in various fields, including chemical manufacturing.

Applications of triple offset butterfly valves

In conclusion, the triple eccentric butterfly valve, as the culmination of the latest valve technology, combines the strengths of various valves while avoiding their weaknesses, and will undoubtedly receive increasing attention from users and designers. Tritec valves from Batie Valve Co., Ltd. offer pressure ratings up to 2500 psi, standard diameters up to 48 inches, and are compatible with various structural lengths including wafer, lug, flange, ring, butt weld, jacket, and more. Furthermore, Tritec's wide range of material choices allows for smooth operation in high and low temperatures and various corrosive media such as acids and alkalis. Especially in large-diameter applications, its zero-leakage advantage is leading to its increasing replacement of bulky gate valves and ball valves in shut-off valves. Similarly, its superior control performance is leading to its increasing replacement of cumbersome gate valves in control valves. In fact, Tritec has been used in various critical pipelines for process control in major industrial sectors, including oil and gas extraction, offshore platforms, oil refining, petrochemicals, inorganic chemicals, and power generation, in China and elsewhere.