Bellow Seal Valve

What is a bellow seal valve?

A bellow seal valve is a control valve that does not have traditional gland packing and instead has a bellow cartridge that is welded to the valve’s bonnet and stem. Because it may be bent in compression or extension, the bellow is similar to a coiled spring. The main difference between a bellow seal valve and a globe valve is that a globe valve has gland packing along the stem, while a bellow seal valve uses bellows instead of packing to prevent leakage. These valves are completely leakproof and capable of handling caustic substances. These valves may be found in the butadiene extraction unit.

What are the characteristics of a bellow seal valve?

• These valves are resistant to extreme temperatures and pressures.
• The bellow seal may prevent the leaking of combustible sensitive material.
• Life span
• It can withstand a significant amount of steam pressure.

Why are the valves below sealed?

The majority of control valves are used to regulate the flow and pressure of process fluid. As a result, the risks of leakage are quite significant; leakage might result in material loss. The substance might be radioactive or chemical, causing several difficulties at a facility. The fluid utilized may be caustic, explosive, or toxic. So, to remedy this issue, we may utilize the seal valve.

How do you put in a bellow seal valve?

A bellow-sealed valve may be fitted in any position, however, it should not be installed with the stem upside down. So, by installing a bellow seal valve, we can avoid the collection of debris in the bellows region. So, before we install the bellow valves, we must check that the pipes and valves are clean. The pipes must be linked in such a manner that there is no unnecessary stress acting on the valve housing.

What is a bellow and how are bellow seal valves made?

The valve body material must be chosen based on the flow media’s pressure, temperature, corrosive, and erosive properties. The bellow cartridge will be welded; there are numerous convolutions in a bellow cartridge, and these convolutions may be squeezed or extended in response to valve stem movement. The bellow’s construction material would be stainless steel with titanium added to it, allowing the bellow to endure extreme temperatures.

Bellows Seal Globe Valve Construction

A Bellows globe seal valve is distinguished by its use of metal bellows. Bellows are classified into two types:

1. Formed Bellows – These are formed by rolling a flat sheet into a tube and longitudinal fusion welding. The tube is then mechanically shaped into a bellow with rounded and evenly spaced folds.
2. Welded leaf Bellow – The washer-like plates of thin metal are welded together in this kind. Welding is done on both the interior and exterior of the washer-like plate. Welded leaf bellows have more folds per unit length.

For both formed and welded-leaf bellows, the amount of movement in each fold is the same. As a result, mechanically produced bellows are two to three times longer than welded leaf equivalents at the same stroke rate.

The lower end and stem assembly are welded by automated seam welding, while the connecting plate is welded by automated seam welding, forming a metal shield between the fluid medium and the environment and assuring zero leakage from the valve stem.

The sealing surface of the valve disc and the valve structure is perfectly ground so that once installed, it is certified that it has 100% passed a pressure test and any risk of leaking is avoided. The stuffing box is constantly retained on the bellows as an auxiliary seal, which increases durability and protection. The metal bellows of the high-pressure valves are multi-layered, ensuring an open/close life of 10000 times at maximum pressure via hydroforming.

What Is the Function of a Bellow Seal Globe Valve?

A Bellows Seal Globe Valve is a kind of control valve with a compact construction that employs bellows to seal the valve stem components. The bellows valve has a bellow, and the lower end of the stainless-steel bellows is welded to the stem to prevent system fluid from eroding the stem. The other end is inserted between the valve’s body and its cover to form a permanent seal. This double-seal construction prevents leakage since the stem packing prevents additional leaking even if the bellows collapse. The bellows are welded to the valve stem to maintain constant working efficiency and to avoid valve stem vibration caused by valve insert movement.

Benefits of a Bellows Seal Globe Valve

1. The double seal design (bellows + packing) is the most obvious benefit of any bellows valve. As a result, even if the bellows fail, the stem packing will prevent any leakage and fulfill international sealing requirements.
2. It decreases medium fluid loss while also ensuring safety and environmental protection. This will finally increase the plant’s safety where the bellows valve has been put.
3. It may help to reduce energy losses due to leakage, making it an energy saver.
4. Because leakage is reduced, the valve does not need to be serviced as often. As a result, valve life is extended.
5. Because of the extended service life, operating and maintenance costs are significantly decreased.
6. The tough bellows seal construction assures no leaking from the valve stem, resulting in maintenance-free circumstances.
7. The installation of a bellows valve improves the safety of workers by reducing emissions of flammable, poisonous, and dangerous substances.

Bellows Selection Guide

• Determine the inner diameter of the bellows based on the diameter of the valve stem. The inner diameter of the bellows should be larger than the 115 mm stem diameter.
• The outer diameter of the bellows is chosen based on the inner diameter of the bellows. The outer diameter and inner diameter are connected by the outer diameter to inner diameter ratio. In general, the outer diameter to inner diameter ratio is 113 to 115.
• The wall thickness, number of layers, number of corrugations, and length of the corrugated pipe must match the pressure resistance, stroke, and cycle life criteria. Under normal conditions, the higher the pressure, the bigger the thickness of the bellows. The thickness of the single layer may be lowered and the number of layers of the bellows can be increased to enhance displacement or reduce stiffness and increase life.
• The multiple designs bellows are suggested for managing larger pressures. The pressure that the bellows can sustain may be enhanced by utilizing two or three metal wall piles, as in the case of multiple designs of bellows. The pressure rating of a two-ply bellow may be increased by 80% to 100% when compared to a single-ply bellow of the same thickness. Alternatively, if a single-ply bellow with a thickness equal to the pressure rating of a two-ply bellow is employed, the stroke length is lowered. As a result, the multiple designs have a clear advantage over the single-ply thick bellows.

Bellows Selection Guide

1. Determine the inner diameter of the bellows based on the diameter of the valve stem. The inner diameter of the bellows should be larger than the 115 mm stem diameter.
2. The outer diameter of the bellows is chosen based on the inner diameter of the bellows. The outer diameter and inner diameter are connected by the outer diameter to inner diameter ratio. In general, the outer diameter to inner diameter ratio is 113 to 115.
3. The wall thickness, number of layers, number of corrugations, and length of the corrugated pipe must match the pressure resistance, stroke, and cycle life criteria. Under normal conditions, the higher the pressure, the bigger the thickness of the bellows. The thickness of the single layer may be lowered and the number of layers of the bellows can be increased to enhance displacement or reduce stiffness and increase life.
4. he multiple designs bellows are suggested for managing larger pressures. The pressure that the bellows can sustain may be enhanced by utilizing two or three metal wall piles, as in the case of multiple designs of bellows. The pressure rating of a two-ply bellow may be increased by 80% to 100% when compared to a single-ply bellow of the same thickness. Alternatively, if a single-ply bellow with a thickness equal to the pressure rating of a two-ply bellow is employed, the stroke length is lowered. As a result, the multiple designs have a clear advantage over the single-ply thick bellows.

Conclusion

The Bellows Seal Globe Valve’s distinctive design and efficiency in providing leak-proof operations make it the best-suited valve for a broad variety of applications, particularly hazardous compounds and when system media is at high temperatures. Bellows valves have the extra advantage of being durable, maintenance-free, and cost-effective. GMK Valve is a professional bellow seal valve manufacturer; please contact us if you have any questions.