Differences between Ordinary Globe Valves and Bellow Seal Globe Valves
A bellow seal valve has a compact structure and is one kind of control valve to balance the pressure. Bellows are used as the valve stem sealing components of the bellow seal valves.
To avoid the leakage of the valve stem, the valve adopts the structure with bellows instead of stuffing boxes generally used for the ordinary valve or the structure with both bellows and stuffing boxes.
The bellow seal valve is particularly suitable for pipelines of steam and flammable, explosive and hazardous media. Moreover, because of bellow’s properties of deformation and aging resistance, the bellow seal valve overcomes the common latent defects, including temperature sensitivity and the aging of the stuffing box, and these defects are owned by the valve sealed by packing.
A bellow seal globe valve is operated as an obstruction between fluids and the air. At the same time, the valve can prevent fluids leaking to the air and guarantee zero leakage of pipelines.
The bottom of bellows are welded to the valve stem of the bellow seal globe valve to avoid process fluids eroding the valve stem. At the same time, the other side of bellows form static seal between the valve body and the bonnet.
With the double seal structure, the bellow seal globe valve can avoid leakage due to the packing of valve stem even if bellows are broken. The structure that bellows is welded to the valve stem guarantees stable working performance and can avoid the vibration of the valve stem caused by the vibration of the valve plug.
In general, the bellow seal globe valve is damaged due to the mechanical squeeze instead of the operation during manufacturing. The globe valve has bellows with various coatings and different grades of elasticity. However, all these bellow seal globe valves have similar wear and tear, which can not be seen from outside and resulted from the adhesion of particles and the surface corrosion owing to media inside the valve. Thus, in daily practice, bellows are required to be replaced before their operation lives end.
Characteristics of bellow seal globe valves
No loss of fluids, better security of the factory’s equipment
Long operating life with less maintenance and fewer operating costs
Durable sealing structures without leakage
Differences between ordinary globe valves and bellow seal globe valves
The bellow seal globe valve has superior sealing performance and is more efficient to guarantee the security of pipelines with hazardous media than the ordinary globe valve does.
The original globe valve is sealed by packing and has the valve stem not in tight contact with packing, causing high leak rates under low temperatures.
Instead of the packing, bellows with good tension and compression properties can be used for the bellow seal globe valve to ensure good sealing performance.
The bellow globe valve, in general, is used for pipelines of permeable media such as ammonia since the pipeline will leak only if bellows of thebellow seal globe valve are broken. At the same time, however, the ordinary globe valve sealed by packing shows worse sealing performance.
Source: China Globe Valves Manufacturer – Yaang Pipe Industry (www.steeljrv.com)