If you want to know about valves or if your job includes these valves, then you are at the right place. Valves are the devices that control fluid flow, including liquids, gases, or any other. In mechanical engineering, these valves are of great importance. These valves are used to manage the moving element in a safe direction or the direction you want.
How bellow valves work
Bellow works like a vertical diaphragm and resembles the hollow flexible hose. These valves are sealed with a valve stem at one end while the valve body is at the other. So, this structure allows a little movement between the valve stem and the valve body. It also helps to prevent fluid leakage out of the bellow surface. The seat or stem tip closes or opens by moving the push.
The valve feature includes the bellow cartridge component and is welded to the valve stem and bonnet. The bellows compress or expand during the valve stroke, along with the sliding stem’s linear motion, with little to no friction.
Potential Failure and Troubleshooting
| Fault | Possible reason | Remedy |
| No flow | 1. Valve closed 2. Flange dust caps were not removed | 1. Open the valve 2. Remove dust caps on the flanges |
| Poor flow | 1. Valve is not open enough 2. Dirty filter 3. Clogged pipeline | 1. Open the valve 2. Clean or replace the screen 3. Check the pipeline |
| Control difficulties | 1. Dry stem 2. Gland packing tightens too much | 1. Grease the stem 2. Slightly slacken gland nuts. Put attention to keeping the stuffing box tightness |
| Stem leakage | 1. Bellow damage | 1. Tighten the gland until tightness is reached. Replace the upper part of the valve as soon as possible. |
| Seat leakage | 1. Shut off not correct 2. Seat or disc damage 3. A pressure difference is too much 4. Medium polluted with solid particles | 1. Tighten the hand wheels without any auxiliary tools 2. Replace the valve and contact the supplier or manufacturer 3. Apply valve with balancing disc. Check if the valve was assembled according to the arrow direction marked on the valve. 4. Clean the valve. Fit strainer before the valve. |
| Broken connecting flange | 1. Bolts tighten unevenly | Replace the valve with a new one |
Bellow types
There are two main types of bellows:
- The Forged Bellow
- The Welded Bellow
Formed-type bellows are made from rolling a flat sheet. Then these thin wall foils are turned into a tube and are then longitudinally fusion welded. This foil tube is mechanically or hydrostatically turned into a bellow with round and widely spaced folds. The welded leaf type below is made by welding washer-like plates of thin metal together at the inner and outer circumference of the washer-like plates.
A welded leaf bellow valve has more folds per unit length than forged bellows. Thus forged bellows are two to three times longer than their welded leaf counterparts for the same stroke length,
Mechanically forged bellows fail at random spots, so it is not safe to use, while the welded leaf fails near a weld. To ensure complete penetration of bellows ends and end coller welding, it is advisable to fabricate using micro plasma welding.
Difference between Metallic Bellows And-Non-Metallic Bellows
Metal bellows vs. Non-metal bellows
Many below designing specifications define the significant differences between the two products. Let’s look at how to check different bellows and ultimately choose the right one.
This article explains the difference between single or multiple flexible metallic bellows and non-metallic bellows.
An expansion joint is used in piping systems and prevents it from being crushed. But among the two, which bellow valve is best for any industrial-specific application? Let’s first understand the two types of these valves; what are these:
Metal Bellows
It is made up of flexible elements (bellows) designed with a relatively thin gauge. It can compress when pressure is applied from outside the vessel, generally formed of stainless steel. These valves are designed to absorb any thermal and mechanical movements expected in service.
Non-Metallic Bellows
These valves are highly flexible connectors formed of natural or synthetic fabric. These non-metallic bellows and convoluted non-metallic dust boots are versatile seals used in various applications. These are designed to relieve stress in the piping industry for thermal movements and mechanical vibration.
Both the bellows have their utility and importance. If you rate on the scale of Good, better, and best. Among metal bellows and non-metallic bellows, metal bellows with a rugged multiple-layer design are considered the best. Because of their multiple-layer design, these bellows are widely used in various industrial applications in the piping industry. They have been deemed the most reliable and trustworthy for the marine industry for decades.
Purpose of the bellows in valves
Bellows seal valves have been used in piping systems to protect against leakage. If you install it correctly, it minimizes the risk of potentially harmful chemicals causing injury. Below valves also act as a safeguard against illness to workers and damage to the surrounding environment.
Applications
Heat transfer media
Hot oil has been used in industries such as synthetic fibres. However, there is always a fire risk due to burning oil spillage on highly flammable chemicals. Here, bellows Valves can stop the leakage.
Vacuum or ultra-high vacuum
In some areas of application, including extracting air from a pipeline is done by using vacuum pumps. So any valve has a conventional use by installing on pipelines through a valve stuffing box. Controlling bellow valves is best solutions to prevent air passage through the stuffing box.
Highly hazardous fluids
For media such as chlorine, hydrogen, ammonia, and phosgene, the bellow valve is an ideal design as leakage through the gland is eliminated. The nuclear plant, heavy water plant: in instances where radiation leakage is to be prevented at all times, the bellow valve is the ultimate choice.
Costly fluids
In some applications, leaks must be avoided simply because of the high cost of the fluid. Here, an economic assessment often favours the use of bellow valves.
Environmental standards
Standards regarding emissions and the environment worldwide are getting more stringent daily. So, it is difficult for companies to expand within a premise. But these bellow valves allow the expansion without causing any further environmental damage.
Features
The thick-walled PFA lining provides high reliability, universal resistance, and maximum permeation resistance.
Due to heavy-duty bellows, it also provides safety at high pressures and temperatures.
Easy to maintain: seat and plug individually replaceable
Summary
BSGV valves combine helpful user features with latest technologies designed for maximum safety in Demanding applications. Key features (some of which refer to special-use models whose purpose specifically requires that feature), are given below:
- Two-part rising stem with outside roll-formed thread; stem coupling with bellows anti-torque device and position indicator
- Full-size safety gland packing made of pure graphite; optionally can be supplied in PTFE.
- Metal back seat with stroke limiter in the open position and bellows anti vibration device
- Multiple walls, fully flushed stainless steel bellows, secured against torsion, designed for 10,000 cycles.
