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Nowadays, the once-inconspicuous ball valve is recognised as a separate valve category from linear and rotary valves. A spherical plug valve was initially used in the 1950s, however, a different name was in use at the time of its introduction.
Since the 1950s, ball valves have become increasingly common due to the availability of various ball and seat materials, as well as the development of machinery capable of accurately producing the ball’s spherical polished surface. The use of these valves has been broadened in recent years due to the development of new seat materials and the introduction of metal seats fabricated from low-wear materials, which have proven particularly useful in applications involving abrasive and high-temperature media.
Ball Valves can have a variety of connection types, including flanged, socket welded, butt welded, and screwed.
Ball valves’ widespread adoption can be attributed to their adaptability; they can be used for a wide range of services, from the relatively mild (water, solvents, acids, and natural gas) to the quite harsh (oxygen, hydrogen peroxide, and other gases). PTFE Lined Ball Valves manufactured by the most popular as well as reliable PTFE Lined Ball Valves manufacturer, are used in a variety of heavy Industrial applications.
Ball valves are often made with a body made of carbon steel (WCB or LCB) and a ball and shaft made of stainless steel (316 or CF8M). The body can be constructed out of stainless alloys for use in low/high-temperature environments or when corrosion is a concern.
Because of it being chemically inert to various fluids and having a low coefficient of friction (less than 0.1), PTFE (Polytetrafluoroethylene) is typically used as the seat material in ball valves.
PTFE Lined Ball Valves manufacturer in India will typically include a pressure/temperature curve to indicate the maximum safe operating temperature and pressure for the valve given that PTFE softens when heated.
Special Nylons, Polyetheretherketone (PEEK), and powder-filled PTFEs are utilised to increase stiffness over the seating face and maximum service temperature beyond what is possible with regular PTFE. Ball valves with metal seats are mandatory above 280°C.
By pressing the ball seats together, the ball is kept in place in this configuration between two ball seats. A shaft that is attached to a slot on the top of the ball drives the ball in order to turn it 90° or quarter turns. Due to the effect of upstream line pressure, the ball can slide a little to the side in the slot. According to the floating ball valve design principle, the downstream seat is always thought of as the principal seat because it is loaded by line pressure. If the upstream seat design includes pre-loading or spring, it may occasionally additionally provide a secondary seal.
The ball in this design is held in place by a trunnion rather than the valve seats, resulting in much-increased pressure and temperature ratings. The idea is to have the trunnion and shaft function as a single unit. To keep the ball from bouncing off the downstream seat, the shaft and trunnion are kept in bearings. The major seat in a trunnion-mounted ball valve is located on the upstream side because this is where the seat is most easily loaded, as it can slide forward against the ball. A spring mechanism is incorporated behind both seats to create a supplementary seal on the downstream side and to provide even seat loading even at low pressures. Trunnion-mounted ball valves have the same bidirectional shutoff capabilities as floating ball valve designs. Trunnion-mounted ball valves offer several advantages over their floating counterparts, the most notable of which being a reduction in operating torque and, by extension, actuation costs.
The ball is inserted into the body via an opening in one of the pipe flanges and sealed with a gasket that is integral to the upper face. This maximises resistance and prevents weak points.
The body of this valve is split in one or two places along the same plane as the valve flanges, giving it the alternate names of 2-piece and 3-piece ball valves. The ball is then secured to the body with bolts. Due to the lighter weight of the components, trunnion-mounted ball valves are more frequent in smaller sizes than their one-piece counterparts, and three-piece ball valves are widely used for these applications. The biggest benefit of split body ball valves is how simple they are to maintain.
An unusual feature of this valve is that the ball enters the valve via a bonnet located above the valve’s opening. The key benefit is that the valve may be maintained without having to remove it from the pipeline. It is frequently utilised in piping systems that include welding.
The valve body in this case is of welded construction and cannot be serviced in any way. These are commonly utilised in gas transmission lines.
Tsuyoshi Kaneko, MD (left), Sary Aranki, MD (center), and Sameer A. Hirji, MD (right)
Central Message
The engineering prowess and creativity with the Starr-Edwards mitral valve has been revolutionary. In many ways, it ushered the modern era of valve surgery.
See Article page e147
1Mechanical heart valves: 50 years of evolution.
2Aortic valve replacement with a caged ball valve.
3Mitral replacement: clinical experience with a ball-valve prosthesis.
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Significant advances have been made during the last half century in the design of mechanical valves. The 1960s, especially, was a significant period in terms of valve innovation and development. Ball valves were first implanted in the descending thoracic aorta by Hufnagel and colleagues (circa 1950s).Harken and colleagueslater, in the early 1960s, implanted the caged ball valve in a subcoronary position. It was not, however, until a retired pump engineer, Miles Edwards, and a young cardiac surgeon, Albert Starr, designed the Starr-Edwards (SE) ball-in-a-cage mitral valve (MV), with promising initial results.SE MV design initially began with the poly(methyl methacrylate) cage design and was later refined into the cobalt-chromium alloy cage design with cloth-covered valve orifice and bare metal struts. Valve design and development progressed remarkably with the advent of the tilting single-disc design to the contemporary bileaflet design, which led to the extinction of the SE valves after discontinuation of their production in 2007.
4Explant of a ball and cage valve 42 years after initial implant.
5Thirty-year results of Starr-Edwards prostheses in the aortic and mitral position.
, 6A case of the Starr-Edwards ball valve (model 6120) in the mitral position for 45 years.
, 7Patient lives almost 50 years after aortic valve replacement with a Starr-Edwards caged-ball valve.
, 8Transcatheter treatment of Starr-Edwards paravalvular leaks.
In this issue of the Journal, Battaglia and colleaguesreport an interesting case of a patient whose SE MV had been implanted 42 years previously (1974) for rheumatic mitral stenosis. Impressively, the patient denied any significant thrombotic or hemorrhagic complications and had only had dyspnea and fatigue develop 2 years previously. Transthoracic echocardiography showed mildly elevated transvalvular gradients with early-onset pulmonary hypertension, tricuspid regurgitation, and right heart dysfunction. At surgery, extensive pannus formation and mitral annular calcification were noted, which necessitated decalcification. Replacement of the SE valve with a 25-mm bileaflet valve, concomitant biatrial cryomaze, and tricuspid repair with a 27-mm Duran band (Medtronic Inc, Minneapolis, Minn) was performed. The patient demonstrated extreme diligence in managing her anticoagulation, which also likely helped to avoid any hemorrhagic and thromboembolic complications such as are often reported with the SE MV.
5Thirty-year results of Starr-Edwards prostheses in the aortic and mitral position.
, 6A case of the Starr-Edwards ball valve (model 6120) in the mitral position for 45 years.
, 7Patient lives almost 50 years after aortic valve replacement with a Starr-Edwards caged-ball valve.
, 8Transcatheter treatment of Starr-Edwards paravalvular leaks.
9Reoperation on a Starr-Edwards ball valve without structural deterioration.
More than half a million SE valves were implanted globally between 1960 and 2007, with 300,000 implanted during the last 7 years of its production (company data). Although lower survivals at 30 years with the SE valves have been reported, recent case reports have demonstrated durability beyond 30 and even 40 years.The observation that many patients still have these valves warrants accurate assessment by clinicians caring for these patients. Accurate assessment of pressure gradients across an SE valve is difficult because of the unique (noncentral) flow pattern. Likewise, pannus formation is challenging to visualize on transthoracic echocardiography,which may also influence treatment decisions. Timing of reoperative mitral surgery in the setting of SE MVs, although arguable, should be based on coexisting symptoms of pulmonary hypertension or right heart failure.
Can the ball-in-a-cage valve make a comeback? This is very doubtful for surgical implants. Perhaps one day, however, a catheter-based mechanical valve may be based on a cage design with a collapsible ball that could be deployed percutaneously. After all, who would have imagined 10 years ago that bioprosthetic transcatheter valve replacement would become an established reality? For now, it is safe to say that the ball has left the cage.
Disclosures: Authors have nothing to disclose with regard to commercial support.
DOI: https://doi.org/10.1016/j.jtcvs.2018.01.009
© 2018 by The American Association for Thoracic Surgery
Elsevier user license
The Journal of Thoracic and Cardiovascular Surgery
Vol. 155
Issue 5
Open Archive
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