Masoneilan 21000 BS Bellows Seal Top-Guided Globe Control Valve

Overview

The Masoneilan 21000 BS is the bellows seal version of the Baker Hughes Masoneilan 21000 Series top-guided globe control valve. In the 21000 numbering system the suffix BS stands for Bellows Seal, and the configuration replaces the dynamic stem leak path of a conventional packing box with a formed metal bellows that moves with the plug stem. Baker Hughes states that the bellows seal configuration is fully compatible with the standard 21000 trim and actuator options and provides equivalent capacity for each valve size, so an engineer can keep the same Cv, noise and cavitation choices and simply change the stem seal.

As the official trusted supplier of Masoneilan in the Sultanate of Oman, Seven Star LLC supplies the Masoneilan 21000 BS to refineries, petrochemical plants and gas facilities in the GCC that must hold fugitive emissions at or near zero. Our valve team in Muscat will confirm the bellows material, the bonnet design and the actuator coupling against the fluid and pressure before an RFQ is raised, because those three items decide how long the bellows will last in service.

Why a Bellows Seal on the Masoneilan 21000 BS

Any control valve with a sliding stem relies on packing to keep process fluid inside, and packing slowly wears and relaxes. Baker Hughes positions the Masoneilan 21000 BS for applications involving highly toxic and dangerous fluids, where positive sealing and long operating life matter more than the lowest purchase price. The bellows is the primary stem seal. The standard packing box and packing options of the 21000 Series remain in the valve as a secondary stem seal, so a single failure of the bellows does not open a direct path to atmosphere.

The formed bellows of the Masoneilan 21000 BS is an externally pressurized design that is capable of operating up to the full valve ANSI B16.34 pressure rating. Guides are located above and below the bellows, which gives the assembly the stability to withstand flow-induced and mechanical vibration. Pressure on the outside of a bellows holds the convolutions together, whereas pressure on the inside would try to elongate them, and this is why external pressurization is the robust arrangement for a control valve that must stroke thousands of times.

Bonnet-Less and Bonnet Designs of the Masoneilan 21000 BS

The technical specification describes two constructions. The bonnet-less design, which Baker Hughes describes as newly re-designed, covers globe control valves up to 4 inch (DN 100). It integrates the bonnet directly into the bellows assembly, reduces the number of parts and minimizes potential leak paths, and its materials tables list a bonnet spud (B003) and an extended bonnet (B007) in place of the plug stem and bonnet of the standard valve. For the larger 6 inch size the Masoneilan 21000 BS uses the bonnet design, in which the bonnet extension is an assembly of an upper flange, a spacer tube and a lower flange held together by a spacer gasket, studs and nuts.

In both versions of the Masoneilan 21000 BS the stem carries anti-rotation flats so that the bellows is not twisted, and mechanical travel stops are designed into the bellows and valve assemblies to prevent over compression or extension. The bellows of the Masoneilan 21000 BS is designed for 50 percent compression and 50 percent extension, a zero-stress condition, at the valve mid-stroke position, which Baker Hughes identifies as the way to maximize cycle life. Each bellows sub-assembly is helium leak tested to verify weld integrity and the complete valve is hydrostatically tested.

Cycle Life, Stroke and Ratings of the Masoneilan 21000 BS

The design stroke of the bellows depends on the valve size: 0.75 inch (19 mm) for 3/4 to 2 inch valves, 1.50 inch (38.1 mm) for 3 and 4 inch valves and 2.00 inch (50.8 mm) for the 6 inch valve. Baker Hughes publishes a minimum expected average cycle life for a Class 300 (PN 50) bellows operating at constant pressure of 100,000 cycles at 100 percent of the design stroke, 600,000 cycles at 50 percent and 3,000,000 cycles at 25 percent. The practical message for the Masoneilan 21000 BS is that a bellows in a valve that makes small corrections around a stable position lasts far longer than one that cycles over the full stroke, so loop tuning matters.

The pressure ratings of the Masoneilan 21000 BS are ASME Class 150 and Class 300 (PN 20 and PN 50), and the standard bellows seal construction is listed for capacities of Cv 1.7 and higher. The weight table states that the bellows seal series is limited to Class 150 to 300. Applications of the Masoneilan 21000 BS above Class 300 are referred to the factory. The bellows can be monitored in the field: Baker Hughes notes that the installed cycle life can be tracked with a Masoneilan SVI digital positioner using actual process data, which helps plan replacement before a failure and avoids premature replacement of a healthy bellows.

Bellows Materials and Construction

The standard bellows material is 316 and 316L stainless steel, and the specification lists the bellows as 316Ti stainless steel with annealed 316L adapters in the standard assembly. Optional bellows and stem assemblies for the Masoneilan 21000 BS are available in Hastelloy C276, Monel 400 (ASTM B164 Class A, UNS N04400) and Inconel 625 (ASTM B446, UNS N00625), which allow the Masoneilan 21000 BS to handle chloride, acid or high temperature fluids that attack stainless steel. Bodies are offered in carbon steel and stainless steel versions, with the bonnet extension in ASTM A216 WCC or WCB, ASTM A352 LCC for low temperature, or ASTM A351 CF8M for stainless steel. The packing is carbon core braided PTFE, the O-ring is Viton-A and the temperature table runs from -50°F (-46°C) up to 800°F (427°C), depending on the material.

Maintenance and Dimensions

The Baker Hughes instruction manual treats the Masoneilan 21000 BS in two dedicated sections. If the plug of a Masoneilan 21000 BS needs replacing, the stem-bellows sub-assembly (B124) must be replaced at the same time, and the technician is warned that the bellows creates a spring back effect that must be measured and added to the over-seat adjustment of the 87/88 actuator. The bonnet spud is tightened with a torque of 55 daN.m (405.7 ft-lb, tolerance 10 percent) for 3/4 to 4 inch valves in Class 150 and 300, and the bellows bonnet assembly uses eight studs tightened to 20 to 30 lb-ft for 1/2 inch studs or 25 to 55 lb-ft for 5/8 inch studs. A No. 6 actuator fitted on a bellows valve needs a three-sectioned coupling.

The additional height of the Masoneilan 21000 BS bellows is visible in the dimension tables. Dimension C of the bellows bonnet is 13.15 in for the 3/4 to 2 inch valves, 24.76 in for the 3 inch, 24.85 in for the 4 inch and 43.85 in for the 6 inch valve. The bellows seal assembly adds an estimated 6 lb (3 kg) for 3/4 to 2 inch valves, 17 lb (8 kg) for 3 and 4 inch valves and 73 lb (33 kg) for the 6 inch valve.

Key Features

The following points summarise the strengths of the Masoneilan 21000 BS, a valve built for low-leakage service:

• Welded metal bellows acts as the primary stem seal, with the standard packing box retained as a secondary seal.
• Externally pressurized formed bellows is capable of operating up to the full ANSI B16.34 valve pressure rating within the Class 150 and 300 limit.
• Bonnet-less design up to 4 inch with fewer parts and fewer potential leak paths, and a bonnet design for the 6 inch valve.
• Designed for 50 percent compression and extension at mid-stroke, with anti-rotation flats on the plug stem.
• Each bellows sub-assembly is helium leak tested and the whole valve is hydrostatically tested.
• Rated cycle life of 100,000 cycles at full stroke and up to 3,000,000 cycles at 25 percent stroke for a Class 300 bellows.
• Bellows in 316/316L stainless steel, with Hastelloy C276, Monel 400 and Inconel 625 options.
• The {K} is compatible with standard 21000 trim, Lo-dB and anti-cavitation options and actuator choices; bellows cycle life can be monitored with an SVI positioner.

Industrial Applications

The Masoneilan 21000 BS suits services where leakage to atmosphere is unacceptable or where the cost of fugitive emissions is high: hydrocarbons with benzene content, hydrogen sulfide bearing streams, chlorine and acid duties, heat transfer fluids, hydrofluoric alkylation and any toxic fluid that would require a vapor recovery or leak-off system on a packed valve. In Oman these services appear in the refining and petrochemical complex at Sohar, in gas processing plants in the interior and in the chemical industries of Salalah.

In Oman and the GCC, Seven Star LLC supplies the Masoneilan 21000 BS in all of its bellows materials and bonnet designs to operators and contractors in Oman and across the GCC. Spares for the standard packed 21000 are listed on the Masoneilan 21000 Series seal kit page, while the smaller Masoneilan 28000 Series Varipak valve is also built in a bellows seal version. A Masoneilan SVI3 digital valve positioner can be added for positioning.

Technical Specifications

The table below summarises the principal published data of the Masoneilan 21000 BS from the Baker Hughes 21000 Series technical specification and instruction manual. Please confirm complete data against the official documents.

The family overview, including trim options, is on the Masoneilan 21000 Series top-guided globe control valve page.

Request a Quote for Masoneilan 21000 BS

Engineers and procurement teams in Oman and across the GCC can send Seven Star LLC a formal RFQ for the Masoneilan 21000 BS with the fluid, pressure, temperature, expected stroke range and emission requirement stated, so that the bellows material, bonnet design and actuator can be confirmed. Regional availability is checked, and the Baker Hughes technical specification and instruction manual can be downloaded from this page. In Oman and the GCC, we back every valve with manufacturer documentation and local support from our Muscat instrumentation division.