Masoneilan 28000 MS Varilog Anti-Cavitation Microflow Control Valve
Overview
The Masoneilan 28000 MS is the Varilog anti-cavitation version of the Baker Hughes Varipak microflow control valve. In the Varipak numbering system the MS suffix marks the anti-cavitation construction, and in the technical specification the valve is described as the 28000 MS Series. It replaces the ordinary contoured plug with a multi-stage axial flow plug and liner so that a very small liquid flow can be let down across a high pressure drop without the erosion and vibration that damage a conventional single-seated microflow valve.
In Oman and the GCC, Seven Star LLC proudly supplies the Masoneilan 28000 MS to refineries, gas plants, chemical injection systems and laboratories across the Sultanate of Oman and the GCC. Our valve team in Muscat can review the fluid, flow rate and pressure drop with you and confirm which Varilog trim number applies before an RFQ is raised.
Why Anti-Cavitation Trim in a Microflow Valve
Microflow control valves, including the Masoneilan 28000 MS, are often used for chemical injection, sampling, fuel metering and pump recirculation, where the flow is measured in fractions of a Cv but the pressure drop can be very large. In that situation liquid accelerates through a tiny restriction, flashes or cavitates, and the collapsing vapour cavities erode the seat and plug. The Masoneilan 28000 MS addresses this by dropping the pressure in several small stages instead of one, which Baker Hughes describes as dirt-tolerant operation with high wear resistance. The Varilog design is used in the same compact body as the standard Varipak and is available with flanged or flangeless connections.
The critical flow factor FL of the Varilog trim is 0.98, which is the practical expression of its multi-stage behaviour: the valve recovers very little pressure at the vena contracta, so the point at which a liquid begins to choke or cavitate is pushed far above that of a conventional trim. The rated Cv range of the Masoneilan 28000 MS is 0.60 down to 0.050 for trim numbers 3 to 6, with a temperature range of -20°F to +650°F (-29°C to +343°C).
Engineering Design of the Masoneilan 28000 MS
Four standard trim numbers define the Varilog capacity. Trim 3 covers adjustable Cv values from 0.25 to 0.60, trim 4 from 0.10 to 0.25, trim 5 from 0.04 to 0.10 and trim 6 from 0.020 to 0.050, and two special Varilog trims are listed with maximum Cv values of 0.007 and 0.034. The actuator of the Masoneilan 28000 MS allows the flow coefficient to be changed in steps by setting a knob, and for the actuator the appendix lists a spring scale of 414 to 1,660 mbar (6 to 24 psi) with a maximum supply of 2.1 bar. Body sizes are the Varipak 1/2, 3/4 and 1 inch (DN 15, 20 and 25).
Materials of the Masoneilan 28000 MS are chosen for hardness. In the stainless steel Varilog construction the valve plug for trim 3 to 6 is cast in Stellite No. 12, the seat ring is type 630 H900 stainless steel, the seat ring retainer is 17-4 PH H1075, the seat ring gasket is Grafoil bonded to 316 stainless steel and the packing is carbon core braided PTFE. A NACE construction to MR 1075 replaces the seat ring and retainer with age-hardened nickel alloy UNS N05500 and limits the temperature to +450°F (+232°C). A circlip in ASTM A564 grade 632 RH950 is listed for the smallest trims, with a maximum Cv of 0.05.
Maintenance and Spare Trim
The Baker Hughes Varilog appendix to the Varipak instruction manual gives the maintenance rules for the Masoneilan 28000 MS that differ from a standard Varipak. The liner, seat ring and plug-stem assembly form a matched set, so if one part is damaged the others must also be replaced; they are supplied as a kit with the seat ring gasket and circlips. The seat ring retainer is tightened to 8 daN.m (59 ft-lb) using a tube with two diagonally opposite lugs, and for Cv values up to 0.034 the packing rings and packing washer are removed first with an extracting tool. Between Cv 0.034 and 0.60 the procedure matches the Varipak with Cv max up to 0.10.
Key Features
The following points summarise the strengths of the Masoneilan 28000 MS:
- Multi-stage axial flow plug and liner give anti-cavitation performance in very low flow applications.
- Critical flow factor FL of 0.98 keeps pressure recovery low and delays cavitation.
- Rated Cv from 0.60 to 0.050 across trim numbers 3 to 6, plus two special trims at 0.007 and 0.034.
- Dirt-tolerant design with high wear resistance, according to Baker Hughes.
- Stellite No. 12 plug and 630 H900 stainless steel seat ring resist erosion at high pressure drop.
- Available with the flanged or flangeless Varipak bodies in sizes 1/2, 3/4 and 1 inch.
- NACE MR 1075 construction is offered for sour service up to +450°F.
- Replacement trim is supplied as a matched kit including gasket and circlips.
Industrial Applications
The Masoneilan 28000 MS is the right Varipak configuration where a small liquid stream drops through a large pressure difference: methanol and corrosion inhibitor injection at wellheads and pipelines, hydrocarbon sampling skids, boiler chemical dosing and high-pressure pump minimum-flow bypass. In Oman, duties of this type arise in oilfield and gas processing facilities, in the refinery and petrochemical area at Sohar and in utility plants along the Batinah coast.
In Oman and the GCC, Seven Star LLC supplies the Masoneilan 28000 MS to EPC contractors and plant operators in Oman and the GCC, including the Sohar and Salalah economic zones. The standard Masoneilan 28000 Series Varipak valve remains the choice for clean services without cavitation, the 28000 Varipak seal and O-ring kit supports routine maintenance, and the Varipak accessory list names HART and Fieldbus digital positioners such as the Masoneilan SVI3 digital valve positioner.
Technical Specifications
The table lists the Varilog data published for the Masoneilan 28000 MS in the Baker Hughes Varipak technical specification (Rev. C, 12/2025) and in the Varilog appendix to the instruction manual. The official documents carry the full dimension drawings and parts lists.
| Parameter | Specification |
|---|---|
| Model | Masoneilan 28000 MS (Varipak with Varilog anti-cavitation trim) |
| Valve sizes | 1/2, 3/4 and 1 in (DN 15, 20 and 25) |
| Rated Cv range | 0.60 to 0.050 (trim numbers 3 to 6) |
| Adjustable Cv by trim | Trim 3: 0.25 to 0.60; trim 4: 0.10 to 0.25; trim 5: 0.04 to 0.10; trim 6: 0.020 to 0.050 |
| Critical flow factor FL | 0.98 |
| Temperature range | -20°F to +650°F (-29°C to +343°C); NACE: to +450°F |
| Plug and seat | Stellite No. 12 plug (trim 3 to 6); 630 H900 seat ring; 17-4 PH H1075 retainer |
| Packing | Carbon core braided PTFE |
| Seat leakage | Class IV standard, Class V optional |
| Seat ring retainer torque | 8 daN.m (59 ft-lb) |
| Actuator spring scale | 414 to 1,660 mbar (6 to 24 psi), maximum supply 2.1 bar |
| Face to face, flangeless | 4.02 in (102 mm) |
| Removal clearance | 5.5 in (140 mm) |
For larger low-noise and anti-cavitation duties see the Masoneilan 49000 Series V-LOG anti-cavitation valve.
Request a Quote for Masoneilan 28000 MS
To request a quotation for the Masoneilan 28000 MS, send Seven Star LLC the fluid, flow rate, inlet and outlet pressure and operating temperature, so that the Varilog trim number and Cv can be matched to the published ranges. Our Muscat instrumentation division checks availability and lead time, and the technical specification and Varilog appendix manual are provided for download on this page. Seven Star LLC is the trusted supplier for Masoneilan in Oman and the GCC, and each valve ships with Baker Hughes documentation and local technical support.
Masoneilan control valves and actuator series
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For spare parts the serial number is decisive, since the factory record behind it lists trim, materials and actuator. Send a clear nameplate photo with serial number, model number, size and pressure class. For a new valve add the process data: fluid, inlet and outlet pressure, temperature, minimum, normal and maximum flow, required leakage class, fail position, air supply and control signal.Browse Masoneilan products by category: Control Valves, Valve Actuator, Regulators, Valve Positioner, Level Transmitter.
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