Masoneilan 525-526 Series Double-Seated Pressure Regulator
Overview
The Masoneilan 525-526 Series is a family of double-seated, globe-style pressure regulators from Baker Hughes for steam, gas and liquid service. Model 525 is the pressure reducing version, which holds a steady downstream pressure, and Model 526 is the back pressure version, which holds a steady upstream pressure. Each member of the Masoneilan 525-526 Series can be ordered with the -50 option (525-50 and 526-50) to control a differential pressure instead of a gauge pressure. All four functions share one body design and are driven by the 10900 Series spring-diaphragm actuator, so a single valve platform covers reducing, back pressure and differential duty across body sizes from 3/4 inch to 4 inch (20 to 100 mm).
In Oman and the GCC, Seven Star LLC proudly supplies the Masoneilan 525-526 Series to plant owners, EPC contractors and maintenance teams in the Sultanate of Oman and across the GCC. Our instrumentation division in Muscat helps engineers translate a pressure, flow and fluid data sheet into the right body size, trim, actuator size and spring range, and every order is supported with genuine Masoneilan documentation and regional service.
Operating Principle of the Masoneilan 525-526 Series
The Masoneilan 525-526 Series is a direct-operated regulator: no positioner, air supply or electronic loop is needed. The controlled pressure is piped from the process to the diaphragm case of the 10900 actuator, where it acts against an adjustable spring. In the 525 reducing model, the spring holds the plug open and an increase in the controlled downstream pressure above the set point pushes the diaphragm against the spring and closes the plug. In the 526 back pressure model the controlled point is upstream of the valve, so the same balance of diaphragm force and spring force opens the plug when upstream pressure rises above the set point and lets it close as the pressure falls back.
On the Masoneilan 525-526 Series, the -50 differential option uses a different actuator arrangement so that two pressures act on opposite sides of the diaphragm. The regulator then maintains one pressure above or below a reference pressure by an adjustable amount, which suits duties where one pressure must be held a set amount above a reference pressure. In every variant the set point is fixed by compressing the actuator spring, and the available spring ranges run from 0.5 to 2 psi (0.03 to 0.14 bar) on the largest 11 inch actuator up to 400 to 750 psi (27.6 to 51.7 bar) on the 3-1/2 inch high-pressure actuator.
Engineering Design of the Masoneilan 525-526 Series
The distinguishing feature of the Masoneilan 525-526 Series is its double-seated, top and bottom guided plug. Baker Hughes describes this as a well-accepted industry arrangement that gives the plug strong support against side loads, and it delivers contemporary double-seated capacity with very little pressure recovery, indicated by a high critical flow factor. A 0.4 factor reduced-capacity trim is available as the most practical way to reduce capacity substantially while keeping desirable flow characteristics. The plug is a disc type with a threaded seat ring, and the standard trim is 316 stainless steel, with a hardfaced 316 stainless steel option for high pressure drop duty. The plug characteristic is quick opening.
The Masoneilan 525-526 Series offers flanged end connections to ASME Class 150, 300 and 600, ISO PN 20, 50 and 100 and EN PN 16, 25 and 40, with socket weld and NPT threaded ends for sizes up to 2 inch. Body materials are carbon steel and stainless steel. For process temperatures above the rating of the diaphragm material, an extension bonnet (EB) is available and the regulator is mounted with the actuator below the body centreline so a condensate barrier in the sensing line and diaphragm case protects the diaphragm. Bonnet packing is carbon core with PTFE jacketing, and the manual states standard Class II seat leakage.
Key Features
The following characteristics make the Masoneilan 525-526 Series a practical choice for process pressure control:
- Top and bottom guiding of the double-seated plug supports the plug against side loads and keeps it stable across its stroke.
- High flow capacity with low pressure recovery lets the regulator pass large flows through a comparatively small body.
- Reduced-capacity trim with a 0.4 factor allows the regulator to be matched to lighter duty without changing body size.
- Four functions, pressure reducing, differential pressure reducing, back pressure and differential back pressure, are available on the same body.
- Body sizes of 3/4, 1, 1-1/2, 2, 2-1/2, 3 and 4 inch cover rated Cv values from about 3.6 up to 125.
- Materials of construction are selected for long life under high pressure drop, including hardfaced trim options.
- High-temperature mounting guidance and an extension bonnet protect the actuator diaphragm in hot steam service.
- The 10900 actuator range includes high-pressure versions with a maximum static allowable pressure of 1,500 psi (103.4 bar).
Industrial Applications
The Masoneilan 525-526 Series is typically specified where a robust, self-acting regulator is preferred to a full control loop: steam pressure let-down to process headers, gas and instrument-air header regulation, liquid pressure holding on pump discharge lines, and back pressure control on vessels, separators and relief headers. In Oman these needs arise in district cooling plants, desalination and RO trains in Muscat and Salalah, refinery utility systems, and the manufacturing and logistics zones around Sohar, where steam, condensate and process water must be held at a steady pressure with minimal maintenance.
In Oman and the GCC, Seven Star LLC supplies the Masoneilan 525-526 Series together with related regulators such as the Masoneilan 172 Series pressure reducing regulator and the Masoneilan 174 Series regulator for smaller flows, and with the Masoneilan 10000 Series double port valve when a fully instrumented control valve is required. Our team can advise which model suits each duty and whether the Masoneilan 525-526 Series is the right fit and can plan the spare parts that go with it.
Technical Specifications
The table below summarises the main Masoneilan 525-526 Series datasheet data as published in the Baker Hughes technical specification. Please consult the official datasheet for capacity tables, spring ranges and dimensions.
| Parameter | Specification |
|---|---|
| Model | Masoneilan 525 (pressure reducing), 525-50 (differential pressure reducing), 526 (back pressure), 526-50 (differential back pressure) |
| Service | Steam, gas, liquids |
| Body type | High-capacity globe, double seated, top and bottom guided plug |
| Sizes | 3/4, 1, 1-1/2, 2, 2-1/2, 3, 4 inch (20, 25, 40, 50, 65, 80, 100 mm) |
| End connections | Flanged ASME Class 150, 300, 600 (ISO PN 20, 50, 100; EN PN 16, 25, 40); socket weld and NPT up to 2 inch |
| Body material | Carbon steel, stainless steel |
| Trim | Disc plug, threaded seat ring; 316 stainless steel standard, hardfaced option; full area or 0.4 factor reduced capacity |
| Characteristic | Quick opening |
| Bonnet | Bolted standard; extension bonnet (EB) optional |
| Actuator | 10900 Series spring-diaphragm |
| Rated Cv | Approximately 3.6 to 125, depending on size and trim |
Face-to-face dimension and body weight by size
| Size | Face to face, Class 150 RF (mm) | Body sub-assembly weight, threaded or socket weld / Class 150 flanged (kg) |
|---|---|---|
| 3/4 inch (20 mm) | 184 | 18 / 36 |
| 1 inch (25 mm) | 184 | 20 / 39 |
| 2 inch (50 mm) | 254 | 23 / 68 |
| 4 inch (100 mm) | 353 | 87 / 138 |
Single-model pages for this family are the Masoneilan 525 pressure reducing regulator and Masoneilan 526 back pressure regulator.
Related Masoneilan pressure regulators include the Masoneilan 535H-536H Series single-seat regulator, Masoneilan 173 Series back pressure regulator and Masoneilan 535V Series microflow regulator.
Request a Quote for Masoneilan 525-526 Series
To request pricing or technical support for the Masoneilan 525-526 Series, send a formal RFQ to the Seven Star LLC instrumentation division with your fluid, inlet and outlet pressures, flow rate and end connection requirements. We confirm size, trim and spring range against your data, advise on regional warehouse availability and provide the Baker Hughes technical datasheet for download from this page. In Oman and the GCC, Seven Star LLC delivers genuine products with manufacturer documentation and responsive local 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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