Masoneilan 171 Series Cast Iron Direct-Operated Pressure Reducing Regulator
Overview
The Masoneilan 171 Series is a direct-operated, pressure reducing regulator from Baker Hughes, built in cast iron for utility and process lines that need a dependable reduced pressure without an air supply, a positioner or an electronic loop. It is offered in body sizes from 1/2 inch to 1-1/2 inch (DN15 to DN40) with NPT or GAS threaded connections only, and Baker Hughes states that it can handle inlet pressures up to 580 psig (40 barg) while holding a set point anywhere between 3 and 217 psig (0.21 to 15 barg). Its short list of selling points, namely an economical design, in-line maintenance, elastomer discs for tight shutoff and rugged construction, makes the Masoneilan 171 Series the entry point of the 171/172 regulator family.
In Oman and the GCC, Seven Star LLC supplies the Masoneilan 171 Series to maintenance teams, packaged-equipment builders and EPC contractors in the Sultanate of Oman and across the GCC. Our instrumentation division in Muscat checks the trim number, diaphragm material and spring range against your pressure and flow data before an order is placed, and every regulator is supported by the genuine Baker Hughes technical specification and instruction manual.
Operating Principle of the Masoneilan 171 Series
The Masoneilan 171 Series is a spring-loaded regulator that, like the 172 design Baker Hughes describes as flow to open, admits more flow as the spring wins over the diaphragm. Downstream pressure is sensed internally and acts on the underside of a diaphragm and diaphragm plate, while the adjustable spring pushes the other way. When demand rises and the outlet pressure falls below the set point, the spring moves the plug away from its seat and admits more flow. When the outlet pressure climbs above the set point, the diaphragm compresses the spring and the plug closes onto an elastomer disc, which is why shutoff is tight at no-flow conditions. Because the sensing port is inside the body, Baker Hughes reminds users that pressure drop in the pipe between the regulator and the point of use reduces the accuracy of the maintained set pressure, and an external 1/8 inch sensing connection is available on request where the pressure must be held at the consumer.
The set point is changed with the adjusting screw after loosening its locknut, and the instruction manual states that units leave the factory at the low end of the range unless the customer specifies otherwise. Clockwise rotation raises the outlet pressure and counter-clockwise rotation lowers it. For very low downstream pressures, normally below 100 mm of water column, the manual asks for the actuator to face downwards and sit horizontally below the pipeline, as shown on the nameplate orientation.
Engineering Design of the Masoneilan 171 Series
The Masoneilan 171 Series shares its working parts with the threaded version of the 172 regulator, with the difference that the body is cast iron and the blindhead is a threaded closure screwed into the body, removed with a 46 mm hex wrench, rather than a bolted cover. The high-pressure body part is 316 stainless steel, the plug stem is 316 stainless steel, the guide bushing is 303 stainless steel and the spring is chrome-vanadium steel. The disc is fluoroelastomer for air, gas and liquids and stainless steel for steam, and a Teflon diaphragm protector is optional. Some versions carry a balancing spring on the blindhead, which the manual asks maintenance staff to note during disassembly.
The numbering system describes the build: the first digit is the action (1 for a reducing metal seat, 2 for a reducing soft seat), the next is the diaphragm (1 metal, 2 elastomeric), then a two-digit trim size from 01 to 22 and an optional 50 for differential action. Rated Cv values follow the trim size, from 0.031 at trim 1 to 12.8 at trim 22 on the 1-1/2 inch body, so the regulator can be matched closely to the flow it must pass.
Key Features
The following characteristics explain why the Masoneilan 171 Series is chosen for compact pressure reduction duties:
- A cast iron body with NPT or GAS threaded ends keeps installation simple on small utility headers and skid piping.
- Elastomer discs give tight shutoff when flow stops, so the downstream pressure does not creep upwards.
- In-line maintenance allows the diaphragm and plug to be inspected without lifting the body out of the pipe when the line can be isolated.
- Fourteen trim sizes, from 01 to 22, give a wide range of rated Cv for each body size.
- Six representative set ranges cover 10.5 to 217 psig (0.72 to 15 barg), with final spring selection made in ValSpeQ sizing software.
- Diaphragm choices of chloroprene, EPDM with PTFE or stainless steel cover service temperatures from 32 to 450°F (0 to 232°C) on the Masoneilan 171 Series.
- Baker Hughes quotes PED 2014/68/EU and ATEX 2014/34/EU for the 171 Series in its technical specification.
- Internal pressure sensing is standard, with an external sensing port on request.
Industrial Applications
The Masoneilan 171 Series suits air and gas let-down on compressor skids, nitrogen blanketing and purge lines, fuel gas feeds to small burners and heaters, and liquid pressure holding on lube and cooling circuits where a self-acting device is preferred. In Oman these duties appear in district cooling plants, water treatment and desalination skids around Muscat and Salalah, workshops and utilities inside the Sohar free zone, and the oil and gas support facilities that serve the interior fields.
In Oman and the GCC, Seven Star LLC supplies the Masoneilan 171 Series together with the flanged and alloy-bodied Masoneilan 172 Series pressure reducing regulator and the very low pressure Masoneilan 174 Series regulator, so a plant can standardise on one manufacturer for its small regulators and spares. The Baker Hughes reference installation shows a safety relief valve and a pressure gauge downstream of the reducing regulator, and the manual advises a filter upstream when the cleanliness of the fluid is uncertain. Our team can quote the Masoneilan 171 Series with these accessories.
Technical Specifications
The table below summarises the Masoneilan 171 Series datasheet published by Baker Hughes as its technical specification. Please consult the official document for the full capacity and sizing tables.
| Parameter | Specification |
|---|---|
| Model | Masoneilan 171 Series (numbering 171-X X XX) |
| Function | Direct-operated, spring-loaded pressure reducing regulator |
| Body sizes and ends | 1/2, 3/4, 1 and 1-1/2 inch (DN15, DN20, DN25, DN40), NPT or GAS threaded |
| Body material | Cast iron; 316 stainless steel high-pressure insert |
| Maximum inlet pressure | 580 psig (40 barg) |
| Set point range | 3 to 217 psig (0.21 to 15 barg) |
| Standard set ranges | 10.5-31, 16-36, 21-57, 52-91, 88-140 and 133-217 psig (0.72-2.2, 1.1-2.5, 1.4-4.0, 3.6-6.3, 6.0-9.7 and 9.1-15.0 barg) |
| Maximum outlet pressure by actuator | Size 140: 145 psig (10 barg); size 130: 350 psig (24.1 barg); size 120: 470 psig (32.4 barg) |
| Diaphragm temperature limits | Chloroprene 32 to 194°F (0 to 90°C); EPDM+PTFE and stainless steel 32 to 450°F (0 to 232°C); fluoroelastomer 32 to 392°F (0 to 200°C) |
| Disc temperature limits | FKM 32 to 392°F (0 to 200°C); PTFE and stainless steel 32 to 450°F (0 to 232°C) |
| Pressure sensing | Internal; external 1/8 inch port on request |
Rated Cv and assembly weight by body size
| Item | 1/2 inch | 3/4 inch | 1 inch | 1-1/2 inch |
|---|---|---|---|---|
| Trim 1 rated Cv | 0.031 | 0.031 | 0.031 | 0.031 |
| Trim 8 rated Cv | 2.1 | 2.1 | 2.2 | 2.3 |
| Trim 12 rated Cv | 4.3 | 4.3 | 4.4 | 4.7 |
| Trim 16 rated Cv | – | 5.9 | 6.1 | 6.6 |
| Trim 22 rated Cv | – | – | – | 12.8 (12.5 with actuator 100) |
| Assembly weight, actuators 100 to 140 | 36.8 lb (16.7 kg) | 36.8 lb (16.7 kg) | 36.6 lb (16.6 kg) | 36.4 lb (16.5 kg) |
| Assembly weight, actuator 220 | 46.7 lb (21.2 kg) | 46.7 lb (21.2 kg) | 46.5 lb (21.1 kg) | 46.3 lb (21 kg) |
Related Masoneilan regulators include the Masoneilan 172-50 differential pressure regulator, Masoneilan 525-526 Series double-seated regulator and Masoneilan 173 Series back pressure regulator.
Request a Quote for Masoneilan 171 Series
To request pricing or technical support for the Masoneilan 171 Series, send a formal RFQ to the Seven Star LLC instrumentation division with the fluid, inlet pressure, required outlet pressure, flow rate and connection size. We confirm the trim number and spring range, advise on regional warehouse availability and provide the Baker Hughes technical datasheet for the Masoneilan 171 Series for download from this page. In Oman and the GCC, Seven Star LLC delivers genuine regulators with manufacturer documentation and responsive local support.
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