Masoneilan 78 Air Filter Regulator (Models 78-4 and 78-40)

Overview

The Masoneilan 78 series air filter regulators, offered as Models 78-4 and 78-40, are compact, lightweight pressure reducing instruments from Baker Hughes that supply a stable source of clean air to process control equipment. Baker Hughes names current-to-pneumatic transducers and control valve positioners as the primary users, and the regulators are also described as a good choice wherever plant air must be regulated for control valve pneumatic accessories. A relief feature and a 5 micron filter are built into the same body, so one small unit replaces a separate filter and regulator on the instrument air tee.

Seven Star LLC is a trusted supplier for Masoneilan and supplies the Masoneilan 78 air sets to refineries, gas plants, power stations and water facilities across the Sultanate of Oman and the GCC. Our instrumentation team in Muscat can match the 5-40 psi or 5-100 psi pressure range to the accessory being supplied, confirm the temperature variant for outdoor installations, and provide the Baker Hughes technical specification so that engineers can verify the data before ordering.

Operating Principle of the Masoneilan 78

The Masoneilan 78 regulator is a spring-loaded, diaphragm-balanced pressure reducing valve. Turning the pressure setting knob compresses the range spring against the diaphragm plate, which opens the main supply valve. As outlet pressure rises it flows through an aspirator and acts on the underside of the diaphragm, moving it upward until it balances the spring force. In this balanced condition the output pressure stays constant despite changes in supply pressure or output load, and the soft-seat plug on the main valve gives positive shutoff.

The relief valve is what separates an air loading regulator from a simple reducer. If the outlet pressure climbs above the set value, for example because dirt lodges under the inlet seat, the extra pressure on the diaphragm opens the relief seat and vents the excess through the spring case to atmosphere. This also allows the operator to turn the setting down without venting the whole line. Baker Hughes stresses that the relief feature must not be mistaken for an auxiliary safety valve, which may still be needed to protect air-operated equipment.

Engineering Design of the Masoneilan 78

The body, spring casing and bottom cap of the Masoneilan 78 are aluminium die-castings, the knob, plug guide, spacer and aspirator are Valox 420, and the adjusting screw, lock screw and drain cock are stainless steel. The diaphragm is nitrile rubber, the plug is neoprene on a 416 stainless steel stem, and the filter element is sintered porous polyethylene with a 5 micron rating. A corrosion-resistant finish and stainless assembly hardware allow use in corrosive atmospheres.

Installation is simple. The unit is small and light enough to be nipple-mounted in most installations, which removes the need for a mounting bracket, although one is available, and two gauge ports allow a gauge on either side. Connections are 1/4 NPT or Rc. The air set must be installed with the drain cock facing down and as close as possible to the device it serves, and the drip well should be drained at intervals set by the actual rate of accumulation. A lock screw holds the knob so that the setting cannot drift. The Masoneilan 78 is certified in Azerbaijan, Armenia, Belarus, Kazakhstan, the Russian Federation and Uzbekistan according to Baker Hughes, and is also ATEX compliant.

Key Features

The following points explain why the Masoneilan 78 is widely specified as the supply regulator for pneumatic instruments:

• Two pressure ranges: Model 78-4 sets 5-40 psi (0.35-2.8 bar) and Model 78-40 sets 5-100 psi (0.35-7 bar).
• Built-in relief valve so that output pressure can be reduced without venting the line.
• Sintered polyethylene filter with a 5 micron rating protects downstream positioners and transducers.
• Lock screw keeps the output pressure at the set value in vibrating service.
• Soft-seat plug on the main valve provides positive shutoff.
• Two gauge ports allow a gauge to be mounted on either side for flexible installation.
• Stainless steel drain cock and a corrosion-resistant finish for outdoor and marine atmospheres.
• Standard, low-temperature and high-temperature versions cover ambient limits from -50 to +100 degrees Celsius.

Industrial Applications

Baker Hughes lists the Masoneilan 78 for power generation, refining, petrochemicals and midstream and upstream oil and gas, with applications that include steam turbine generators, condensers, cooling towers, gas turbines, heat recovery steam generators, distillation, hydroprocessing, compression, refrigeration and liquefaction. In practice it sits on the instrument air branch ahead of a positioner, an I/P transducer or a booster, ensuring that each accessory sees the correct clean air pressure. In Oman, sand and humidity make a 5 micron filter and a stainless drain particularly valuable on coastal sites such as Sohar, Duqm and Salalah.

In Oman and the GCC, Seven Star LLC supplies the Masoneilan 78 with the positioners and actuators it serves. It is a natural companion to the Masoneilan SVI3 digital valve positioner, to the Masoneilan BR200 booster relay and to Masoneilan Type 87/88 spring-diaphragm actuators. We can also advise on the supply pressure each accessory needs, since positioners and boosters often require a setting well below the plant air header pressure.

Technical Specifications

The table summarises the published data for the Masoneilan 78 series from the Baker Hughes technical specification and instruction manual.

Related Masoneilan positioners and accessories include the Masoneilan 4411 I/P transducer, Masoneilan SVi1000 digital valve positioner, Masoneilan 4700P/4800P pneumatic positioner and Masoneilan BR400 volume booster relay.

Request a Quote for Masoneilan 78

To request pricing or technical support for the Masoneilan 78, send a formal RFQ to the Seven Star LLC instrumentation division stating the model (78-4 or 78-40), temperature range and quantity. We can confirm the correct variant, advise on availability and lead time and provide the Baker Hughes technical specification from this page. In Oman and the GCC, Seven Star LLC delivers genuine products with manufacturer documentation and local engineering support.