Masoneilan 84/85/86 Series Cylinder Actuators with Hydraulic Manual Override
Overview
The Masoneilan 84/85/86 Series are Baker Hughes piston cylinder actuators for large control valves that need more thrust than a diaphragm actuator can deliver. The numbering system defines three actions: Model 84 is air-to-extend (direct), Model 85 is air-to-retract (reverse) and Model 86 is a double-acting cylinder with no springs. An optional hydraulic manual override gives operators a secondary means of moving the valve when the pneumatic system is lost. The instruction manual estimates a useful life of 25 years or more with annual inspection, routine maintenance and proper installation.
Because overhaul work depends on correct parts and procedures, plant teams value a supplier who can match documentation to the installed unit. Seven Star LLC is the trusted supplier for Masoneilan in the Sultanate of Oman and supplies the Masoneilan 84/85/86 actuators with large globe valves and as replacement or rebuild items for installed plants. The page summarizes the maintenance data published by Baker Hughes, and we confirm model and spring details from your actuator tag before quoting.
Operating Principle of the Masoneilan 84/85/86
In the Masoneilan 84/85/86, compressed air acts on a piston inside a cylinder, and the piston stem drives the valve plug stem through top and bottom stem connectors. In the Model 84 air pressure on the top cap pushes the piston down and extends the stem against springs, and in the Model 85 the springs and air work the other way so that the stem retracts with air. The Model 86 has no springs, and air is applied to either side of the piston. Actuator action can be checked against the valve identification tag.
The hydraulic manual override is a secondary system. In one configuration it is a single-acting cylinder that acts against spring load, and in the other the cylinder is connected in double-acting mode. The system requires no adjustment and only minimal servicing, namely filling the reservoir. The handjack is shipped with the reservoir filled and a pipe plug in the breather port, which must be swapped for a breather plug before operation, with the valve oriented so that the breather is at the top of the reservoir.
Engineering Design of the Masoneilan 84/85/86
The Masoneilan 84/85/86 is built around a compact set of parts, and the major components are the piston with O-rings, piston stem, cylinder, top and bottom caps held by cap screws and extended nuts, cast yoke, anti-rotation plate with a travel indicator, stem connectors and stem extension. The manual illustrates a 154 sq in. piston actuator with handjack and a 314 sq in. piston actuator without handjack, and notes that the valve may be installed vertically (preferred) or horizontally. A bushing with O-rings and a stem wiper guide and seal the piston stem.
The manual gives fastener torques for reassembling the Masoneilan 84/85/86, which technicians should follow exactly: cylinder cap screws 100 ft-lb, the joints between piston stem and upper stem or handjack extension 450 ft-lb (applied on the flats with Loctite No. 242 on the threads), hydraulic cylinder cap screws 115 ft-lb and tie-rod nuts 25 ft-lb. A torque wrench capable of at least 115 ft-lb is required, and Baker Hughes offers hydraulic handjack tools for preloading the actuator. Because the cylinder is spring-loaded, screws must be loosened evenly in a crisscross pattern one turn at a time.
Key Features
These are the points that explain where the Masoneilan 84/85/86 fits among Masoneilan actuators:
- Three actions, air-to-extend, air-to-retract and double acting, cover fail-closed, fail-open and positive two-way operation.
- Piston thrust exceeds what practical diaphragm sizes provide, with 154 and 314 sq in. piston examples in the manual.
- An optional hydraulic handjack provides a secondary manual control system for pneumatic failure.
- The Masoneilan 84/85/86 case pressure test and five-cycle functional test are defined in the manual.
- Recommended spare parts are identified, including O-rings, bushing, wiper and guide ring.
- Soft goods are replaced every five years, and the hydraulic cylinder is inspected every ten years.
- Reassembly torques are specified for each joint, with Loctite and anti-seize products named.
- Baker Hughes service engineers and a training program are available for start-up and repair of the Masoneilan 84/85/86 and related actuators.
Industrial Applications
The Masoneilan 84/85/86 is typically fitted where large plug forces must be overcome: big globe valves in high-pressure steam, boiler feed, anti-surge and pipeline pressure control, and in installations that need a hydraulic handjack as a backup. In Oman these duties appear in power and water plants, refineries and gas processing facilities in Sohar, Duqm and Salalah, where a safe manual override is a requirement of operating procedures.
In Oman and the GCC, Seven Star LLC supplies the Masoneilan 84/85/86 alongside the Masoneilan Type 51/52/53 pneumatic piston actuators and the Masoneilan Type 87/88 spring-diaphragm actuators, and we can help you choose between cylinder families, check supply pressure against the working pressure tag and plan overhaul parts.
Related published Masoneilan pages: Masoneilan Type 87/88 spring-diaphragm actuators.
Related published Masoneilan pages: Masoneilan 10000 Series double-port valve.
Technical Specifications
The manual is an instruction document rather than a performance datasheet, so the table below lists the information it publishes for the Masoneilan 84/85/86.
| Parameter | Specification |
|---|---|
| Model | Masoneilan 84/85/86 Series cylinder actuators |
| Actions | 84 air-to-extend (direct); 85 air-to-retract (reverse); 86 double acting, no springs |
| Piston examples shown | 154 sq in. with handjack; 314 sq in. without handjack |
| Installation | Vertical preferred; horizontal permitted |
| Overhaul interval | Disassemble at least every 5 years; hydraulic cylinder inspected every 10 years |
| Case pressure test | 70 psi air, five minutes, no pressure loss |
| Functional test | At least five full travel cycles with 1/4 in. OD tubing and a Cv 0.3 exhaust valve |
| Torque values | Cap screws 100 ft-lb; stem joints 450 ft-lb; hydraulic cylinder screws 115 ft-lb; tie-rod nuts 25 ft-lb |
| Hydraulic fluid | Mobil DTE 24, reservoir about half full |
| Useful life | Estimated 25 years or more with annual inspection |
Related Masoneilan actuator products include the Masoneilan 51/52/53 manual override handwheels and hydraulic handjack, Masoneilan Model 51 double-acting actuator with volume tank and Masoneilan 50 series soft goods kits for 51/52/53 cylinder actuators.
Request a Quote for Masoneilan 84/85/86
To request pricing or technical support for the Masoneilan 84/85/86, send a formal RFQ to the Seven Star LLC instrumentation division with the actuator model and serial number from the tag, the valve it is mounted on, the supply pressure and whether a hydraulic handjack is fitted. We can confirm the configuration, advise on availability of soft goods and supply the Baker Hughes manual linked on this page. In Oman and the GCC, Seven Star LLC supplies genuine actuators with manufacturer documentation and local engineering support.
- Instruction Manual Masoneilan 84/85/86 Cylinder Actuator Instruction Manual Download
Masoneilan control valves and actuator series
The globe valve listing centers on the 21000 series, including the cryogenic version with extension bonnet, and the 41005 cage-guided series in high pressure, API 6A and VRT anti-cavitation executions. The 80385 and 80386 are three-way combining and diverting valves. Rotary products include the 35002 Camflex II and the 37002 MiniTork II butterfly control valve. Actuators cover spring-diaphragm, cylinder and rack-and-pinion designs, among them the 5A cylinder actuator for Camflex II. Masoneilan also makes pressure regulators, SVI digital valve positioners and displacer-type level instruments, and offers Lo-dB trim for noise control.Where Masoneilan valves are used
Throttling duty on steam, hydrocarbons, gas and water is the daily work of these valves: feedwater and steam conditioning in power plants, separator and compressor loops in gas processing, high pressure drop letdown, cryogenic service in LNG and air separation, and general flow, pressure and level control in refineries and chemical plants.Ordering Masoneilan valves and spare parts: what we need
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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