Masoneilan 12840 Pneumatic-Set Proportional Level Controller
Overview
The Masoneilan 12840 is the pneumatic-set version of the Baker Hughes 12800 Series proportional level controller. It carries the same displacer, torque tube and proportional mechanism as the 12800, but the local control setting knob is omitted. In its place a pneumatic set bellows lets another instrument adjust the level set point by air pressure, so the setting can be positioned from a control room, a ratio station or the output of another controller instead of by hand at the vessel.
Seven Star LLC supplies the Masoneilan 12840 to pneumatic process plants in Oman and the GCC. Because the loading source determines how the set point moves, we ask what drives the set bellows, the specific gravity, displacer range and valve action, then confirm the model and provide the Baker Hughes manual.
Operating Principle of the Masoneilan 12840
The measuring side is familiar: a displacer and torque tube turn level into rotation, a reversing arc and control link move a control arm, the arm positions a flapper against a nozzle and a relay amplifies the nozzle pressure into a 3-15 psi output. A proportional bellows feeds the output back so that output pressure is proportional to level movement over the chosen band.
The pneumatic set mechanism is an additional bellows unit. Loading it turns the nozzle bracket about its axis and so moves the nozzle and flapper relative to the control arm, shifting the level at which the controller holds the process. The loading can come from the 3-15 psi output of another controller, from a transmitter or from a manually adjusted loading regulator. A rise in loading pressure always raises the controller output, and the 100 percent set band is not adjustable.
Engineering Design of the Masoneilan 12840
The parts list of the Masoneilan 12840 adds a pneumatic set bellows assembly to the standard 12800 items. It also adds one pipe connection: the loading source is piped to the 1/4 in. NPT pneumatic set connection on the back of the case, below the supply and output manifold. The relationship is fixed: a 3 psi load corresponds to low level, 15 psi to high level and 9 psi to mid-range.
Pneumatic Set Compared with Knob Setting
On the other 12800 models a control setting knob turns a gear, pinion and cam bearing on the alignment micrometer, and the cam rotates the nozzle bracket. The Masoneilan 12840 omits that mechanism and rotates the same bracket with the set bellows instead, so the level target can be moved by air pressure alone.
Alignment of the Masoneilan 12840
The proportional procedure is varied at two points. First set the proportional band index at 100 percent and load the set bellows with 9 psi, read on the output gauge of the loading source, before the usual alignment steps. After alignment, load the set bellows with the pressure that gives the wanted control setting (for example 9 psi for mid-range) and set the proportional band from experience. To change the control setting later, simply change the loading pressure.
Routine Maintenance of the Masoneilan 12840
Baker Hughes lists three regular checks: removing condensate from the filter-regulator drip-well through its petcock, inspecting the control valve, and checking the metering orifice and nozzle at a frequency that depends on air quality. The orifice has a clean-out plunger that pushes a small wire through the jewel orifice and can be removed while the relay stays on the air manifold. The nozzle hole is 0.020 in. (No. 76 drill), so with the air shut off a smaller drill or wire is pushed through it and the tubing is blown out with clean, dry air.
Diagnosing Drift on a Masoneilan 12840 Loop
The manual names three causes of drifting: too little air or a supply pressure set too low, leaks in the output air system, and excess pressure drop in the control valve line, which only higher upstream pressure can cure, not a larger valve. Inside the controller, dirt in the relay, friction in the mechanism or a partly plugged nozzle or metering orifice can degrade control. On a remotely set loop also confirm the pressure on the set bellows, because any change in that loading moves the control setting.
Key Features
- The set point is positioned by air pressure on the pneumatic set bellows, with no knob on the instrument.
- A 3-15 psi loading signal covers the range from low to high level.
- Loading can come from another controller, a transmitter or a manual regulator.
- The Masoneilan 12840 gives rising output with rising set loading, which simplifies loop wiring.
- Proportional band is adjustable from the 100 percent alignment point; interface service is supported.
Industrial Applications
A remotely set controller is useful when the level target must follow another process variable. The Masoneilan 12840 can take its set point from the output of a master controller in a cascade arrangement, or from a loading regulator that an operator adjusts at a panel, which fits refining and gas processing units at Sohar, Duqm and Salalah that keep pneumatic instrumentation.
Seven Star LLC supplies it with the control valves and actuators of the loop, including the Masoneilan 10000 series double-port valve and the Masoneilan Type 87/88 actuators.
Related published Masoneilan pages: Masoneilan 35002 Series Camflex rotary control valve.
Technical Specifications
Published data for the Masoneilan 12840 from the 12800 Series instruction manual.
| Parameter | Specification |
|---|---|
| Model | Masoneilan 12840 proportional level controller with pneumatic set |
| Control mode | Proportional, with the set point positioned pneumatically |
| Set point signal | 3-15 psi on the set bellows; 3 psi low level, 15 psi high level |
| Set band width | 100 percent, not adjustable |
| Output signal | 3-15 psi or 6-30 psi |
| Alignment start values | Proportional band index 100 percent; set bellows loaded with 9 psi |
| Pneumatic set connection | 1/4 in. NPT on the back of the case below the supply and output manifold |
| Supply | 50 to 125 psi gauge to the filter regulator, set to 20 psi for 3-15 psi output |
Related Masoneilan level instruments include the Masoneilan 12800 Series pneumatic level controller, Masoneilan 12400 Series digital level transmitter, Masoneilan 12810 proportional-reset level controller, Masoneilan 12820 pneumatic level transmitter and Masoneilan 12830 differential-gap level controller.
Request a Quote for Masoneilan 12840
To obtain pricing for the Masoneilan 12840, send an RFQ to the Seven Star LLC instrumentation division with the displacer range, mounting type, specific gravity, the loading source for the set point and the valve action. We confirm the model, advise on stock in the region and provide the Baker Hughes instruction manual attached to this page.
- Instruction Manual Masoneilan 12840 Level Controller 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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