Masoneilan Lo-dB Expansion Plate 1-Stage and 2-Stage Noise Attenuator

Overview

The Masoneilan Lo-dB Expansion Plate is a line-size device that Baker Hughes provides for plants that must bring valve noise under a limit without installing a heavy, expanded silencer. It is a drilled-hole plate in a machined housing, designed in one-stage and two-stage constructions, and it is mounted downstream of a control valve where it takes a large percentage of the pressure drop that would otherwise be handled by the valve itself. The traditional drilled hole expansion plate has been engineered by Baker Hughes into a device that balances acoustic efficiency against flow capacity, and the result is noise reduction of up to 20 dB without making the control valve larger.

The trusted Masoneilan supplier in Oman, Seven Star LLC, offers the Masoneilan Lo-dB Expansion Plate to gas processing, power and refinery sites in the GCC that sit close to people and housing. Our Muscat instrumentation division can help translate a valve noise calculation into a plate size, stage count and capacity factor.

Expansion Plate Operating Principle

A control valve that operates above its critical pressure ratio generates noise in proportion to the energy in the jet leaving the trim. The Masoneilan Lo-dB Expansion Plate works by raising the pressure at the valve outlet while maintaining choked flow across the valve, which lowers the downstream velocity and ensures that the noise generated in the downstream pipe does not exceed the noise of the valve. Because it acts as a barrier to the sound waves produced upstream, it reduces both noise and related vibration at source instead of muffling it afterwards as a conventional silencer does.

Placement of the Masoneilan Lo-dB Expansion Plate matters in a predictable way. If the plate is mounted directly against the valve outlet flange, or separated from the valve only by a reducer, a further net reduction of 6 dB in valve sound pressure level is obtained. Beyond that the position is flexible: the distance between the valve and the plate, or between adjacent plates in series, is not critical, and the plate may be installed in any convenient location in the downstream piping. Valves and reducers with heavier walls than the adjoining pipe provide additional attenuation. Baker Hughes notes that plates are generally more restrictive than Lo-dB cartridges of the same nominal size, so they give more back pressure and are more effective at reducing noise.

Engineering Design of the Masoneilan Lo-dB Expansion Plate

The Masoneilan Lo-dB Expansion Plate employs either a single-stage or a two-stage flow path. Both stages of the Masoneilan Lo-dB Expansion Plate use drilled-hole plates in 304 stainless steel whose hole arrangement is designed to give the optimum pressure reduction, and in the two-stage plate the first-stage and second-stage plates are separated by a plate spacer that provides alignment during fabrication and structural support in service. Limiting velocity variation from stage to stage creates thorough mixing of the fluid, which contributes to the high noise reduction of the design. An optional Type RTJ flange seal groove is available.

The Masoneilan Lo-dB Expansion Plate is built in a housing machined from carbon or stainless steel, and the plates are compressed and welded around the full circumference during assembly. The plates are 304 stainless steel welded to a carbon steel housing for use up to 650 degrees Fahrenheit, with a 304 stainless steel housing for higher temperatures up to 750 degrees Fahrenheit. Wafer-style units fit between flanges from 2 to 24 inch, large units from 16 to 36 inch can have butt-weld ends, and large plates carry an eye bolt for positioning. Pressure ratings are ANSI 150 to 2500 for 2 to 12 inch, 150 to 1500 for 12 to 24 inch and 150 to 600 for 26 to 36 inch.

Key Features

The following features, drawn from the Baker Hughes technical specification, show why the Masoneilan Lo-dB Expansion Plate is specified for noise control on gas and steam letdown:

• The Masoneilan Lo-dB Expansion Plate reduces noise by up to 20 dB, with a further 6 dB when the plate is mounted against the valve outlet flange or behind a reducer only.
• One-stage and two-stage constructions let the designer match the amount of back pressure to the noise target.
• Rated Cv from 12 to 10,000 across sizes from 2 to 36 inch, with capacity factors from full down to 0.5 on one-stage plates.
• Line-size installation means no large expanded silencer housing and no larger control valve in most applications.
• Flexible location: the plate can be installed in any convenient position downstream, and plates can be placed in series.
• Drilled-hole 304 stainless steel plates welded in carbon or stainless steel housings resist the temperatures of steam and hot gas up to 750 degrees Fahrenheit.
• Passages are sized so that normal foreign material in process piping can pass, although cleanliness before start-up is still essential.
• Uni-directional flow is indicated by an external flow arrow, which simplifies correct orientation during installation.

Industrial Applications

Baker Hughes describes the Masoneilan Lo-dB Expansion Plate for control valve applications where an additional stage of pressure reduction is needed to reach a noise limit of 85 to 90 dBA at one meter, particularly where the operating pressure drop exceeds the critical limit. The plates are used with Lo-dB valves when the pressure ratio is high and with standard valves when their sound pressure level needs a reduction of 20 dBA or more. In Oman these conditions arise on steam letdown stations, gas pressure reduction skids and vent systems beside occupied areas of refineries, gas processing facilities and industrial zones.

Seven Star LLC supplies the Masoneilan Lo-dB Expansion Plate together with valves it can be paired with, such as the Masoneilan 41005 Series cage guided control valve, and actuation can be specified from the Masoneilan Type 51/52/53 piston actuators. The Masoneilan Lo-dB Cartridge reaches its reduction through a 16-stage grille element instead of drilled plates, so the two devices differ in construction. A Masoneilan SVI3 digital valve positioner can be added for positioning.

Technical Specifications

The table sets out the data that the Baker Hughes technical specification (Rev. C, 01/2025) publishes for the Masoneilan Lo-dB Expansion Plate. The dimensions table and the pressure drop versus temperature chart remain in the official document.

Related Masoneilan severe-service valves include the Masoneilan 77000 Series multi-stage high-pressure valve and Masoneilan 72000 Series large mass flow valve.

Request a Quote for Masoneilan Lo-dB Expansion Plate

To obtain a quotation for the Masoneilan Lo-dB Expansion Plate, send Seven Star LLC the fluid, flow rate, inlet and outlet pressure, temperature, line size and schedule, the noise limit and the control valve model. We confirm one-stage or two-stage construction, check availability and lead time and provide the Baker Hughes technical specification for download from this page. As trusted supplier for Masoneilan in Oman and the GCC, we deliver genuine products with manufacturer documentation and local support.