Emerson Rosemount 485 Annubar

Emerson Rosemount 485 Annubar

Introduction

The Rosemount™ 485 Annubar™ Primary Element represents a field-proven averaging pitot tube technology designed to deliver reliable measurement accuracy across an exceptionally wide range of flow rates. Built with a patented T-shaped sensor design, the Rosemount 485 Annubar maintains a minimal profile within the pipeline, significantly reducing permanent pressure loss while increasing energy savings compared to traditional primary elements such as orifice plates or Venturi tubes-1.

This comprehensive technical guide provides engineers, procurement specialists, and instrumentation professionals with detailed specifications, ordering information, installation guidelines, and application insights for the Rosemount 485 Annubar Primary Element. As a standalone primary element or as part of a fully integrated flow meter assembly paired with Emerson Rosemount pressure transmitters—including the 3051CFA, 3051CFC, 3051CFP, 4088 MultiVariable, and 3095FC models—the 485 Annubar delivers the measurement performance and operational efficiency that industrial facilities worldwide demand-28.

Key Technical Specifications

The Rosemount 485 Annubar is designed to meet ASME MFC-7M (formerly ANSI/API 2530) and ISO 5167-1 standards. For high-temperature applications beyond 850 °F (454 °C), the Rosemount 585 Annubar Primary Element is available, with a process temperature range up to 1500 °F (815 °C) while maintaining the same ANSI B16.5 2500# maximum operating pressure rating-35-38.

Key Features and Technical Advantages

Patented T-Shape Sensor Design

The Rosemount 485 Annubar incorporates a patented T-shaped averaging pitot tube that creates a fixed separation point, delivering differential pressure signal improvement across a wider flow rate range compared to conventional averaging pitot tube designs-1. The sensor’s stagnation zone is strategically positioned to reduce flow-induced noise, minimize measurement inaccuracies, and prevent particulate accumulation that can cause clogging in dirty service applications-9.

The T-shape design offers very low permanent pressure loss—typically 80% to 90% lower than an orifice plate under equivalent flow conditions. This translates directly into reduced pumping or compression energy requirements, lowering operational costs over the life of the installation.

Single Pipe Penetration Multi-Variable Measurement

The T-shaped sensor is capable of measuring temperature, pressure, and flow via a single pipe penetration when equipped with an integral thermowell option-36. This design eliminates the need for separate process penetrations for temperature sensing, reducing potential leak points, installation costs, and maintenance requirements.

Textured Surface for High Reynolds Number Applications

The front surface of the Rosemount 485 Annubar primary element is textured for high Reynolds number applications, typically gas and steam service. The surface texture creates a more turbulent boundary layer on the front of the sensor, ensuring consistent differential pressure signal generation even under high-velocity flow conditions-.

Lightweight Design for Large Line Sizes

The Rosemount 485 Annubar offers a lightweight design at large line sizes, providing a cost-effective primary element solution compared to heavier alternatives such as Venturi tubes or large-bore orifice plates-35. This characteristic simplifies handling, installation, and maintenance, particularly in pipeline diameters exceeding 24 inches (600 mm).

Flo-Tap Installation Capability

The Flo-tap design of the 485 and 585 Annubar primary elements allows installation and removal without system shutdown, enabling hot-tap insertion under full process pressure-. This feature is particularly valuable in applications where process interruption is not feasible, such as refinery operations, power generation facilities, and pipeline transmission systems.

Complete Model Number Examples

The Rosemount 485 Annubar Primary Element follows a structured ordering code that defines fluid type, line size, material construction, and configuration options. Below is a comprehensive list of complete model number examples to assist with specification and procurement.

Fluid Type Selection

Line Size Matrix

Gas Service Configurations

Steam Service Configurations

Material Configuration Examples

Integrated Assembly Model Numbers

Installation Guidelines

Straight Run Requirements

Correct orientation and straight run requirements must be met for accurate and repeatable flow measurements. The Rosemount 485 Annubar requires specific minimum pipe diameter distances from upstream disturbances, with requirements varying based on whether straightening vanes are used-11.

For installations with straightening vanes, the upstream straight run requirement is reduced. Consult Table 1-1 in the Rosemount 485 Annubar Flanged Assembly Quick Start Guide (document number 00825-0100-4809, Rev DD) for the exact minimum pipe diameter distances based on the specific upstream disturbance configuration-11.

When longer straight runs are available, position the sensor such that the majority of the straight run is upstream of the Annubar for optimal flow profile conditioning. The Rosemount 485 Annubar installation allows for a maximum sensor misalignment of 3° from the intended orientation axis-19.

Orientation Guidelines

Air and gas applications: Install the sensor in the upper half of the pipe to prevent condensate accumulation-20

Liquid applications: Install the sensor in the bottom half of the pipe to ensure the sensor remains fully submerged-20

Steam applications: Mount the sensor at 45 to 75 degrees above horizontal to allow condensate to drain back into the process pipe

Vertical pipes: The sensor can be installed in any position around the circumference of the pipe, provided the vents are positioned properly for bleeding or venting. Optimal results for liquid or steam are obtained when flow is upward-19

Temperature Limitations for Direct Mount

The maximum temperature for a direct-mounted pressure transmitter on the Rosemount 485 Annubar is 500 °F (260 °C). For applications exceeding this temperature, a remote mount configuration must be used. For remote mount installations, the impulse piping should slope up slightly from the instrument connections on the Rosemount Annubar to the cross fittings, allowing condensate to drain back into the pipe-11.

Installation for High-Temperature Service

For process temperatures between 500 °F and 850 °F (260 °C to 454 °C), remote transmitter mounting is required. The Rosemount 485 Annubar with integral thermowell option allows simultaneous temperature measurement via the same penetration, simplifying installation while reducing potential leak points.

Square or Rectangular Duct Installations

Consult the factory for instructions regarding use of the Rosemount 485 Annubar in square or rectangular ducts, as straight run requirements and sensor sizing differ from circular pipe installations-11.

Ordering Information and Model Code Structure

The Rosemount 485 Annubar Primary Element follows the ordering structure detailed in Table 14 of the Rosemount 3051SFA Reference Manual (document number 00809-0100-4809, Rev DA). The complete model number is constructed by selecting the appropriate code for each ordering parameter-5.

Ordering Code Components

The standard offering represents the most common options and should be selected for best delivery lead times. Expanded offerings are subject to additional delivery lead time-5.

Line Size Selection Reference

The Rosemount 485 Annubar is available for line sizes from 2 inches (50 mm) up to 96 inches (2400 mm)-5:

Certifications and Approvals

The Rosemount 485 Annubar Primary Element is manufactured in locations approved by Rosemount, including the USA, Singapore, and China. It is certified under the European Community Directives and carries applicable hazardous location markings-.

Available Certifications

NACE MR0175 / ISO 15156: Materials conformance for sour service applications (Alloy C-276 configurations)-28

Hazardous Location Approvals: Explosion-proof, Flameproof, and Intrinsically Safe (I.S.) certifications available-19

ASME MFC-7M: Meets ASME performance standards for flow measurement

ISO 5167-1: Compliant with international orifice plate flow measurement standards

PED: European Pressure Equipment Directive compliance

Each flowmeter is clearly marked with a tag indicating the approvals. To maintain certified ratings for installed transmitters, install in accordance with all applicable installation codes and approval drawings. Verify that the operating atmosphere of the transmitter is consistent with the appropriate hazardous locations certifications-.

Comparison: Rosemount 485 vs. 585 Annubar

For applications exceeding 850 °F (454 °C), the Rosemount 585 Annubar Primary Element is the recommended solution, offering solid sensor construction and capabilities for severe service environments-38.