EPS Leading meter1 and HPmeter1 Single Chamber Orifice Fittings

What Is a Single Chamber Orifice Fitting?

A single chamber orifice fitting is a differential pressure metering body that holds the orifice plate concentrically in the line and gives access to it through a cover on the body. With a conventional pair of orifice flanges, changing the plate means removing the bolts and spreading the flanges apart; with a single chamber fitting, the pipeline stays mechanically in place and the plate is withdrawn from the body together with its carrier.

The single chamber in the name indicates that the section housing the plate is directly exposed to line pressure. Before the plate can be reached, the relevant line section must therefore be isolated with valves and its pressure safely vented. Metering stops while the plate is changed; if flow has to continue, a bypass line is used. This makes the single chamber design a sensible option for measuring points operated with planned shutdowns or with redundant meter runs.

Within the EPS Leading product family, meter1 has been developed for the standard pressure classes and HPmeter1 for the high pressure classes. Both products are designed with ease of manufacture and assembly in mind, have a reduced number of parts and can be installed in horizontal or vertical lines.

How a Single Chamber Orifice Fitting Works

The measuring principle is the same for every orifice meter: the plate restricts the flow and the resulting differential pressure is related to flow rate. What sets the single chamber fitting apart is how the plate is held in the body and how it is removed for maintenance. A typical plate change follows these steps:

1.      Metering position: The plate is held in its carrier, sealed and concentric with the pipe axis. The differential pressure taken from the pressure tappings in the body is passed to the differential pressure transmitter.

2.      Isolating and venting the line section: The valves upstream and downstream of the fitting are closed, or the flow is routed to the bypass. The pressure in the isolated section is vented to a safe location and zero pressure is confirmed.

3.      Opening the access cover and removing the plate: The cover is opened and the plate carrier is drawn out of the body. The quick-release plate system shortens this task and prevents the plate from being refitted the wrong way round.

4.      Inspection or plate change: Edge sharpness, flatness and bore diameter are checked; if the flow range has changed, a plate with a different bore is fitted. The seals are examined at the same time.

5.      Closing and returning to service: The cover is closed, tightness is checked, the line section is repressurized in a controlled way and the valves are opened to restart metering. The new plate bore is entered in the flow computer.

Key Difference Between Single and Dual Chamber Designs

In a dual chamber fitting, the plate is raised into a second chamber while the line is under pressure; that chamber is separated from the line by a sealing valve and then vented, so the plate can be changed without stopping the flow. A single chamber fitting has neither the second chamber nor this valve. As a result, the single chamber design has fewer moving parts and a simpler maintenance routine, but the line has to be isolated for every plate change. Which design suits a plant depends on how often plates are changed and how far the operation can tolerate an interruption of flow.

Difference Between meter1 and HPmeter1

The two products share the same operating principle; they differ in pressure class and in the associated body material. meter1 is offered in the ANSI 150#–900# classes with cast carbon steel bodies suited to low-temperature and general service. HPmeter1 is produced for ANSI 1500# and 2500# and for API pressure classes, with a cast body in high-strength, heat-treated low-alloy steel. Because the HPmeter1 range has been standardized, the aim is to shorten lead times.

Key Features

·         Plate access without separating flanges: The plate is removed through the access cover on the body; the pipeline and its flanged joints stay in place.

·         Reversal-proof quick-release plate system: The plate carrier seats in one orientation only, so the sharp edge always faces the flow, while the quick-release mechanism shortens maintenance time.

·         Simple design with few parts: Designed with manufacture and assembly in mind (DFM/DFA), the body has fewer complex parts and is straightforward to operate.

·         Modern sealing solutions: Seals are selected to suit the application; a simple seal arrangement makes inspection and replacement easier during maintenance.

·         Field-repairable construction: The fitting is designed so that it can be repaired on site rather than being sent back to a workshop.

·         Horizontal or vertical installation: Both products can be installed in horizontal or vertical lines, giving flexibility in station layout.

·         Analysis-verified design and pressure testing: Each fitting is verified at design stage by finite element analysis (FEA) and, after assembly, pressure tested against industrial safety requirements and European pressure guidelines.

·         Stainless internals as standard: Internal components are 316 stainless steel as standard; duplex and nickel-based alloy options are available for demanding service.

·         High-pressure version: HPmeter1 brings the same simple operating logic to high-pressure lines in the ANSI 1500# and 2500# classes and in API pressure classes.

Technical Specifications

The values below show the typical design scope of the meter1 and HPmeter1 single chamber orifice fittings. The final configuration should be confirmed at project stage according to pressure class, size, material and connection type.

On HPmeter1, the 2500# class is offered up to 12 inch; high-pressure requirements in larger sizes are assessed per project.

Key Advantages

·         Simple construction, easy maintenance: With no second chamber or isolation valve, there are few moving parts and the maintenance routine is short and easy to follow.

·         Minimal maintenance requirement: A body with few parts and modern seals keeps maintenance needs low throughout operation.

·         Assembly error eliminated: The reversal-proof plate system removes the measurement error that a plate installed in the wrong orientation would cause.

·         Same operating logic at high pressure: Thanks to HPmeter1, the same maintenance procedure can be applied at standard and high-pressure measuring points.

·         Layout flexibility: The choice of horizontal or vertical installation makes piping layout easier at stations with limited space.

·         A system matched to the meter tube: Supplying the fitting with a meter tube machined to suit it removes uncertainty caused by misalignment.

Application Areas

Single chamber orifice fittings are chosen where the flow can be routed to a bypass during a plate change, or where the measuring point can be taken out of service for a short time.

Gas Metering Stations with a Bypass

At gas transmission and distribution stations within the scope of ASME B31.8, they offer a simple, economical plate-access solution on meter runs whose flow can be switched to a standby line.

Process Lines Operated with Planned Shutdowns

On ASME B31.3 process lines where plate inspection can be scheduled into planned maintenance shutdowns, the single chamber design is an adequate and practical option.

High-Pressure Production Lines

With ANSI 2500# and API pressure classes and API 6A flange options, HPmeter1 can be used on high-pressure production and gathering lines.

Power Plants

Can be applied as a flow measuring point on lines covered by ASME B31.1 power piping.

Sour Service Applications

With material selection in line with the NACE MR0175 design code, the fittings can be used on lines carrying sour gas.

Selection Criteria for meter1 and HPmeter1

Choosing the right single chamber fitting depends on the plant's maintenance scenario as much as on pressure class. For a technical assessment we recommend clarifying the following information:

Maintenance and Operating Scenario

·         How often will plates be inspected and changed?

·         Can the measuring point be isolated and depressurized for a plate change, and is there a bypass line?

·         If a flow interruption is not acceptable, consider a dual chamber fitting; if proved isolation is required, a double isolation fitting

·         Likelihood that uninterrupted maintenance will be needed in future

Pressure Class and Nominal Size

·         ANSI 150#–900# (meter1) or 1500#–2500# and API classes (HPmeter1), according to design pressure

·         Line size, and whether the chosen pressure class is offered in that size

·         Beta ratio and the expected range of plate bore diameters

Material and Seal Selection

·         Minimum design temperature and a suitable casting material

·         Sour service or corrosive component content

·         Compatibility of the seal material with the fluid and temperature

·         Coating requirement for external bolting

Installation and Meter Tube

·         Horizontal or vertical installation and the maintenance clearance needed for the access cover

·         End connection, flange standard and flange facing

·         Need for a meter tube machined to suit the fitting and a straightening vane / profiler

·         Scope of differential pressure, pressure and temperature transmitters and flow computer

Because the fitting is a mechanical device, hazardous-area assessment should be made per project for the electronic components connected to it, such as transmitters and the flow computer.

Design Codes and Measurement Standards

meter1 and HPmeter1 single chamber orifice fittings are designed within the framework of the following standards and codes.

Additional project-specific certification or customer specification requirements should be clarified with TLY Enerji at quotation stage.

Single Chamber Fitting Solutions from TLY Enerji

TLY Enerji evaluates the choice of a single chamber fitting together with the maintenance scenario of the measuring point. Once plate change frequency, bypass options and the operation's tolerance to flow interruption are clear, we decide with you whether a single chamber design is sufficient or whether a dual chamber option should be considered instead.

We work alongside you in selecting a body material suited to the pressure class and minimum design temperature, pre-sizing the plate bore, defining the meter tube and transmitter scope, preparing technical documentation and commissioning on site. We also help prepare a site-specific procedure for your maintenance teams covering isolation, venting and plate change steps, so that every plate change follows the same safe sequence and is properly recorded.

Frequently Asked Questions

What is a single chamber orifice fitting?

A single chamber orifice fitting is a metering body that holds the orifice plate concentrically in the line and allows the plate to be removed through an access cover on the body without separating the flanges. Because the chamber housing the plate is directly exposed to line pressure, the relevant line section must be isolated and its pressure vented before the plate is changed.

What is the difference between meter1 and HPmeter1?

Both work on the single chamber principle. meter1 is offered in 2–24 inch sizes for the ANSI 150#–900# classes, with cast carbon steel bodies. HPmeter1 is produced with an ASTM A487 4D cast body for ANSI 1500# and 2500# and for API pressure classes; the 2500# class is available up to 12 inch and the 1500# class up to 24 inch.

Does line pressure have to be released for a plate change in a single chamber fitting?

Yes. In a single chamber fitting the plate sits in one chamber that is open to line pressure. Before the cover is opened, the valves upstream and downstream of the fitting must be closed or the flow routed to a bypass, and the pressure in the isolated section safely vented and confirmed as zero. Where flow must not be interrupted, a dual chamber fitting should be chosen.

How is an orifice plate prevented from being installed backwards?

The sharp-edged face of an orifice plate must face upstream; a plate installed in reverse causes a significant measurement deviation. The quick-release plate system in meter1 and HPmeter1 is designed so that the plate can only be placed in its carrier in the correct orientation. This removes the risk of an assembly error during plate changes in the field.

Can a single chamber orifice fitting be used in a vertical line?

Yes. meter1 and HPmeter1 can be installed in horizontal or vertical lines. In vertical installations, flow direction, fluid phase and impulse line routing affect measurement quality; in liquid service, or in gas service with a risk of condensation, the arrangement of pressure tappings and transmitter connections should be assessed separately at project stage.

How is the body material selected?

Selection depends on pressure class, minimum design temperature and fluid composition. ASTM A352 LCC, A216 WCC or A216 WCB cast bodies are used in the standard pressure classes, and ASTM A487 4D in the 1500#–2500# classes. Internals are 316 stainless steel as standard. Duplex and nickel-based alloy options can be considered for sour or corrosive service.

Why should the fitting and meter tube be supplied together?

When the fitting and the meter tube are machined to suit each other, the bores of tube and fitting stay on a common axis and the uncertainty that misalignment would otherwise introduce is removed. A straightening vane or profiler can be added to the meter tube, and differential pressure and process transmitters, a flow computer and an enclosure can be defined within the same scope.

Can an installed meter1 be converted to a dual chamber design later?

The modular concept of the EPS Leading product family makes this possible: a meter1 installed in the line can be converted to a meter2 dual chamber design without removing it from the pipeline. This gives flexibility to stations where a single chamber design is sufficient today but uninterrupted plate changes may be needed in future. Feasibility must be confirmed for the size and pressure class of the existing body.