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Ronsor Bulletin

The past few months have been truly challenging for everyone, especially so in our current environment where the fight against the COVID-19 pandemic needs to be a collective effort. Many of our lives have been disrupted due to this and plans have been put on hold as part of a collective effort to stop infected numbers from rising.

On our part, we are taking measures to ensure everyone is well and following good hygiene practices. Hopefully all of us are able to emerge out of this stronger and more resilient than ever.

In this bulletin, we will introduce and discuss some of the new products that we are handling and their principle of operations. These are namely BS&B Nacional Pressure Relief Valves, ABB Swirl Flow Meters and ABB Vortex Flow Meters.

BS&B Nacional Pressure Relief Valves

Introduction - What is Pressure Relief Valve?

The function of a pressure relief valve is to protect pressure vessels, piping systems, and other equipment from pressures exceeding their design pressure by more than a fixed predetermined amount. It must be capable of operating at all times, especially during a period of power failure; therefore, the sole source of power for the pressure relief valve is the process fluid.

Pressure Relief Valve Main Components

The safety valve protects a pressurized installation. It remains closed until the force exerted by the pressure of fluid P1, against the disc, is equal to the force of spring Fr. (Fig.1). From this point of equilibrium, the disc holder comes away the nozzle, releasing a small amount of fluid, (valve set pressure) which is applied in the ring chamber (C) formed between the disc holder and adjusting ring (Fig. 2). Chamber pressurization (C) creates an additional force contributing to total instantaneous valve opening (Fig.3). Maximum valve lift shall be achieved without the installation exceeding 10% of overpressure, regardless of whether fluid is a gas or liquid. Once the overpressurization has dissipated, the pressure will reduce to a certain value below the set pressure, closing the valve. The difference between set pressure and re-seating pressure (blowdown), may be between 7% and 15% depending on whether the valve is designed for a gas or liquid. Overpressure and blowdown values may be corrected by positioning the adjusting ring closer to or further from, the internal disc holder surface.

Pressure Relief Valve

BS&B Nacional Pressure Safety Valves General Features

Nacional PRV Model 6400 is an angular type safety valve at 90º between the inlet and the outlet connections. It has flanged connections, a full nozzle, direct action and is spring loaded. There are three types: Conventional, Balanced (with bellows) and Balanced-Piston. All three are designed with specific trims to work with gases, steam and liquids.

*Information from BS&B Nacional Brochure

ABB Swirl Flow Meter


Swirl flow meters combine the advantages of turbine and vortex flow meter technologies. They have a high turndown ratio and is highly accurate. They are also highly reliable, robust and maintenance free. ABB Swirl flow meters can be utilized for highly accurate measurement of the flow of gases, liquids and steam over a wide range of temperatures in almost any application. Swirl meters are ideal for use on petrochemical raw materials, demineralized water and for direct, cost- effective steam mass flow by employing integral temperature measurement.

Swirl Flow Meter

Principle of Operation

The swirl meter operates under the same technology as the vortex flow meter. It takes advantage of vortex shedding principles that occur when a flowing fluid comes up against a bluff obstacle in its path. Additionally, the swirl meter adds a "twist" in conditioning the fluid, which results in the reduced installation considerations mentioned above, while improving performance.

The swirl meter forces incoming fluid through a fixed swirl inducing element located at the upstream inlet of the meter body. The "swirler" imparts a tangential velocity to the fluid, and then accelerates the flow via a reduction in the meter body bore.

The primary fluid rotation caused by the swirler has at its core a low-pressure zone. This low-pressure zone is thrown into a secondary rotation proportional to flow rate. The same piezoelectric sensor as used in vortex meters measures the frequency of this phenomenon at the point of maximum fluid velocity.

An increase in the meter's bore as the fluid approaches the meter outlet decelerates the fluid to its original velocity. A "deswirler" welded to the meter body near the outlet eliminates the tangential velocity imparted to the fluid at the inlet. This avoids affecting operation of other downstream instrumentation.

Swirl Flow Meter

Compact, space-saving installation

Swirl meters create their own flow profile within the meter, so they require only three straight pipe diameters upstream and one downstream. So the swirl flow meter better fits applications with tight piping requirements. Swirl meters require lower flow velocities for proper operation, and so usually may be sized the same as the process pipe size.

Swirl meters have a turndown ration of up to 30:1. Additionally, swirl meters can perform to viscosity of up to 30 cp while vortex meters are generally limited to 8-10 cp maximum. Swirl meters offer a higher degree of accuracy, up to 0.5% better than most vortex meters in gas applications.

*Information from the ABB Swirl Flow Meter catalog.

ABB Vortex Flow Meter

VortexFlow Meter

Principle of Operation

A Vortex flow meter measures flows of liquids, gases and steam by sending the frequency at which vortices are alternately shed from a bluff body. The frequency at which the vortices are alternately shed is directly proportional to the flow velocity. Vortices are formed on both sides after the bluff body the vortices generate periodic pressure and velocity variations. The piezo-sensor convert the resulting pressure forces into an electrical measuring impulse signals which can be amplified.

Vortex Flow Meter Straight Run

Inlet and outlet sections

The figures below show the recommended inlet and outlet sections for Vortex flow meter various installations.

*Information from the ABB Vortex Flow Meter catalog.

More Information

BS&B Model 64 Pressure Relief Valves

BS&B Model 51 Pressure Relief Valves

ABB Swirl Flowmeter

ABB Vortex Flow Meter