Control Valve Designed for On/Off Operation

Cutaway view of the Mark 76 on/off control valve,
a sliding gate design.
Image courtesy Jordan Valve

Not every fluid control application needs a modulating valve. In some cases, a two state control algorithm, flow or no flow, is the best solution. Opting for a less complex control method can deliver up front benefits of lower first cost and easier implementation. Continuing savings in maintenance time and the ease of understanding the control sequence accrue for the life of the installation.

The Mark 76 On/Off Control Valves, from Jordan Valve, are an advantageous choice for applications as described above. They exhibit very rapid opening and closing times with the short stroke sliding gate design. The pneumatically operated valve can be configured to open when pressure is applied, or to close. The counterforce spring returns the valve to its normal state when no air pressure is applied to the actuator. This allows the valve to be controlled using a small solenoid valve.

The sliding gate design does not use soft seats, but delivers tight shutoff and is suitable for steam service. The low air pressure requirements and short stroke required by the sliding gate contribute to the longevity of the Mark 76 in control applications.

More information is in the datasheet included below. Share your fluid control requirements of all types with valve application specialists, leveraging your own process knowledge and experience with their product application expertise to develop an effective solution.

Mark 76 On/Off Control Valve from Hile Controls of Alabama, Inc.

Bourdon Tube Pressure Gauge Manufacture

Even with the forward march of technology in process measurement, some methods in use for many years maintain their popularity due to performance, ruggedness, or simplicity that can be attractive for many applications. Mechanical pressure gauges certainly fall in that group.

Mechanical pressure gauges employing Bourdon tubes are found throughout industrial process control operations. They provide accurate and immediate indication of the pressure at their connection point, without the need for external power. It can be useful to see and understand how instruments are built and upon what principles they operate. The video included with this post shows the process.

Bourdon tube gauges rely on the principle that a flattened and bent tube will straighten and regain its circular cross section, to some predictable and repeatable degree, in response to an increase in the pressure of a fluid inside the tube. You can see it happen in the video. The balance of the gauge is a case, a face, and mechanical linkage to transfer the Bourdon tube motion into rotation of the indicator needle on the instrument face.

Watch the video. It's informative and well done. Wika, a globally recognized manufacturer of temperature, pressure, and level measurement instrumentation, produced the video at their manufacturing facility. Share your process instrumentation challenges and requirements with a process measurement specialist, leveraging your own knowledge and experience with their product knowledge and application expertise.

Turbine Flow Meters

Turbine flow meters area available in a wide range
of sizes and construction materials.
Image courtesy FTI Flow Technology, Inc.

Precision turbine flow meters are specially designed to accommodate a broad range of precise fluid measurement applications, though differing models and variants tend to be targeted at specific application conditions. They accommodate greater flow rates with lower pressure drops than other meters in their class. The turbine rotates as process fluid passes through the instrument, and special pickups placed around the perimeter of the meter sense the passage of the rotor blades. This produces a high-frequency digital output suitable for interfacing with an assortment of processing, readout and recording equipment. Some turbine flow meters have a symmetrical bi-directional design that supports reverse flow applications without a reduction in accuracy or capacity.

Operating Principle

The following paragraph is mostly excerpted from "FT Series Turbine Flow Meters", an IOM published by Flow Technology, Inc. (document ID is TM-86675, Rev AG) ...with some editing.

A turbine flow meter is a volumetric flow measuring instrument. The flow sensing element is a freely suspended, bladed rotor positioned axially in the flow stream with the flowing fluid pushing against the blades. The rotational speed of the rotor is proportional to the velocity of the fluid. Since the flow passage is fixed, the turbine rotors rotational speed is also a true representation of the volume of fluid flowing through the flow meter. The rotation of the turbine rotor generates electrical pulses in the pickoff that is attached to the flow meter housing in close proximity to the turning rotor. Each one of these pulses represents a discrete volume of fluid. The frequency or pulse repetition rate represents the volumetric flow rate and the accumulated pulse total represents the total volume measured.

Maintenance

A turbine flow meter is a mechanical device. The primary moving part is the rotor, but its balance and bearings need to be kept in good working order to avoid offset of the flow reading. Regular maintenance commonly involves withdrawing of the rotor and internal parts from the body and conducting a cleaning and inspection for corrosion or contamination of the rotor assembly by accumulation of foreign material. In some cases where foreign material buildup is inevitable, a means to isolate and flush the meter with a solvent after use can contribute greatly to reducing the overall maintenance burden.

Installation

Electrical connection and grounding requirements for turbine flow meters are similar to other process measurement instruments. Mechanical installation requires consideration of a number of factors that my impact unit performance. Delivering properly conditioned flow to the instrument inlet and removing or dampening forces and conditions which may produce velocity profile disturbances is a key element of a successful installation. Paying careful attention to flow conditioning at the outset of installation and planning will yield results for the life of the unit. Here is an example of a recommended installation profile, courtesy of FTI Flow Technology, Inc.

Schematic representation of turbine flow meter installation.
Image courtesy FTI Flow Technology, Inc.

Summary

Turbine flow meters, with their simple, durable construction and wide operating range, are an effective and beneficial choice for a number of industrial process applications. As with all instrumentation, there are a number of factors to consider when making a selection. Share your flow measurement challenges and requirements with instrumentation specialists, combining your process knowledge with their product application expertise to develop effective solutions.

Radar Level Measurement

Non-contact radar level transmitter installed in process tank.
Image courtesy Tek-Trol

Radar is a means by which electromagnetic waves of short wavelength (microwaves) are used to detect the presence, distance and location of a remotely located object. While well known for its use in miltary and air traffic control applications, radar ranging technology is used in industrial processing to measure liquid and solids levels in containers of many types.

Condensed to a simple explanation, a radar level measurement instrument emits timed electromagnetic energy bursts, measuring the time interval from each burst emission to return. The emitter directs the microwaves toward the surface of the material to be measured. As the distance from the emitter to the material surface increases, so does the transit time of the wave on its round trip from emitter to media surface and back to a detector antenna. This transit time is proportional to the distance from the emitter to the media surface and can be used to calculate the media level.

Radar level transmitters can provide onboard processing of the raw signal, delivering a standard industrial process control signal which is scaled to a useful value range indicating percentage of tank fill, or some other useful representation of media level. It is necessary for the surface of the material to be measured to have properties which will reflect a sufficient amount of the radiation to allow a detection of the return signal. This is not problematical for most materials, but each application should be discussed with an instrumentation specialist to confirm suitability.

Radar level technology is utilized in a guided wave format, where the emitted energy travels down a tube extending into the medium, and non-contact configurations with the microwave emissions dispersing as they travel from the source antenna. Both types deliver excellent accuracy and have their specific application criteria where they may be preferred.

Properly selecting and applying level measurement instrumentation requires consideration of many operational and technological aspects of each process. Share your process measurement challenges with application specialists and leverage your own knowledge and experience with their product application expertise.

Radar Non-Contact Level Transmitter from Hile Controls of Alabama, Inc.