Foot Valves: Basic, Hidden, Essential

Foot valve showing inlet filter screen
Colton Industries

A foot valve is a purpose specific check valve. Designed for immersion in a well, tank, or other liquid containing vessel, it serves as a one-way inlet valve on piping leading to the suction side of a pump. Foot valves and their connected piping will extend downward from the pump suction elevation. The purpose of the valve is to maintain prime on the pump by preventing the water column in the suction line from collapsing, due to gravity, and draining all the liquid from the suction side of the pump system.

For industrial applications, there are numerous versions of foot valves available in varying sizes, capacities and materials of construction. The function of the valve is simple, so the key selection criteria can be focused on features that will contribute to longevity and reduce or eliminate any maintenance burden.

The data sheet below provides some good illustrations of a foot valve and how it is installed. Share your fluid processing and control challenges with application experts, combining your process and facility knowledge with their product application expertise to develop effective solutions.

Foot valve for industrial pump applications from MSJacobs-Cali

Pneumatic Volume Booster Function

Pneumatic Volume Booster
Fairchild

A volume booster is used in a pneumatic control system to relay a low flow signal as one with greater flow volume. The common configuration is to provide a 1:1 ratio between the input and output pressure, keeping the input and output signals the same pressure. Products are available that deliver different ratios.

The general purpose of a volume booster is to provide a relay between a system with low flow volume and one with higher volume requirements. A typical example is a pneumatic actuator. The flow available through the pneumatic signal line may be insufficient to deliver the response rate desired from the pneumatic actuator. A volume booster, with control over an independent air supply, solves this challenge with increased flow volume at the same pressure as the control signal.

Volume boosters are simple in operation. The input signal applies force to one side of a diaphragm, the output pressure to the other. An imbalance between the two applied pressures will cause the diaphragm to move, changing the position of the valve and the outlet pressure until the two forces are again in balance. Little maintenance is required when the units are properly installed and supply air is of good quality.

The unit pictured is from Fairchild, a well recognized manufacturer of industrial pneumatic components, and provides a 1:1 ratio. There are some key points in the selection process, so reach out to a product specialist with your pneumatic system challenges and requirements. Combining your process and facility knowledge with their product application expertise will produce effective solutions.

Volume Booster for Pneumatic Control Signal from MSJacobs-Cali

Conductivity Controller For Boiler Applications

Conductivity controller for boiler applications
Lakewood Instruments

Modern boilers using the Rankine cycle require feedwater and make-up feedwater quality maintained within certain limits with respect to alkalinity, conductivity, and other factors in order to maintain boiler operating efficiency and minimize maintenance requirements.

Controlling the feedwater quality can be accomplished with the addition of controlled amounts of the right chemicals to regulate various aspects of water quality. Another method is to purge, or blowdown, the boiler in a measured fashion that allows fresh feedwater to replace overly contaminated water. Filtration, which I generally deem to include ion exchange, reverse osmosis, and mechanical filtration, is a third method. All deal specifically with a limited scope of contaminates that have an impact on boiler operation and longevity.

Boiler blowdown can be used to limit the amount of total dissolved solids in the boiler drum water. As water boils, the dissolved solids in the water concentrate in the remaining liquid water. Blowdown purges a portion (or all) of this water, allowing the addition of water, presumably treated, with substantially lower total dissolved solids.

Boiler blowdown has an energy cost, since the replacement water must be heated to the design condition. It follows that executing this procedure should be undertaken when necessary, but not more frequently. A conductivity monitor and controller can accomplish properly timed blowdown cycles. The system consists of a conductivity sensor and a control unit that provides all the necessary functionality in a single integrated package. A data sheet is included below for one such unit from Lakewood Instruments.

Share your boiler operation challenges with an instrumentation specialist an explore how a properly instrumented steam system can provide operational savings and extended time between failure.

Water Treatment Controller For Boiler Applications from MSJacobs-Cali

Process Control - Annunciator Panel as Cyber Defense Measure

Standalone Annunciator Panel
Ronan Engineering Company

There are numerous applications for annunciator panels, stations, and equipment throughout the various industrial markets. One such application, arising and growing with the connectivity of industrial control systems to the internet, is in the cyber defense arena.

Industrial control systems are increasingly internet connected, making them vulnerable to cyber attack. There was a time when all that was necessary for plant or operation security was installing a perimeter fence around the property and posting a guard at the gate. Our industrial control systems are now subject to mischief or malicious attack from locations and parties unknowable and worldwide.

Do you know of ICS-CERT? If involved in industrial control, you should. It is the Industrial Control Systems Cyber Emergency Response Team, a part of the Department of Homeland Security that provides operational capabilities to defend control systems against cyber threats. You can follow them on Twitter, @ICS-CERT, and monitor the vulnerabilities and threats that they discover in the industrial control sphere. New items are added almost daily, naming specific vulnerabilities uncovered in named systems and equipment. Chances are that you will discover some of the equipment in your plant listed.

Annunicator systems and equipment can be employed as an isolated "watcher", monitoring process performance and providing alerts when conditions exceed specified limits.

A major impact of a potential cyber attack scenario is that, as operator, you can no longer fully trust what your software based internet connected control system is telling you, or whether it is doing everything it should and only those things that it should. An annunciator system, isolated from the primary control system and the internet, monitoring critical process conditions, incorporates a substantial level of safety against cyber attack.

There is more to be learned. Browse the document included below for a detailed visual demonstrating the set up of annunciators that can be isolated from your network. Share your process control challenges with specialists, and combine your process and facility knowledge with their product application expertise to develop effective solutions. And start following @ICS-CERT on Twitter and build your awareness and knowledge of industrial control cyber threats. 

Cyber Defense - Annunciators as watcher for critical process applications from MSJacobs-Cali

Silicone Rubber Heater Blankets - Flexible Heat Where You Need It

Silicone rubber heater in one
of its simplest forms
BriskHeat

Electric heaters for industrial and commercial applications are available in an almost dizzying range of types, materials, and forms. One of those is the silicone rubber heater.

Stock shapes and sizes are available from many manufacturers, but one distinct advantage of silicone rubber heaters is their flexibility. The resistance heater wires are encased in a silicone rubber sheet, providing the ability to wrap the assembly around an object or manipulate it into a close fit with the target of a heating application. The silicone rubber encasement also provides a high level of protection for the heater wires from impact, moisture, and some chemicals.

The watt density of the heaters can be specified to provide a good match between the delivery of heat and the need for it. Custom shapes and configurations can be manufactured to order, and on board or remote controllers provided. Pressure sensitive adhesive is a common option that facilitates the installation of the heater assembly to a part or vessel.

The maximum application temperature is in the range of +450°F (+232°). These heaters are a useful selection option for a large range of operations demanding heat to be applied directly to a surface, object, tank, drum, or other vessel. Share your industrial heating requirements with product specialists for the best match up between heater technology and your application.

Applying Precision Turbine Flow Meters

High precision turbine flow meters
Courtesy Cameron Measurement Systems

Precision turbine flow meters are specially designed to accommodate a broad range of precise fluid measurement applications. They accommodate greater flow rates with lower pressure drops than other meters in their class. Some have a self-flushing design for longer sustained accuracy. The turbine's high-frequency digital output is suitable for interfacing with an assortment of 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 is excerpted from Model 700 Series Turbine Flowmeter User Manual, from Cameron Measurement Systems....with some editing)

Fluid flows over a diffuser section and is accelerated onto a multi-blade hydro-dynamically balanced turbine rotor. The rotor speed is proportional to the volumetric flow rate. As the rotor turns, a reluctance type pickup coil (mounted on the meter) senses the passage of each blade tip and generates a sine wave output with a frequency that is directly proportional to the flow rate.

The rotor is the only moving part of the turbine flow meter. The small lightweight rotor hubs ensure fast response to process flow changes. The rotor is hydro-dynamically balanced during operation, eliminating the need for mechanical thrust leveling. This low-friction design improves metering linearity and reduces wear and maintenance.

A variable reluctance generating pickup coil contains a permanent magnet and a wire winding. In some cases, the rotor blade of the turbine meter is made of a ferritic stainless steel such as grade 430. The movement of the rotor blade in proximity to the magnetic field of the coil tip produces an AC type voltage pulse within the coil winding. An alternate arrangement finds the ferritic bars embedded in the rotor shroud, where they can interact with the pickup coil. Increasing the quantity of bars on the shroud to outnumber the rotor blades provides more pulses per unit volume (resolution). This feature can be valuable when proving large-capacity meters with a small-volume prover. Shielded wire cable conveys the output of the pickup coil to compatible electronic instruments to indicate flow rate, record, and/or totalize the volumetric flow. The coil itself does not require electrical power to operate.

The meter may be factory-fitted with multiple coils for redundancy, indication of flow direction or pulse train verification. The pickup coil type and magnetic strength vary with application requirements.

The turbine flow meters are calibrated in a horizontal position. Therefore, the best correlation of calibration occurs when the meter is operated in this plane. However, the meter will operate satisfactorily in any position.

System Pressure

The maximum and minimum system pressures must be considered when applying the turbine meter. To obtain proper response, a back pressure should be applied to the meter. This back pressure should be at least twice the pressure drop of the meter at maximum flow. For liquid meters, the back pressure should be twice the pressure drop of the meter at maximum flow, plus twice the fluid vapor pressure.

Summary

Turbine flow meters, with their simple, durable construction and wide operating range, may be the right choice for a number of 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 the most effective solutions.

Turbine Liquid Flow Meters from MSJacobs-Cali

Video Demonstration of Transit Time Difference Method of Flow Measurement

Portable Ultrasonic Flow Meter
Flexim

The measure of flow is a pervasive task in fluid process control. There are several differing technologies employed for measuring fluid flow, each with its own set of performance and application attributes that might make it the advantageous choice for a particular operation.

Ultrasonic flow measurement uses several methods for determining the average velocity of a fluid. One of those methods employs the difference in the transit times of ultrasonic pulses travelling with the flow direction and against the flow direction. The flow velocity of the media will offset the transit times between the flow and counterflow measurements. The measured difference in transit times can be used to determine average flow velocity and, with additional processing, mass flow.

Ultrasonic flow meters are accurate and provide repeatable results, making them suitable for custody transfer operations, as well as many other process control applications. Little maintenance is required and the units have no moving parts. Measurement instruments are available with in-line or clamp-on mounting, providing a high level of installation and application flexibility.

The short video below provides a clear explanation of how transit time difference measurement works. Share your flow measurement challenges and requirements with a product application expert, combining your process knowledge with their product expertise to develop effective solutions.