Flow Control of Slurries and Liquids With Entrained and Suspended Solids

Cutaway view of  manually
operated pinch valve
Courtesy General Rubber

Industrial process control can involve the manufacture, storage, or transport of almost any imaginable fluid. Media can range from water to concrete, hydrogen gas to steam, and anything in between or outside of those boundaries. Valves are a favored control device for regulating fluid flow and they are available in uncountable varieties, each with particular aspects making them more or less suitable for a particular media or application.

Most industrial valves consist of a body, a stem, and some form of flow obstruction which is located within the media flow path. Operation of the stem repositions the obstruction to allow or block the flow. All of these valve types have a defined sealing surface where the obstruction contacts the body. They also have additional seals where the stem penetrates the body. These design features, while providing certain functions and application advantages, also add to the operational complexity and parts count for the valve.

There is a valve type with a simple operating principle that provides superior performance when the application involves certain media characteristics. It is called a pinch valve, and here is where it excels.

• Resistance to abrasion and corrosion from slurries or fluids containing suspended solids and the ability to provide tight shutoff around particulates
• Media and environmental temperature range -40 deg F to +300 deg F
• Low to moderate operating pressure
• Flow regulating capability and tight shutoff
• Non clogging
• Straight through full bore design with minimal flow resistance
• Isolation of the valve body and workings from the media
• Low parts count, low maintenance, easy repair/replacement

A pinch valve consists of a sleeve, through which fluid flows, and a means to compress or "pinch" the sleeve to reduce the open area inside the sleeve. The sleeves are most often fabricated from elastomers with various types of fiber reinforcement. Closure is commonly achieved through movement of one or two bars to squeeze the sleeve, providing throttling or positive closure. The flexibility of the sleeve material allows for tight shutoff, even with fluids containing suspended solids. The valves can be coupled with electric or pneumatic actuators and are available with industry standard connections. One valve variant has a body that can be pressurized to close the sleeve, without the need for a separate actuator. Pinch valves are available with and without an enclosing body.

You should be familiar with the capabilities and forms of this unique valve type. When confronted with certain application challenges, a pinch valve can be a superior solution.

Analynk is committed to excellence in process control, providing wireless communications for process signals, as well as explosion proof enclosures for wireless access points.

Signal Alarms for Process and Operations Monitoring

Telmar 500 Series Signal Alarm
Analynk

Signal alarms provide functionality related to a monitored process condition, which serves as the input to the device. High, low, or both high and low alarm points can be set on the device. When the process condition reaches one of the setpoints, a relay changes state. The relay, rated at 5.0 amperes at 120 VAC, can be used to annunciate the alarm occurrence or activate another device to take some other appropriate action. A number of input options are available that accommodate a broad range of process applications.

• Thermocouple
• Millivolt DC
• RTD
• AC or DC Current
• Slide Wire
• Strain Gauge
• Tachometer
• AC or DC Voltage

The standalone signal alarms can be incorporated into new control installations, or added to existing control systems to expand functionality. More information can be found in the data sheet included below, or reach out to Analynk and share your signal or process monitoring challenges and requirements.

Signal Alarms for Process Monitoring from Analynk Wireless, LLC

Not Your Regular Lightning Protection Scheme

Predictive protection for sensitive electrical equipment
from lightning strikes

Lightning strikes constitute extreme releases of energy. A direct hit to your equipment has a high probability of rendering it unusable. The pathways of this destructive energy can be diffuse and unpredictable, leaving the best protection effort as disconnection of electrical equipment from wiring infrastructure and breaking the conductive path into the equipment.

Alokin Industries, manufacturer of Lightning Shield™ protection systems, identifies four threats to electrical equipment that originate from lightning activity.

• Direct Lightning Strike: Direct lightning strikes to equipment result in high voltages flowing through the equipment grounding path or the circuit serving the equipment.
• Nearby Lightning Strike: These strikes can induce voltage or current on building infrastructure conductors.
• Lightning Ground Potential Rise ( L-GPR): This is the electrical energy flowing out from a strike that can saturate a building's grounding system.
• Off-Voltage Events: Sags and spikes in service line voltage that can damage electrical equipment.

The Lightning Shield™ provides protection by disconnecting electrical equipment when a field energy increase is detected preceding a cloud to ground lightning strike. Isolating equipment from the AC power grid through a positive disconnecting means provides a high level of protection from cloud to ground lightning strikes and their residual impact. The controller will maintain isolated operation for a predetermined amount of time, then switch back to normal AC power. Equipment can be operated from battery or generator sourced power during the isolation period, if needed.

Lightning Shield™ provides predictive protection of electrical equipment by isolating equipment before the occurrence of a cloud to ground lightning strike. The system basically consists of a controller, detector, and whatever disconnecting means (contactor) are needed to accommodate the user's equipment.

Find out more about the Alokin Lightning Shield™, and share your equipment protection challenges with a product application specialist. 

New Hazardous Area Wireless Access Point Enclosures

Model AP 412 Hazardous Area Access Point Enclosure

Analynk Wireless has added two new entries to their line of wireless access point enclosures for use in hazardous areas. Each access point enclosure is shipped ready for installation of your access point device, with hazardous area antennas, cables, mounting bracket, and antenna cables included.

Analynk access point enclosures are preconfigured to house a specific manufacturer and model number access point. Review the product offering and see the long list of accommodated access points. If you want to use an access point not shown on the list, contact Analynk for a solution.

The new models are designed to house the Cisco 2802E and 3802E Dual Band Access Points. Data sheets for both are included below.

Analynk manufactures a diverse array of equipment utilized in establishing wireless connections between industrial process control devices. Share your wireless connectivity challenges with the experts at Analynk and get effective solutions.

Hazardous Area Wireless Access Point Enclosure from Analynk Wireless, LLC

Hazardous Area Wireless Access Point Enclosure from Analynk Wireless, LLC

Magnetic Level Indicators For Tank Level Measurement

Magnetic Level Indicator
Courtesy Orion

The magnetic level indicator (MLI), also called a magnetically coupled liquid level indicator or a magnetic level gauge, is in wide-spread use throughout process industries around the world. Originally designed as an alternative to sight glass gauges, MLIs are now commonly specified in new construction and plant expansions.

Principle of Operation

Magnetic level indicators use magnetic force couple the position of a float to a scale that indicates actual liquid level in a tank. The float movement and scale can be used to activate a switch or provide continuous level data via a transmitter. Unlike a sight glass, magnetic coupling allows the MLI to indicate liquid levels without direct contact between the externally-mounted visual indicator and the fluid in the vessel.

A magnetic field consists of imaginary lines of flux originating from the north and south poles and completely surround the magnet. This field acts on other objects (magnets or ferromagnetic materials) through these forces. When a magnetic field acts upon another body with sufficient force to influence it, the pair are said to be magnetically coupled to each other. In the case of a magnetic level indicator, the float is magnetically coupled to the indicator scale.

The MLI float, located inside the chamber and specifically engineered to provide proper buoyancy in the targeted fluid, dynamically tracks the surface of the liquid as it rises and falls. The magnet assembly inside the float generates a magnetic field that penetrates through the chamber wall to couple with the visual indicator.

Typical applications include:

• Alkylation units 
• Boiler drums
• Feedwater heaters
• Industrial boilers
• Oil / Water separators
• Process vessels
• Propane vessels
• Storage tanks
• Surge tanks
• Wastewater tanks

Advantages of the MLI

A magnetic level indicator is often used in applications where a sight glass (or glass sight gauge) is unsafe, environmentally risky, or difficult to see.

Typical shortcomings of glass sight gauges include:

• High pressures, extreme temperatures, deteriorating seals, and toxic or corrosive materials may cause a risk of fugitive emission of dangerous substances. 
• Some chemical materials within a process vessel or storage tank can attack the glass, causing discoloration of the sight gauge, thus decreasing level visibility. 
• Liquid/liquid interfaces can be very difficult to read in a sight glass particularly if the liquids are of similar color. Clear liquids can also be difficult to see in a sight glass. 
• Liquids that tend to coat or build-up on surfaces can hinder visibility by forming an opaque film on the glass. 
• To cover a large measuring span, sight glass assemblies typically must be staggered using multiple sections. 

Key reasons for selecting an MLI over a sight glass are:

• Improved safety due to the absence of fragile glass and a substantially reduced number of potential leak points. 
• Greatly increased visibility 
• Reduced maintenance. 
• Easier initial installation and addition of transmitters and switches without interrupting the process 
• Lower long-term cost of ownership and legitimate return-on-investment benefits. 
• Single chamber measurement over 20 ft. (6 m) without staggering chambers.

When using a transmitter in conjunction with a magnetic level indicator, consider using a wireless connection to deliver the process signal from the transmitter to the monitoring and control unit. Analynk has effective solutions that can be easily implemented. A video shows an application example.

Setting Up the A16000 Wireless Expansion Module

How Far Is Too Far with Wireless Process Signals?

Wireless communication technology, adapted for industrial use, has brought a host of benefits to companies bold enough to include it in their process control infrastructure. The use of wireless communications to deliver operating data from sensor to control station is no longer avant garde. The innovators, those first to deploy new technology, have long ago pushed the industrial process control world sufficiently up the learning curve to a point where applying wireless is a fairly straight forward matter.

Are there limits, practical or theoretical, to the length of a wireless connection?

Consider the bandwidth options for wireless transmission of a process signal. The 2.4GHz and 900MHz frequency bands each have their advantages for shorter distances in the range of a few feet to several miles. The ability to connect over any distance is impacted by a number of factors, not the least of which are allowable transmission power level and obstacles to the clear line of sight. One way to extend the range of a device is to install a repeater at some point along the transmission path. Repeaters will receive a fading process signal and transmit the signal at the full available strength, increasing the distance over which the information can be transmitted. Repeaters can also be useful for bypassing obstacles in the transmission path.

What if connection is needed over a longer distance?

There are other options for bandwidth that can extend beyond a few miles. If service is available at transmission and receiving sites, cellular networks may be a workable option. Satellite data transmission is also a viable option that can provide global connectivity.

Distance is not really a great hurdle to overcome when it comes to establishing an industrial wireless connection. Share your industrial wireless challenges with application experts. Combining your process knowledge with their wireless expertise will produce effective solutions.