Introduction to a Closed Loop Control System

Closed Loop Control System

The video below explains the concept of a closed loop control system, using a steam heat exchanger and food processing application as an example.

A closed loop control system uses a sensor that feeds current system information back to a controller. That information is then compared to a reference point or desired state. Finally, a a corrective signal is sent to a control element that attempts to make the system achieve its desired state.

A very basic example of a temperature control loop includes a tank filled with product (the process variable), a thermocouple (the sensor), a thermostat (the controller), and a steam control valve feeding a tubing bundle (the final control element).

The video outlines all the major parts of the system, including the measured variable, the set point, the controlled variable, controller, error and disturbance.

Contact http://www.ivesequipment.com with any process control or instrumentation requirement. Call 877-768-1600 for immediate assistance.

Level Instrumentation for Your Entire Industrial Plant

Siemens level controls.

Whether you are measuring liquids, slurries or bulk solids, Siemens provides the ideal level measuring instruments for every job. Siemens level measurement devices set the standard in their respective disciplines for water, cement, mining, chemical, petrochemicals, food, beverage, pharmaceutical and other industries.

Point Level

Siemens level switches for point level measurement are distinguished by their outstanding performance. Their robust design ensures reduced cost of maintenance, spare parts, and downtime. Siemens level measurement instruments offer easy commissioning, connection to alarm or control systems, long service life, and low operating costs. Technologies include capacitance, rotary paddle, ultrasonic and vibrating.

Continuous

The product portfolio for continuous level measurement covers both contacting and non-contacting measurement. Radar, ultrasonic and gravimetric technologies are available for the non-contacting applications. Capacitance, guided wave radar and hydrostatic technologies are available for the contacting applications. As well, don’t forget that the safest engineered level measurement solution includes switches for back-up, overfill, low level and dry run protection. Technologies include radar, guided wave radar, ultrasonic, gravimetric, capacitance, and hydrostatic.

Interface

Siemens broad portfolio includes a large number of devices for many interface measurement applications, and includes the following products. SITRANS LC500, Pointek CLS 100, CLS 200, CLS 300 and CLS 500 are capacitance instruments for a wide range of tasks. The SITRANS LG uses guided wave radar technology.

Watch the entertaining video below to get a better idea of what level solutions Siemens (and Ives) has to offer.

Consider Controlled Environment Room Air Flow

Air flow characteristics can determine how well a controlled
environment room or chamber performs for an application

Environmental chambers, whether of the reach-in or walk-in variety, all rely on the movement of air within their controlled space to attain performance specifications. Various manufacturers will employ differing strategies for chamber air movement, and the manner in which their designs disperse air flow throughout a chamber of any size can have an impact on the work or process held within the chamber.

This article is about controlled environment rooms, but much of what is included here is also applicable to smaller sized chambers.

The design of air flow in a controlled environment room can be impacted by a number of factors, some of which may be based on specific application requirements, and others that may be influenced by cost, production simplicity, or other factors unrelated to the performance goal of the equipment.

What aspects of controlled environment room air flow bear on performance?

• Velocity - In the common usage of the term when referring to air flow, the speed of the moving air. Depending upon the air moving equipment arrangement and any dispersion devices, such as perforated suspended ceilings or wall plenums, air velocity can vary throughout a chamber. Users should consider how their work may be impacted by air flow velocity. The storage of material in closed and sealed containers may be impervious to air velocity effects because the "product" within the container is not in contact with the moving air. Plants and insects, on the other hand, are an example of items that may be significantly or severely impacted by air velocity. Higher air velocity at a chamber location exposes that location to more air per unit of time. Desiccation is one possible concern that is exacerbated by increased air velocity. Higher velocity can also be beneficial, even necessary, for some applications. Rapid cooling or heating of materials placed within a chamber is enhanced by increased air movement across the material surface.
• Volume - The volumetric flow of air through a controlled space or chamber is needed to transfer heat to or from the space in order to maintain temperature control. Much of the air in a controlled environment room is recirculated, with cooling, heating, and in some cases moisture applied to condition the air in the room to the setpoint. The volume of air movement is loosely related to velocity, so increasing volume will result in an increase in velocity unless other design changes are made with respect to how the air is dispersed throughout the room. Higher volume, or turnover rate, contributes to better temperature uniformity in the room. As with velocity, there may be application specific requirements for low air movement. Keep in mind that low air movement creates challenges to the attainment of close temperature control and uniformity. 
• Pattern - The way in which air is distributed throughout the controlled environment room can impact system performance once materials are placed in the room or process work is commenced. Empty chambers generally perform well, regardless of the air flow pattern, because there is little in the way of a load on the system and no solid materials in place to block or redirect air flow. Consideration should be given to the way in which air is dispersed throughout the work area. Loading patterns for stored product or the placement of work in process should be accommodated by the air flow pattern.

Matching the right air flow characteristics to the work to be achieved in a controlled environment room will result in better overall performance, not just when empty chamber tests are conducted, but when real work is being accomplished.

Share your environmental chamber and controlled environment room requirements and challenges with application experts. The combination of your own experience and knowledge with their specialized technical expertise will yield an effective solution.

Monitoring Catalyst Presulfiding

Catalyst ‘presulfiding’ is a practice which reduces the extent of early catalyst deactivation on by preventing coking (carbon deposits). The procedure involves passing a gas stream containing H₂S over the catalyst or into the reaction feedstock.

In order to generate the H₂S which will interact with the catalyst, a sulfur carrying agent (e.g. dimethyl sulfide) is injected into the stream. Under high temperature and catalytic reaction, the agent decomposes and releases its sulfur component, forming H₂S. The H₂S reacts with the catalyst’s metallic surface to substitute sulfur atoms for oxygen atoms.

Read the document below to learn more about monitoring this process with the Applied Analytics OMA-300 H₂S Analyzer

Monitoring Catalyst Presulfiding Step from Ives Equipment

Ives Equipment Business Groups

Ives Equipment organizes its extensive product line into four distinct groups:

Ives Equipment and Controls, providing instrumentation and control products to the chemical, petro-chemical, refining, bulk storage, primary metals, pulp & paper, powergen, gas & oil distribution and OEM markets.

Pharmaceutical, Bio-pharm, and Sanitary, providing hygienic, ultra-pure and sanitary instruments, connectors, fittings, tubing and gaskets to the pharma, bio-pharm, food and beverage, life-science and labortory industries.

Analytical Instruments, used to analyze process material samples and record the data for quality, conformance and compliance.

Water and Wastewater Treatment, providing instruments, analyzers, valves and controls for the transfer, storage, analysis, treatment, and logging of municipal and industrial water treatment systems.

Definition: Industrial Valve Actuator

Pneumatic actuator on ball valve.
(Worcester)

Actuators are devices which supply the force and motion to open and close valves. They can be manually, pneumatically, hydraulically, or electrically operated. In common industrial usage, the term actuator generally refers to a device which employs a non-human power source and can respond to a controlling signal. Handles and wheels, technically manual actuators, are not usually referred to as actuators. They do not provide the automation component characteristic of powered units.

Electric actuator (Worcester)

The primary function of a valve actuator is to set and hold the valve position in response to a process control signal. Actuator operation is related to the valve on which it is installed, not the process regulated by the valve. Thus a general purpose actuator may be used across a broad range of applications.

In a control loop, the controller has an input signal parameter, registered from the process, and compares it to a desired setpoint parameter. The controller adjusts its output to eliminate the difference between the process setpoint and process measured condition. The output signal then drives some control element, in this case the actuator, so that the error between setpoint and actual conditions is reduced. The output signal from the controller serves as the input signal to the actuator, resulting in a repositioning of the valve trim to increase or decrease the fluid flow through the valve.

Electro-hydraulic actuator
(MIH Trident)

An actuator must provide sufficient force to open and close its companion valve. The size or power of the actuator must match the operating and torque requirements of the companion valve. After an evaluation is done for the specific application, it may be found that other things must be accommodated by the actuator, such as dynamic fluid properties of the process or the seating and unseating properties of the valve. It is important that each specific application be evaluated to develop a carefully matched valve and actuator for the process.

Hydraulic and electric actuators are readily available in multi-turn and quarter-turn configurations. Pneumatic actuators are generally one of two types applied to quarter-turn valves: scotch-yoke and rack and pinion. A third type of pneumatic actuator, the vane actuator, is also available.

For converting input power into torque, electric actuators use motors and gear boxes while pneumatic actuators use air cylinders. Depending on torque and force required by the valve, the motor horsepower, gearing, and size of pneumatic cylinder may change.

There are almost countless valve actuator variants available in the industrial marketplace. Many are tailored for very narrow application ranges, while others are more generally applied. Special designs can offer more complex operating characteristics. Ultimately, when applying actuators to any type of device, consultation with an application specialist is recommended to help establish and attain proper performance, safety and cost goals, as well as evaluation and matching of the proper actuator to the valve operation requirements. Share your fluid process control requirements with a specialist in valve automation, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Contact Ives Equipment for any valve actuator application. Visit http://www.ivesequipment.com or call (877) 768-1600.

Principles of Ultrasonic Flow in Industrial Clamp On Flow Meters

The video below demonstrate the principles applied to industrial clamp on flow meters using the SITRANS FS as an example.

The ultrasonic technology of the SITRANS clamp on flow meter provides highly accurate measurement of liquids and gases. With no pressure drop or energy loss, a wide turn-down ratio and no need to cut the pipe or stop the flow, installation is easy and maintenance is minimal.

For more information about ultrasonic flow meters, contact Ives Equipment at 877-768-1600 or visit http://www.ivesequipment.com.