Happy 4th of July from Process Control Solutions!

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Harry S. Truman

Process Control Solutions: Delivering Innovation, Professionalism, Knowledge and Experience

Control Systems - Turn-key process automation and systems integration services, including SCADA, PLC & HMI programming, industrial control panels fabrication, product testing, and Wonderware integration.

Fluid Systems - Specializes in the design and manufacture of custom fluid power systems, test stands, and special machinery.

Fluid Power - Your source for fluid power equipment and control products.

Flow Control - Your source for valves, valve actuation, pressure relief devices and other related accessories as well as services required by the diverse process industry.

Field Services & Repair - Industrial service company with decades of experience in flow solutions, on-site and off-site repair, maintenance and installation, and product sales and application support.

Understanding Sequence Diagrams in Fluid Power

A sequence diagram is a type of illustration that graphically represents the physical state of each component in a system sequencing charts can be used in electrical fluid or combined systems. They are used to aid the user in understanding the operation of the system and to help identify which components are actuated or energized at any given time during the system cycle. Many sequence diagrams are used as auxiliary documentation to assist with illustrating the information conveyed on schematics or circuit diagrams. While there is no official standard for drawing a sequence diagram, most are drawn with the time lapse on the horizontal axis and the action accomplished on the vertical axis. to build a sequence diagram each major component is assigned a horizontal line. the width of the line shows the time period during the cycle that each component is actuated or energized.

This video provides a visual understanding of the sequence diagram, and its associated electrical and mechanical schematic diagrams.

Process Controls Solutions
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What Are Custom Hydraulic Power Units?

Custom HPU's for assembling automotive drivelines
(Process Control Solutions)

There are many manufacturers of standard model hydraulic power units (HPUs), all of which provide an off-the-shelf, readily available, generically configured system. These standard HPUs are a quick and easy solution when hydraulic power is needed. Many times though, standard HPU's don't fit the bill, and a more customized unit is needed. What to do then?

Custom Designed HPUs
Custom manufactured HPUs are hydraulic power solutions designed to fit a customers exact requirement. Customization generally involves the inclusion of special manifolds, cooling fans, level controls, heat exchangers, filtration systems, relief valves, pressure switches and temperature control.

Why Custom?
Certain processes require unique features. A user's proprietary application might require higher pressures, faster response, or continuous operation. While is sounds antithetical, custom HPUs can actually be less expensive than prebuilt, standard model units. This is because custom units are sized and equipped with only the components the application requires. So in actuality, deciding on a custom HPU can potentially lower initial cost and increase profits by improved long-term performance.

Applications
Custom hydraulic power units are used in widely in compacting applications, automotive manufacturing equipment, transportation equipment, mining equipment, agricultural equipment, and in many industrial applications.

Vendor Selection
The variety of specialized features for hydraulic power units is endless, making engineering depth and broad application experience very important. Make sure this is proven when interviewing a prospective vendor. The more diversified they are in applying hydraulic power units, the more likely you'll have a positive outcome.

Industrial Butterfly Valves

Resilient seated butterfly valve (Pratt)

Industrial process control valves are available in a very wide array of materials, types, and configurations. The first step of the selection procedure for a valve application should be choosing the valve type, thus narrowing the selection field to a more manageable level. Valve types, ball, butterfly, globe, and plug for example, are generally defined by the closing mechanism of the valve.

High performance butterfly valve (Pratt)

A butterfly valve uses a  flat disc that is positioned, paddle-like, in the fluid flow path. It rotates around a central axis (the stem) over a 90 degree rotational arc from open (position parallel to the flow direction) to closed (perpendicular to flow). Butterfly valves referred to as resilient seated are generally used in lower pressure, lower temperature applications and create a seal through compressing the disc into some type of elastomer seat. Another type of butterfly valve, used in higher pressure and higher temperature applications, are known as high performance butterfly valves (HPBF). They have highly machined discs and seats which are precisely seated together. Butterfly valve body materials include cast iron, bronze, and stainless steels. It is common to line the butterfly valve with another material to provide special protection from the process media.

Butterfly Valve Advantages:

• Lower cost
• Minimal lay length
• Easy to automate
• Generally lower torque

Butterfly Valve Disadvantages:

• High wear rate - seals are in flow paths
• Not a good choice as a control valve. Has a very nonlinear flow coefficient. 
• Not great for erosive flowing media.

Butterfly valves, like other valve types, have applications where they outperform. Careful consideration and consultation with a valve expert is a first step toward making a good selection.

Rotary Actuators in Fluid Power Systems

A rotary actuator is an output device for a fluid power system that delivers an oscillating motion over a limited range in less than one full revolution of the circle.

A true rotary actuator produces work by direct action of fluid pressure against internal vanes. Work is defined as a force applied over a distance. Rotary actuators produce a special type of rotational work called torque.

Torque occurs when a force acts on a radius. Since rotary actuators operate at low speed with high torque, torque output rather than the horsepower is used for the rating and identification purposes. Speed is a secondary consideration when choosing a rotary actuator for a particular application.

The typical units of measurement for torque are foot pounds (lb·ft). For example, if a rotary actuator with an arm length or radius of two feet were used to lift the two hundred-pound weight, then the resultant torque required to accomplish the work would be 400 lb·ft.

Understanding the relationship between the output torque required and the physical set up a fluid system enables designers to determine the appropriate rotary actuator for each unique application.

The video below illustrates the mechanics and the physics behind rotary actuators.

Pinch Control Valve for Wash Water Discharge in Treatment Plant

In wastewater treatment plants a pressure control valve is often needed on a standby pump to control discharge of wash water from the wash water pumping station.

Wash water discharge diagram using pinch control valve (Red Valve) 

Red Valve Series 5400

The main pump and the standby pump are rated to provide maximum flow at a constant pressure. A pressure sensor with integral transmitter is required to continually monitor system pressure. Under normal operating conditions, the pressure control valve is normally closed. After the surface wash shuts down, pressure from the discharge pump changes. The sensed line pressure is transmitted to a controller which sends a signal to the positioner on the control valve.

As the line pressure increases, a Red Valve Series 5400 control pinch valve opens. As the flow demand increases, line pressure decreases, and the valve closes. This system constantly maintains the pressure needed to operate the system. From the pressure control valve, the system discharges to atmospheric pressure over a clear well.

Due to the potentially high pressure drop conditions, the pressure control valve needs to be able to withstand the effects of possible cavitation. Red Valve Series 5400 control pinch valves, with their one-piece elastomer cone sleeve construction, are ideally suited for this application. The flow characteristics and pressure drop capabilities of the cone sleeve controls the flow and handles the pressure drop in the system. To assure cavitation does not occur, a TFO variable orifice to stage the system pressure drop by creating back pressure on the control valve. This setup fulfills the need of the treatment plant, and is a proven cost-effective, maintenance-free solution.

Reprinted with permission from Red Valve.