Friday, June 19, 2015

Industrial Control Valve Basics - An Introduction

Industrial process control valve
Globe Valve with Pneumatic Actuator
Courtesy Warren Controls
Valves, mechanical devices able to control flow or pressure in a process or system, are as ubiquitous as any industrial process control element. As essential components of piping systems conveying liquid, gas, vapor, or slurry, valves are a component with which almost every industrial process and control engineer will require more than entry level familiarity. They are the controlling element in almost any fluid handling system. What are some of the very basic knowledge points for specifying and selecting a control valve?

There are numerous types of valves available, including butterfly, ball, check, globe, gate, diaphragm, plug, and control valves as the most common. Particular valve types can be better suited to the medium being controlled, or have functional capabilities making them a better selection for your process application. Within each type there will be a wide range of options and features that allow for close tailoring of the complete valve assembly to match the application requirements.  Some valves can be self-operated, while others require manual operation. A pneumatic, hydraulic, or electric actuator can be employed on certain configurations to provide for remote control of the valve by a human operator or automatic controller.
General valve functions include:
  • Flow start or stop
  • Flow rate increase or reduction
  • Diversion of flow in another direction
  • Regulation of a flow or process pressure

Industrial process control valves are often classified according to their mechanical movement. Some common examples include:
  • Linear motion valves, in which the closure element moves in a straight (linear) direction to control the flow. Gate, globe, and diaphragm valves are in this category.
  • Rotary motion valves have a closure that follows an angular or circular path. Butterfly and ball valves are in this group.
  • Quarter turn valves, a subset of the rotary motion class, traverse from the open to closed state when the closure element (for example, the ball in a ball valve) is rotated through a quarter of a full turn. This type is best suited for operations calling for either fully open or closed regulation, with no need for control at points in between those two states.

Each industrial control valve application and installation will have its own set of very specific requirements. The goal of the specification and selection process should be to provide safe operation, low maintenance requirements, robust and accurate operation. A manufacturer's sales engineer can be a useful source for application and specification information and assistance.
Oil Pipeline Valve
Ball Valve Installed in Pipeline
Courtesy DHV

Thursday, June 11, 2015

The Often Undervalued Sales Engineer

Call a sales engineer
Sales engineers add value.

Process and control equipment is most often sold with the support of sales engineers working for the local distributor or representative. Realizing what they have to contribute, and taking advantage of this available talent, will help you save time, cost, and also assist in achieving a better outcome for the project.

Consider these contributions:

Product Knowledge: Sales engineers, by the nature of their job, are current on new products, their capabilities and their proper application. Unlike information available on the Web, sales engineers get advanced notice of product obsolescence and replacement. Also, because they call and work with so many different types of companies, sales engineers are a wealth of tacit knowledge that they readily share  with their customers.

Experience: As a project engineer, you may be treading on fresh ground regarding some aspects of your current assignment. You may not have a full grasp on how to handle part of a control loop. Call in the local sales person - there can be real benefit in connecting to a source with past exposure to your current issue.

Access: Through a technical sales engineer, you may be able to look “behind the scenes” with a particular manufacturer and garner important information not publicly available. Sales reps deal with people, and make it his/her business to know what’s going on with products, companies, and industries.

Of course, sales engineers will be biased. Any solutions proposed are likely to be based upon the products sold by the representative. But the best sales people will share the virtues of their products openly and honestly, and even admit when they don’t have the right product. This is where the discussion, consideration and evaluation of several solutions become part of achieving the best project outcome.

As an engineer who designs or manufactures a product or process, it's highly recommended you develop a professional, mutually beneficial relationship with a technical sales expert. Look at a relationship with local sales engineer as symbiotic. Their success, and your success, go hand-in-hand.

Friday, May 29, 2015

Industrial Valve Body Style and Flow Path: A Visual Illustration

fluid dynamics image
(Image courtesy of Wikipedia)
There are many types of valves body styles, each with their own unique flow characteristic and pattern. Valve design generally dictates optimum application service for any given use. For instance, globe or diaphragm valves provide excellent flow control because of a very linear flow characteristic and are used widely as flow control valves. Conversely, standard ball or butterfly valves are not good control valves because of their very non-linear flow characteristic, and special modifications need to be made to their discs or balls to improve linearity.

The following video illustrates the design and flow pattern for (4) types of valve:

Monday, May 18, 2015

And Now for A Little Shameless Self Promotion ...

A little shameless self promotion to spread the word of what lines Mountain States Engineering and Controls carries should anyone out there need assistance.

MSEC, Inc. is a Manufacturer's Representative & Distributor of process equipment and controls headquartered in Lakewood, Colorado since 1978.

We serve the markets of Colorado, New Mexico, Wyoming, Montana, Utah, Nevada, Idaho, and the western Dakotas.

Monday, April 27, 2015

Differences Between a Regenerative Turbine Pump and a Centrifugal Pump

Regenerative turbine pump have double row vanes cut in the rim. The impeller rotates within two liners into which annular channels have been milled. Liquid flows in at the suction and is picked up by the impeller vanes. In completing nearly one revolution in the annular channel, the fluid develops a high velocity and pressure increases dramatically before being sent out the discharge. The liquid re-circulates between the impeller vanes and the annular chamber. Because of this action, the fluid flows in a path like a helical spring laid into each of the annular grooves as the fluid is carried forward. Energy is added to the fluid by a number of vortex impulses in the impeller vanes, as it travels from suction to discharge.

These impulses have the same effect as multi- staging in a centrifugal pump. In a multistage centrifugal pump, the pressure is the result of energy added in each stage. In a turbine pump, pressure is added to the fluid stream by circulating many times through the vanes of a single impeller.

One of the most remarkable features of the regenerative turbine pump is its performance characteristics when pumping highly volatile liquids. The manner in which the turbine impeller imparts velocity/energy to the fluid, as described above, is quite different from conventional centrifugal or positive displacement designs. The continuous, progressive building of pressure in a regenerative turbine pump essentially eliminates the sudden collapse of bubbles that is destructive cavitation.

turbine pump can develop about ten times the discharge pressure of a centrifugal type having equal impeller diameter and speed. Pressure increases nearly uniformly around the impeller rim. At the impeller hub, the pressure is about one half the discharge pressure. This lower pressure, plus suction pressure, is what is seen in the stuffing box. Holes through the impeller keep the impeller centered to reduce wear, prevent unbalanced pressures on the impeller and reduce end thrust on the bearings.

  • Develop higher pressures
  • Can be run at lower motor speeds
  • Eliminate cavitation
  • Operate with lower NPSHr
  • Deliver specified capacity with input pressure variations
  • Meet performance with fewer stages
  • Smaller size
For more information on regenerative turbine pumps, contact:

Mountain States Engineering and Controls
1520 Iris Street
Lakewood, CO 80215
303.232.4100 Phone
303.232.4900 Fax

Tuesday, April 14, 2015

Wet Cooling Towers

Cooling tower (courtesy
of Delta Cooling Tower)
Water cooling towers are some of the most essential pieces of equipment for commercial and industrial buildings today.

Cooling towers may either use the evaporation of water to remove process heat to cool the process fluid, or may use forced or convective air to cool the process fluid.

Wet cooling towers use the natural process of evaporation (of water) to cool equipment.  They rely on an exchange of heat between the equipment, the water in the tower, and the air passing through the tower.

Excess process heat is absorbed by the water in the cooling tower as it passes through a labyrinth of fins and tubes in the structure. As the water is warmed, it comes into direct contact with cool air passing through the tower. The interaction between cool air and warm water causes the warmest water droplets to evaporate and is released out of the tower into the atmosphere. The remaining water cools back down and can be reused through the system again.

Common applications include cooling the circulating water used in refineries, chemical plants, power stations and HVAC systems for cooling buildings. Due to the cost-effectiveness and readily available supply of water, companies use wet cooling towers to provide cooling continuously and cheaply.

While cooling towers are normally defined as “a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature”,  one must keep in mind that the “waste heat” emissions are just water droplets, and are not harmful to the atmosphere nor to the environment.

Friday, April 10, 2015

Electrical Pressure Sensor Types

Here is an introduction to the basics of electrical pressure sensors, from Tony Kuphaldt's Lessons in Industrial Instrumentation.

This presentation explains how a variety of electrical pressure sensors work, including piezoresistive (strain gage), differential capacitance, and resonance sensors.

Sensor principles, sensor mounting and associated hardware design for pressure transmitters and differential pressure transmitters are also described.

Click on the image below to open the presentation (viewable on all devices).

pressure sensors
Click on image to see presentation.