Thursday, December 31, 2015

Happy New Year from the Mead O'Brien Team

Everyone at Mead O'Brien would like to wish all of our customers, vendors, suppliers, families and friends a very happy, healthy and prosperous 2016!

We look forward to serving our customers and working alongside you for our mutual success and growth.

Cheers!
The Mead O'Brien Team

Tuesday, December 29, 2015

The Rotary Globe Control Valve

Neles Rotary Control Valve
Neles Rotary Control Valve
Neles, a division of Metso, offers their "RotaryGlobe" control valve designed to control a wide range of process liquids, gases and vapors. Its provides reliable and rugged construction and is available with a variety of different trim choices.  An excellent candidate for general, difficult and even severe service control valve applications for many industries including chemical, petrochemical, water treatment, pulp and paper, and power generation. The Neles RotaryGlobe valve provides excellent control accuracy with the inherent benefits of a rotary valve. The optimized design results in reliability and control stability and also reduces lifetime costs and maintenance needs.

See the video below for a "look inside".

Monday, December 14, 2015

Valves Designed for Severe Service. Not Just Heavy Duty

severe service control valve
High performance butterfly
valve (Jamesbury)
From time to time, industrial process control applications involve very stringent and challenging performance requirements for the valves, process piping, and instruments that are part of the control loop. Control valves are a significant example where the impact of extreme fluid conditions require careful design and selection consideration to assure proper performance and safety levels are maintained in a predictable way.

Severe service is a term that describes valves used in application at the extremes of pressure, temperature, cycling, and material compatibility. While there are plenty of published and accepted standards for industrial valves, one does not exist to precisely define a severe service valve.


So, what then defines the selection of severe service valves, as opposed to general purpose valves?

There are a number of basic selection criteria that might point you in that direction, but in general they are:
  • Very extreme media or environmental temperature
  • High pressure drop operation that may cause cavitation
  • Rapid and extreme changes to inlet pressure
  • Certain types or amounts of solids contained in the fluid
  • Highly corrosive, or erosive process media.
Certainly, any of these criteria might be found in an application serviceable by a general purpose valve, but their presence should be an indicator that a more involved assessment of the fluid conditions and commensurate valve requirements is needed. The key element for a specifier is to recognize when conditions are apparent that might exceed the capabilities of a general purpose valve, leading to premature failure in control performance or catastrophic failure that produces an unsafe condition. Once the possibility of a severe service condition is identified, a careful analysis of the possible operating conditions will reveal the performance requirements for the valve.

When in doubt, its critical to discuss your special requirements with an experienced product application specialist. They have access to technical resources that can help with selecting the right valve components to meet your severe service applications.

For more information contact:

Mead O'Brien
(800) 892-2769

Saturday, December 5, 2015

Closed Loop Control System Basics

closed loop control
Closed loop diagram
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.