Valve Magazine

Fri04182014

Last updateThu, 17 Apr 2014 1pm

Tank Cars

Tank Cars

The next time you‘re stopped at a crossing waiting...

Extracting Nutrients, Saving Resources through Livestock Water Recycling

Extracting Nutrients, Saving Resources through Livestock Water Recycling

Giant livestock farms, which can house thousands o...

The Expanding Network of Valves

The Expanding Network of Valves

As industry itself reaches into more and more area...

Valve Packing & Gasket Research and Development Devices

Valve Packing & Gasket Research and Development Devices

The continuous improvement of valve packing techno...

VALVE Magazine Print & Digital

Subscribe spr14

Read
the latest digital edition


Subscribe to the digital edition

Subscribe to the print edition

  • VMA Links

  • Gallery of Valves

Ball Valve Butterfly Valve Check Valve Control Valve Diaphragm Valve Gate Valve Globe Valve Needle Valve Pinch Valve Plug Valve Relief Valve
BUYERS GUIDE 300x80

Sponsored Products

  • ja-news-1
  • ja-news-2
  • ja-news-3
Advertisement

Web Only

Magazine

Tank Cars

Tank Cars

The next time you‘re stopped at a crossing waiting for a mile-long train you thi...

The Expanding Network of Valves

The Expanding Network of Valves

As industry itself reaches into more and more areas of the world, getting the eq...

The Expanding Reach of Plastic Valves

The Expanding Reach of Plastic Valves

Although plastic valves are sometimes seen as a specialty product—a top choice o...

When Accessories Become Necessities

vmspr10 beyond valves 1This automated valve assembly is made up of a process ball valve, pneumatically operated actuator, solenoid valve and inductive non-contact valve position sensor and target.Specification sheets for selecting automated valves list requirements for the valve and actuator but often lump all other devices together as related instrumentation or accessories.

Since the definition of an automated valve is a flow control device that can be remotely operated, a typical selection hierarchy is:

  1. Select the best valve for the service conditions
  2. Select a suitable actuator to operate that valve
  3. Provide enough information on accessories so the valve supplier or end user can just add them as needed.

A comprehensive valve data sheet may enumerate 40 to 50 line items of information that define the scope of the valve assembly. Since performance and safety of that assembly are greatly impacted if any component in the assembly fails, the more forethought put into the specification, the more likely the final assembly will perform as intended. The purpose of a specification is not to exclude any manufacturer but rather to include only those products the specifier perceives as most closely meeting the equipment application requirements.

THE SPEC SHEET

If we look at all system devices as necessities instead of accessories, we can divide the specification sheet into three sections.

  1. Under Process Components all devices that are in contact with the media would be listed. That would include the valve and instrumentation such as flow meters and other process variable transmitters.
  2. Under Force all devices that supply the motive power to operate the valve would be listed. This would include the actuator—pneumatic, electric or hydraulic; hand-wheel overrides; linkage kits/mounting brackets; solenoid valves; filter regulators; pressure gauges, etc.
  3. The third column would be headed Intelligence. This category would include valve position sensors. Intelligent devices interface the operator’s commands and the valve’s response. Without supervision/control, the automated valve will not function; therefore, the process will not function.

vmspr10 beyond valves 2The automated valve assembly shown here is for use in a hazardous location. It consists of a process ball valve with pneumatically operated actuator, solenoid valve and inductive NAMUR non-incendive valve position sensor and target. Note that the solenoid valve is driven from the valve position sensor, which simplifies wiring.Valve position sensors indicate to the plant operator that an automated or control valve is open, closed, or between open and closed. A valve position sensor or switch can take numerous forms: inductive proximity sensor, reed switch or mechanical switch. Sensors can be directly mounted to a rotary pneumatic actuator, bracket-mounted to a linear valve, enclosed inside a switch box or an electrically operated actuator, or inside a valve positioner.

An inductive proximity sensor is a non-contact device, which means the sensor is free from wear. A common metal target is mechanically attached to the actuator stem of a linear or rotary travel valve. When the target comes into range of detecting the sensor, an electronic switch changes state, which confirms the position of the valve. Actuation speed or frequency has no effect on inductive proximity sensors. They are typically used in pairs, one for the valve’s open position and another for the closed position, although sensing other positions can be easily accomplished. Dual sensors directly mounted onto a pneumatic actuator provide valve open and valve closed switching in one compact package. Proximity sensors are available in a variety of configurations and voltages and can be an integral part of a valve assembly, especially when the sensor’s full capabilities are utilized.

 

Valve Magazine Digital Edition

SPR14 CVR 160x214Inside the Spring 2014 issue…

• Tank Cars
• DBBS & DIBS
• Shale Gas
• New Globe Standard

CLICK HERE TO REQUEST YOUR
DIGITAL EDITION PREVIEW EMAIL