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Last updateWed, 27 Jul 2016 7pm

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Basics of Elastomeric Seal Design

Basics of Elastomeric Seal Design

Engineers need critical design informati...

Wastewater Treatment

Wastewater Treatment

Society’s desire for a clean envir...

Controlling Our Water Systems, Part II

Controlling Our Water Systems, Part II

To better understand the actuators and c...

Controlling Our Water Systems

Controlling Our Water Systems

Actuators and controls are a critical pr...

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Industry Headlines

ValvTechnologies Names Bryant Holt Industry Director, Fossil Power

11 HOURS AGO
ValvTechnologies Names Bryant Holt Industry Director, Fossil Power

ValvTechnologies, Inc. has appointed Bryant Holt as industry director for the company’s fossil power division. Holt will succeed George Stover, who has served in this role since 2014.

Based in Houston, Holt will have global management responsibility for ValvTechnologies’ fossil power group ...

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Crane Co. Reports Second Quarter 2016 Results

1 DAY AGO

Crane Co. reported second quarter 2016 GAAP earnings of $1.15 per diluted share, compared to $0.95 per share in the second quarter of 2015. Excluding Special Items, second quarter 2016 earnings per diluted share were $1.21, compared to $1.06 per share in the second quarter of 2015.

Second quarter 2016 ...

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LNG’s Surge from Decade-Low Seen Fizzling as Supply Ramps Up

14 HOURS AGO

“LNG’s surge is running out of gas. Liquefied natural gas in Asia, which was in such over-supply that prices in Japan fell to a decade-low in April, has risen by almost half in the past three months as production outages stifled supply, demand rose in places like China and India and a co...

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Chemical Activity Barometer Grows for Fourth Consecutive Month

1 DAY AGO

The Chemical Activity Barometer (CAB) expanded 0.4% in July following a revised 0.7% increase in June, 0.8% increase in May and 0.6% increase in April. All data is measured on a three-month moving average. Accounting for adjustments, the CAB remains up 2.6% over this time last year, an improvement ove...

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U.S. Durable Goods Orders Down 4% in June

15 HOURS AGO

New orders for manufactured durable goods in June decreased $9.3 billion or 4.0% to $219.8 billion, the U.S. Department of Commerce announced. This decrease , down two consecutive months, followed a 2.8% May decrease. Excluding transportation, new orders decreased 0.5%. Excluding defense, new orders d...

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Sharpest Rise in U.S. Manufacturing Production Since November

2 DAYS AGO

July data signaled a further rebound in business conditions across the U.S. manufacturing sector, led by a robust expansion of incoming new work and the fastest upturn in production volumes for eight months. Job creation also strengthened in July, with the latest increase in payroll numbers the fast...

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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.

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