04202018Fri
Last updateThu, 19 Apr 2018 4pm

i

Air Valves in Piping Systems

Air Valves in Piping Systems

Liquid piping systems are prone to colle...

Are Valves from Low-Cost Countries Getting Better?

Are Valves from Low-Cost Countries Getting Better?

The last 25 years have seen standards cr...

Managing the Generation Gap: Much Ado About Nothing?

Managing the Generation Gap: Much Ado About Nothing?

The baby boomer generation was the most ...

SubscribeSPR18

FREE SUBSCRIPTION*

• Print magazine
Digital magazine
• VALVE eNews
Read the latest issue

*to qualified valve professionals in the U.S./Canada

The Weekly Report

New Products

  • ja-news-2
  • ja-news-3

Industry Headlines

Emerson and BlueFin Form Strategic Partnership

Thursday, 19 April 2018  |  Chris Guy

Emerson and BlueFin have signed a working partnership agreement to deliver the Roxar gauge technology to the U.S. Gulf of Mexico (GoM) region. The part...

Readmore

Loading...
Advertisement
i

Industry Headlines

Emerson and BlueFin Form Strategic Partnership

8 HOURS AGO

Emerson and BlueFin have signed a working partnership agreement to deliver the Roxar gauge technology to the U.S. Gulf of Mexico (GoM) region. The partnership will deliver a combined offering of Emerson's technology coupled with BlueFin's installation services and chemical injection systems.

BlueFin, a...

Readmore

Flowserve Expands Partnership with Unisys

1 DAY AGO

Flowserve, a client of Unisys Corporation, will expand its use of the Unisys Stealth microsegmentation solution through a new agreement to implement the solution more broadly across the enterprise. Under the new agreement , Flowserve will increase the number of servers and endpoints protected by Steal...

Readmore

OECD Natural Gas Production Up 2.4% in 2017

9 HOURS AGO

An assessment of monthly data shows that in 2017 Organization for Economic Co-operation and Development (OECD) natural gas production grew by 2.4% compared to 2016. This growth was driven by increases in production across all OECD regions, particularly in Asia Oceania (+17.7%), whilst the Americas and...

Readmore

Major Trends Changing the Chemical Industry

2 DAYS AGO

“The accelerated globalization of the chemicals market is one of four major trends that we at SAP see shaping the chemical industry through the remainder of 2018 and beyond,” writes Stefan Guertzgen, global senior director for industry solution marketing, chemicals at SAP.

“Amid such ...

Readmore

Beige Book: Solid Outlook Despite Tariff Concerns

10 HOURS AGO

Economic activity continued to expand at a modest to moderate pace across the 12 Federal Reserve Districts in March and early April. Outlooks remained positive, but contacts in various sectors including manufacturing, agriculture and transportation expressed concern about the newly imposed and/or prop...

Readmore

IMF Predicting Global Economic Upswing

1 DAY AGO

World growth strengthened in 2017 to 3.8%, with a notable rebound in global trade. It was driven by an investment recovery in advanced economies, continued strong growth in emerging Asia, a notable upswing in emerging Europe, and signs of recovery in several commodity exporters. Global growth is exp...

Readmore

Advertisement

Controlling And Monitoring Control Valve Fugitive Emissions

vmsum12_fugitive_emissionsSince valves are the number one source of leakage, those faced with reducing fugitive emissions need to look at the most challenging type: control valves.

Process plant managers have a host of good reasons to minimize fugitive ­emissions from their facilities and reduce the amount of process fluid released into the atmosphere and surrounding environment. Those reasons include keeping employees and neighbors safe, lessening the facility’s environmental impact, complying with increasingly stringent air-quality regulations, optimizing the plant’s energy ­consumption and maximizing plant operating efficiency.

Industrial valves are a leading source of leakage from typical process plants. In fact, studies of refineries have shown that valves and relief valves account for about 75% of fugitive emissions.1

Because of this reality, monitoring, ­controlling and reducing valve leakage can make a significant impact on overall plant fugitive emissions. Of particular concern are control valves, which pose a greater challenge than other industrial valves because of their typical operating mode and potential leak paths. There are, however, techniques, technologies and strategies that plant owners and managers can implement to better manage fugitive emissions from the control valves in their facilities. This article highlights some of these options for typical control valve features, characteristics and options.


CONTROL VALVE LEAK PATHS

Standard control valve designs include a number of potential external leak paths. For example:

Globe-style Control Valves

vmsum12_fugitive_emissions_1Figure 1. Potential leak paths in globe-style control valvesFigure 1 shows a cross-section of a typical globe valve or linear operating valve, with the key potential leakage locations highlighted. The process fluid is contained within the valve body, which is a pressure vessel designed in compliance with standard ­pressure vessel codes, such as American Society of Mechanical Engineers (ASME), Deutsches Institut für Normung e.V. (DIN; in English, the German Institute for Standardization) or Japanese Industrial Standards (JIS).

There are several static joints or locations interfacing with the valve body where external leakage is possible, including the pipeline-flange connections and the valve-body-to-bonnet joint. Leakage at these joints is uncommon because of the static nature of these joints and the fact they are typically sealed with gaskets and then bolted together. Leakage is still possible, however, so these joints should be monitored.

The primary valve leak path is the stem-seal interface, which is typically sealed using packing installed within the valve bonnet. This is a dynamic interface, as the stem moves up and down through the packing box area during operation.

Control valves are typically applied in continuously throttling services to maintain a specific set point or operating range for different process variables, such as pressure, temperature and flow rate. As a result, the valve packing wears over time, allowing more leakage across this interface. In addition, thermal expansion and contraction caused by the process fluid and ambient temperature changes can further increase the leakage rate. Thus, the packing must be periodically tightened or fitted with some kind of mechanical compensation, such as “live loading” the packing with springs to maintain the seal integrity and control leakage to the atmosphere.

Another key contributor to packing wear in globe-style control valves—and, thus, another source of potential fugitive emissions—is the presence of foreign particles or debris in the surrounding atmosphere. Since the globe valve strokes in a linear motion, the valve stem moves up through the packing area as the valve opens and then moves back down into the packing area as the valve closes. As the valve cycles from open to close, a portion of the stem is exposed to the environment, creating an opportunity for particles to attach to the stem surface and potentially impact the packing wear rate and sealing capabilities. These particles also can increase the operating friction, which reduces the overall responsiveness and controllability of the valve.

Rotary-style Control Valves

vmsum12_fugitive_emissions_2Figure 2. Potential leak paths in rotary-style control valves Figure 2 shows a cross-section of a ­typical rotary-style or rotating-motion-design control valve. As with globe-style valves, the pipe-flange connections and the stem seal area are potential paths for process fluid to leak into the environment. However, many rotary-style ­control valves have an integrated body and bonnet, eliminating that location as a potential leak path.

A key advantage of rotary-style control valves in managing fugitive emissions is the rotating motion of the valve stem as the valve is opened and closed. The stem stays within the stem seal or packing area, minimizing the possibility of introducing foreign particles or debris into the sealing interfaces. As a result, these valves are typically more effective in reducing the possibility of fugitive emissions leakage, and normally deliver greater reliability and operating efficiency from this perspective.

  • Latest Post

  • Popular

  • Links

  • Events

BUYERS GUIDE 300x220

Looking for a career in the Valve Industry?

ValveCareers Horiz

To learn more, watch the videos below or visit ValveCareers.com a special initiative of the Valve Manufacturers Association