04232017Sun
Last updateThu, 20 Apr 2017 11pm

i

Relevance in a Digital Age

Relevance in a Digital Age

The distribution model of the past 50 ye...

Video Game Technology Changing the  Offshore Industry

Video Game Technology Changing the Offshore Industry

One of the most powerful innovations in ...

Reshoring, Robots and What Happens if We Do Bring Jobs Back?

Reshoring, Robots and What Happens if We Do Bring Jobs Back?

While offshoring is painted as the major...

The Weekly Report

New Products

  • ja-news-2
  • ja-news-3

Industry Headlines

ExxonMobil, SABIC Plan $10B Petrochemical Plant Near Texas Coast

Thursday, 20 April 2017  |  Chris Guy

ExxonMobil Chemical Company and Saudi Arabia Basic Industries Corp. (SABIC) have selected a site in San Patricio County, TX for potential development ...

Readmore

Loading...
Advertisement
i

Industry Headlines

VanAire Names Steven Soderman CEO, Quality Manager

3 DAYS AGO

Steven Soderman has joined the leadership team of VanAire, Incorporated as CEO and quality manager. Bill VanDeVusse will continue in his role as president having previously filled the positions of both president and CEO.

Soderman has held key quality positions throughout his career most recently fillin...

Readmore

Chromatic Industries Adds Two Former Cameron Executives

4 DAYS AGO

Mark Gamber has joined Chromatic Industries as CEO effective April 10, 2017. Wayne Hall will continue in his role as president. Gamber most recently served as vice president of operations at Cameron in its Distributed Valves Group.

Additionally, Mark Cordell has joined Chromatic as a senior advisor. Be...

Readmore

ExxonMobil, SABIC Plan $10B Petrochemical Plant Near Texas Coast

3 DAYS AGO

ExxonMobil Chemical Company and Saudi Arabia Basic Industries Corp. (SABIC) have selected a site in San Patricio County, TX for potential development of a jointly owned petrochemical complex on the U.S. Gulf Coast. The proposed project is one of 11 ExxonMobil announced as part of its 10-year, $20 bill...

Readmore

Visibility Clears on 2nd Wave of U.S Petrochemical Projects

5 DAYS AGO

The visibility into the second leg of U.S. petrochemical expansions is getting clearer, according to ICIS Chemical Business. While many projects were shelved or in doubt amid the crude oil price decline in 2014-2015, the recent relative stability in oil coupled with a renewed sense of optimism on lo...

Readmore

Fed Beige Book Showing Continued Economic Expansion

3 DAYS AGO

Economic activity increased in each of the twelve Federal Reserve Districts between mid-February and the end of March, with the pace of expansion equally split between modest and moderate . In addition, the pickup was evident to varying degrees across economic sectors.

Manufacturing continued to expand...

Readmore

IMF Raises Global Growth Forecast to 3.5% This Year

3 DAYS AGO

Global economic activity is picking up with a long-awaited cyclical recovery in investment, manufacturing and trade, according to the IMF’s World Economic Outlook. World growth is expected to rise from 3.1% in 2016 to 3.5% in 2017 and 3.6% in 2018. Stronger activity, expectations of more robust ...

Readmore

Ball Valves in Power Plants

vmwnt12_nuclear_plantCan metal-seated ball valves provide effective long term, economical solutions for critical applications in steam-generating power plants? The answer lies in knowing the design limitations of the valve, in correctly identifying the application requirements and in proper installation techniques.

During the last 20 years, advances in machining, tooling, measuring and coating technology have led to ball valve designs that provide positive sealing solutions for the power industry. These new “power plant ball valves” can withstand temperatures and pressures that make them a viable solution for the industry.


THE HISTORY

Before these new designs, creating true and matching spherical sealing surfaces was limited so that one surface—the ball—typically was metal and highly polished. The second sealing surface—the seat—generally was a fluoropolymer or elastomeric compound. This combination works well in lower temperatures and pressures, and still is widely used today. However, it is not suited for the extremes seen in steam power generating stations.

vmwnt12_Figure-1Figure 1. Typical Y-pattern globe valveInstead, traditionally rising-stem globe valves have been the work horses for stop and isolation service in steam-generating power plants (Figure 1). These valves have massive stems, plugs and seats. They are top-entry valves and often have welded or pressure seal bonnets.

The sealing areas of the plug and seat are matched conical surfaces, which are well-suited for the high pressures, temperatures and velocities found in vent, drain and continuous process services. Operation of the valves is intuitive: If the stem is in the “up” position, the valve is open; if the stem is in the “down” position, the valve is closed.


METAL-SEATED BALL VALVES

Computer numerically controlled (CNC) machines with special tooling can now produce virtually perfect spherical metal-to-metal sealing surfaces—both concave, and convex for ball and seat—with almost infinite repeatability. Highly qualified and specialized coating contractors also can provide many varieties of flame-sprayed carbide coating compounds applied with exacting precision in laboratory conditions by CNC robotic machines. These coatings carry a toughness and hardness far exceeding that of the cobalt-based weld overlays traditionally used in rising stem globe valves, and the final coated surface exactly mirrors the machined contours of the underlying part. These technologies have lead to the emergence of the power plant ball valve, capable of withstanding temperatures in excess of 1050° F (566° C) and ­pressures in excess of 3000 psig.


CONSTRUCTION FEATURES

Many power plant ball valve manufacturers are machining valve bodies from forged bar stock materials with massive wall thicknesses far exceeding that of rising stem valves. Several use the same valve body design on 1.5-inch and smaller sizes for all pressures classes—so that an ASME Class 1500 valve may actually have an ASME Class 4500 body. This standardization reduces raw material inventory, streamlines machining, shortens production times and allows for virtually unlimited alloy material selection. Usage is restricted by the pressure and temperature rating stated on the original equipment manufacturer (OEM) tag and relevant American Society of Mechanical Engineers (ASME) and American National Standards Institute (ANSI) standards.

vmwnt12_Figure-2Figure 2. Two-piece end-entry design

 

vmwnt12_Figure-3Figure 3. One-piece end-entry design

vmwnt12_Figure-4Figure 4. Top-entry designValve manufacturers produce a ­variety of power plant ball valve body designs, including two-piece end entry (Figure 2), one-piece end entry (Figure 3) and bolted bonnet top entry (Figure 4). Different seat designs are produced: integral seat, pressed-in seat, welded seat and locked seat. All designs incorporate a downstream sealing seat, with an upstream ring used as a guiding, balancing and bearing surface.

vmwnt12_Figure-5Figure 5. Live-loading methodThese designs all include a large cross-section conical load spring (Belleville washer) behind the upstream bearing ring. The designs feature live-loaded stem packing, although several methods provide this live-loading (Figure 5). Some use one large central Belleville spring, while others use four, equally spaced spring sets. Packing design varies among manufacturers—some use a single die-formed ring with wire-braided backup while others use multiple die-formed rings, and still others use top- and bottom-braided rings with internal die-formed rings.

  • Latest Post

  • Popular

  • Links

  • Events

Advertisement

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