10222019Tue
Last updateTue, 22 Oct 2019 7pm
Annual Meeting: Sandler Celebrated, New VMA Leaders Announced

Annual Meeting: Sandler Celebrated, New VMA Leaders Announced

Bill Sandler spent much of the 81st VMA/V...

The Future of After-sales Service

The Future of After-sales Service

After-sales service has many definitions...

Pinch Valves: An Uncomplicated Valve with an Important Purpose

Pinch Valves: An Uncomplicated Valve with an Important Purpose

Pinch valves are a simple valve design t...

Online Marketplaces Moving into B2B

Online Marketplaces Moving into B2B

In business-to-business (B2B) sales and ...

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Industry Headlines

Industry Headlines

BHGE Changes its Name to Baker Hughes Company

4 DAYS AGO

Baker Hughes, a GE company (BHGE) has successfully changed its name to Baker Hughes Company. The company will be known as Baker Hughes and on Oct. 18, 2019 its Class A common stock began trading on the New York Stock Exchange under the symbol “BKR”.

Since Baker Hughes has a portfolio that s...

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EnPro Acquires LeanTeq to Boost Technetics Group

5 DAYS AGO

EnPro Industries has closed the acquisition of LeanTeq Co., Ltd., a privately held, Taiwan-based company. EnPro initially announced an agreement to acquire LeanTeq on July 22, 2019. LeanTeq will become part of EnPro’s Sealing Products segment and be integrated into its Technetics division.

Founded ...

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U.S. Now Exports Crude Oil to More Places Than It Imports

3 MINS AGO

As U.S. crude oil export volumes have increased to an average of 2.8 million barrels per day (b/d) in the first seven months of 2019, the number of destinations (which includes countries, territories, autonomous regions, and other administrative regions) that receive U.S. exports has also increased....

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Polyurethane Production Up in North America from 2016-2018

35 MINS AGO

The Center for the Polyurethanes Industry (CPI) has released the results of a two-year survey on the polyurethanes industry in the U.S., Canada and Mexico. The 2018 End-Use Market Survey on the Polyurethanes Industry in the U.S., Canada and Mexico shows that polyurethane production rose to over 9 billi...

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Leading Economic Indicators Down Second Straight Month

1 DAY AGO

The Conference Board Leading Economic Index (LEI) went down (0.1%) in September for the second consecutive month. New orders for manufactured goods continued to be a drag on the LEI, with building permits and the interest rate spread also negatively impacting activity in September. However, the streng...

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Industrial Production Down 0.4% in September

5 DAYS AGO

Industrial production fell back 0.4% in September after advancing 0.8% in August. For the third quarter, industrial production rose at an annual rate of 1.2% following declines of about 2% in both the first and the second quarters. Manufacturing output fell 0.5% in September but rose at an annual rate...

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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.

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