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Applications in Water Harvesting Systems

Applications in Water Harvesting Systems

Water harvesting in commercial projects ...

Safety Relief Valve FAQs

Safety Relief Valve FAQs

Companies that repair, test, maintain or...

An Update on U.S. Valve-Related Standards

An Update on U.S. Valve-Related Standards

It takes much time and effort by many pe...

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Industry Headlines

Leading Economic Indicators for the U.S. Increased in July

Wednesday, 23 August 2017  |  Chris Guy

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.3% in July to 128.3 (2010 = 100), following a 0.6% increase in June, and a ...

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Low Cracking Pressure in Chemical Processing Condensate Lines

Low Cracking Pressure in Chemical Processing Condensate Lines

Tuesday, 22 August 2017  |  Arie Bregman

Steam condensate is the liquid by-product formed when steam goes from the vapor state to the liquid state; this process occurs in a wide range of appl...

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Industry Headlines

Velan Names Duc Tran Vice-President, Engineering

14 HOURS AGO

Velan Inc. has appointed Duc Tran as its new vice-president, engineering. Tran will be a key member of the company's senior management team and is succeeding Gil Perez, who has assumed a new mandate as vice-president, product technology and strategic initiatives. He will report directly to president...

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AIV and Gulf Coast Modification Opening NW Houston Facility

1 DAY AGO

AIV, LP has announced plans for a new 320,000+ square-foot facility at NW Lake Drive, near Telge Road and Highway 290 in northwest Houston. The 32-acre construction site allows for the future expansion of up to 700,000 sq. ft. This facility will consolidate AIV and Gulf Coast Modification ’s curr...

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Group Asking Feds to Halt LNG Exports

12 HOURS AGO

The Industrial Energy Consumers of America recently sent a letter to the Secretary of Energy on two LNG export demand scenarios. They argue that the Obama Administration’s “public interest” LNG export studies, which are still being used to justify LNG export approvals to non-free tra...

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Chemical Activity Barometer Shows Modest Slowing

1 DAY AGO

The Chemical Activity Barometer (CAB) from the American Chemistry Council remained unchanged from July, continuing a modest deceleration of growth. The flat reading follows a 0.1% increase in July and a flat reading in June. Compared to a year earlier, the CAB is up 3.2% year-over-year, an easing fr...

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Leading Economic Indicators for the U.S. Increased in July

9 HOURS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.3% in July to 128.3 (2010 = 100), following a 0.6% increase in June, and a 0.3% increase in May.

“The U.S. LEI improved in July, suggesting the U.S. economy may experience further improvements in economic activity in the...

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U.S. Factory Output Declined in July

5 DAYS AGO

Manufacturing output edged down 0.1% in July. The index for durables decreased 0.5%. Among durable manufacturing industries, with the indexes for primary metals and for furniture and related products each dropped more than 1%. The index for other manufacturing (publishing and logging) moved down 0.4%....

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On the Sea and Under the Ground

Today’s ships are much more than floating tanks. They are power generation and wastewater treatment plants, HVAC systems, plumbing and transmission pipelines all in one. Meanwhile, under the ground, the nation’s mines offer up a wealth of solid materials that must be tapped for use in many of this nation’s industrial processes.These two sectors present the valve industry a unique set of challenges.

MARINE VALVE INDUSTRY IS WIDE IN SCOPE AND VALVE NEED

By Greg Johnson

Most valve industry professionals who don’t live near the water, have little idea of the breadth of the marine valve industry. In the U.S., this industry is vibrant and interesting and equals many other valve industry segments in scope. It is stocked with virtually every type of valve, manufactured out of a host of common and not-so-common materials. An unpowered barge may contain a few valves for regulating ballast, while a modern supertanker will contain hundreds of valves of all sizes and types.


HISTORY OF MARINE VALVES

The birth of the steamship during the industrial revolution kicked off the marine valve industry. The steam and fire-belching engines that turned paddlewheels and propellers throughout the 1800s were all controlled by globe valves made of iron and brass. During the latter half of the 19th century, these early steam valve designs were adapted to other marine uses as the industry grew rapidly.

The development of the U.S. Navy “ironclads” (armored battleships) at the turn-of-the century set the pace for naval valve production that would reach a towering peak during World War II. Beginning in the mid-1950s, the Naval valve industry would further refine and define itself by providing the unique valves required for Admiral Hyman Rickover’s fledgling nuclear Navy.

The continuing use of steam to power merchant ships of all sizes helped maintain a huge market for lower pressure steam service valves until the move to diesel power was complete in the 1970s. The birth of the oil tanker in the early 20th century would also create opportunities for valve suppliers, and these opportunities are still viable in this age of the giant super-tanker.


THE MANY DUTIES OF MARINE VALVES

Marine valves perform a number of different duties both above and below decks. For example, all vessels need some form of energy to power their engines, and valves regulate the loading and storage of this commodity. There may only be one fuel valve on a diesel tugboat, but large cargo ships may have a complicated system of pumps and manifolds with multiple valves directing the fuel to various tanks on the ship. Oftentimes, these tanks are located at strategic points on a large ship to aid in the ballasting of the vessel.

Water ballast and bilge systems are extremely important as well. These systems may use piping and valves that are hand-held size or as large as NPS 30 (national pipe size for a 30-inch valve). Needless to say, valves handling seawater must be hearty and designed to withstand the rigors of a harsh seawater environment. Firefighting piping systems are also important on ships since there are no local fire departments to call in case of an emergency at sea. Firefighting system valves must work when called upon, so their valves have to be ultra-reliable.

Fifty years ago, both gray water and black water (sewage) wastewater was just piped overboard while at sea. Today, that practice is taboo, so efficient wastewater piping systems are required to handle and process this unpleasant effluent. These systems also need to be very dependable and able to withstand the harsh wastewater environment.

Ships carrying liquid cargo obviously have need for extensive piping systems. These vessels, from oil barges to LNG tankers, are loaded with valves of every description. The valves need to be carefully selected to handle the products that run through them, such as petrochemicals or cryogenic LNG. But they also must have a stout exterior to hold up against the corrosive sea water environment.


VALVE TYPES

For nearly a hundred years, the most common valves on ships and barges were gate, globe and check valves. Extra space is always at a premium on a ship. In the case of gate valves, the outside screw and yoke, rising stem design, often took up too much valuable space onboard. This resulted in the adoption of the non-rising stem (NRS) design, which became commonplace because of the additional headroom it afforded above the handwheel. The venerable NRS gate valve is still used primarily in marine applications.

Today’s ships and barges are home to virtually every type of modern valve, not just the old school gate, globe and check valves. Ball valves are increasingly popular, including metal-seated types. Still, the lined butterfly valve has probably made more inroads then any type in this segment, which was previously dominated by gate valves. The selection of the smaller and lighter butterfly valves also has proven to be a popular one for many marine applications.

Many tankers and tank barges are required to haul different fluids in multiple onboard tanks. The loading and diverting valves feeding these tanks are usually required to have block and bleed capability to keep from cross contaminating their liquid cargoes.

Automation has become very common on modern ships, and this translates to the piping systems. Automated valve packages are seen more and more in the engineering rooms of modern vessels. These systems often interface with sophisticated computer systems that are used to control all of the common shipboard engineering functions.


VALVE MATERIALS

Because of oxidation, water is hard on piping systems. Even marine valve materials for fresh water applications must be chosen carefully. More and more, stainless-steel valves and piping systems are being installed in fresh water marine applications, replacing the previously common carbon steel materials.

Salt water is a different case altogether. Bronze valves or iron valves with bronze trim were the most common seawater service marine valves for a long time, and a carbon steel piping system will not last for any length of time in a salt-water environment.

Seawater valves today are quite often still bronze alloys, Cu/Ni or even higher alloys such as Ni/Cr or titanium. Aluminum bronze is still quite popular because of its adequate seawater corrosion resistance combined with relatively low cost. The most interesting material choice today, however, is titanium. Titanium is a noble alloy with extremely good corrosion resistance, especially in seawater service. But titanium has other advantages for the marine environment including its high strength and more importantly, light weight.

Although titanium piping systems (and valves) are expensive, the Navy has chosen the material for many of its key piping systems because of its overall lower cost of ownership. The titanium valves are particularly long-lived and require much less repair than other valves. Some metallurgists predict that titanium piping systems will even outlast the ships in which they are installed. Although complete titanium piping systems are relatively easy to fabricate and install, it is a tricky process to attach a titanium valve to non-titanium piping components because of the possibility of galvanic corrosion. Insulating bolt sleeves and gaskets must be used to keep this type of corrosion from occurring.

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