December 2006 Mechanical Engineering Departments: Tech Focus, Pt. 2

This section was written by Executive Editor Harry Hutchinson.

Technology Focus part 2:
Fluid Handling and Fluid Power

Waste Not

Using a steam plant's waste heat to preheat the combustion air stream can increase coal boiler efficiency by as much as 25 percent, according to a manufacturer of heat recycling equipment. The manufacturer, Paragon Airheater Technologies of Corona, Calif., tells us that, as long as the system's seals are tight, a 500 MW plant can reduce coal consumption by as much as 1,500 tons per day by capturing heat before it goes up the flue.

According to Paragon, leakage in air heaters wastes energy and money, and most plants have no idea how bad their actual air leakage really is. The company estimates that after 10 years of service, an air heater not using high-performance seals can be assumed to be leaking at least 25 percent of its heat. Paragon said that in some plants leakage has been found to be more than 40 percent.

Of course, Paragon is interested in telling us about the problem because it is in the business of selling a solution. The company claims that air heater leakage can be cut in half at most plants.

The company has designed self-adjusting radial seals that incorporate a bellows-like section, which produces a spring force to maintain contact with the sealing surface. It also has designed interlocking circumferential seals to be used on the perimeter of the air heater's rotor. According to Paragon, they are designed to resist the type of leakage suffered by standard-type seals during rotor turndown.

Coriolis Brew

There are a lot of people who need to keep track, all at once, of the mass flow, volume flow, density, and temperature of process fluids. The Micro Motion division of Emerson Process Management makes a Coriolis flowmeter designed to do exactly that. Recently, the company sold its 500,000th unit.

Micro Motion, which is based in Boulder, Colo., claims that it has sold more of its Coriolis meters than everybody else combined, but we were unable to confirm that. Micro Motion's first Coriolis flowmeter was introduced in 1977.

Processors can use the devices with Emerson's PlantWeb digital factory architecture to keep tabs on slurries, liquids, and gases. The 500,000th unit sold went to Anheuser-Busch, which puts them to use in one of the most ancient of arts, the brewing of beer.

Tom Moser, president of the Micro Motion division, personally delivered the half-millionth unit to Jeff Steinhart, Anheuser-Busch vice president for engineering, at Anheuser-Busch's headquarters in St. Louis.

Let's hope that they hoisted a glass together.

Seeing Spots

A die-casting company in Pennsylvania saw writing on the wall several years ago. And the writing was in Chinese.

Seeing that its chief line of business was going to foreign competitors, the company, Performance Metals in Bechtelsville, Pa., decided it was time for a change, according to its president, Martin Wigg. The company is still in the die-casting business, but has switched to production of low-volume, high-value products, which customers have not sought offshore.

But Performance Metals also entered another line altogether. It came up with a new take on an anti-corrosion device called a sacrificial anode, which it makes and sells largely to recreational boaters. Now it has licensed a manufacturer to go after industrial markets.

To dissolve and protect: Sacrificial anodes from Performance Metals contain a red plastic indicator that appears as a red dot when the anode has worn to half its original size and its anti-corrosion protection is waning. Boat owners use the anodes to protect their hulls.

Corrosion is caused by a loss of ions, leaving electrons to flow into areas that are more positive. Metals exposed to water—condensers and tanks, the hulls of ships, and undersides of oil platforms—are particularly susceptible to corrosion. What's more, when two dissimilar metals are attached to each other and exposed to water, the loss of ions accelerates. That's where the sacrificial anode comes in.

It is made of zinc or another metal that oxidizes more readily than the metal to be protected. When the two metals are in contact, the anode loses ions. The protected metal, more positive, attracts the electrons, which slow oxidation. The idea is called cathodic protection.

The sacrificial anode, as the name implies, is put in place to be lost. It dissolves, and when the anode is gone, it is the protected metal's turn to lose ions and begin to oxidize.

That's why Performance Metals builds in an indicator that tells users when an anode needs to be replaced. The company calls them wear indicator anodes, and each one contains a red plastic insert that appears as a red dot when an anode has worn to half its original size.

The company sells the anodes in blister packs, like consumer products. They go for $15 to $20 each, or $60 for a set of six, mostly to boat owners to protect the hulls of their craft. According to Wigg, the company decided to offer bulk sales
of anodes without the indicators to industrial customers, and was surprised to find little demand for them. The customers wanted the red dot. He said some industrial customers go to the marina to buy the blister packs.

To go after the industrial market, Performance Metals has licensed its Red Spot indicator technology to MESA Products. MESA, based in Tulsa, Okla., is a supplier of cathodic protection systems largely to oil and energy companies, according to Terry May, MESA's president.

According to Wigg, the red dot isn't the whole story. The company is working on an alternate design with a remote means of monitoring an anode on a ship bottom. Instead of the red plastic indicator, the anode would hold a probe that would send a signal when the anode wore far enough to expose it to water.

Performance Metals' anodes are made of an alloy developed years ago for military use. Called Navalloy, it is mostly aluminum, with 5 percent zinc and traces of indium, which, the company says, assures that the anode stays active. That is, it keeps dissolving on the job.