Closing the loop, Part I

Features

Remodeled Tigerloop oil de-aerator sets a new standard for the industry

By Lindy Lindtveit

‘Why, that looks just like R2D2 from ‘Star Wars’!”

That’s the typical reaction you hear from a burner tech that sees the new Tigerloop oil de-aerator for the first time. And while it’s not exactly a duplicate of that little robot, it does look quite different from the former Tigerloop. The new Model TN, introduced in early 2005 by Westwood Products, the U.S. importer of the Tigerloop, replaces the Model T60I, which, since its debut more than 25 years ago, has become the standard by which all oil de-aerators are judged worldwide.

And while it might be said ‘when you have a winner, stick with it,” the makers of Tigerloop saw the natural evolution of the product as meeting the challenges for better performance and the industry-wide emphasis on more environmentally friendly oilheat systems. Hence, the new Model TN, an environmentally friendly package boasting 33 percent greater de-aeration capacity, dual-chamber design for added safety, and easier mounting and installation. And like the former Tigerloop, the new Model TN is the only UL-approved oil de-aerator available. Truly, oil de-aeration has reached a new level.

But to fully appreciate the new Model TN Tigerloop and what it does, let’s get technical for a moment. What is an ‘oil de-aerator” and what does it do? Simple put, an oil de-aerator removes the air, or more precisely the bubbles, from the fuel so that these bubbles don’t cause all kinds of mischief in the fuel system.

Bubbles cause mischief, you ask? How can those soft little things that make bubble baths, champagne and exotic dancers so much fun cause mischief? Well, in a fuel system they can. Remember, safe, reliable oilheat needs basically two things: good equipment that is well maintained and clean fuel that is free of contamination. And by contamination we mean no dirt, water or bubbles. So, let’s look at why ‘bubbles are bad.”

We find two kinds of bad bubbles in fuel systems: air and gases. If it’s air bubbles, it means either a leak in the system, or the bubbles were delivered with the oil. Leaks can be fixed if they can be found. Delivered air is another story.

These bubbles are suspended in the oil when it arrives and are the result of the oil having been churned up during loading, transporting and delivery. Take and fill an empty soft drink bottle with fuel oil and give it a shake to simulate the kind of treatment that fuel oil gets between the loading rack and its ultimate destination in the customer’s tank. You’ll see how long it takes to clear and that’s just the bubbles you can see with the naked eye. The really small bubbles you can’t see and those are the ones that can accumulate in even the tightest of systems. No job is immune; all systems have these bad bubbles.

So, what do these air bubbles do that make them so bad? Take a look at Diagram 1. It’s a cut-away diagram of a pump operating normally, except for the air bubble lodged in the nozzle line (see arrow). The bubble is deceivingly small, since its size has been compressed by the 100 psi pressure in the nozzle line. As long as the pump operates, the bubble will remain small and compressed, having no effect on burner operation.

But when the pump shuts down, it’s a different story. As the pump’s rpm decreases, the piston will close against the nozzle seat, cutting off the flow of oil from the pump, but not the flow of oil from the nozzle. The expanding bubble has taken over for the pump in supplying the pressure pushing oil out the nozzle (Diagram 2). Oil flow does not cease until the bubble has expanded back to its original size and nozzle line pressure has dropped to zero (Diagram 3). The result is virtually no cut-off, with a sooty, smoky shutdown. Ever heard of ‘nozzle coking?” It’s a popular phrase nowadays. And a solenoid valve won’t help this problem. It’s strictly a bubble thing. But there’s more.

Glance over at Diagram 4. It’s a cut-away of a pump’s strainer chamber, with the pump operating normally. Note that the level of the oil does not fill the entire strainer chamber. This is normal because during bleeding the oil level only rises high enough to just cover the inlet to the gear set, about two-thirds of the way up the strainer chamber. But that’s not bad because the air cushion at the top quiets the hydraulic whine of the gear set and doesn’t affect pump operation. As long as the inlet to the gear set stays covered, all is well.

But, if air enters the pump it will immediately rise to the top, pushing down the oil level in the strainer chamber and partially uncovering the inlet to the gear set (Diagram 5). The gear set starts gulping air and oil and the pressure becomes unstable, resulting in poor combustion, noise, rumbling, pulsation, etc. If enough air enters, the oil level drops completely below the inlet to the gear set (Diagram 6). Pressure is lost and the burner eventually locks-out.

The second kind of bad bubbles are gases. These come from dissolved vapors and volatiles that are drawn out of the oil when it’s exposed to vacuum. The higher the vacuum the more bubbles produced. Such things as high lift, long runs, undersized tubing, restricted lines, partially plugged filters and sticky check valves are all major causes of high vacuum that can literally boil volatiles out of the oil, creating bubbles.

Diagram 7 shows the familiar story. The bubbles drawn out of the oil rise to the top of the strainer chamber, the oil level falls, the gear set gulps foamy oil, pressure becomes unstable and the burner eventually locks out.

Certainly, safely handling the problem of bad bubbles is a major feature of the new Tigerloop. But, it’s more than just a bad bubbles problem-solver. All systems benefit from the use of a Tigerloop, as you will see when we continue exploring the new Tigerloop and its application and installation next month.

Lindy Lindtveit is a graduate of Hofstra University and works as a vice president of Westwood Products, South River, N.J. He is also a member of the National Association of Oil Heating Service Managers and a member of the National Oilheat Research Alliance’s Fuels Quality Committee.