No, you haven’t wandered into an infomercial for an enhancement product you’d just as soon not want your kids to ever know existed, nor is this a promo for Godzilla II—Zilla Takes L.A. I’m talking, of course, about pneumatic conveying systems for delivering those pesky raw materials to extruders, mixer/coolers, and other points of manufacturing (what else could it have been?).

Flashback

I bought my first “real” new car in 1988, a V8 Ford Mustang LX coupe, a real sleeper with zip. One salesman tried to sell me the 4-cylinder turbo-charged Mustang SVO, another cool ride, for more money. I ended up making the call when a gearhead that I trusted impressed upon me these immortal words: “There’s no replacement for displacement!”

Flashforward

The engine of any pneumatic conveying system is the blower unit. Whether pushing with pressure or pulling with vacuum, your blower is the device that paces your system. It’s also the easiest device to tinker with when the extruder demand of 2000 lb/hr that your system was designed for that will never, ever increase goes up to 3000 lb/hr six months after installation. Change the belts, modify the sheaves, install a turbo-charger—tisk, tisk. You can get some short term gain here, but at what cost?

Blower Challenges

Blowers cost good money. So do vacuum receivers. When faced with a capital budget dilemma, one of the first things a cost-conscious project manager will elect to do is down-size and up-tempo. Buy ‘em smaller, run ‘em harder.

Translation:

harder = higher pressure = hotter = frequent breakdowns = you don’t really want to go there, do you?

Let’s take a look at some typical problems with conveying material that can be traced to system and blower package design.

Ultimately any pneumatic system is all about balance—the balance between pressure and velocity, between the volume of material being moved and the volume of air to move it—and maintaining that balance over time. When blowers, convey lines, and receivers are undersized, your options for performance enhancements are limited (without buying new ones of course). Pressures increase to force more material through a fixed diameter line, creating velocity challenges and material damage while simultaneously placing equipment in the critical operation zone. Receivers have to discharge more often to meet demand, meaning more cycles and start/stops at the blowers. The interesting thing is that in many cases, increasing the blower velocity and pressure does NOT move more material through the convey line, often compressing powders and passing right over the lump of stuff in the bottom of the line.

Hidden Costs

“But wait just a minute, smart guy, my smaller blowers cost me less—take a look at my receipt!” Really? Maybe a quick lesson on cost versus what I call price.

Price (pris) n. single point or one-time consideration, esp. money, demanded in consideration for something.

Cost (kâst) n. the price paid, or outlay, for a thing or service, over its useful life.

It’s really amazing to me how often people mix these up. Undersized blowers are priced less, and you know, if you’re in charge of capital procurement and not operations, that helps you and might be all you really care about. If you’re the GM, tasked with running the whole operation, other stuff comes into play for you, and you’re more likely concerned with overall cost (some sales types use this to demonstrate total value perception). Let’s talk about a few elements of cost that are hard to quantify, but are there anyway sucking at your operating cash like a ShopVac on steroids:

Heat

You don’t have to watch too many Castrol commercials to know that heat is generally a bad thing for mechanical components, be they cars or blowers. Run blowers at higher velocities, generate more heat, it’s as much a physical law as gravity. Add that destructive element to the start/stop wear and tear I spoke about earlier and you can start thinking about replacing these sooner than you anticipated (or budgeted!). I’m waiting for the first smart aleck to email me that the extra blower heat saves HVAC load on the plant and that you can roast marshmallows off the back of the motor. I’ve got one word for you my friend—summertime.

Here’s a quick definition of maintenance common sense and lean thinking: we keep an extra of every size blower in inventory just in case the one on the line breaks. Now that’s a classic two-bagger. We get that a lot.
M A Y B E  I T ‘ S  B E C A U S E  Y O U ‘ R E  R U N N I N G  T H E M  T O O  H O T !

Energy

But wait, it gets better! Blowers operating at or near their maximum output rate (I know you would never push them beyond the recommended rate, would you?) draw more current than those not taxed as heavy, and Charlie, that means more electric consumption during what are generally peak hours (1 st shift). Procurement guy doesn’t usually think about that little nugget, yet some pencil pusher somewhere in your organization is laying into somebody in operations about kVA.

Noise

Quiet little things, these blower packages, aren’t they? Just when y………… ...……………………………………………. Hey! Turn that blower off! I can’t hear myself think. More sound means more dB, more operator complaints, bad site tours for customers and that division president from Switzerland, and more Excedrin. We’ve actually had to install soundproof curtains and rooms around existing blowers in-plant left behind by others. Pretty economical, huh? Depending on your local codes, some other smart design, and personal tolerance, it needn’t be that way.

Right-Sizing

So how does size help? Upsizing blower capacities just one tick provides a larger volume flow band at lower pressures. Larger end receivers mean longer fill times and less frequent cycles, saving on equipment maintenance costs and downtime in production. Combined with larger blowers, increased line sizes allow for more air to convey product at lower pressures and velocities to prevent plugging, material damage and minimize poor performance.

Do I really need to get into a full-blown cost analysis of power consumption and the other hidden costs from the previous section? For a small fee, call me and I’ll do it, but only if you promise not to cry when you see the results.

Sounds simple enough, but the facts are that many systems we assess and ultimately repair or replace have insufficient blower capacity as the source of the problem. This pneumatic conveying stuff ain’t splitting the atom, but it isn’t for the untrained professional either, so don’t try this at home. Find a good specialist who knows this stuff cold, get him or her to size your system right, and sleep easy knowing you’ve got the best, most cost-effective system for your operation.

By the way, if you want to lay hands on the top 9 Technical Tips for Optimal Blower Design and Operation email me at mrbulky@oanewton.com and mention BLOWER TIPS in the subject line or click here. Never forget than when it comes to pneumatic conveying blowers, size really does matter!

Karl Walinskas is the Vice President of the Engineered Material Handling Solutions division at OA Newton, a Delaware-based firm that specializes in delivering smarter material handling solutions that increase capacities and reduce operational expense for manufacturers in the plastics, composites, rubber, food and other powder-challenged industries. He can be reached at karl.walinskas@oanewton.com or toll free at (800)726-5745.