I Bought a McLanahan Vibratory Screen with the Wrong Number of Decks. Here’s What That Cost Me.

If you're looking at a McLanahan MD vibratory screen, don't size it for your best-case scenario. I did that. It cost us about $12,000 in rework and lost production over six months.

That's the short version. Here's the long one, so you don't make the same mistake.

I'm a plant manager for a mid-size aggregate operation in the Midwest. We process limestone and some granite. I've been handling equipment procurement for about eight years. The McLanahan screen was supposed to be a simple capacity upgrade for our secondary circuit. It was not.

My Mistake: The Number of Decks

The core issue was the deck configuration. We bought a McLanahan MD vibratory screen with two decks. Looking back, I should have gone with three. Here's why.

We were processing a 3-inch minus feed and needed to produce three products: 1.5-inch clean, 3/4-inch clean, and a -3/4-inch base material. With a two-deck screen, you get two product splits. The top deck makes the largest separation, the bottom deck makes the second. Everything else goes through to the bottom. This means you have to decide which product is 'the fines' that fall through.

In our case, we set it up to make the 1.5-inch on the top deck and the 3/4-inch on the bottom. That worked fine for the top two products. But all the -3/4-inch material—the base material—ended up in one pile. It wasn't a clean product. It had too many fines and dust, which made it hard to sell for the premium base material price.

If I'd bought a three-deck screen, I could have made a clean 3/4-inch product on the second deck and a clean -3/4-inch product on the third. We would have had three marketable products right off the machine.

This was true 10 years ago when the secondary market for base materials was less demanding. Today, the specs are tighter. A two-deck screen for three products is a gamble I shouldn't have taken. (Source: My own expensive mistake, Q2 2023.)

The Financial Fallout

The screen itself was around $85,000. The mistake wasn't the machine; it was the spec. We tried to fix it by recirculating the bottom-deck product through a separate fines screen. That required new conveyors and chute work, which added another $8,000 in fabrication. The downtime to install it cost us about $4,000 in lost production.

I still kick myself for not pushing the vendor harder on the product mix. If I'd sat down and mapped out the exact tonnages and market values for each size fraction, the choice for a three-deck screen would have been obvious.

There's something satisfying about a perfectly executed plant circuit. After all the headaches, when we finally got the recirc loop working, it was a good feeling. But it was an expensive lesson in upfront planning.

Why We Switched to a McLanahan Crusher

The screen experience wasn't all bad. The build quality of the MD vibratory screen is excellent. It runs smooth, the side plates are thick, and the drive is robust. That experience was the main reason we looked at McLanahan again when we needed a new secondary crusher six months later.

Our old cone was due for a major rebuild. Instead of putting money into aging equipment, we spec'd a new McLanahan crusher. We went with a Universal HSI (Horizontal Shaft Impactor). The decision was based on our material characteristics and the desire for a higher reduction ratio in a single pass.

The Crusher Decision: HSI vs. Cone

For our limestone, an impactor makes more sense than a cone. It gives us a more cubical product and we can run it with a larger feed opening. The McLanahan crusher has been running for about 10 months now. The throughput is good, and the wear parts are holding up better than I expected.

• Mclanahan crusher performance: We're consistently hitting 250-275 tons per hour on the secondary, which is a solid 20% improvement over our old setup.
• Product quality: The chip shape is better, which our concrete customers like.
• Maintenance: Change-outs are straightforward. That's a big deal when you're on a tight schedule.

One thing I learned from the screen debacle: ask the 'what if' questions. With the crusher, I asked what would happen if the feed had more clay. The answer from the McLanahan team was solid—they recommended a different rotor configuration. We went with it, and it's paid off.

Now, about the noise. Someone in our industry a few years ago told me, 'McLanahan is good for screens, but their crushers aren't as proven as the big guys.' That thinking comes from an era when they were less aggressive in the crushing market. That's changed. Our experience says the crusher is just as well-engineered as the screen.

Practical Takeaways for Your Next Buy

If you're in the market for a McLanahan MD vibratory screen, here are three things I wish I'd known.

1. Over-spec the decks. If you think you need two decks, price out a three-deck. The difference in initial cost is usually less than the cost of fixing it later.
2. Map your product value. Don't just think about tonnage. Think about the dollar value of each product you're trying to make. A dirty base product is worth less than a clean one. A three-deck screen can make you more money on the back end.
3. Talk about the 'bad' scenarios. The McLanahan team is good. But they don't know your specific blend of feed material and market demand. Push them on the edge cases. It's your money.

Prices as of early 2024—verify current rates. A McLanahan crusher, for our size, was in the $150k-$200k range depending on configuration. The screen was about half that. These are rough numbers, but they give you a baseline.

Regulatory information on allowable fines in base materials varies by state. Verify current regulations at your local DOT website. Don't rely on what worked five years ago.

To sum it up: the McLanahan equipment is solid. The mistake wasn't the brand. It was my specification. Ask the deck question first, and you'll save yourself a headache.