Howden Screw Compressors vs. Howden Roots Rotary Lobe Blowers: A Cost-First Guide for Plant Buyers

Procurement managers don't land on a page like this for fun. There is usually a deadline, a budget, and an engineer saying “we just need more air.” I run procurement for a 200-person food processing plant, and for the past six years I've managed a $1.8M annual maintenance and equipment budget, negotiated with 20+ vendors, and logged every order in our cost tracking system.

So when someone asks me about Howden screw compressors or a Howden roots rotary lobe blower, I don't start with horsepower. I start with the duty. There is no single best answer, because the right choice depends on the pressure, volume, and service conditions the machine will actually see. A Dewalt leaf blower can move leaves in my driveway, but it is not a replacement for a Howden roots rotary lobe blower. And a roots lobe blower, however well built, is not a replacement for a screw compressor if your process really needs pressure.

Classify the job first, not the brand

This is basically a decision tree. I put three branches on my whiteboard when I'm comparing equipment:

• High pressure, continuous duty: compressed air or gas at roughly 3 bar gauge and above. This is where a screw compressor earns its keep.
• Low pressure, high volume: large flow at under about 1.5 bar gauge, like aeration or pneumatic conveying. This is roots lobe blower territory.
• Heat transfer, not air transfer: an ice maker machine, a water heating system, or a boiler plant. Stop comparing blowers and start comparing heat exchangers and refrigeration packages.

That third branch confuses a lot of people. It's tempting to think that if a machine moves air, it's a blower, and if it makes hot water, it's a water heater. But the reality is way more specific.

Scenario A: You need stable pressure — Howden screw compressors

If your process demands a reliable discharge pressure, not just a lot of flow, start with a screw compressor. Screw compressors are positive displacement machines. They take in gas and squeeze it continuously, which gives you a stable pressure over a wide operating range.

From the outside, a screw compressor looks like an oversized motor with plumbing. The real story is in the rotor profile, seals, and control logic. For a procurement person, the bigger issue is total cost. The purchase invoice is only the beginning. I've audited compressor packages where the energy draw ended up $8,000 per year higher than the original quote implied. That kind of gap doesn't show up in a simple price comparison.

People assume the lowest quote means the vendor is more efficient. What they don't see is which loads are being left out of the proposal: oil, filters, a proper dryer, remote monitoring, commissioning. One compressor quote came in at $48,000. Another was $41,500. I almost signed the cheaper one until I added the items the other vendor had included in an appendix—controls, pulsation dampening, and the first two sets of filters. The actual difference was only about 6%, not 13%. The paperwork made the cheap option look much cheaper than it was.

Scenario B: You need volume at low pressure — Howden roots rotary lobe blower

Now the opposite side. If your application moves large volumes of air or gas against modest resistance, a roots rotary lobe blower is often the better fit. This is the machine I think of for pneumatic conveying lines, wastewater aeration, or low-pressure process gas movement.

Here's the surface illusion: both a leaf blower and a lobe blower blow air, so people assume they are the same thing scaled by size. A Dewalt leaf blower is a high-speed fan. It's brilliant in my garage, but it doesn't have the sealing and positive displacement behavior of a Howden roots rotary lobe blower. The lobe blower moves gas in discrete pulses and can handle a defined pressure differential. The leaf blower moves air through an open space and stops being useful when the system pressure rises.

In cost terms, this distinction can save a ton of money. Trying to push a low-pressure system with a compressor is like using a boiler when you only need a water heater. Wait—that analogy matters.

Scenario C: You're moving heat, not air — ice maker machines, water heaters, and boilers

This is where the equipment vocabulary starts to hurt people. Take the water heater vs boiler question. It's tempting to think a water heater and a boiler are basically the same machine because both end up producing hot water. But a residential or commercial water heater is designed for point-of-use hot water: it heats a tank of potable water to a set temperature and delivers it to faucets or process stations. A boiler is designed to generate heat for a system, often as steam or hot water circulated through pipes to radiators, coils, or process equipment.

Those two machines have different pressure ratings, different controls, and different failure modes. If you spec one when you need the other, you've bought an expensive mistake. The same is true in the air mover family. A screw compressor and a roots lobe blower may both have compressor or blower in their names, but they are optimized for different pressure-volume conditions.

Now for ice: an ice maker machine is not an air compressor application. It's a refrigeration application. In large industrial plants, this often means an ammonia refrigeration system. Howden builds ammonia refrigeration equipment for those duties. Our plant uses it for process cooling. Honestly, I stopped thinking of it as compression and started thinking of it as heat transfer. The compressor is part of a refrigeration cycle, not a pneumatic utility.

Scenario D: The urgent breakdown — pay for certainty

One more branch: the “I need it yesterday” branch. In an ideal world, every piece of equipment has a planned outage and a spare parts kit. In reality, a blower fails on a Tuesday and the buyer gets a choice.

In March 2024, we lost a roots lobe blower on our packaging line. One vendor said they could get a replacement lobe set to us in four days if we paid an expedite fee. Another said “maybe two weeks” at a lower price. The difference was roughly $4,000. Our downtime cost was around $6,000 per day. I paid the expedite fee. Actually, I paid it before I finished the sentence.

The upside was saving $4,000. The risk was missing the production deadline. I kept asking myself: is $4,000 worth potentially losing a customer order? No. In emergency procurement, the uncertain cheap option is usually the most expensive option.

“Probably on time” is not a delivery date.

How to tell which branch you're in

If you're still not sure, answer three questions. (Should mention: I use a one-page TCO sheet for this, and it has saved me from at least two bad purchases.)

1. What is the discharge pressure, not just the flow? If your system needs stable pressure above roughly 3 bar, look at screw compressors. If it needs a lot of volume against a modest back pressure, look at roots lobe blowers.
2. Is the gas being compressed for pneumatic use, or is it part of a refrigeration/heat transfer loop? The latter means you want a refrigeration compressor or heat exchanger specialist, not someone quoting an industrial air package.
3. What happens if it's late? If the answer is lost production and a missed customer promise, build expedite fees into your budget. A boiler might be a fine water heater—until you need 20 psi of steam.

Three cost traps I always check

The equipment price is one number. The total cost is another. Here's where I look for hidden gaps:

• Claims without data. Per FTC business guidance (ftc.gov), claims about a product's performance need substantiation. When a sales rep says this is the most efficient, I ask for the motor efficiency sheet. If it isn't available, the claim isn't procurement information.
• Freight and rigging. The USPS price for a First-Class letter is $0.73 as of January 2025, according to usps.com/stamps. But a 400-pound lobe set is not shipped with a stamp. Ask for total landed cost—crate weight, freight, rigging, commissioning, training. This is where cheap quotes quietly double.
• Spare parts lead times. I've seen a $1,800 filter stop a production line for nine days because nobody checked the lead time. The replacement part's price was small. The downtime was not.

Bottom line

There is no single best choice between Howden screw compressors and Howden roots rotary lobe blowers. There is only the best match to your duty. If you need pressure, choose the screw compressor. If you need low-pressure volume, choose the lobe blower. If you're making ice, think refrigeration. If you are choosing between a water heater and a boiler, ask what you're heating and why.

And when the deadline matters, pay for certainty. It's not waste. It's risk management. Honestly, the most expensive equipment purchase I ever made was the one I delayed for two weeks to save 8% on a purchase order. The line was down, the customer was waiting, and no one had asked about lead time.

Or rather, no one except me. I remember. That's why I built the spreadsheet in the first place.