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Some factors to consider when rebuilding a rubber mixer

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TOPEKA, Kan.—There are several factors to consider when making the decision on whether or not to try to rebuild a rubber mixer, or replace it completely.

Kim Bahner, sales manager with HF Mixing Group, said during a presentation at the firm's recent International Mixing Seminar in Topeka that rebuilding a mixer can provide several advantages, especially for companies that are on a tight budget.

“Probably the main advantage is the reduced cost. Depending on the condition of the used mixer you can save up to 50 percent by going with a rebuild verses buying new,” he said.

Bahner identified 10 questions companies looking to rebuild should ask of the firm it chooses to rebuild the mixer. They include:

• Is the company well established in the industry?

• Can the company supply installation support?

• Can the company service the mixer?

• Does the company have the required engineering support and drawings to remanufacture the mixer to new specifications?

• Can the company supply process, service and parts support throughout the life of the mixer?

• What are the manufacturing capabilities?

• Are installation and parts manuals supplied?

• Are final as built dimensions supplied?

• Are inspection reports/certifications on critical components available?

• What details should be investigated when determining the scope of supply for a rebuilt mixer?

“Evaluate perspective mixer rebuilders,” Bahner said. “You will save yourself a lot of time and headache if you compare them all and make sure you make the right decision.”

Firms should then look closely at the parts detail the rebuilding company is supplying. Bahner suggested asking questions and traveling to the site to perform a parts inspection. The time and money spent on the trip will be well worth it, he said.

Companies looking to rebuild also can build in upgrades with improved parts on a case-by-case basis.

Bahner outlined a number of key parts in the mixer and whether or not—generally speaking—they should be rebuilt or outright replaced, though he noted all need to be inspected to see whether or not the repair is feasible.

• Rotors—Yes, depending on age and condition.

• Chamber sides—Yes, if the chamber bores are within tolerance and in fairly good condition, HF can reuse them.

• Rotor end plates—Yes, Bahner said 80 percent of the time these have to be bought new, but sometimes can be rebuilt.

• End frames—Yes, Bahner said 95 percent of the time HF can reuse end frames, as long as they're not cracked.

• Bearings—No, Bahner said HF will replace all bearings because if one goes out in a mixer, the firm will have just paid several times over what it would have paid simply to replace them.

• Door support—Yes, Bahner said 90 percent of the time a door can be rebuilt as long as it doesn't show any cracks or major problems.

• Drop door shaft—Yes, Bahner said as long as there isn't a lot of wear on it.

• Door top—No, Bahner said usually not a rebuildable part, but sometimes it can be reused if it isn't too old.

• Latch assembly—Yes, Bahner said sometimes it is not even changed.

• Throat plates—No, Bahner said the floating weight destroys them all the time.

• Chamber covers—Yes, most of the time these are rebuildable.

• Dust top assemblies—No, Bahner said always replace with new.

• Coupling hubs—Yes, as long as the teeth are checked. Bahner said a mixer can get pretty good life out of its couplings.

• Lube, process and grease—No, Bahner said always replace with new.

• Hydraulic cylinders/actuators—Yes, Bahner said sending these out for rebuilding can save quite a bit of money on a rebuild as actuators have gone up in price over the last few years.

• Fasteners, brushings, seals—No, Bahner said to replace all of them.

• Hopper—Bahner said customers should consider replacing the hopper at the same time it replaces the mixer.

• Sides, back, neck extensions—Yes, all can be rebuilt or reused.

• Front hopper door—No, Bahner said usually not rebuildable because it tends to get bent or warped.

• Hopper cover—Yes, Bahner said firms can save money because it can usually be rebuilt.

• Hopper cylinder—Bahner said these are a case-by-case basis, but generally recommends to replace.

• Rod, piston plates, cup seals—No, Bahner said most of the time these need to be replaced.

• Floating weights—Yes, as long as they are cast steel. Bahner said HF generally doesn't rebuild cast iron floating weights.

Like with parts, he said firms should go and inspect the mixer before it ships back to ensure the rebuilding company did everything it said it was going to do.

“You need to decide if a rebuild mixer is the right way to go,” Bahner said. “That decision can only be made by the companies involved, and it's an important decision to start.”