McNamara Contracting details benefits of recent screen investment

McNamara Contracting is a third-generation infrastructure contractor located in Rosemount, Minnesota.

With more than 60 years of experience, McNamara’s team assists customers in project design through completion. McNamara mines and processes all of the aggregates it uses in its asphalt and base materials, and the company performs infrastructure services such as grading, base construction, concrete and utility installation, and paving.

In addition to mining virgin aggregates, McNamara recycles every ton of asphalt and concrete from its projects, crushing it for reuse to minimize the use of natural resources.

The challenge

At its sand and gravel pit, McNamara crushes and screens aggregates to the specific sizes necessary for its asphalt mix. McNamara use mainly portable equipment in its pit, including jaw crushers, cone crushers and vibratory screens.

On one occasion, the shaft and bearings went out on McNamara’s vibratory screen deck.

“Our old screen deck finally had its wear and finally just broke down to where we had to upgrade,” says Joseph Adelmann, the crusher operator at McNamara.

The solution

As a next step, McNamara rented a McLanahan Corp. 6-ft. x 20-ft. triple-deck horizontal screen from Viking Aggregate Equipment, which is McLanahan’s dry processing dealer in Minnesota.

The horizontal screen features McLanahan’s triple-shaft mechanism with an aggressive oval stroke and optimum adjustability, as well as an end-tensioned bottom deck for simplified maintenance and access holes with covers along the middle and bottom decks to assist with screen media replacement. The screen features adjustable speed, stroke and amplitude to give a producer like McNamara the ability to fine-tune to its application.

The McLanahan screen was installed on a portable chassis – complete with wide walkways, dual access ladders and a sliding discharge chute for improved accessibility – and it was delivered to McNamara’s sand and gravel pit. Adelmann says Viking handled all of the fine adjusting for McNamara and “made sure everything was running [well] for us so we could hit the ground running.”

Ultimately, McNamara took to the screen so much that the company purchased it from Viking and permanently added it to the operation.

“We ended up liking it,” Adelmann says. “It handled a lot more material, and just the way everything was set up on it with the sliding chute and the accessibility to get to the screens worked really well with that screen deck.”

As the finishing screen, the horizontal screen splits all crushed material from the primary and secondary crushers into the three products necessary for McNamara’s asphalt mix. The vibrating motion of the screen causes the material to move across the screen decks, affording particles plenty of opportunities to fall through openings in the screen media.

Material that is too large to fit through openings moves down the length of the screen and discharges onto the appropriate product conveyor. Oversize is directed back to the crushing equipment for further reduction.

The results

According to Adelmann, the McLanahan horizontal screen is capable of processing more material than McNamara’s old screening unit. The new screen also provides McNamara with better separation.

“It shakes a lot more to where it’s able to sift a lot more and handle a lot more material to where we can put more out,” Adelmann says. “I feel like we gain more with the horizontal screen than we did with our past one.”

As for maintenance, McNamara says it has experienced the benefits of the end-tensioning screen feature, having changed the screen media on the bottom screen deck twice. As Adelmann describes, the process was easier and quicker because of an accessibility improvement.

“Our last screen, you had to unbolt a 100-pound plate at the end and put that off to the side,” Adelmann says. “That’s how you got into the screens. It’s really nice to slide that chute back to where you can get in there and get everything. I really do like the end-tensioned screens.”

In addition to the end-tensioned screen deck and the sliding discharge chute, Adelmann likes the wide walkways around the screen and the ladders on both sides.
“Everything is way nicer with the McLanahan horizontal screen,” Adelmann says.

Information for this article courtesy of McLanahan Corp.

Related: Improving inefficiencies in raw material screening