Concrete Batch Plant Equipment Blog

Tailor-Made Concrete Batch Plants Let You Save Now, Expand Later

Customized tailor-made concrete batch plants

A tailor-made batch plant will allow you to custom design your plant from the ground up. This approach will result in a plant that fits your needs in terms of property layout and constraints, production needs, storage needs, and the ability to utilize your budget in the areas that are most important to you. Designing a batch plant tailor made for you is often a superior choice to the standard plant.

Buying a new concrete batch plant can be a difficult process to take on. Batch plant design, layout, capacities, options, and controlling overall cost all come into play. Plant manufacturers offer standard batch plant designs or “cookie cutter” options to make the process easy, but does it satisfy all of your needs?

Liddell Industries and Sterling Concrete Equipment work diligently to provide our customers with the batch plant that will best perform for their needs. All concrete ready mix producers’ operations are different, so settling for the cookie cutter plant design may not be the best investment. Key areas we focus on with custom designed batch plants are flow of traffic on the site, the ability of the plant to grow as your operation grows, ease of maintenance and accessibility, and ease of operator ease.

Traffic flow and management on your batch plant site is integral to a successful operation. Designing a plant that fits the site and accounts for all traffic flow will speed up your operation. No matter how fast a batch plant can batch, it’s only as fast as its slowest part. Ensuring efficient flow of traffic for the plant to receive material and load trucks is key to increasing your production.

Designing a batch plant with the ability to grow can benefit you in two ways, decreased initial cost and lowered expansion cost in the future. Building an oversized batch plant from the start will dramatically increase your overall start-up cost for something you will not immediately use. Designing a plant that fits your operational requirements now and that has the ability for planned expansion lowers your start-up investment. Planned expansion capability is the best choice for many producers, it helps them be budget friendly at the start and gives them the flexibility to grow with the market in the future.

All batch plants no matter their age require maintenance daily, weekly, monthly, and annually. Designing a plant that fits your accessibility and maintenance needs is pivotal to reducing down time and delivering for your customers. Accessibility of the batch plant reduces maintenance cost, cuts down on maintenance time, and allows for better visual inspection areas to catch problems early.

Ease of operator use of your plant through design, automation, accessibility, and personal preferences increases plant output and overall plant moral. Designing a plant with the operator in mind has great long-term benefits. Proper design of accessibility and automation decreases the daily hassles of operating the plant. This decrease results in less mistakes, better product, and less downtime.

Designing a custom batch plant made for your operation comes with many benefits that a standard plant may be unable to provide. Liddell Industries and Sterling Concrete Equipment take pride in providing our customers with batch plants that fit their needs for all aspects of their operation. Delivering value through design is something you can count on.

How to Increase Plant Production, 3 Types of Hoppers: Holding, Surge, & Gob Hoppers

An average 12-yard dry concrete batch plant has a typical theoretical production rate of 200 yards per hour. However, a batch plant can only produce as fast as the mixer truck will take the product. Depending on the truck, a typical mixer truck will charge at a rate of 165 to 185 yards per hour. The weigh up time for a dry batch plant is 1/3 of the overall batch time.

During the weigh up time the mixer truck will be idle under the plant until the start of the discharge of material. By incorporating discharge hoppers, the weigh batchers can be cleared sooner allowing the next batch to start while the current truck is being charged.

3 types of discharge hoppers:

Surge Hoppers are typically 3 to 4 yards in capacity and allow the aggregate on the transfer conveyor to collect if the mixer truck charge rate is exceeded. As the truck hopper begins to choke, incoming aggregate is surged into the surge hopper, and relieved into the mixer truck by gravity as the mixer pulls the material into the drum. By clearing the aggregate weight batcher faster, the next batch can be started sooner, increasing overall plant production.

Holding Hoppers are 12-yard capacity and should have separate hoppers for aggregate and cement. The individual weigh batchers weigh up and discharge into the individual holding hoppers. The holding hoppers are on separate scales which provide control of the discharge flow rate into the mixer truck. Mixer trucks are charged by the holding hoppers instead of directly from the weigh batchers. These hoppers allow the next batch to start and completely weigh up while the current batch is being discharged into the truck.

Gob Hoppers are used with central mix plants and allow the mixer to discharge the finished product into a hopper above the mixer truck. The truck is then fed the mixed material through the gob hopper versus directly from the mixer. This allows the plant to batch the next load into the mixer and begin the mixing process while the current batch is being discharged into the truck.

Dust Collectors, Central versus Individual, Compare the 2 types

Two types of dust collection systems are available for concrete batch plants, central and individual. Central systems utilize ducting and one central unit that collects at all dust points of the batch plant; silos, cement batcher, truck collection hood for dry batch plants, and mixer for central mix batch plants. Individual systems vent each silo, cement batcher, mixer, and truck collection hood separately with individual units.

Determining the best option for you requires accounting for all dust collection points and their CFM requirements. It is always a wise practice to overestimate the CFM to account for loss of efficiency over time. Below is a list of average CFM requirements and Pros and Cons of each system.

Silo CFM Truck Blower: 850 CFM
Silo 60HP Blower: 1,250 CFM
Silo 75 HP Blower: 1,800 CFM
12 Yard Mixer: 5,000 CFM
Truck Collection Hood: 7,000 CFM
Cement Batcher: 750 CFM

Pros and Cons of Central Dust Collector System:

PRO – Central maintenance point
PRO – Does not require climbing to silo tops
PRO – Only need one cartridge or bag size
CON – Increased cost and requires ducting
CON – Requires damper valves

Pros and Cons of Individual Dust Collection System:

PRO – Less cost than central systems
PRO – Individual collected material will not be cross contaminated
PRO – Reclaim same material directly back into silo
CON – May require multiple cartridge and bag sizes
CON – Multiple collectors to maintenance at different locations

How to save time filling cement silo, the 2 factors

Two main factors come into play when reducing cement silo filling times, dust collection and blower CFM. Cement silos can be round or rectangular and are typically filled by a 4-inch or 5-inch fill pipe. High volume batch plants will often have two fill pipes per cement compartment.

The cement, slag, or flyash is transferred by a pneumatic blower, the blower size will determine the amount of cement that will transfer into the silo per minute. Although blower size is a key factor to speed, dust collection plays just as important of a role. If the silo is unable to expel the air being charged into the silo to move the material, the load time per minute will be drastically reduced.

Dust collection should be appropriately sized to handle the CFM of the blower being used to transfer the material. It is important to know the manufacturer’s specifications before purchasing a new dust collector or a new blower. Buying a larger blower with higher CFM than your existing dust collector can handle will not increase loading speed.

850 CFM – Typical truck mounted blower
1,250 CFM – Typical 60HP blower
1,800 CFM – Typical 75HP blower

Under sizing the silo dust collector will not only reduce loading speed, but may lead to bigger problems. Typical cement silo is capable of handling 3 PSI of pressure. If you over pressurize the silo and the emergency pop-off valve fails, the silo could get damaged or even split the silo.

How to trouble shoot cement silo problems: low/no flow in your silo

Material flow issues of cement, flyash, and slag in silos can be a real headache. Below is a list of typical flow rates for cement through various size butterfly valves and screw conveyors and a list of troubleshooting tips. Aerated cement has a typical flow rate of 74 pounds per cubic foot.

Cement Butterfly Valve Estimated Gravity Flow Rate:

8” Diameter = 144 Tons per Hour
10” Diameter = 226 Tons per Hour
12” Diameter = 325 Tons per Hour
14” Diameter = 443 Tons per Hour

Cement Screw Conveyor Estimated Delivery Rate:

8” Diameter = 80 Tons per Hour
10” Diameter = 115 Tons per Hour
12” Diameter = 200 Tons per Hour

Slag and flyash materials will flow and convey at a slower rate because of their aerated bulk densities being lower than cement. Slag has an aerated bulk density of 60 pounds per cubic foot and flyash at 45 pounds per cubic foot.

If you have a diminished flow check the following:

Confirm all of the aeration pads are receiving 9 psi of dry air
Confirm the butterfly valve is opening up vertical the entire way.
Check the silo top dust collection unit to ensure it has air flow and is not packed full.
Check the silo top for any signs of water being able to enter the silo.
Empty the silo and confirm the cone section does not have buildup, a plugged cone, or chunks of hard material.

Tip: Proper aeration is key to material flow, condensation in air lines feeding aeration pads can cause major problems in a cement silo. In recent years more and more producers have installed low-pressure aeration blowers which drastically reduce the probability of water entering the silo cone through the aeration pads.