Category Archives: Hammer Mills

Extruders? What are they and what are they used for?

Huh?It has come to my attention that not many people know what an extruder is and what it’s used for. Let’s hope I can address this injustice in this article!

Extruders are used to create objects of a specified length or size, this process is known as extrusion. Commonly extruded materials would be metals, polymers, ceramics, concrete and even food.

At Quadro Alloys Trading Enterprise we specialize in the design, manufacture and maintenance of extruder units/machines used in food extrusion; the process whereby a specific set of ingredients are mixed together and forced through a large, rotating screw which is tightly fitted inside a stationary barrel and then through a perforated plate or die, the resultant mix is known as the extrudate.

The end product can be anything from fish pellets to dog food.

I mentioned earlier that not knowing all of this was an injustice, well, here’s what I mean: In Africa (and some other countries) poverty is an issue that affects health conditions; some are struggling with malnutrition and some even die from it. Our extruders (in conjunction with our hammer mill machine) can be used to help solve this problem; the soya bean, a legume native to East Asia, is an amazing source of cheap protein used for things like oil, meal, flour, infant formula, dietary (meat and dairy) extenders or substitutes and cattle feed. In addition to these, floating fish feed (something we specialize in and are especially proud of) is often used in feeding the “water chicken”, a species of fish called the Tilapia (which is easily farmed). This fish has now become an accepted mechanism used for the feeding of the poor which is probably one of the easiest ways to feed them – and our philosophy is “feed the fish, feed the poor”.

Extruder machines are miracle inventions, and with your help as an entrepreneur, we can work together and make a difference in this world.


The farming & feeding of Tiapia – the importance of floating fish food and the use of full fat soya

Tilapia farmingTilapia is a species of fresh water fish, which is indigenous to Southern Africa and which produces a high quality white flesh comparable to that of hake.

In South Africa, Hake has traditionally been the white fish of choice and fishing quotas for 2007 were 120 000 tons p.a., down from 175 000 in 2002. South Africa, who is the only fishery in the world to be certified by the European Ecological Label, now finds itself in a position where hake quotas will have to be slashed further, in order to recover hake stocks, or face losing its EE certification.

Tilapia is also known as Bream, Chambo or a variety of Kurper and is the traditional protein source in a number of sub Saharan countries such as Malawi and Zambia, where it is harvested from the local lakes.

As with the international ocean fish stocks, harvesting has put this resource under severe pressure, where harvests from Lake Malawi have decreased from 8 000 tons p.a. in 1986, to under 500 tons p.a. at the turn of the century. Currently, whole slaughtered fish are sold at ZAR80.00 / kg in the markets on Lake Malawi.

The over harvesting and decreased supply has moved the fish from a subsistence level protein, to that of a semi luxury protein in these regions.

Due to it’s ideal qualities for aquaculture, in 2003 Tilapia was ranked as the 6th largest edible seafood product imported, by volume, into the USA.

Tilapia is increasingly referred to as the “Aquatic Chicken” of the 21st century and provides an affordable alternative food source for internationally depleted hake & cod stocks.

With the growing populations across Africa and the growing food crisis that we face as we head into the future, it is an essential to focus on sustaining the fish stocks by focusing on aquaculture and farming.

An instrumental part of farming Tilapia and other species is determining the correct feed pellet. Not only is the nutritional blend of ingredients essential but also the very nature of the pellet being floating or sinking. What determines this fact will be the determined by the feeding habits of the fish in question. Tilapia and trout are surface feeders and for that reason floating fish food is more suitable. Determining the size of the pellet will be determined by the size of the fish in the breeding pond from fingerling to adult.

Soya is an important ingredient in the fish food. Soybeans are one of the world’s best non-fish sources of essential omega-3 fatty acids, healthy proteins, and unsaturated fats. High-quality soy protein is fed to farmed fish and shellfish, to support their growth and healthy development.

Soybean meal, soy protein concentrates, soybean oil, and other vegetable proteins and oils, can replace from one-third to one-half of the fishmeal in feeds for many farmed species, reducing the need for wild-caught fish for fishmeal.

Soybean meal costs significantly less than most animal meals, including fish meal. Reducing feed cost is critical to improving efficiency and maintaining sustainability in aquaculture operations. Because the nutrient requirements of farmed fish and shellfish are so complex, each feed ratio is formulated based on the individual species’ needs. Most farm-raised fish and shellfish can easily digest soymeal, which helps the fish more efficiently transform ingested protein into body weight.

The extrusion process to manufacture floating fish food involves using a hammer mill to process the raw material of soya or bone meal etc. An extruder is then used to produce the pellets. A more detailed breakdown of the process is as follows:

The individual ingredients are fed into a ribbon blender via dosing augers for the vitamin premixes and ingredients to be added. The product blended for approx. 3 minutes for maximum blend.

It is taken via the variable speed drive auger into the hammer mill (available in 7.5kw, 22 kw, 30kw, 37kw, 55kw, 75kw) with the suitable screen size (available in 0.75mm, 0.9mm, 1.2mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.2mm, 5mm, 8mm & 10mm. Our finest screen 0.75mm is able to produce a product of under 200 micron). It is milled to a spec size then blown via the 7.5kw external drive material blower into a cyclone with rotary valve which feeds into an open trough auger on top of shortened volumetric feeders.

The product is then fed into a pre-conditioner which then feeds the extruder (55kw or 75kw). The product is extruded at 115 degrees Celsius on the gauge then cut with a direct mount VSD cutter unit into the relevant size required for the finished fish food product. It is then transported with an open trough conveyor with blower and canopy into a bucket elevator which feeds a dryer via a rotary valve and then dried. It is then fed onto a conveyor via the rotary valve, this fish food can now be bagged.

Hammer Mills – What are they and how do they work?

Producers of animal feed all know a simple truth: when processing cereal grains for animal feed, finished particle size matters.

Corn - Before and After

Blend-ability and digestibility – even the economics of feed production – are all affected by the finished particle size of the grains.  But this is not a one-size-fits-all situation.  The ideal finished particle size varies by the grain being processed, and depending on the species, the life stage of the animal.  With all of this in mind, selecting the proper method of size reduction is a critical decision.

Small Hammer Mill

Why use a Hammer Mill ?

Unlike the angular shaped particles produced in a roller mill, the pulverizing action of the hammer mill results in particles that are more rounded. These smoother surfaces make it easier for the grains to be blended with other components of the feed.

The Milling Process

A hammer mill is essentially a steel box surrounding a rotor. Swinging hammers attached to the rotor, flail out when the rotor spins. A screen covers the discharge opening to regulate the finished particle size.

As material enters the hammer mill, it is pulverized by a combination of hammer blows, particle on particle contact, and impact with the walls of the hammer mill. The material remains in the grinding chamber until it is able to pass through the screen covering the discharge area.

But those are just the basics. There are myriad styles of hammer mills: industrial mills, full circle screen hammer mills, horizontal grinders, tub grinders, and more.  As for size, hammer mills can range in size.  Choosing the right hammer mill for your purposes depends greatly upon the material you are processing, and your production goals.

Quadro Alloys is able to design and manufacture Hammer Mills according to these goals.

Hammer Mills are available in a Plain and Blower Option. “Plain” – the milled product passes through the mill and straight into a bag.  “Blower” – The milled product passes through the mill and is moved via a blower into a cyclone where it is bagged off from a two-way bagging attachment.  Typical hammer mill designs operate at 2800RPM with various screen sizes available.

Hammer-mill screen sizes available:
0.75mm, 0.9mm, 1.2mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.2mm, 5mm
Our finest screen 0.75mm is able to produce a product of under 200 micron.

Typical units vary from  • 7.5kw Hammer Mill – 75kw Hammer Mill