A multinational milk processor needed three agitated milk ageing tanks for its Victorian site. The room they were going into was 7 m long, 3.8 m wide and short on headroom. So the brief came with a catch: the agitator shafts had to come out for maintenance without anyone cutting a hole in the ceiling.
What the customer asked for
- Three identical 7,000 L agitated tanks
- Insulation behind seal-welded cladding
- Agitator shafts that can be removed in low headroom
- A hygienic shaft joint, with no crevices in the product zone
- Safe access on the tank tops for maintenance
- An overflow that gets cleaned with everything else
The tanks
Each tank is 1,870 mm inside diameter with a 2,600 mm straight shell, a coned top and a coned bottom, standing on legs. Product-contact parts are 316 stainless steel, with internal welds ground flush and strip polished to 180 grit. The cladding, legs and railing are 304.
The shell carries 50 mm of insulation behind a 2 mm stainless skin. We seal-welded every cladding seam, so washdown water can’t get into the insulation. Wet insulation means hidden corrosion, poorer insulation performance and a place for bacteria to grow on the outside of the tank, which is the last thing you want in a dairy.
Two pieces, one shaft
Each tank has a Nord 5.5 kW gearmotor turning a 60 mm shaft at 26 rpm, with two sets of folded paddle blades about 1,200 mm apart. It’s gentle, even mixing through the full 7,000 L, without whipping the milk.
The tanks stand 4.1 m tall, 4.49 m to the top of the drive. A one-piece shaft would be about 3.3 m long, and there’s nowhere near that much clear height above the motors. So we split it: an 1,857 mm stub shaft and a 1,500 mm lower shaft, each short enough to lift out on site.
The catch with splitting a shaft is the joint. A bolted or keyed coupling leaves gaps and threads in the milk, and that’s exactly where solids lodge and bacteria grow. We designed and machined our own joint instead:
- The lower shaft screws into the stub on an M50 thread, so no bolts, keys or pins touch the product
- The two halves meet on machined flat faces, clamping a food-grade nylon washer that keeps milk out of the thread
- The outside is a smooth, chamfered 90 mm profile that drains freely and is reached by the CIP spray
It comes apart with hand tools and presents a smooth surface in service.
Cleaning the overflow too
A rotary spray ball in the top head cleans the shell, the head, the shaft and the impellers on every CIP cycle.
The overflow is usually where things go wrong. It runs down the outside of the tank as a standpipe, and a tank spray ball can’t reach it, so it becomes a dead leg full of old milk residue. We fitted a static sprayball at the top of each standpipe, fed from the CIP supply, so the whole overflow line is flushed with the tank.
Safe on top
Each tank top has a full-circle 950 mm stainless handrail with a kick plate, so tools and fittings can’t roll off, and a chained opening for stepping on from a ladder or platform. The railing bolts on, so it comes off for transport.
The result
Three tanks in a row at 2,250 mm centres, 250 mm apart and 250 mm off the back wall, with every manway facing the same way for the operators. Low headroom solved with a two-piece shaft, hygiene protected by a crevice-free joint and sealed cladding, and nothing in the product zone left out of CIP.
Building tanks for a tight dairy room? See our dairy processing equipment or talk to us.
In this guide
Planning a dairy project?
Send us your volumes and site limits. We’ll work through the design with you.
Request a quoteRelated solutions
Case studies
Talk to Us About Your Dairy Project
Tight room, low ceiling, a plinth to reuse? Send us the limits and we’ll model the vessel in 3D before anything is built. See our dairy processing equipment or contact us.