Concetti Case Study

Perfect packing Graham Rawlings, Concetti S.p.A, presents a US case study on the supply of an automatic plant for packaging cement, and explains why using PE film bags can help reduce product waste, provide a longer shelf life and encourage more flexible stock management. visit to a local building products store can be a dirty business. This is often down to the bulk products section and fine powdery materials, particularly cement, leaking from old fashioned paper valve bags more suited to industrial rather than retail use. And the dust problem does not just affect the customer – store managers spend a disproportionate amount of time and effort on constant cleaning which costs money.

When a well-known US building products retailer was considering a new automatic plant for packaging bulk materials, the primary need was for fully sealed and dust free bags to improve the retail environment.

In addition to Portland cement, the plant also needed to handle various dry concrete and mortar mixes in a wide range of different pack sizes from 60 lb (27 kg) to 92.6 lb (42Kg) plus some wet products too. This meant lines capable of rapidly switching format and product without cross-contamination were necessary.

It represented quite a challenge.

Prioritising PE

Packaging fine powders like cement into PE film instead of the more traditional ‘self-closing’ (but often very dusty) paper valve bags has now become an option through recent technical advances in both film and machines. A fully sealed PE bag provides the manufacturer and retailer with significant benefits even beyond a clean, secure pack and high-quality presentation. Rainproof packaging also enables a longer shelf life and more flexible stock management, including outside storage. These advantages are behind a growing trend in Europe and Australia towards this type of packaging for cementitious products.

PE film is regarded as more recyclable and environmentally more responsible in Europe, and the US retailer’s preference for the larger 42 kg pack sizes also helps reduce the overall amount of packaging used. Another environmental factor is

the substantial reduction in product waste through moisture contamination.

Concetti S.p.A of Bastia, Umbria, Italy, which has an established sales and service office in Hoschton GA, US, was capable of providing such a system.

Detailed discussions about the demanding specification took place over a long period and resulted in Concetti proposing two multi-station Continua ‘Form, Fill, Seal’ machines, operating in tandem to reach the necessary speed for dry products, and a separate Continua FFS-E for wet materials. Both wet and dry lines feed, at separate times, to a single high-level PS-AA/20S automatic high-level palletiser.

Concetti’s horizontal design uses tubular film, avoiding the troublesome long vertical seal and permitting effective cleaning of any product contamination around the bag mouth before closing, ensuring a secure seal.

Operational overview

Cement pallet.

CONTINUA FFS six stations.

The order was placed in the middle of 2019 and the final arrangement includes novel features.

For example, all dry products, including dry concrete mixes, are dosed by weight using twin screw fed Concetti net weighers. Each inverter driven inclined twin screw for coarse and fine feed is of extra heavy-duty design with hardened wear surfaces and is equipped with features for easy automated cleaning between products. When changing from a coarse concrete mix containing gravel to pure Portland cement for example, the feeder runs in reverse and product residue is ejected from a rear door to an outlet at floor level via a chute.

Simultaneously, air jets fitted to the screw casing clean the slowly revolving flights.

This cleaning sequence is automatic and controlled from the operator’s keypad. Cleaning time is adjustable. At the cycle end, the rear door is cleaned by compressed air before closing. Facilities are also provided to enable the fine feed screw to be easily withdrawn if necessary, to check or aid further cleaning. Interlocked inspection doors are fitted at various points.

Each Continua FFS machine produces bags from a reel of flat or gusseted tubular PE film up to 11.6 in. (295 mm) wide. Bags up to 31.5 in. (800 mm) in length can be handled, although World Cement Reprinted from February 2021

even larger sizes are available in the Continua range is made by servo motor. There are no manual spanner if required. The PE film tube contains an innovative adjustments to be made between programmes labyrinth venting arrangement to allow any air trapped anywhere on the lines. after sealing the bag to be released without exposing This allows a programme – essentially a table of the contents to moisture during outside storage. In user adjustable parameters (weight, volume, bag combination, total output speed is up to 1200 bags/hr length, layer pattern, flattener height, etc.) – to be maximum, depending on product. set using an operator keypad from a single position The tubular film is cut to length according to via the network. Selecting a specific programme pre-printed registration marks or a precision automatically adjusts the weight controller, the shaft encoder for plain (unprinted) film. A corner screw speed, bag length and FFS settings for each sealing system (K seal) improves bag stability and individual product as well as the palletiser layer appearance. pattern, the number of layers and whether a bottom The Continua machines, specially developed for sheet has to be applied or not. This minimises these applications, each have six stations for forming changeover time and avoids operator errors. Only the the bag (cutting and sealing the bottom), filling and target weight of the checkweigher needs manually deaerating of powder products (three stations), changing. closing (cleaning and sealing the bag mouth) and The electrical installation complies with cooling. Vibrating tables at stations 2, 3 and 4 help North American regulations (UL/CSA for Industrial to settle the contents and a partial vacuum can be Control Panels, wire colours and cable standards). applied at the closing station.

Moving parts are protected by fence type guarding Filling is shared across two stations, with half taking with interlocked access gates. place at station 2 and the remainder at station 3 to improve compaction.

Testing A separate Concetti FFS-E handles wet product Factory acceptance testing was carried out using the (crushed rock, gravel, aggregates and various sands) client’s own products on the fully assembled line in dosed by volume (0.5 ft3 or 14.16 l) from a conical, Concetti’s ultra-modern 14 000 m2 plant overlooked stainless steel buffer hopper using a belt feeder fitted by the ancient city of Assisi in Umbria. with a high-resolution encoder on the non-driven shaft This factory testing is the customer’s assurance to provide close volumetric control. A vibrator helps that the entire line complies with the specification and product flow from the hopper to the belt. performs as required before being shipped. It also Contact parts are constructed in corrosion-resistant ensures a rapid, trouble-free re-assembly and start up stainless steel with a low friction Teflon covering at a on site with no unwelcome surprises. speed of 1000 bags/hr.

All three FFS machines have a bag leakage About the author detection system followed by a series of flat belt Graham Rawlings has enjoyed a long career with conveyors which merge and transfer filled bags via a several manufacturers, in both process control checkweigher (user supplied) and reject device, to a and bag filling systems, and was Concetti’s single high-level push type Concetti palletiser model sales representative in the UK. He now provides PS-3A/20S. The inclined belt feeding unit is fitted with support for Concetti’s world-wide marketing a motorised height adjustable bag flattener. activities.

The palletiser has two pallet stacking positions and a fork type dispenser to handle 40 in. x 48 in.

(1016 mm x 1220 mm) GMA type four-way entry pallets. A dispenser applies cardboard or rigid plastic bottom sheets if required.

Layer patterns of 5, 6, 7, 8 or 10 bags per layer are possible and up to 12 layers or 52 in. (1320 mm) high including the pallet.

Separate Siemens S7 PLC controllers are linked by a network allowing the entire line to be set up from the FFS operator panels.

As standard, Concetti FFS machines are fitted with motorised bag length adjustment. Elsewhere, on the bag flattener for instance, adjustment for different pack sizes Concetti high-level palletiser.

Reprinted from February 2021 World Cement