A manufacturer of chemical products for the building industry including adhesives, sealants, latex, concrete, levelling compound, screed, etc are using a variety of Pinch Valves on their high speed pneumatic packer machines.

Valves assisting abrasive product flow

The construction related powders are quite aggressive, some with a similar consistency to sand. Therefore, the valves have to be able to withstand the abrasion from the product.

The Pinch Valves installed on the powder line within the packing/bagging machines at this site are used for product flow. Once the paper bag is in position, the machine releases the air off of a normally closed valve to allow the powder to come through. The machine knows when the bags have received the correct amount of powder from the scales that are attached to the saddles, so air is then applied onto the valve to squeeze it closed, preventing the powder coming through.

pneumatic packer machine
pneumatic powder packing machine

Valves working in conjunction with Venturi System

There are an impressive number of five different types and sizes of AKO Pinch Valves on each of the bagging machines. That’s five different valves, each with an important role, handling abrasive powders with ease. One valve is used in conjunction with a Venturi extraction system.

The Venturi is a piece of equipment for measuring the flow rate of powders in pipes, with accuracy. It is a system for speeding the flow of powder or fluid (in this case, powder), by constricting it in a cone shaped tube. In the restriction, the powder must increase its velocity reducing its pressure and producing a partial vacuum. As the powder leaves the constriction, its pressure increases back to the ambient or pipe level.

An AKO VM type Valve operates in conjunction with the Venturi system. The pair of VMC valves either side of the machine blow pressure in and blow pressure out back into the system. When a bag is put onto the machine, an inner spout opens and closes the vacuum to suck the excess powder out. One of the VF Valves in size DN65 at the top of the system below the hoppers blows the product in, and the other VF valve in size DN40 in the upright position is an exhaust valve.

The whole hopper load of product cannot be released at once as it compacts, so it needs to be released in stages, which is what the VF Pinch Valve assists with. A vacuum system is not in place within this application as it pulls too much product down into the line at once. Instead, the venturi system blows just a small amount through.

pneumatic bagging machine

A closer look at how the machines work and valve cycles

The ambient powdered materials are blown through the valves at 1.5 bar, and the valves are being shut off with 6 bar air pressure. The company could regulate the closing pressure down, but this would cause more of a disruption and an inconvenience to them since 6 bar is the standard air supply on most machinery, and they are happy with the current set up.

VM type Pinch Valve sucking out excess powder
VMC Pinch Valves blowing pressure in and out

The machine runs 24 hours Monday to Friday, with one night rest. i.e: it will not run 10pm – 6am Thursday. This is to enable maintenance tasks on the machines to be carried out. As needed, there will also be production on Saturdays 6am – 2pm where the machine would be in operation.

Based on the three machines that are running constantly, filling 450 bags per hour, which is 150 bags per machine per hour, we worked out that each machine runs for 112 hours per week, and produces 16,800 bags per week. This is 873,600 bags a year.
Each Valve is operated once per bag, therefore the amount of cycles per valve per year is 873,600.
The durable elastomer sleeves inside the Pinch Valves are replaced on a planned maintenance schedule. Spares are kept on the shelf for emergency failures, including complete refurbished valves to swap in and out of line to reduce downtime. All valves on all machines are replaced at once where possible.
“Pinch Valves are a lot simpler than Pneumatic Valves”

The construction powder manufacturers have another set of bagging machines on a different powder line, this time on a rotary system. It does the same job as the other machines, but a cone plunger in the hopper releases to let the product up. The product is released into bags as it travels around the rotating machine. There are different construction materials bagged into 20kg paper sacks every hour, with a digital display showing when a bag is full.

The company have been using these powder bagging machines since the day they opened, many years ago, and the valves were already installed on the machines. One of the engineers on site told us at AKO UK that they find the AKO Pinch Valves a lot simpler than electrically controlled versions. The majority of their production line is pneumatically controlled, so the Pinch Valve suits the application well.

VMC Pinch Valves blowing pressure in and out

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