Venturi mixing offers a practical, safe and inexpensive way to dilute chemicals from concentrates to their ready-to-use form. This article looks at a variety of different venturi mixing systems that mix concentrated cleaning chemicals with water and considers the trade-off between practicality/ease of use and user safety.  

Why keep chemicals in concentrated form?

Cleaning chemicals, be they sanitisers, caustics, or acid cleaners are often stored in a concentrated form. This is then diluted to perform the necessary cleaning function. Using concentrates rather than prediluted chemicals saves storage and gives greater versatility because dilution levels can be varied depending on the specifics of each application.

The downside of using concentrated chemicals is that they can be more dangerous in their concentrated form. This presents some user safety issues during the mixing process. In addition to safety issues, it is also obvious that the mixing needs to be accurate and performed well to ensure a uniform and correctly diluted end product is applied. 

Basic principles of dilution

The standard guidance given for the safe mixing of chemicals from concentrate follows basic common sense i.e.:

• Always ensure accuracy
• Ensure only trained personnel conduct the dilution
• Use the diluted chemicals right away, do not store for later use
• Wear the correct PPE
• Ensure the concentrate is put back properly to where it is supposed to be stored
• Add the concentrate to the water, not the other way around

The choice of equipment to enable accurate delivery of diluted product to where it is needed can affect all of this commonsense advice. Good kit used well will enhance and meet all the advice points above but, conversely, inappropriately used equipment can be detrimental to safety and effectiveness. Below is a short guide on the various venturi mixing equipment that can be deployed. It focuses on the balance between operator safety, spill hazard, and the flexibility of the mixing system.  

Venturi mixing basics

A venturi mixer will use the venturi principle to automatically mix concentrate with a water stream. The venturi principle

states that when a fluid is forced through a narrow opening it accelerates and this will result in a loss of fluid pressure. This localised low pressure can be utilised to create a suction effect where fluid will naturally move from an area of higher pressure to the generated low pressure area. This siphoning effect can be used to automatically mix cleaning chemicals with a water flow. The amount of suction can be controlled by throttling the siphon tube and by controlling the flow rate of the water. 

Venturi mixing offers a practical, safe and inexpensive way to dilute chemicals from concentrates to their read- to-use form. As venturi mixing requires no pumps, power or moving parts it is a robust and very commonly deployed alternative to the manual dilution of cleaning chemicals. It has a further advantage in that the concentrate will typically be well mixed in the hose, resulting in a very even mixing without the need for further stirring. 

A concentrate poured into a container of water may often require a secondary agitation to ensure it is fully mixed. Venturi systems will provide natural agitation as the fluids move together through the hose system. 

Options for venturi systems

These systems can be deployed in 4 main configurations:

1 Mix to container

These systems will be wall mounted mixing stations that are designed to deliver the required diluted chemical into another container. This container will then be moved elsewhere to be used. These systems replace the need for manual mixing and stirring. As such they offer greater user safety when mixing. As only the diluted liquid is moved around the factory the risk of a hazardous leak of the concentrate is eliminated.

The concentrate used in such systems can be locked away if necessary and so is completely inaccessible to the end operator. Only the diluted product can be dispensed in a predetermined dilution. These systems offer the ultimate in safety. However, they come at the price of practicality. As the diluted solution needs to be moved in a container to where it will be used, this may present problems in terms of time and effort.  

2 Mix at wall

These systems will mix the concentrate straight into to the wash down hose that is being used in the cleaning operation. This means that only the diluted cleaning solution is ever under fluid pressure. The automatic mixing at point of delivery means that only the required amount of concentrate is used. This eliminates the potential for wasted diluted chemicals being made or running out of dilute part way through a job. Mix at wall systems offer great versatility and ease of use whilst maintaining high safety standards. 

3 Mobile mixers

These venturi mixing stations are a hybrid system somewhere between the mix at wall system and the mix at gun system. The mixing occurs at a wheeled, mobile mixing station which will be hooked up to a suitable water supply. This means venturi mixing can be “delivered” to any part of factory and will eliminate the need for long hose runs from fixed wall mounted units.

In terms of safety and chemical security they are somewhere in between the fixed wall and mix at gun units. They have the safety advantage of the chemical being in a large container that would not have to be decanted into a small bottle and the concentrate is stored some distance from the operator. This reduces the risk of operator harm when compared to a mix at gun unit. 

On the flipside, these units still involve concentrates of cleaning chemicals to be moved around the factory. The wheeled, mobile mixing stations are of a robust design so the chance of spillage or leaking is minimal but it is, nonetheless, higher than for wall mounted units. 

4 Mix at gun

These systems will have a small pot of concentrate situated under the cleaning gun. This is then mixed at the spray gun itself. No chemical is passed through the main hose. In one respect this offers a safety advantage in that any accidental hose leaks will only result in water being sprayed. However, in another respect we now have concentrate very near to the end user which could be inherently more dangerous. The big advantage of such systems is their flexibility. A mix at gun system can be connected to any suitable water supply around the factory and used to deliver accurately diluted cleaning chemicals where needed.

Conclusions

As with most things in life there is a trade-off occurring here between flexibility and security. It should be noted that mix at gun solutions are not inherently unsafe or unsecure; they are an entirely appropriate system for many cleaning applications. Once this trade off is understood then sensible decisions can be made as to what is the best solution for your application.

If you have high concentrates of nasty caustics or acid based cleaners then mixing at the gun is unlikely to be appropriate, for example. Similarly, in a very large factory setting that uses standard non-hazardous wash down liquids, mix at gun systems offer incredible flexibility and will greatly speed up clean down operations. It is all about what is most appropriate.