This page contains some clarification on the more important aspect of a separator, and at the end of the page a calculation tool that gives an idea of the real capacity of a separator.
One of the bigger and more expensive piece of equipment a brewer will consider once up and running for a while, looking for cutting product losses, get a faster (and better?) beer clarification process, or simply being able to get rid of any type of solids that are present in the beer.
There are several suppliers out there all claiming they have the ideal machine for your needs. There are plenty of process reasons to consider when going for a separator, but It usual boils down to the following points:
- Will my beer be clear enough? Will I be able to reach x EBC?
- What’s the O2 pick-up to expect?
- Will it run at xx hl/h flowrate?
On a separator point of view, beer clarity will be influenced by:
- mechanical design,
- rotation speed,
- bowl size,
- residential time of the beer in the machine.
These 4 variables can’t be compared separately to judge whether one machine or the other will perform better. For example, if separator 1 rotates much faster than separator 2, separator 1 is not necessarily clarifying the beer better than separator 2.
The ingredients, and whole process will also have an impact on how clear a beer can be. Therefore, it is not possible to have a guaranteed turbidity EBC value for a certain separator.
After fermentation, the introduction of Oxygen into the beer has to be avoided. O2 content in the beer is measured in ppb (parts per billions) and brewers try to keep it as low as possible, usually below 50 to 100ppbs (before filling). It is essential to check the future equipment’s ability to keep O2 out of the product.
Separators for beer processing are therefore built in a way to minimize O2 pickup and suppliers will advertise a guaranteed minimum O2 pickup over their separators (inlet vs outlet). This O2 pickup, mostly happens at the inlet and outlet seals (rotating vs fix part) of the separator. To separate the beer from the atmosphere, some machines are equipped with a hydro-hermetic seal and others are with a mechanical seal.
A water ring is created in order to separate the beer from the atmosphere in order to prevent a high O2 pickup. In case of a discharge, a short vacuum happens, the water seal breaks and some O2 can get dissolved into the product. This usually is accepted since it is creating a peak in DO (dissolved O2) for a very short time.
This type of seal needs a constant water supply during production. It is important to use DAW (deaerated water usually containing around 5 to 20ppbs) in order to reduce the potential risk of O2 pickup. It is also usually compulsory to meet the advertised minimal O2 pickup from the supplier. If normal water is used, the O2 pickup can be higher than what is promised because of the high dissolved O2 content migrating to the beer.
A mechanical seal (similar to a centrifugal pump) is used to separate the product from the atmosphere. It is therefore not needed to have a continuous supply of DAW (deaerated water) in order to keep the DO low.
It will however still need some water supply in order to keep it lubricated and prevent it from being damaged when the separator runs on stand-by.
A separator has a hydraulic capacity that is set by its static pump on the outlet. This static mechanical part is similar to the impeller of a pump but in this case, the liquid is rotating. As a pump, it has a working range. The hydraulic capacity is the widest flow range the separator can run at. It however gives a wrong idea of what the separator will run at on beer.
The production flow rate will be largely influenced by the solid content on the beer inlet to be removed by the separator. The below sketch shows solid chambers, where the solids are accumulated during production.
The volume of this solid chamber will ideally be emptied during a discharge, every time it is full of solids. The higher the beer flow , the higher the solid flow , and the higher the discharge frequency. The volume of this solid space and the maximum discharge frequency are two important factors to consider when selecting a separator: If the hydraulic flow rate is high, but the volume of the solid chamber is too small for a certain concentration of solids in the beer, the beer flow might have to be reduced drastically in order to cope with the maximum discharge frequency.