In UK and Europe and most of the world (1 litre = 1.75975 pints):-

1 bbl = 1 barrel of beer = 36 Imperial gallons = 288 Imperial pints = 163.66 litres = 1.6366 hectoliters.

A brewery will describe it's 'brew capacity' in various multiples of this volume, according to the size of the tanks it uses.

1 bbl = 4 Firkins = 8 Pins, so a 'Poly-pin' = 36 pints.

Kegs can vary in size. A Euro-keg is most commonly 50 litres but can also be 30, 25 or 20 litres (EU legislation).

In USA:-

They measure volumes differently from the rest of the world. (1 litre = 2.1134 US pints).

1 bbl = 1 US barrel = 31 US gallons = 248 US pints = 117.35 litres.

1 US keg = 124 US pints = 58.67 litres.

Beer is made with four main ingredients: water, malted barley, hops and yeast.

Water:

The type of water is of course important, some say that hard (mineral laden) water is good for brewing.

Malted Barley:

Barley is a cereal grain, like wheat or oats.
Malted barley is grain that has germinated, then dried in a kiln. In a malt house (malting) the barley is spread out in a 30 cm deep layer on a concrete floor, then sprayed with water. Warm air is blown over it for several days until it starts to sprout. It is then passed through a kiln, which dries it out and stops the growth process. Some of the malt is kilned for longer, become darker in colour, ranging from pale brown to completely black. This is how speciality malts, like caramel, Munich, chocolate, and black malts are made. These darker malts are used to give colour and flavour.

Malted barley is the source of fermentable sugar in beer. Most of the simple sugars extracted from the malt during the brewing process are transformed by the yeast, producing carbon dioxide and ethyl alcohol. Some more complex sugars remain unfermented and remain in the beer as 'residual sugar', which gives the beer its body and malty sweetness. Some beers have a greater amount of residual sugar than others. A 'bock' beer, which is very sweet, has lots, whereas a 'dry' beer is brewed to have virtually no residual sugars, and hence a 'dry' flavour.

Hops:

Hops are the flowers of a climbing perennial vine. They are used as a 'seasoning' in beer. Hops contribute bitterness and fragrance, there are many different varieties of hops, each having a different flavour. Some hops impart a flowery almost perfume-like fragrance, others are more earthy or spicy.
The character of a good beer is a balance between the characteristic sweetness from the malt, and the bitterness and fragrance of the hops.

Certain tree barks, juniper berries, ginger root and other substances can be added, to impart different flavours.

Yeast:

Yeast is a single-cell organism which causes the beer to ferment. During fermentation, the yeast consumes sugars extracted from the malted barley and produces alcohol, carbon-dioxide and other by-products, which affect the flavour and fragrance of the beer.

Brewers' yeast is one of thousands of different types of yeasts, all of which are adapted to live in a specific environment. Although there are hundreds of strains of brewers' yeast, they all fall into one of two general categories: ale (top fermenting) and lager (bottom fermenting) yeasts.

Ale yeasts ferment at room temperature (18 to 24 °C). They typically impart certain 'fruity' flavours (from compounds known as esters).
Lager yeasts ferment at lower temperature (7 to 13 °C) and generally do not produce the same fruity flavours.

The Brewing Process:

1. Milling the grain:

The different types of malted barley, depending of the recipe, are measured, mixed together and ground into a coarse 'grist' in a mill.

2. The Mash:

The grist is transferred into the Mash Tun and combined with hot water to form a thick 'porridge', called the mash. This soaks at 65 °C for about an hour. During this time, the starch in the malt is being broken down and converted into sugars by enzymes in the grain.

After the mash has sat for forty minutes, sparging begins: hot water at 75 °C is sprayed on the mash and a the sugary liquid extract, called wort, is drawn off the bottom of the tank and into the Brew Kettle ('Copper'). About two-thirds of the dry weight of the original grist is converted into sugar and ends up in the Copper.
Afterwards, the spent grain is shovelled out of the Mash Tun and can be used for animal feed.

Notes:-

a. The hot water required is heated to 75 °C in a Hot Liquer Tank, insulated and conventionally using cheaper 'night rate' electricity. Alternatively, a stainless steel heat exchanger could be installed inside the HLT, heated by hot water from a diesel fueled boiler, and linked from the Chiller (heat exchanger) which cools the wort after the boil, so heat extracted from that is used to heat the water in the HLT.

b. A spray-ball system can be fitted in the top of the Mash Tun, to use for sparging, and subsequently for CIP of the Mash Tun.

3. The boil:

The wort is then boiled in the Brew Kettle (Copper) for ninety minutes. Bitter hops are added at the start of the boil and finishing (aromatic) hops are added at the end.

After the 90 minute boil, the wort is left in the Copper for 30 to 40 minutes. This allows the hops and sediment to settle out. Then it is pumped, still at over 93 °C, through a heat exchanger, cooling it to 13 to 18 °C.

A spray-ball system can be fitted in the top of the Copper, to use for CIP.

The secret to any brewery’s success is scrupulous sanitation practice. The fermenting beer must be free of any microbes other than the particular strain of yeast the brewer is using: no bacteria, no moulds, and no other yeasts can come into contact with the beer, because they will contaminate and spoil it.
Up to the heat exchanger, sanitation is not a problem because of the high temperature, but as soon as the temperature falls below 71 °C, the beer is vulnerable to contamination, and every surface it comes in contact with from this point on – pipes, hoses, tanks – must be sterile.

4. Fermentation:

The cooled wort leaving the heat exchanger passes through a hose into a fermentation vessel (FV), ideally with cooling jacket, ideally a cylindro-conical fermenter.
A spray-ball system can be fitted in the top of the FV, to use for CIP.

A wort aerator can be installed in the hose inlet to the FV.

A pure, liquid yeast slurry is added as the wort enters the FV.

There are three alternative procedures:-

  a. 'Bottle conditioned' beer, bottled immediately, before fermentation (which takes place in the bottle) using a gravity bottle filler, with 4, 6 or 8 nozzles. For 33cl bottles it's worthwhile having an 8 bottle filler.
A small pump is used to transfer the beer from tank to bottle filler.
Crown caps (26mm) are crimped on the bottle tops immediately after filling.
Alternatively, kegs can be filled and sealed.

  b. The FV can be a normal 'pressureless' tank, with an air-lock (or pressure-relief-valve) to release the CO₂ given off in the fermentation. After fermentation, a carbonator is used to add more CO₂ to the beer. An 'in bottle' carbonator can be used, which avoids the need for an expensive counter-pressure (Isobaric) filler. For faster production an in-line carbonator followed by a counter-pressure filler is used.

  c. A 'pressure tank' can be used, holding pressure up to 2 bar or 3 bar, which retains the CO₂ in the beer. After fermentation a counter-pressure (Isobaric) filler is used, to fill bottles or kegs. There is no need for a pump as the pressure in the pressure-tank causes the beer to be transferred.

5. Filtration and conditioning:

After fermentation in tank, the beer - as it is now - is chilled in the tank to about 1 °C (- 2 °C to + 3 °C) and allowed to settle for several days to months, depending on the beer style.

Lager beers are passed through a filter. However, most ales remain unfiltered, clarifying by allowing the yeast to settle out naturally at the cold temperature, a process known as cold conditioning.

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