Tank Carbonation

Packaging is by far the most technically and financially intense area of brewery operations. A missed step in financial planning, brewery operations, bottling or marketing can spell disaster for the brewery. In this article we will explore some of the aspects involved with becoming a successful packaging operation.

One of the first things to consider and evaluate completely before entering any packaging operation is evaluating your potential market and establishing realistic and achievable goals. Ask yourself what is my market in terms of types of product that appeal to my potential audience, geographical statistics regarding population and percentage that would be interested in my product, cost and pricing analysis. After all without this detailed information you will not be able to establish a basis for the feasibility of your proposed operation.

Market
The market is your demographic audience, including population density, type of audience white collar, blue collar, income levels, recreations, etc. and area of distribution. This means the first step is to identify with that audience as to which aspects are important to your evaluation including where you yourself are in the group. Chances are you are looking for the segment of the market that shares your interests in foods, beers, sports and other activities and those that would be attracted to your product. Ultimately this is a business to produce and sell a product, so you want to make and market a product that has the most appeal will establish a loyalty to your brand. These days the group that is attracted to Micro brewed and beers of more distinct flavor are diverse and span groups of many interest and income levels. This is a good thing for planning your product types and styles that will be received well and continue to appeal to your audience. One thing you can do to get started is simply start gathering information about population and making notes as to the job types, income, age group and interests of your target area. You want to use this information to determine not only the volume of potential customers, but also the types of products you want to package, advertising and labeling materials that will attract your audience. Much of this is gut feel from your prospective it is a good idea to involve others whose opinions you trust to help with the information, evaluation of the market.

Once you have some idea of the product you want to sell and the audiences you hope to sell it to, you need to consider how you will go about getting the product to the consumer. This is simply do I want to use distributors to place my product or am I going to stay small and distribute myself or maybe simply package for a pub. You need to do this so that you can start to estimate the size of equipment you will need to support your plan. Let’s say for example you have established from your research that you are going to do your local region with bottled product using 2-3 distributors. These distributors often have a pretty good feel for the amounts of your product they can move for you. You want to make you best estimate, add a little for growth and future expansion of your market. Always plan for bottling capacity that is adequate for your plans with some room for expansion as this will effect the size and type of equipment you need.

Now you have estimates in hand and some idea of production needed to support your developing plan. Its time to start looking at costs associated with your packaging. This means you have established what type of product you intend to sell, what its retail pricing should be to be competitive with other products already on the market and what it is going to cost you to get the product to market. Lets say for example the target retail selling price is $7.00 in the grocery store and the store has a 20% mark up and the distributor has a 20% mark up. This will help you to establish how much you will be able to sell your beer to the distributor. Now for the hard part, estimating all the breweries costs getting the beer to the distributor which when subtracted from the sale price to the distributor will give you the profit. Brewery costs need to be complete and accurate so a little leg work will be involved and some estimating as well. The cost of the beer is relatively easy to establish as you already know what your costs are and should be able to translate that cost directly to the bottled product. The costs incurred to start a packaging can be surprising especially with minimum orders of such things as 6-pack carrier, bottles, caps, labels and boxes. These consumable items may also have die and printing charges and will take up floor space in your brewery which all has to be figured into the cost of startup. The following is and example of package costs, the figures are made up and you should determine your own actual costs to do a good evaluation.

Example costs

Bottles @ $0.20ea. 2,500/pallet, min order 5 pallets	$2,500
Labels @ $0.05ea. 100,000 min.	$5,000
6-pack carrier @ $0.35ea. 50,000 min.	$16,000
Case Box @ $0.85ea. 5,000 min.	$4,250
Crowns @ $0.02ea. 5,000 min.	$150
Total:	$27,900

For this example with art work fees and shipping costs we would estimate initial package costs to be $30,000. Next we need to establish the equipment size needed to support the proposed market. In this example machinery producing 1,200bph would be adequate to support the need, but one should also consider the labor cost involved for operating the equipment as a per package cost. A larger machine producing say 2,000bph or more most likely can be operated using the same labor, but the cost of labor per package is reduced by 40% which in a short period of time could make up the cost difference of the larger machine. Many considerations will come into play for choosing the equipment which will discussed later on. For now we will just use some basic budgetary numbers for our plan. Assume the bottling machine and labeling equipment of this scale will cost a total of $65,000. This is were estimating cost per package can get tricky as you need to establish a life of the equipment and try to account for interest costs and square footage costs over time. This is something you will have to work out for yourself, but for this example I will use $0.01 per bottle for the equipment, for the labor based on 3 people at 2000bph $0.02 per bottle and $0.11 per bottle for the beer.

Before going any further we need to find out if bottled beer will be profitable for this example. To do that we can simply calculate out costs verse what the distributor will be paying for the beer. Distributors will be taking full cases, so for this example working backwards from retail, the distributor would pay you $16.80 per case. Now let’s compare our costs.

Cost per bottle $0.39 x 24 bottles	$9.84
Six pack carriers $0.35 x 4	$1.40
Case box	$0.85
Total cost for brewery per case	$12.09

Take the price the distributor pays you per case of $16.80-$12.09 that it costs the brewery to produce and the brewery should make about $4.71 per case.

Choosing a filler/capper
Now that you have established you can make a profit selling packaged beer with this estimate, its time to look into filling equipment to suite the need and provide the quality of product needed to ensure success. You may find that the cost estimate for the equipment needs to be adjusted for the plan and make changes accordingly. In the beer industry quality bottling means the best sanitation, gentle smooth pouring, and little to no air pick up in the product from the bottling process. Air pick up is by far the most critical issue for quality control and shelf life and is the main reason for freshness dating of bottled beers.

Air or oxygen in beer causes it to go stale and develop a cardboard sort of taste so the less oxygen in the finished bottle the longer the shelf life and the longer the beer will remain fresh. In many cases process changes in the brewery will be needed to minimize oxygen in the beer before it ever gets to the bottling machine. Common sources of oxygen being imparted to the beer in the brewery are valves, filters, pumps and just moving the beer. Keep all brewing equipment in good condition and replace seals and parts associated with filters and tank transfers in good condition. On the bottling machines the up take of air can have several sources from the pressure bowl on top to the capper where the beer needs to be foamed up just before capping. Not all bottling machines use pressure bowls, but for those that do you need to be certain that the head space in the bowl is properly filled with CO2 and the seals and valves are all in good condition.

By far the biggest pickup point for unwanted air is the capping station. To have finished bottles with low airs the machine must have some mechanism to cause the beer to be foamed up just before capping. The foaming releases CO2 from the beer which displaces air from the neck of the bottle, then just as the foam mushrooms over the top of the bottle, put the cap on. Several mechanisms are used for causing the foaming of the beer from pressure changes at the filling station, pingers which hit the side of the bottle with a small hammer and a stream of warm water run over the beer can be used to promote the foaming. Regardless of how it is done this is essential step for acceptable airs in the finished package.

Basically there are two types of filling heads used for beer filling machines, a short tube and long tube. The short tube is pretty much what it sounds like; the filling tube is very short and will only stick into the bottle a short distance. When filling the beer flows over a small hat shaped piece that directs the flow to the sides of the bottle so the beer is delivered more gently than pouring and stops splashing. The draw back to this type of filler from an air pick up perspective is the beer is spread into a thin moving layer which allows maximum to the atmosphere in the bottle. To avoid excessively high air pick up using short tubes the machine need to have at least one, if not two pre-evacuations. Evacuations are the process where a vacuum is drawn on the bottle to draw out some of the atmosphere then CO2 is put back in its place. If the pre-evacuation is repeated again before counter pressure and filling with beer the atmosphere it the bottle is low enough to produce acceptable levels of air in the finished bottle. Generally it is accepted that 1ml of dissolved air in a 355ml bottle will have adequate shelf life.

Long tube fillers have tubes that extend nearly to the bottom of the bottle and fill from the bottom up. This configuration has far less exposure to the atmosphere in the bottle and less turbulence and agitation as well which equates to less pick of the atmosphere by the beer while being poured. Just like short tube machines, long tube fillers are available with pre-evacuation and will generally have lower air pickup than short tube fillers.

Another aspect which is often forgotten, but very important to quality control and operating costs is the maintaining of the filler. The filler is no different in its requirements for cleanliness and sanitation than any other piece of equipment used in the brewery. Due to it complexity, moving parts and valves many bottle filling machines have much more vigorous cleaning regiments than other equipment. Machines with pressure bowls have not only the contact surfaces of the bowl, but also the valves and seals used for each filling station. These machines require a good Clean In Place (CIP) system to remove beer stone and for sanitizing. Also machines using pressure bowls will require periodic maintenance of valves, seals and conveyors. Some machines with computer controls such as Merlin fillers by Meheen Mfg. are able to use the bright beer tank in place of the pressure bowl. This has several advantages from a cleaning, maintenance and moving parts. The regular maintenance, replacement of consumable parts and repairs should also be factored into your machinery evaluation of overall operating costs.

Brewery operations for bottling
Brewery operations and beer handling can greatly affect bottled beer quality and presentation. The two critical factors in the brewery are again air pickup in the product and CO2 levels. Air pick up in the beer before reaching the filler most often comes from transferring and filtering operations. One notorious source of air pick is using centrifugal pumps to move and filter beer. Centrifugal pumps work by bringing the beer in through the center, then slinging it toward the outside of the pump housing, this creates a low pressure at the center of the pump causing the beer to be drawn in. It is this low pressure which also can draw air in through the shaft seal and drive it into the beer. Any time beer is moved you run the risk of picking up air and another place to be very careful about air pickup is the filtering. To minimize air pick up in the brewery always maintain good seals in all you valves, pumps and filters and avoid moving the beer anymore than is necessary. One thing you can do to help displace air that may have been picked up during transfer and filtering operations is to perform your final carbonation in the bright tank before sending it to the filler. The CO2 will help to displace the air and ensure the CO2 levels are where you want them.

One of the most critical operations in the brewery is temperature and CO2 control. When you start getting product on the store shelves your customers will expect that each bottle of your beer will be identical to the last. This means CO2 levels must be consistent at all times. CO2 is a major component in mouth feel and provides some bite to the beer affecting its flavor. I cannot stress the importance of consistent CO2 levels enough. The importance of CO2 can be demonstrated with a can of cola. Take tow cans of cola, remove the CO2 from one compare it to a carbonated can served at the same temperature. The non carbonated can will be excessively sweet compared to the carbonated can. Well the CO2 in beer serves much the same function and if the CO2 levels change in your beer from batch to batch then your product changes. To maintain consistency in CO2 levels a strict procedure for carbonating should be adopted in the brewery and followed to the letter every time. Of course part of the carbonation formula depends on temperature so the cooling system in must work properly and hold consistent temperatures to be successful.

While several methods of carbonating beer are used, one of the easiest to understand and use is tank carbonation using a stone to create small bubbles of CO2 which is absorbed into the beer. The following is one method of performing the carbonation process using a refrigerated pressure tank.

Dynamics of tank carbonation

To understand the dynamics of CO2 dissolved in beer, we must first understand the solubility of CO2 in beer and the terms and measurements used to describe it. CO2 is very soluble in beer, and its solubility increases with pressure and decreases with temperature. The amount of CO2 dissolved in beer is most often referred to in terms of volumes. Volumes of CO2 are defined as the volume the CO2 gas would occupy if it were removed from the beer at atmospheric pressure and 0o C, compared to the original volume of beer. Thus if a quart of beer were carbonated to 2.5 volumes and all the CO2 were removed from the beer, it would occupy 2.5 quarts. Most packaged beers are considered normally carbonated with 2.45 to 2.85 volumes of dissolved CO2. Generally speaking during the bottling and keging process 0.1-0.15 volumes will be lost and should be added in the tank above the desired packaged content.

Determining the volumes of CO2 in beer is easily obtained by using the temperature and pressure conditions of the beer at equilibrium conditions and reading the volumes directly from a chart. Equilibrium means the same amount of CO2 is diffusing out of the beer as is being dissolved back into solution. It is critical that the readings used for determining CO2 volumes are taken under equilibrium conditions and the instruments used are accurate. The impact of false readings on determining the volumes of CO2 can easily be demonstrated by referring to the chart on the next page. For example the largest errors often come from pressure readings taken from gauges which are often plus or minus as much as 1-7 psi. If we have a container of beer at 35oF and our faulty gauge reading is 10 psi, we see from the chart our beer is 2.52 volumes, but the actual pressure is 15 psi, so in reality we have 3.02 volumes. Not only is the beer beyond normal gas levels, but excessively high pressures can be dangerous due to container over pressurization.

Other factors can often give false volume readings from the chart even if you have good instruments. One example of this might be a gas leak from a man way or pressure relief valve and you are using your tank readings in determining volumes. Your volumes determination will be incorrect because the tank does not represent equilibrium conditions. To be certain tank carbonation is correct a sample should be properly taken from the tank and tested. The tester will be a device which seals to the sample container and is equipped with a thermometer and pressure gauge for reading the equilibrium conditions in the sample container. The tester must be shaken vigorously several times before the readings are taken. This is to ensure that as much CO2 is coming out of solution as is being dissolved back into solution and equilibrium conditions are obtained. If you do not have a tester and tank conditions are used in determining CO2 levels, always be certain your tank is under equilibrium conditions and you have accurate instruments.

Tank carbonation is most often accomplished by kraeusen or CO2 introduction into the tank through a carbonating stone. For the purpose of this discussion we will only be concerned with carbonation using a stone. At the end of normal fermentation, beer contains about 1 volume of CO2. The carbonating stone will be used to introduce the remaining CO2 into the beer and bring it to the desired carbonation level.

Beer carbonation at various temperatures and pressures

Pounds per Square Inch

	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25
30	2.23	2.36	2.48	2.60	2.70	2.82	2.93	3.02
31	2.20	2.31	2.42	2.54	2.65	2.76	2.86	2.96
32	2.15	2.27	2.38	2.48	2.59	2.70	2.80	2.90	3.00	3.11	3.21
33	2.10	2.23	2.33	2.43	2.53	2.63	2.74	2.84	2.96	3.06	3.15	3.25
34	2.06	2.18	2.28	2.38	2.48	2.58	2.69	2.79	2.90	3.00	3.09	3.19
35	2.02	2.14	2.24	2.34	2.43	2.52	2.63	2.73	2.83	2.93	3.02	3.12	3.22
36	1.98	2.09	2.19	2.29	2.38	2.47	2.57	2.67	2.77	2.86	2.96	3.05	3.15	3.24
37	1.94	2.04	2.14	2.24	2.33	2.42	2.52	2.62	2.71	2.80	2.90	3.00	3.09	3.18	3.27
38	1.90	2.00	2.10	2.20	2.29	2.38	2.48	2.57	2.66	2.75	2.85	2.94	3.03	3.12	3.21
39	1.86	1.96	2.06	2.15	2.25	2.34	2.43	2.52	2.61	2.70	2.80	2.89	2.98	3.07	3.16	3.25
40	1.83	1.92	2.01	2.10	2.20	2.30	2.39	2.47	2.56	2.65	2.75	2.84	2.93	3.01	3.10	3.19	3.28
41	1.79	1.88	1.97	2.06	2.16	2.25	2.34	2.43	2.52	2.60	2.70	2.79	2.88	2.96	3.05	3.14	3.23
42	1.75	1.85	1.94	2.02	2.12	2.21	2.30	2.39	2.48	2.56	2.65	2.74	2.83	2.91	3.00	3.09	3.18	3.26
43	1.72	1.81	1.90	1.99	2.08	2.17	2.26	2.34	2.43	2.52	2.61	2.69	2.78	2.86	2.95	3.04	3.13	3.21
44	1.69	1.78	1.87	1.95	2.04	2.13	2.22	2.30	2.39	2.47	2.56	2.64	2.73	2.81	2.90	2.99	3.07	3.16	3.24
45	1.66	1.75	1.84	1.91	2.00	2.08	2.17	2.26	2.34	2.42	2.51	2.60	2.69	2.77	2.86	2.94	3.02	3.11	3.19
46	1.62	1.71	1.80	1.88	1.96	2.04	2.13	2.22	2.30	2.38	2.47	2.55	2.64	2.72	2.81	2.89	2.98	3.06	3.15	3.23
47	1.59	1.68	1.76	1.84	1.92	2.00	2.09	2.18	2.26	2.34	2.42	2.50	2.59	2.67	276	2.84	2.93	3.02	3.09	3.18
48	1.56	1.65	1.73	1.81	1.89	1.96	2.05	2.14	2.22	2.30	2.38	2.46	2.54	2.62	2.71	2.79	2.88	2.96	3.04	3.13
49	1.53	1.62	1.70	1.79	1.86	1.93	2.01	2.10	2.18	2.25	2.34	2.42	2.50	2.58	2.67	2.75	2.83	2.91	3.00	3.07	3.15
50	1.50	1.59	1.66	1.74	1.82	1.90	1.98	2.06	2.14	2.21	2.30	2.38	2.46	2.54	2.62	2.70	2.78	2.86	2.94	3.02	3.10
51		1.57	1.64	1.71	1.79	1.87	1.95	2.02	2.10	2.18	2.26	2.34	2.42	2.49	2.57	2.65	2.74	2.82	2.90	2.97	3.05
52		1.54	1.61	1.68	1.76	1.84	1.92	1.99	2.06	2.14	2.22	2.30	2.38	2.45	2.53	2.61	2.68	2.76	2.84	2.92	3.00
53		1.51	1.59	1.66	1.74	1.81	1.89	1.96	2.03	2.10	2.18	2.26	2.34	2.41	2.49	2.57	2.64	2.71	2.79	2.86	2.94
54			1.56	1.63	1.71	1.78	1.86	1.93	2.00	2.07	2.15	2.22	2.30	2.37	2.45	2.52	2.59	2.66	2.74	2.81	2.89
55			1.53	1.60	1.68	1.75	1.82	1.89	1.97	2.04	2.12	2.19	2.26	2.33	2.40	2.47	2.54	2.62	2.69	2.76	2.83
56			1.50	1.57	1.65	1.72	1.79	1.86	1.93	2.00	2.08	2.15	2.22	2.29	2.36	2.43	2.50	2.57	2.64	2.71	2.78
57				1.54	1.62	1.70	1.77	1.83	1.90	1.97	2.04	2.11	2.18	2.25	2.32	2.39	2.46	2.53	2.60	2.66	2.73
58				1.51	1.59	1.67	1.74	1.80	1.87	1.94	2.01	2.08	2.15	2.21	2.28	2.35	2.42	2.48	2.55	2.62	2.69

To use this chart: First find the beer temperature along the left hand vertical edge. Then read the pressure across the top and where the two cross, read the volumes of CO2.

Carbonating stones are made of ceramic or sintered stainless steel with very small openings which produce very small bubbles when CO2 is forced through them. Very small bubbles have a large surface area of exposure to the beer and are easily dissolved in to the beer. Stones are placed in the bottom of the tank and off center to produce a rolling action of the beer. Since carbonating stones have minute pores, the capillary resistance of the stone must be overcome before any bubbles are produced in the beer. This capillary resistance is often referred to as wetting pressure, which can be between 1-8 psi. Additionally the liquid head pressure above the stone also affects the total internal pressure required for the stone to produce bubbles. Every 28" of liquid height is the equivalent of approximately 1psi, consequently the higher the liquid above the stone, the higher the internal pressure to overcome the wetting pressure of the stone.

Beer carbonated in the tank using a stone can be carbonated from a few hours to several days. Generally the best results are achieved using a relatively slow carbonation. It is also highly desirable at the beginning of the carbonating process to use a relatively low differential pressure between the stone and the head space in the tank while bleeding gas from the top of the tank. This will scrub unwanted dissolved air out of the beer which was picked up during transfer or the brewing process.

The following is an example of carbonating beer at 34oF, using a carbonating stone with a wetting pressure of 5 psi. First determine the desired volumes of CO2 you want in the finished product, such as 2.58 volumes. From the CO2 chart we read 32oF on the left side and follow it to the right until we read 2.58, then move to the top of the chart and the corresponding pressure is
10 psi. The next step is to determine the head pressure of the beer above the stone. In this example the beer is 84" above the stone, divide this by 28"/psi and we obtain 3 psi head pressure. It is important to mention at this point that 28"/psi is an approximation for water and you may wish a more accurate figure, especially for higher gravity beers. To obtain a more accurate pressure multiply the total inches of liquid above the stone by the specific gravity of the finished beer then divide by 27.684"/psi. Generally speaking this sort of accuracy is not warranted for most conditions.

To obtain the total pressure needed for the carbonating stone to begin producing bubbles, add the wetting pressure of the stone (5 psi) to the liquid head pressure above the stone (3 psi) = 8 psi. This means that with 8 psi pressure applied to the carbonating stone and the head pressure of the tank at atmospheric pressure the stone will begin releasing bubbles into the beer. Since we want to carbonate slowly, the differential pressure should be kept low. 9 psi at the stone would give a differential of 1 psi above the bubble break over pressure with atmospheric pressure in the head space of the tank. As the pressure in the head space in the tank increases it is necessary to increase the pressure to the carbonating stone. Since the target carbonation level in this example is 2.58 volumes at 34oF the head pressure gauge on the tank should be 10 psi when the beer is carbonated and the pressure on the stone will the wetting pressure, plus liquid head pressure, plus the final equilibrium pressure (5+3+10=18).

Carbonating in the tank in this manner requires accurate pressure gauges and a great deal of attention. One option to reduce the amount of labor required for tank carbonating is a commercial Unit Tank Carbonator which maintains a constant differential pressure for you during the carbonating process. Even though you have carefully carbonated the beer and have accurate pressure gauges, it is still a good idea to check the beer using a good carbonation tester.

Filling operations:
Before any filling can take place the packaging equipment needs to be thoroughly cleaned as sanitized to avoid any biological or protein contamination being transferred to the finished package. This includes the hoses, fitting valves and any surfaces which the product will be exposed to. Many different chemicals are available today which perform these tasks well. Each brewery will need to choose which chemicals will work best for them. Bottling machine manufacturers may recommend specific chemicals and cleaning procedures which work best for their equipment. Recommendations from chemical suppliers and other brewers may also help to choose the best chemicals for your particular application.

Starting procedures vary based on the type of machine you are using and will be different for machines using a pressure bowl than those that do not. Our machines do not have a pressure bowl, but rather use the dispensing tank with head space pressure to push the beer to the filler. One portion of the starting process will be similar regardless of the type of machine and that is cooling the equipment and establishing constant flow conditions. Machines with pressure bowls will take a little longer for the equipment to cool to the beer temperature simply because they have more contact surfaces to cool. Typically with our machines you will only loose a few rows of bottles before the equipment is cooled to the point needed for normal operations.

Because these are counter pressure fillers, when the bottles are pressurized for pouring the pressure needs to be adequate to maintain the level of CO2 gas in solution. Because the beer is warming on its way to the bottle, generally you want the counter pressure in the bottle to be as needed for the beer conditions. This means that if the beer is 2.6 volumes of CO2 at 32F in the tank and the beer temperature has risen to 34F by the time it reaches the bottle you will want a slightly higher pressure at the bottle to compensate for the added temperature of the beer. It is easy to estimate the needed pressures by referring to the equilibrium table in the Tank Carbonation portion of this article.

One of the most critical portions of bottling operations is keeping the air pickup in the product to a minimum. To attain this, you must foam the beer to the top of the bottle just before capping. There are many ways of doing this and controlling foaming to achieve an ideal fob. Machines where the crowner is separated from the filler will often use a device of some sort right at the crowner such as hot liquid or jet to cause the foam. On our machines the filling and crowning stations are only 1 bottle diameter apart, so the open time of the bottle before crowning is very short. This allows for fob controls to be built directly into the filling head in the form of a CO2 pulse which is controlled from the operator’s panel.

Once a steady flow has been established, operations of the bottling become fine tuning and watching for trouble areas such as excess foaming, proper filling, crowning and making adjustments as needed to keep the process going. This includes supply of bottles, crowns, labels and case packing of finished products. Each brewery and brewing operation will be different so be flexible and adaptable with your packaging operations.