A 7 BBL isobaric tank is usually bought for one of two reasons: you are carbonating in the vessel itself, or you need to move finished beer under counter-pressure without flashing off CO2. Both come down to the same thing — the tank has to hold pressure and hold temperature at the same time. That is why we build these as true pressure vessels rather than repurposed atmospheric tanks.

What the vessel actually is

Seven barrels is roughly 217 US gallons of working volume. We normally size the shell so you have about 25 percent headspace above the beer line for krausen and foam during carbonation. The body is cylindrical with a conical or dished bottom, and the top head is domed to take pressure evenly. Because you are carbonating in place, the tank is rated for a design pressure matched to your relief setting, not to some generic shop number.

Material and fabrication

Standard builds use 304 stainless for the product contact surfaces. If you are running sour programs, fruit additions, or anything with chlorides, we will quote 316L instead — the molybdenum content is what resists pitting, and 304 will eventually show it. Wall thickness is chosen from the pressure calculation and the vacuum case, not from a catalog default.

Welds are full-penetration TIG, purged on the inside, then ground and polished. Product-contact polish runs to around 0.4–0.8 micron Ra; the exterior is usually a 2B or brushed finish since nobody needs mirror outside. Every pressure joint gets dye-penetrant or hydro testing before it ships, and the vessel is hydro-tested as a whole at 1.5 times design pressure.

Cooling, seals, and fittings

Dimple or channel jackets on the cone and lower cylinder carry glycol. The jacket area matters more than most buyers expect: undersized jackets mean slow crashes and uneven carbonation, especially in a 7 BBL tank sitting in a warm room. Seals are EPDM or silicone depending on your cleaning chemicals. Manways, racking arms, sample valves, and carbonation stones are all specified to the same pressure rating as the shell — a 15 psi clamp on a 30 psi tank is a leak waiting to happen.

Cleaning and connections

CIP is done through a spray ball mounted in the top head, with the return pulled from the bottom outlet. You want the ball sized to the tank diameter so coverage is complete without overloading your pump. Typical connections are tri-clamp for product and CIP, and threaded or flanged for glycol. We label every port on the drawing so your crew is not guessing during installation.

Specifications

Common questions

Why cone versus dished bottom? A cone gives you a clean yeast dump and better trub collection. Dished bottoms are cheaper and fine if you are not cropping yeast regularly.

How does the relief valve relate to working pressure? The relief is set at or below the tank\’s design pressure. Never run a tank above what the relief allows — it exists for the worst case, not the normal case.

Do I need a separate bright tank? If you carbonate in the fermenter and serve from it, no. If you want clear presentation beer, you will transfer under pressure to a bright tank.

Small brewery versus commercial? Small ops often use unitanks for both fermentation and carbonation to save floor space. Larger breweries separate the two so each vessel stays in its most productive role.

Tell us your batch size, beer type, number of fermentation tanks and available space. We can recommend the tank volume, cooling area and configuration for your brewery.