One of the most common questions we get at Zwirner Equipment is “which tank do I need?” To help answer this question for our customers, we will break down the different questions that need answered to determine which tank is the right tank for your processing needs. We will touch on the space and shape of a tank, the heating and cooling aspects, and your agitation needs.
Are You Processing or Storing Your Product?
The first step to picking the right tank is determining what you plan on using it for. Processing is done in smaller batches and storing is done in larger batches. This aspect will determine whether you need a processing tank or a storage tank.
What Are Processing Tanks Used For?
Processing tanks are most commonly used for…wait for it…processing! They are the best option for processing purposes because of their bottom shape. They come with either a cone, dish, reverse dish or slope bottom. Vertical and horizontal tanks can be used for processing but we highly recommend using a processing tank if you are processing a heavy product.
How To Pick a Processing Tank
Vertical and horizontal tanks have a sloped bottom of approximately ¾ of an inch per foot. However, this slope limits you to lower viscosity products only. Therefore, if you have a thicker product, you will need a cone or dish bottom processing tank. Vertical and horizontal tanks are most commonly used for storage.
Vertical tanks are difficult to find with vertical agitation. Most often they have horizontal mechanical agitators due to cost. However, they are the most common orientation used. We often find that customers avoid horizontal tanks due to space limitations. Vertical silos require much less space than a horizontal tank. If you are limited on space, a vertical silo is your best choice.
Horizontal tanks are most cost effective and work best if you need to heat or cool your product efficiently. Horizontal tanks have more surface area coverage, which means they can move product more easily because of its orientation. They are much more cost effective because it is a lot easier add vertical agitation and less expensive to transport. If you are looking for a tank that is cost effective and highly efficient, a horizontal tank is your best choice. Space and shape are big factors in selecting the right tank for your application. In order to choose the right tank, you first must decide if you plan to use it for processing or storage. Once that has been determined, you then must evaluate the space you have to house this tank. While reading about vertical and horizontal storage tanks, you may have asked yourself if it is important to efficiently heat or cool your product.
Heating exchange surfaces come in three forms; steam, hot water or an internal heating element. When choosing the right processing tank, you have to make sure you have an appropriate PSI rating to achieve the desired result (for jacketed tanks only). To begin, there are two questions to ask: 1. How much surface area do you need to heat? 2. How quickly do you need the product heated? Direct steam is much hotter than water but not all jackets are rated to handle the pressure of steam. You can also inject steam in to hot water. Hot water, however, can only get to a temperature below 212°F before it transforms to steam. Therefore, if your product needs to be above 212°F, direct steam or injected steam is your best surface choice.
Internal coils (also known as an internal heating element) are great for products outside of sanitary industries such as rubber. This is because the actual coil comes in contact with the product to heat it, making it harder to clean and creating a risk of burn on. It is cheaper to install because it does not require a jacket, but harder to maintain temperatures. Most used tanks can be modified to use the heating exchange surface of your choice.
Cooling Your Product
A cold wall tank has a cooling media that runs between the walls of the tank to cool the product. When choosing the right tank, you have to make sure you have enough cold wall to achieve the desired result. Similar to heating, there are two questions to ask: 1. How much surface area do you need to cool? 2. How quickly do you need the product cooled? Once these requirements are established, you then will need to choose a type of cooling media. There are three cooling medias to choose from including Freon, Glycol (chilled water), and Ammonia. If you are shopping for a used tank, you will have to take into consideration what type of media was previously used on the jacket. Below are the following recommendations from Zwirner Equipment about switching medias in a jacket:
How To Switch Medias In a Jacket
If a used tank was previously using Freon, we do not recommend switching medias. Freon requires special copper piping and switching could be costly and risky.
If a used tank was previously using Glycol, we do not recommend switching to ammonia. Glycol leaves hard water deposits in the walls of the jacket and switching could cause deposits to flush into the ammonia compressor, ruining the compressor.
If a used tank was previously using Ammonia, we can switch the media to Glycol.
Heating and cooling are big factors in selecting the right tank for your application. Once you have determined the space and shape requirements of your tank, you will then decide if you need any heating or cooling components. From there, you will evaluate your heating and/or cooling medias. Almost all products that require heating and/or cooling also require agitation. Now, are you wondering if you need agitation?
Do I Need Agitation?
Agitation is the action of stirring, mixing or moving a product within a vessel. It is used primarily to keep your product moving. Almost all products that use heating and/or cooling will need some form of agitation. Components of agitation always include a shafted blade, gearbox and motor, which can be customized to the speed you need to mix. These components must fit the RPM and horsepower that is required to achieve a higher or slower rate of speed and torque. What Is Your Desired Result? Agitation is a critical part of processing and should be chosen appropriately. When choosing a type of agitation, you should consider the result you are trying to achieve. There are multiple types of agitation that produce different results, which include mixing, moving and shearing. Based on the desired result, that will determine the type of agitation you will need on your tank. Below are the following results that you should consider to determine your agitation needs:
Do you want to mix your product?
High viscosity mixing: Products of higher viscosity will require a heavier and slower agitator. Often times with higher viscosity products, it will require a sweeping or scraping type agitation.
Scraping: Agitator makes contact with the sides and bottom of the tank to scrap the product off the walls. This is great for stickier products such as peanut butter. Scraping will assist a heavy product down the outlet and prevent burn-on or freezing.
Sweeping: Briskly sweeps the product from the tank walls. This is great for less adhesive products such as yogurt or custard. Most low viscosity products will have a bottom sweep and with high viscosity products you can add a side sweep.
Do you want to keep your product moving?
Standard propeller type agitator: This keeps the product moving to avoid hotspots, settling or separating. It also maintains a better overall cooling and/or heating rate and maintains an evenly regulated temperature. This is great for products that settle or separate such as raw milk.
Do you want to shear your product?
High shear mixer squirrel agitator: These always move at a high speed. It cuts through and breaks up a product. Similar to how you would stir up yogurt when it is first opened. This is great for products that need to be evenly mixed such as sauces.
Time To Choose Your Processing Tank!
There are three main parts to choosing the right tank; space and shape, heating and cooling, and agitation. We hope that this guide has helped you better understand each factor that goes into choosing the proper tank for you. Now that you have the knowledge to choose the right tank for your application, check out our available used stainless steel tanks. For more information or assistance on choosing the right tank, contact Zwirner Equipment today. Call Today