Why buy a German vacuum machine when I can get a Chinese machine for a third of the price?

In the workshop, we repair and service vacuum machines on a daily basis, all ages, and makes (almost). We have completely stopped working on Chinese machines because of the difficulty to source spares. The biggest problem, however, is that you fix one thing today and the next day something else will break.

When it comes to Chinese machines the saying, “you get what you pay for”, applies. You get 2 to 4 years life (not trouble free) out of these machines. On the other hand, you can easily get between 30 and 40 years from a German machine. Cost savings on the manufacturing of the Chinese machines are clearly visible by just looking at the components and the materials used.

There is only one way to manufacture a machine for a third of the price and that is to cut quality and reliability by two thirds.

When investing in a new machine always consider the total cost of ownership.  Total cost of ownership is the purchase price of an asset plus the costs of operation. On a Chinese machine, the purchase price is small but the cost of operation is high and the lifespan is short. On a German machine, the purchase price is high, the cost of operation is low and the lifespan is long.

Let us start by looking at atmospheric pressure and the boiling point of water first. At the coast atmospheric pressure is about 1000 mbar and water boils at 100 deg Celsius.

Now here where we are in Johannesburg we are higher above sea level with less Atmosphere pressing down on us. Atmospheric pressure here is 840 mbar and boiling point of water is 95 deg Celsius. As you can see as the atmospheric pressure came down the boiling point of water also dropped. Inside the chamber of a vacuum machine the pressure drops to below 10 mbar in order to get a good vacuum. At 10 mbar the boiling point of water is a low 7 deg Celsius.

This means that when I vacuum my piece of steak the moisture in it will start to boil if it is above 7 deg Celsius. Looking at it the other way round: if I vacuum a moist product that is too warm the moisture in it will start to boil giving off vapour (and lose weight).

The pump will try to lower the pressure but the vapour forming will keep the pressure from lowering. This will result in an inadequate vacuum and air still left in the bag. When vacuuming products with marinade it is important to keep the marinade refrigerated in order to keep it from boiling out of the bag and messing in the machine.

When you insert a bag in a vacuum machine and close the lid the vacuum pump removes all the air (pulls a vacuum) in the chamber as well as in the bag. After this process, the bag gets sealed. After sealing atmospheric pressure enters the chamber and the bag gets pressed down onto the product leaving no air in the bag.

So how much vacuum is needed for a good result?

The vacuum pumps found in vacuum machines are normally rated 0.5 mbar. Theoretically, this is then what could be reached inside the chamber. In real life, there is always the possibility of small leaks or other factors that will influence the vacuum achieved in the chamber. We normally consider 10 mbar as the border between good and bad vacuum with figures of about 5 mbar being very good.

When gas flushing food, preserve gas is put in the bag after vacuuming and before sealing. This is needed when the product needs to be loose in the bag like sliced biltong or grated cheese.

The biggest enemy of a vacuum machine is moisture. The moisture in the air and the moisture in the product being vacuumed goes into the vacuum pump. This moisture gets trapped there and causes the pump to corrode if not removed. Komet vacuum machines have warmup cycles designed to remove this buildup of moisture. Regular servicing of a vacuum machine and running the warmup cycle will prolong its life significantly and a life of between 30 and 40 years is easily achievable on a good quality machine. Servicing must include the replacement of the pump’s oil separator. A genuine part oil separator and service of the machine will give the following benefits:

  • The machine will vacuum faster.
  • The machine will run quieter.
  • The machine will use less electricity.
  • The machine will last longer with fewer breakdowns.