The importance of steam quality for the sterilization

1, Introduction

High temperature steam sterilizer has the advantage of no residue, no pollution to the environment, no damage to the product surface, low cost and easy operation, so it is used as the first choice for CSSD(central sterile supply department) sterilization.

Have you encountered the following problems during the work of steam sterilization?

Yellow bag

Rusty

Wet pack

Failure

These problems are mostly related to the quality of steam.  Steam quality is easy to be neglected, and how much influence does it has?

2,  Four index of steam quality

The temperature of water will rise up after being heated. When the temperature of water reaches the boiling point, odorless and colorless gas is produced. That’s steam. Even if the steam is continuously heated, the temperature will not change, but the saturated steam will go upwards. That’s the steam used in the sterilizer which is called saturated steam.

The related standard requirements of saturated steam is as follows:

Quality of steam condensate

3, What’s the four index

Non-condensable  gas

The condensable gas in the steam are mainly air and carbon dioxide . If the steam contains air or non-condensable gas, although the pressure gauge shows the normal pressure, the saturated temperature corresponding to the pressure cannot be reached. The air carried by steam to the hot surface will form a thermal insulation layer .

Thermal resistance: 1mm air =15m copper

Dryness value

The dryness value is used for measuring the moisture content of steam. If the steam contains 10% moisture, it means the steam dryness is 90% or 0.9 If the dryness is too low, it will cause wet packs, pipe erosion, water hammer, etc.

Wet pack caused by low dryness

Super heat

If we continue to heat the saturated steam, the temperature will continue to rise up and steam will become superheated steam. It has the following disadvantages:

1, Low heat transfer coefficient and poor penetration

2, The steam temperature cannot be adjusted by pressure control

3, Super heat steam releases latent heat for a long time which easily causes the sterilization failure.

Saturation curve

Steam condensate

The impurities in the steam may be attached on the sterilized items during the sterilization process. The sterile medical devices and diagnostic supplies may be harmful to the patient. Meanwhile, impurities attached on the sterilized items affect the penetration  of steam and affect the sterilization effect.