Laboratory

Vertical Autoclave- Design, Types, Uses, Pros, Cons, Handling

A vertical autoclave is a type of autoclave that works on the principle of moist heat sterilization. It can either be gravity displacement autoclave or vacuum displacement autoclave. 

The pressure cooker type autoclave can also be a type of vertical autoclave, if the autoclave looks like a pressure cooker, having a whistle in it.

Vertical Autoclave Parts

Vertical Autoclave Parts
Image Source:- https://www.gpcmedical.com/253/AU617/gas-cum-electric-operated-vertical-autoclave

 

Vertical autoclave consists of a double or triple layer of high-quality stainless steel. The outer layer is made up of mild steel, 304 SS, etc. The inner layer is made up of 316/ 316L/ 304 stainless steel.

The upper layer is covered with a removable lid. Similarly, the lower portion is a hollow chamber.

The basic parts, present in almost all types of vertical autoclaves are stated below.

  • Heating Element (Water Immersion Heater):- For heating the water. There can be one or more heating elements for fast operation.
  • Gasket:- For preventing the loss of vapor and heat.
  • Steam Releasing Valve:- To replace air present within the autoclave before sterilization and steam after sterilization.
  • Safety Valve:- To release excess steam if the stop cock fails to operate properly.
  • Sterilization Basket:- To store the objects for sterilization.
  • Water level Indicator:- Allows to externally see the level of water present within the chamber.
  • Vacuum Releasing Valve (Optional):- To create a pre-vacuum, prior to its operation.
  • Drainage Valve:- Gets rid of all the water from the chamber.

For Digital Autoclave

  • Temperature Controller:- Allows to set, observe, and control the temperature within the chamber.
  • Timer:- Allows to set the time for sterilization. Once the sterilization time is over, the machine will stop.

For Analog Autoclave

  • Pressure Regulating Valve (Stop Cock):- To maintain the vapor pressure within the chamber by releasing excess steam during sterilization.

Besides these, there can be many more features such as door sensor, digital alarm, low/high water cut-off sensor, temperature chart recorder, ports for printer connection, etc.

Vertical Autoclave Working Principle

The vertical autoclave works on the principle of moist heat sterilization.

The heating element present at the base of the vertical autoclave causes the heating of the water. When the water starts to vaporize, it displaces the air present within the chamber. If there is a pump system in the autoclave, then the pump will draw out the air from the chamber.

Once the lid of the autoclave is closed, the vapor begins to exert pressure within the chamber. After about 20 mins, the indicator of the pressure gauge will begin to rise up. When the indicator of the gauge reaches towards 15 psi pressure, the vapor pressure will become greater than that of the weight of the stop cock (pressure regulating valve). Thus, the stop cock will begin to whistle. (Note:- In a digital autoclave, you may not find the stop cock).

After 15 mins of operation, the sterilization will be complete. In case, the stop cock fails to operate properly, the safety valve will whistle.

In the case of a digital autoclave, you can pre-set the required temperature in the temperature controller. So, as per the requirement,  operating pressure can be more than 15 psi. Similarly, there will be a timer board. So, once the set temperature is reached, the sterilization will begin. The countdown for the timer will begin. Once the set timer reaches 0 mins, the sterilization will be over.

Types of Vertical Autoclave

The vertical autoclaves can be differentiated in a number of ways.

1. On the basis of automation

  • Manual:- In these kinds of autoclaves, you need to pour water into the chamber. After sterilization is over, you need to manually close the machine.
  • Semi-auto:- In these kinds of autoclaves, you need to pour water into the chamber. After the sterilization is over, the machine will stop on its own.
  • Fully- auto:- In these kinds of autoclaves, the machine will draw the water when the level in the chamber decreases. Also, after the sterilization is over, the machine will stop on its own.

2. On the basis of control

  • Analog:- The temperature and the pressure is controlled with the help of a pressure regulating valve. Until the heater is turned off, it will keep on heating the water. So, the accuracy of the analog autoclave will be lower in comparison to that of the digital autoclave.  The other drawback is that you will not be able to set any temperature and pressure. So, you will need to work with the set value.

However, the analog types are cheaper to purchase. Also, the maintenance cost is low.

  • Digital:- The temperature and the pressure can be controlled with the help of a digital controller such as a temperature controller. In comparison to the analog system, The heater gets on and off continuously, to maintain the set temperature. So, in comparison to that of the analog autoclave, it provides higher accuracy. Besides that, the temperature can be set from around 105°C to 134°C.

However, the digital types are expensive to purchase and repair.

Vertical Autoclave Procedure

(How to use vertical autoclave?)

Since the verticle autoclaves are found in different variations, I may not be able to explain the procedure for all of them. However, here I will be explaining to you the general procedures.

  • After cleaning the objects to be sterilized, place them inside the sterilization basket. Attach the chemical or biological indicators within the basket.

(Note:- Do not overload the basket. Also, do not place different types of objects within the same basket)

  • Place distilled or RO water, sufficient enough to submerge the water immersion heater. You can observe the level of water in the autoclave with the help of a water level indicator (mostly glass tube).

(Note:- If the water immersion heater is exposed to the atmosphere during operation, it will overheat and get damaged. Similarly, if you supply tap water, the minerals and ions present in the water will react to the internal layer of the autoclave at high pressure and temperature. )

  • Then, place the sterilization basket within the autoclave.
  • Close the lid and tighten the screws to prevent leakage.
  • Turn on the power supply.
  • Open the steam release valve to release the air trapped within the chamber.
  • Observe the indicator of the pressure gauge.

(Note:- When the water begins to boil, the vapor pressure will cause the indicator of the pressure gauge to increase. During this time, the trapped air within the chamber will continue to escape into the surrounding. )

  • When the indicator of the pressure gauge stops to increase, close the steam release valve.

(Note:- For a digital autoclave machine, close the steam release valve, when the temperature reaches 105°C ).

  • When the vapor pressure within a vertical autoclave reaches 15 psi (121°C), the pressure regulating valve will release steam to maintain the pressure.

(Note:- In the case of the digital system, the controller will control the temperature and pressure of the machine. You can even pre-set the temperature above 121°C.)

  • Continue operating the machine for 15 mins.

(Note:- In the case of a digital system, the machine will sterilize up to the set time, that you have set in the timer board. ) 

  • After 15 mins of operation, turn off the machine.

(Note:- In case of digital autoclave, the machine will stop operating when the set time is over)

  • Then open the steam release valve.
  • Once, the indicator of the pressure gauge goes to 0, remove the lead of the autoclave.

(Note:- Do not open the lid of the autoclave at once. Else, the vapor will cause a severe burn on your face and hands. )

Vertical Autoclave Specification

The different models of autoclaves can have different specifications. So the table shown below is not the specification of a single model of the vertical autoclave. However, almost every type of vertical autoclave will lie within the given specification.

Details Remarks
Volume 22 liters to 200 liters
Temperature Range 1050C to 1340C
Pressure Range 15 psi to 30 psi
Safety Features (Optional) Safety Valve, Water Level Indicator, Low water level cut off, Alarm, etc.
Accessories (Optional) Temperature Controller, Timer, Autoclave Bag, Sterilization Basket, Temperature Chart Recorder, etc.
Power Consumption 2 KW to 6 KW
Operating Temperature 50C to 400C
Operating Humidity Less than 85% of relative humidity

If you are going to purchase a new vertical autoclave, the given specification can be useful to you.

Vertical Autoclave Uses

  • Useful in multiple applications such as sterilization of autoclavable glassware, plastic ware, culture media, etc.
  • Useful in sterilization of surgical tools, blades,  etc.
  • Used in bacteriological and research laboratories, hospitals, and clinics, and food and beverage units.

Advantages of Vertical Autoclave

  • Available in various sizes with accessories
  • Easy to operate
  • Simple in design
  • Easy to clean and maintain

Disadvantages of Vertical Autoclave

  • Much more expensive in comparison to the pressure cooker type autoclave.
  • Generally, it belongs to class N autoclave.
  • The power consumption is quite high.

Cleaning

  • Before you put the sterilizing instruments into the sterilization basket, clean it properly. Based on the material, the cleaning can be done by washing machines, cleaning agents, distilled water, etc.

(Note:- While putting the equipment in the sterilization basket, place the different categories of equipment respectively in different baskets. Also, there should be a sufficient gap among the products placed in the same basket. The tubes and bottles should be open to the bottom upright position during sterilization. This will allow an easy replacement of cold air by the saturated steam. )

  • De-scaling of water immersion heater should be done periodically. Rinse the heater thoroughly with RO water and prevent it from acids.
  • Daily clean the internal chamber of the machine with distilled or RO water.

Maintenance

During transportation or operation, the vertical autoclave can undergo different kinds of faults. So, in such cases, you may need to repair the machine.

The maintenance process stated below is for the experts. General users are not supposed to do anything related to maintenance.

1. Power

Since the vertical autoclave draws too much current, the problem can arise in the power supply. The power cord or the 3- pin plug can burn. The indicators, switch, etc, can also be damaged.

In any case, you need to replace the components with new ones.

2. Heating Element

The heating element might be damaged if it does not get sufficient water when being operated. When the rod gets damaged, the rod will become black and deformed.

When the heating element is damaged, it will not heat the water. Sometimes, the heating element operates partially. In such a case, the water might get warm but will fail to boil. The other reason can be due to the low voltage supply to the water immersion heater.

The heating rod should be replaced with a new one having the same rating. A high wattage heater can damage the power supply unit. Also, the system may not be able to handle it. Similarly, if the wattage is low, the water will take more time to heat. So, selecting a proper rod is essential.

3. Vapor Pressure 

The pressure of the chamber is displayed by the pressure gauge. So, if the pressure gauge does not show the set pressure during the phase of sterilization, there can be issues related to the vapor pressure.

  • Pressure Gauge

The pressure gauge can be defective. This means that, even if the pressure within the chamber has reached the required value, the pressure gauge will fail to show the actual pressure. In such a case, you generally need to replace the gauge with a new one.

  • Pressure Regulating Valve (Stop Cock)

In the case of an analog vertical autoclave, there can be a defect in the pressure regulating valve. The spring within the valve can lose its elasticity. Also, there can be a blockage within the valve. Or, the valve can undergo blockage due to storage for a longer period of time, rusting, etc. In the above cases, the valve will not operate properly.

In case of blockage, rusting, etc, you may try cleaning. Else, you need to replace it.

  • Steam Releasing Valve

In case you forget to close the steam releasing valve during operation, the vapor will escape from the valve. Thus, the pressure within the chamber will never rise to the set value.

  • Vacuum Releasing Valve

In some cases, the vertical autoclave is designed to operate in the form of a vacuum displacement autoclave. In such a case, the vacuum releasing valve should be properly closed, before you operate. Else, the vapor will leak through it.

  • Safety Valve

The safety valve is useful only when the pressure regulating valve fails to act properly.

Sometimes, there can be leakage through it. So, in such a case you need to replace it with a new one.

  • Gasket

The gasket is a circular, silicon rubber that is found in the mouth of the chamber or at the base of the lid. This helps to prevent the loss of pressure and heat from the lid. So, if the gasket is not fixed properly, or gets damaged, then the vapor will leak through it. Also, the problem may arise due to the presence of residues on the layer of the gasket.

You can clean the gasket with warm water to get rid of the residue. For other problems, you need to readjust or replace the gasket.

4. Rusting

The rusting of the machine can be either internal or external. If the rusting is external, it degrades the aesthetic looks of the machine and the surrounding. On the other hand, if the rusting becomes internal, there can be chances of contamination during sterilization. So, in such a case, it is better to replace the machine with a new one.

5. Sensor

The sensors such as door sensor, pressure or temperature sensor, water level sensor, etc, may be faulty. In such a case, you need to replace it.

6. Controller

If the controller fails, the actual temperature within the system may not stabilize to the set value. In such a case, you may need to auto-tune the controller (if possible). Else, replacing the controller will be the better option.

 

 

 

 

 

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