1. Elizabeth Stoneham Kathryn A. Ramirez-Aguilar, Ph.D.
Autoclaves on House Steam: Metering results of electricity, steam, and water usage
Elizabeth Stoneham
Kathryn A. Ramirez-Aguilar, Ph.D.

2. Learning Objectives
Learn about the different ways steam is produced and used by autoclaves.
Learn about the metering set-up used on two house steam autoclaves to better under the consumption of these units.
Learn the steam, water, and electric power usage numbers of two models of autoclaves on house steam.
Understand the impact of cycle variations and operating conditions on steam, water, and electricity usage for two different models of autoclaves on house steam while maintaining passing sterilization tests.

3. Inside an Autoclave
Two elements are used to form a high pressure/high temperature environment:
The autoclave chamber is where the items-to-be-sterilized are placed.
Here, steam is pumped in and air is pumped out until the desired pressure and temperature is reached. Then, a valve regulates the pressure so it remains constant.
The jacket has steam running through it in order to keep the chamber at the desired temperature.
This then leads to effective sterilization of items after 30 minutes to over an hour.
[1]

4. Steam Usage in Autoclaves
In general, there are 3 types of steam autoclaves:
1.) The kind that generates steam from water (sometimes distilled) to be used in the chamber and jacket.
2.) A hybrid that generates steam only for the chamber while using house steam for the jacket.
3.) The kind that uses house steam for BOTH the chamber and jacket.
In a different category, there are also autoclaves that do NOT employ a jacket.
[2]
[3]

5. Sources of Inefficiency in Autoclaves
Generating steam from water for the both the chamber and jacket can require a large amount of electricity.
Older autoclaves dump massive amounts of water down the drain in order to cool the condensate (hot steam that is cooled down into water) during the purging of old/dirty steam to make way for new steam.
The dumping rate of water can range up to gal/min.
CU Boulder uses house steam as a better approach

6. Riverside Study vs. Green Labs Study
A previous study was performed by the University of California Riverside to analyze the energy consumption of electric steam generators in autoclaves.
Some types of autoclaves were proven to be very energy intensive.
Of course energy consumption varies by usage.
Our study seeks to complement this study by comparing the energy consumption of electric steam generation vs. house steam.
Riverside’s Study:
*Consumption varies by usage.
Energy consumption over all.
Compare to find most efficient method.
Energy comparison of steam generation vs house steam
Studies should complement each other.
Adding to data that is already out there.
[4]

7. Efficiency Solution: Recycled House Steam
Since the items-to-be-sterilized never come in contact with jacket steam, this steam does NOT need to be of the same quality as the chamber steam.
This allows for jacket steam to be pulled from house steam and then recycled back into the pipes which can then be used elsewhere in the building.
This study aims to analyze the efficiency benefits of allowing steam/water to be returned to house steam pipes instead of disposed of as waste.
Going in as steam?? One interesting thing is this house-return method.

8. Efficiency Solution: Water Mizers
“The patented Water-Mizer® is a water saving and tempering device for steam sterilizers that efficiently mixes cold water with steam condensate to reduce the discharged water temperature before it enters a municipal sewer system [5].”
Have the potential to provide water savings of 1,000 gallons a day or greater [5].
Mizers can be non-electric which adds to power efficiency.
And of course you know our autoclaves have water mizers.
NOT new and exciting.

9. Autoclave Study Details
This study will center around the comparison of steam and water usage between an older autoclave model from Primus and a newer model from Consolidated Sterilizer Systems.
The effects of recycling jacket steam and autoclave efficiency overall will be quantified.
VS.

10. Primus Autoclave Installed in 1996
Uses house steam to keep jacket at a constant 250ºF/121ºC temperature
Does NOT recycle this steam
Retrofitted with water mizer 12 years ago
Retrofitted with an electric time- out meter that shuts off steam usage after a certain time interval 12 years ago
*Figure out volume of chambers and jackets.
*Newer one probably has bigger jacket/chamber???

11. Consolidated Sterilizer Systems (CSS) Autoclave
Installed 2018
Recycles house steam
Highly programmable so jacket can be easily turned on/off
Contains “Auto Idle Shutoff” feature
Came with water mizer
Page 11 of manual
3.1.4 Auto Idle Shutoff
Auto Idle Shutoff is a feature that will cause the jacket and generator to turn off automatically
after the sterilizer has been idle for a settable amount of time. This option can be enabled or
disabled by pressing the AUTO-IDLE ON/OFF key at the bottom of the Auto Idle Shutoff screen.
The time before shutoff can be changed by pressing AUTO-IDLE TIME and entering the new
time in minutes.
To summarize, two autoclaves. Old and new. House steam for both jacket and chamber.

12. Water Meters
These water meters are installed on the water pipelines for CSS (left) and Primus (right) and measure gallons of water used. Both meters can measure up to 1/10th of a gallon usage.

13. Steam and Electric Meters
The steam meter has high resolution down to 1/1000th of a pound and is comprised of:
An analog meter (left)
A digital display (right)
It will be used to measure steam consumption of individual autoclaves and the aggregated steam of both.
While there are power meters installed per autoclave, these readings are measured in whole kWhs; each autoclave cycle only consumes a fraction of a kWh.

14. VERIS Accelabar® Flow Meter
[6]
Typically don’t handle flow of a single piece of equipment.
Low-flow steam meter.
Steam meters typically measure the flow of entire buildings.

15. Test Methodology
The methodology to test each autoclave’s performance will be:
Gravity
Keep sterilization time constant
Vary dry time
Vary sterilization time
Keep dry time constant
Liquid
Vary sterilization time
Idle
Measure idle consumption of steam/water

16. Preliminary Results: Dry
WATER STEAM
Not too much data yet.
Why old uses less.
Why steam
Consumption was measured during sterilization and dry time separately.

17. Preliminary Results: Sterilization

18. Future Plans More tests will be performed in which:
Time between tests will be analyzed to see if an effect on consumption is noticeable
Spore tests will be placed in cycles to make sure both autoclaves are sterilizing
This is a key feature as the older autoclave model has grown more unreliable over the years
Recycled steam will be measured
CSS jacket steam will be switched over to the mizer as opposed to being recycled in order to have a more 1:1 comparison
House Steam vs. Electric Steam Generation Comparison
White Paper

19. References
[1] advantages-disadvantages/
[2]
[3] l/autoclaves/ autoclave-steam-electric-24lt
[4] PROCUREMENT-DF.pdf
[5]
[6] EN.pdf

20. Questions?
Contact Information:
Kathy Ramirez-Aguilar, Ph.D.
CU Green Labs Program Manager
University of Colorado at Boulder
Contact Information:
Elizabeth Stoneham
CU Green Labs Assistant
University of Colorado at Boulder