Hi Sandra,
Here's what the National Center for Home Food Preservation says:


The National Center collaborated with the University of Wisconsin to have research conducted on appropriate use of atmospheric steam canners. As long as certain critical controls can be maintained at various steps in the canning process, there are many products appropriate for canning in atmospheric steam canners.  They go on to add the following, but pay attention to the description of the canner in second paragraph.

Atmospheric steam canners are used for processing naturally acid or properly acidified foods with natural or equilibrated pH values of 4.6 or below. They are not pressurized vessels used for processing for low-acid foods.

Sufficient studies and peer review have been completed that we are now able to say that as long as certain critical controls at various steps in the canning process are achieved, USDA and NCHFP process times for canning acid or properly acidified foods (pH of 4.6 or below) at home with properly research based recipes and procedures can be used. The research looked at temperature distribution in the steam environment surrounding the jars in a dome-style steam canner, heating patterns of several different food types during processing in the canner, and the contribution of standardized cooling procedures at the end of the process time.

Some of the key controls in addition to the acidity of the food product are knowing that the canner has had the air vented out of the steam before processing begins, and that the pure steam is at the temperature of boiling water at the start and during processing. Jars must be preheated before filling with food and cooling prior to processing must be minimized. Processing times must be adjusted for altitude, and must also be 45 minutes or less, including any altitude modification. The processing time is limited by the amount of water the canner base will hold, and the canner cannot be opened to add water or for any reason at any time during the process. Finally, cooling of jars must take place in still, ambient air without any forced, more rapid cooling. The slow cooling of processed jars is important to the overall food safety of the whole canning procedure.

Dr. Ingham provides further instructions and details about carrying out canning in an atmospheric steam canner using USDA acid food processing recommendations at her webpage: https://fyi.uwex.edu/safepreserving/2017/10/24/safe-preserving-using-a-steam-canner/.

Please also see this update in her blog postings: https://fyi.extension.wisc.edu/safefood/2020/08/18/an-update-on-safe-use-of-steam-canners/

The results of this research were published in a peer-reviewed scientific journal in May 2015.
Willmore, P, Etzel, M, Andress, E. and Ingham, B. (2015). Home processing of acid foods in atmospheric steam and boiling water canners. Food Protection Trends, Vol 35, No. 3 (May-June), p.150–160.

Based on this information Sandra I can't recommend that you use your pressure canner as a steam canner.  I can't find any research that would validate that as a safe process for home food preservation.  Thanks for reaching out!
Melinda Hill

OSU Extension, Wayne County Ohio

Sandra,
According to the National Center for Home Food Preservation, this is the current guidance:

Atmospheric steam canners are used for processing naturally acid or properly acidified foods with natural or equilibrated pH values of 4.6 or below. They are not pressurized vessels used for processing for low-acid foods.

Sufficient studies and peer review have been completed that we are now able to say that as long as certain critical controls at various steps in the canning process are achieved, USDA and NCHFP process times for canning acid or properly acidified foods (pH of 4.6 or below) at home with properly research based recipes and procedures can be used. The research looked at temperature distribution in the steam environment surrounding the jars in a dome-style steam canner, heating patterns of several different food types during processing in the canner, and the contribution of standardized cooling procedures at the end of the process time.

Some of the key controls in addition to the acidity of the food product are knowing that the canner has had the air vented out of the steam before processing begins, and that the pure steam is at the temperature of boiling water at the start and during processing. Jars must be preheated before filling with food and cooling prior to processing must be minimized. Processing times must be adjusted for altitude, and must also be 45 minutes or less, including any altitude modification. The processing time is limited by the amount of water the canner base will hold, and the canner cannot be opened to add water or for any reason at any time during the process. Finally, cooling of jars must take place in still, ambient air without any forced, more rapid cooling. The slow cooling of processed jars is important to the overall food safety of the whole canning procedure.

Dr. Ingham provides further instructions and details about carrying out canning in an atmospheric steam canner using USDA acid food processing recommendations at her webpage: https://fyi.uwex.edu/safepreserving/2017/10/24/safe-preserving-using-a-steam-canner/.

Please also see this update in her blog postings: https://fyi.extension.wisc.edu/safefood/2020/08/18/an-update-on-safe-use-of-steam-canners/

The results of this research were published in a peer-reviewed scientific journal in May 2015.
Willmore, P, Etzel, M, Andress, E. and Ingham, B. (2015). Home processing of acid foods in atmospheric steam and boiling water canners. Food Protection Trends, Vol 35, No. 3 (May-June), p.150–160.

Based on this information, I can't recommend using your pressure canner as a steam canner.  If you have further questions, maybe Dr. Ingham would be able to assist you?  I'm also happy to try and answer your questions, thanks for reaching out!
Melinda Hill

OSU Extension, Wayne County Ohio