I now that I can use standard SW template to get round this problem but it is interesting for me and may be interesting for someone else.
Some time ago I renamed 'Default' config to 's', switched off 'create derived config for weldment' in document options and saved this file as part template.
Now I`ve decided to restore default SW behavior for weldment but can`t do this. I don`t understand what`s wrong with this part template.
Thanks in advanced