var blob_source: tstream;
    blob_target: TIBBlobStream;
begin
  table.Insert;
  table.FieldByName('xyz').AsInteger:= 5;  
  try
    blob_source:= tstream.Create;
    // fill the stream with any data you want here
    blob_target := tibblobstream(table.createblobstream(table.FieldByName('xyz'),bmReadWrite)); // create blob container
    blob_target.CopyFrom(blob_source,blob_source.size);    // save stream into blob
  finally
    table.Post;   // post the changes
    blob_source.Destroy;
    blob_target.Destroy;
  end;  // try finally