\documentclass{article}
\usepackage{gastex}

\begin{document}

% Arrows

\begin{center}
\begin{picture}(60,40)(-30,-17)
% \put(-30,-17){\framebox(60,40){}}
  \drawline[AHangle=30,AHLength=3,AHlength=0,
            ATnb=1,ATangle=90,ATLength=2,ATlength=0](-15,20)(15,20)
  \drawline[AHnb=2,ATnb=2](-15,15)(15,15)
  \drawline[AHnb=2,AHangle=30,AHLength=3,AHlength=0,AHdist=1,
            ATnb=2,ATangle=30,ATLength=3,ATlength=0,ATdist=1](-15,10)(15,10)
  \drawline[AHnb=1,AHangle=30,AHLength=3,AHlength=1,
            ATnb=1,ATangle=140,ATLength=3,ATlength=1.5](-15,5)(15,5)
  \drawline[AHnb=2,AHangle=30,AHLength=3,AHlength=0,AHdist=1,
            ATnb=2,ATangle=150,ATLength=3,ATlength=0,ATdist=1](-15,0)(15,0)
  \node(A)(-15,-10){}\node(B)( 15,-10){}
  \drawbpedge[AHnb=6,ATnb=6](A,60,25,B,240,25){}
  \gasset{AHnb=1,AHangle=30,AHLength=3,AHlength=0,
          ATnb=1,ATangle=30,ATLength=3,ATlength=0}
  \drawloop[loopangle=180](A){}
  \gasset{AHnb=3,AHangle=30,AHLength=3,AHlength=1.5,AHdist=1.8,
          ATnb=3,ATangle=30,ATLength=3,ATlength=1.5,ATdist=1.8}
  \drawloop[loopangle=0](B){}
\end{picture}
\end{center}

\end{document}