Automatic flow control valve

A valve comprising:

• a valve body having a fluid inlet, a primary valve stem, a first chamber, a first throughbore, a first intermediate chamber, a secondary valve stem, a second intermediate chamber, a second throughbore, a second chamber and a fluid outlet;
• in an open position of the valve said fluid inlet, said first chamber, said first throughbore, said first intermediate chamber, said secondary intermediate chamber, said second throughbore, said second chamber and said fluid outlet in communication with each other;
• said primary valve stem and said secondary valve stem slidably mounted with respect to said valve body;
• in a closed position of the valve a first primary portion of said primary valve stem and a second primary portion of said primary valve stem exposed to a first pressure condition within said first chamber, a first secondary portion of said secondary valve stem and a second secondary portion of said secondary valve stem exposed to a second pressure condition within said second chamber, in said closed position of said valve one of said second primary portion and said second secondary portion sealably positioned within one of said first throughbore and said second throughbore, a first diameter of said first primary portion sized differently than a second diameter of said second primary portion, a first diameter of said first secondary portion sized differently than a second diameter of said second secondary portion;
• and
• bias means for urging at least one of said primary valve stem and said secondary valve stem in an axial direction toward one of said open position and said closed position.