Proportioner for a fire protection system

A proportioner, comprising:

• a body portion, the body portion defining,
• a fluid passage for transporting a fire protection fluid, and
• a foam passage for transporting a foam concentrate, the foam concentrate to mix with the fire protection fluid to form a fire protection solution;
• a restrictor assembly having a restrictor disk and an orifice plate, the restrictor assembly configured such that a flow of the foam concentrate through the foam passage is based on a distance of the restrictor disk from the orifice plate;
• a clapper assembly connected to the rod member, the clapper assembly configured to control a flow of the foam concentrate through the foam passage by varying a distance between the restrictor disk and the orifice plate,
• wherein the clapper assembly is configured to move the restrictor disk so as to maintain a foam concentrate percentage in the fire protection solution within a target concentration that provides effective fire protection for flows of the fire protection solution within a target flow ratio in a range of 10 to 70, and
• wherein a viscosity of the foam concentrate is greater than 1300 mPas.