Fully piggable differential pressure actuated valve with variable restrictor

A system including a differential pressure actuated valve configured to control a flow of material through a pipeline and to enable a pigging device to pass through the system, the system comprising:

• the pipeline configured for transporting the flow of material and including:
• an upstream portion receiving the flow of material into the pipeline;
• and
• a downstream portion wherein the flow of material flows from the upstream portion, through a variable flow restrictor, and into the downstream portion;
• the variable flow restrictor configured to selectively operate in one of a fully open state and a partially restricted state, wherein the variable flow restrictor is further configured for providing a restrictive orifice within the pipeline and creating a pressure differential in the flow of material across the variable flow restrictor including relatively high-pressure material in the upstream portion and relatively low-pressure material in the downstream portion, and wherein the relatively low-pressure material includes a pressure less than an ambient pressure outside of the pipeline;
• a low-pressure tube connected to the downstream portion and receiving a portion of the relatively low-pressure material;
• a low-pressure chamber connected to the low-pressure tube and receiving the portion of the relatively low-pressure material, wherein the low-pressure tube includes an opening within the low-pressure chamber and wherein the low-pressure chamber includes a secondary flapper configured for selectively blocking the opening;
• a primary flapper including a hinge enabling the primary flapper to move between an up position and a fallen position, disposed between the upstream portion and the low-pressure chamber, and configured to be disposed in one of:
• the up position, wherein the primary flapper separates the relatively high-pressure material in the upstream portion from the portion of the relatively low-pressure material in the low-pressure chamber, is held in the up position by the pressure differential, and enables the flow of material to flow through the pipeline, and wherein the primary flapper, when the primary flapper is in the up position, is configured for including a shape similar to the pipeline;
• and
• the fallen position, wherein the primary flapper spans an internal diameter of the pipeline and blocks the flow of material through the pipeline, and wherein the primary flapper is configured to move to the fallen position when a leak in the downstream portion causes air or water at the ambient pressure to enter the downstream portion and reduce the pressure differential;
• and
• wherein the variable flow restrictor being in the fully open state and the primary flapper, being in the up position, are configured for enabling the pigging device configured for traveling through the pipeline to pass through the system.