Storm Choke® H safety valves are ambient-type, wireline retrievable valves that are normally closed and precharged with a set dome pressure. When the well flowing pressure drops below the predetermined dome-pressure charge, as a result of a rupture in the flowline or surface equipment, the dome pressure and valve spring are designed to close the valve, shutting in the well. The H valve is used in wells producing large volumes of abrasive fluids. Its large bore is not restricted by a flow bean. The valve is designed to resist pressure surges. A metal-to-metal (MTM) ball and seat is used as the primary closure mechanism. The H valve is ideal for protecting wells with declining bottomhole pressure because this valve is tubing pressure sensitive instead of velocity sensitive. To reopen, the valve pressure must be fully equalized either by applying pressure in the tubing from the surface or by running a prong to allow equalization from below. The valve will reopen when the tubing pressure acting on the internal piston area overcomes the dome charge. Applications » Wells producing large volumes of abrasive fluids » Wells with declining bottomhole pressure » Wells with no provisions for surface-controlled valves Features » Large bore not restricted by a flow bean » MTM ball and seat » Designed to resist pressure surges *description excerpted from manufacturers catalogue.