A center feed system for use in a delayed coking system, the center feed system comprising: a spool; and an inlet sleeve comprising a flanged surface for connecting the inlet sleeve to a flanged inlet of the spool; characterized in that: the inlet sleeve includes a curved pipe segment having a flanged component utilized to connect the inlet sleeve to a delivery main for feeding residual petroleum byproduct into the inlet sleeve; and the inlet sleeve contains a retractable injection nozzle slidably engaging with a straight portion of the inlet sleeve between an extended position in which the retractable injection nozzle extends out of the inlet sleeve into the interior of the spool, and a retracted position in which the retractable injection nozzle is retracted into the inlet sleeve, wherein when in the extended position, the residual petroleum byproduct enters the curved pipe segment, encounters inlet, travels from inlet through the retractable injection nozzle and exits outlet, and into the spool, and when in the retracted position, the retractable injection nozzle seals an opening in the curved pipe segment to block the residual petroleum byproduct from flowing from the curved pipe segment into the inlet. a spool; and an inlet sleeve comprising a flanged surface for connecting the inlet sleeve to a flanged inlet of the spool; characterized in that: the inlet sleeve includes a curved pipe segment having a flanged component utilized to connect the inlet sleeve to a delivery main for feeding residual petroleum byproduct into the inlet sleeve; and the inlet sleeve contains a retractable injection nozzle slidably engaging with a straight portion of the inlet sleeve between an extended position in which the retractable injection nozzle extends out of the inlet sleeve into the interior of the spool, and a retracted position in which the retractable injection nozzle is retracted into the inlet sleeve, wherein when in the extended position, the residual petroleum byproduct enters the curved pipe segment, encounters inlet, travels from inlet through the retractable injection nozzle and exits outlet, and into the spool, and when in the retracted position, the retractable injection nozzle seals an opening in the curved pipe segment to block the residual petroleum byproduct from flowing from the curved pipe segment into the inlet. the inlet sleeve includes a curved pipe segment having a flanged component utilized to connect the inlet sleeve to a delivery main for feeding residual petroleum byproduct into the inlet sleeve; and the inlet sleeve contains a retractable injection nozzle slidably engaging with a straight portion of the inlet sleeve between an extended position in which the retractable injection nozzle extends out of the inlet sleeve into the interior of the spool, and a retracted position in which the retractable injection nozzle is retracted into the inlet sleeve, wherein when in the extended position, the residual petroleum byproduct enters the curved pipe segment, encounters inlet, travels from inlet through the retractable injection nozzle and exits outlet, and into the spool, and when in the retracted position, the retractable injection nozzle seals an opening in the curved pipe segment to block the residual petroleum byproduct from flowing from the curved pipe segment into the inlet.