Apparatus for joining solar receiver tubes

An apparatus for joining solar receiver tubes, where said solar receiver tubes includes a first solar receiver tube, a second solar receiver tube, and a third solar receiver tube, where each of the solar received tubes includes an inner tube and an outer tube each having the same longitudinal axis, where the inner tube has an inner tube length between a first inner tube end and a second inner tube end, where the outer tube has an outer tube length between a first outer tube end and a second outer tube end, where the inner tube is coaxial with and inside of the outer tube and where the outer tube has a length that is less than a length of the inner tube, and where each of the solar receiver tubes further includes a first metal collar extending radially inwards from the first outer tube end to a location on the inner tube, where the location is a longitudinal distance from the first inner tube end and a second metal collar extending radially inwards from the second outer tube end to the location on the inner tube, where the location on the inner tube is the longitudinal distance, such that each end of each solar receiver tube includes an exposed length of the inner tube that extends beyond a corresponding metal collar by a longitudinal spacing, said apparatus comprising:

• a first weld head having a first electrode;
• a second weld head having a second electrode;
• a first perch sized to accept the outer tube of the First solar receiver tube with the first inner tube end of the first solar receiver tube near said first weld head;
• a second perch sized to accept the outer tube of the second solar receiver tube with the first end of inner tube of the second solar receiver tube near the first weld head and with the second inner tube end of the second solar receiver tube near said second weld head;
• a third perch sized to accept the outer tube of the third solar receiver tube with the first end of the outer tube of the third solar receiver tube near the second weld head;
• one or more translation stages configured to position the inner tubes of the accepted first, second, and third solar receiver tubes in said first weld head and said second weld head, and configured to move the first ends of the inner tubes of each solar receiver tube in a direction transverse to the longitudinal axis of the solar receiver tube in said first weld head and said second weld head;
• a metal piece electrically grounded relative to said first weld head and to said second weld head, and positioned to contact at least one metal collar of the end of one of the accepted first, second, or third solar receiver tube;
• and
• a purge as delivery system to provide purge gases during the operation of the first weld head and the second weld head, where the purge gases are provided to:
• 1) the interior of the first inner tube end of an accepted first solar receiver tube, 2) the interior of the first inner tube end of an accepted second solar receiver tube, 3) the interior of the second inner tube end of an accepted second solar receiver tube, and 4) the interior of the first inner tube end of an accepted third solar receiver tube,
• such that the first inner tube end of the first accented solar receiver tube and the first inner tube end of the second accepted solar receiver tube are adjacent to said first weld head, and
• such that the second inner tube end of the second accepted solar receiver tube and the first inner tube end of the third accepted solar receiver tube are adjacent to said second weld head.