Oilfield Consultant in Surface and Subsea Wellheads Equipment,Christmas Trees,Flow Control Equipment,Seals(Elastomerics & Metal-to-Metal)                  Contact me NEW E-mail: country45ve@yahoo.com

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This is the final component in the hook-up of any well's completion, and it's name is derived to a similarity with the Christmas tree used during the holidays, but is only coincidence.The purpose of this assembled element is control live pressure of oil that is coming out of the well's reservoir, and at the same time permit in a safe way, to work-over the well, by an appropriate tool attachment, generally on top of it.

The control of the oil is carried out by a set of valves mounted vertically attached to the tubing bonnet, please take a look at drawing and notice that there is two one following the other and the name of that is : first and second master valve the reason for having a pair is safety, if one fail, the other must close the gate and stop the oil, then there is only one on the top of the tee, and the name is swab valve , generally used are gate valve because they are reliable, and safe, and can be repaired on site in some way with a minor leak failure. The Christmas tree has a set of vertical valves and a cross, or tee which changes the flow direction of the oil, in a horizontal set of valves called wing valves, which generally are connected to a choke , or a set combined of them (positive, and adjustable) .

The Christmas Tree for the above reasons is called Flow Tree,or Flow Assembly, in many cases due to the flow of oil that has to deal with . Next a standard configuration of a Christmas Tree widely used .

FLOW ASSEMBLY: 3-1/8 x 2-1/16 - 5.000 PSI ( PSL-1 / PR-0 )

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Next Drawings are details of the assembly above, making close-ups to some of it's components. In first plane is the a positive choke mounted in the horizontal run, or wing valves, please notice the attachment to the tee API 3-1/8 x 2-1/16 -5,000 PSI studded. The choke on the left side is a Positive style, which means no adjustments to the quantity of flow delivered, it only has a predetermined flow restriction internal called flow bean, or choke bean in 1/64" of diameter increasing, made of tungsten carbide insert, or full hardened body 660 SS, or 410 SS.The drawing on the right is an adjustable choke 2-1/16-5,000 PSI.

   POSITIVE CHOKE  2-1/16-5000 PSI WP                        ADJUSTABLE CHOKE 2-1/16-5000 PSI WP            

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The Positive Choke shown on left  is a positive type, and inside it has a choke bean, or graduated flow reductor that allow the flow of oil to be calculated in quantity of gallons desired. Note the needle valve in top of the choke cap this is an accessory is not part of the choke, but for safety reasons with the addition of  this accessory, it may save the operator's life, by first relieving the pressure trapped (if any) by means of  the needle valve, then he has safe access to the choke bean to be replaced.

Next Drawing detail of the vertical run top, Lubricator adapter or Christmas tree top cap, it is a piece that always comes in the top of any Christmas tree and allows the work-over of the well, as well as the procedure to install / remove the back-pressure device from the tubing hanger, inside . It has a connection cap that generally is a ACME thread, but in many cases, vary from clamps many kind to other connection styles like ring gasket, and generally a tool device is used to attach to the top of it, for the well's intervention, the other end of the tool is made in compliance with the Wire-Line Company connection that makes the work-over. So it may vary, nevertheless, an Otis Acme is wide used.

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Notice that the lubricator adapter has a series of  lugs side to side,   because this version is for hammer lock cap nut allowing the access to the internal thread connection, where an 8RD EUE Series type is typical. This Hammer nut version is suitable for  up to 5,000 PSI Working Pressure.

Christmas Trees (Flow Assemblies) may come in various styles and configurations ahead there are some of the many arrangements possible, in single wing style, and this ones has Pneumatic Actuated Valves in the wings and in the Vertical run.

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Updated on:02/01/04Copyright @2003 Daniele Molaro Consulting

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