Inverted pull-up riser tensioner

A riser tensioner, comprising:

• a cylinder barrel;
• a rod reciprocally carried within the cylinder barrel and having an external end sealingly extending out of a proximal end of the cylinder barrel;
• a piston on an interior end of the rod that slides and seals against an inner surface of the cylinder barrel;
• a selectively sealed low pressure chamber in the cylinder barrel between the piston and a distal end of the cylinder barrel and fillable with a low pressure fluid;
• a first high pressure seal extending around the piston in sealing engagement with the inner surface of the cylinder barrel;
• a low pressure seal extending around the piston in sealing engagement with the inner surface of the cylinder barrel, the low pressure seal closer to the low pressure chamber than the high pressure seal;
• a low pressure seal lubricant conduit extending to a point between the high pressure seal and the low pressure seal, the low pressure lubricant conduit at the same pressure as the low pressure chamber;
• and
• a selectively sealed annulus between the rod and the cylinder barrel, the annulus extending between the piston and the proximal end of the cylinder barrel and fillable with an annulus fluid at a pressure higher than the low pressure fluid, thereby urging the piston and rod towards the distal end of the cylinder barrel and the riser tensioner towards retraction.

A method of tensioning a riser, comprising

• pressurizing a low pressure chamber of a riser tensioner, the low pressure chamber formed between a piston and a distal end of a cylinder barrel, wherein the piston is sealed against an inner surface of the cylinder barrel via a seal and coupled to a rod extending from the piston and beyond of a proximal end of the cylinder barrel, and wherein the cylinder barrel is adapted to connect to a riser and the rod is adapted to connect to a floating platform;
• pressurizing an annulus of the riser tensioner at a higher pressure than the low pressure chamber, the annulus formed between the rod and the cylinder barrel;
• filling a low pressure seal lubricant conduit at least partially with a low pressure lubricant, the low pressure lubricant conduit extending to a point on a low pressure side of the seal;
• and
• filling a high pressure seal lubricant conduit at least partially with a high pressure lubricant, the high pressure lubricant conduit extending to a point on a high pressure side of the seal.