Editorial Technical Reference

Telescoping joint (slip joint) at the top of a marine drilling riser: barrels, stroke and the annulus packer

Floating drilling · outer and inner barrel, tension ring, lock, air- and hydraulically energised packers, API 16F test pressures

A floating drilling vessel moves up and down with the waves while the marine riser is fixed to the subsea wellhead. The telescoping joint at the top of the riser absorbs that motion: its outer barrel is fixed to the riser and carries the tension ring, the inner barrel slides inside it from the drill floor, and a packer seals the annulus between them so returning drilling mud does not escape. The two questions a buyer settles are the stroke and load the joint carries, and how the sliding seal is pressurised and replaced.

Telescopic (slip) joints for low-pressure marine drilling risers on floating rigs: inner and outer barrels, tension ring interface, locking mechanism and annulus packers. Riser joints, couplings, auxiliary lines and buoyancy are covered on the Marine riser system page; tensioner cylinders, wirelines and accumulators on the Riser tensioner system page; winch heave compensation on the Active heave compensation system page.

CNFX editorial research · Sources checked October 17, 2026 · 4 sources

Size stroke and load Specify the packer

Telescoping Joint in a manufacturing environment — Representative product image. Confirm appearance and specifications with the manufacturer.

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Size stroke and loadWave motion, tension. Specify the packerPressure, energising, change-out.

Stroke and tension carried through the outer barrel

Oil States' patent for an elastomeric-sleeve telescoping joint describes the outer barrel fixed to the riser and the inner barrel sliding inside it as the vessel heaves, with hydraulic or cable tensioners connected through a tension ring to keep a nearly constant riser tension. A locking mechanism fixes the inner barrel to the outer barrel during installation, maintenance and abandonment. [1]

The same patent states that the stroke needed is based on predicted wave patterns and that roughly 50 feet (15 m) is among the longer strokes. Its example joint is sized for 21 inch (53.3 cm) riser pipe, may carry 4,000,000 lbf (17,800 kN) of tension, and notes that API Spec 16F (first edition, August 2004) lists tension load ratings up to 4 million pounds. [1]

Lengthening the barrels for more stroke runs into the limits of the vessel's handling and installation equipment; the patent's answer is a multi-barrel joint whose stroke exceeds its own retracted length. [1] Vetco Gray's control-line patent routes the packer, locking and cooling-fluid lines through ports in the outer barrel. [3]

Packer pressure, energising medium and seal change-out

A Cooper Industries application states that specifications had been adopted requiring telescopic joint packers to seal against up to 200 psi, and that some operators were asking for 500 psi; at such sealing pressure no lubricating mud leaks past the packer, raising wear and in extreme cases stopping the joint from moving. [4] Oil States cites the API 16F Section 11.6.2.1 hydrostatic test at 25, 50, 100 and 200 psi (0.17, 0.34, 0.69 and 1.38 MPa), each held without leakage for at least 15 minutes. [1]

These are patent descriptions of competing designs, not product ratings. A purchase specification should state the packer test pressure and API 16F edition required, the energising medium and supply pressure, whether a backup seal is fitted, and how the packer is replaced offshore.

Source	Packer arrangement	Issue addressed
Vetco Gray, US 5,727,630	Upper packer energised by air, lower packer by hydraulic fluid, both supplied from the vessel. [3]	Getting control lines to the packers through the outer barrel. [3]
Cooper Industries, EP 0 531 038	Resilient packer pressed by line pressure, with a restricted passage feeding pressure fluid inside as lubricant. [4]	Sealing high pressure without excessive friction and wear. [4]
Cameron, US 9,725,978	Two radially energised seals, one backing up the other. [2]	Changing seals needs the diverter removed and a hard hang-off on the riser spider, which can take ten hours or more. [2]
Oil States, US 9,441,426	Folded elastomeric membrane rolling between the barrels; 1/4 in (6.4 mm) rubber for 200 psi in the example. [1]	Abrasion wear of a sliding rubber packer. [1]

Data the joint maker needs

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Riser: [OD; coupling; API 16F edition]
Stroke: [required; vessel heave basis]
Tension: [rating; tension ring type]
Packer: [test pressure; air/hydraulic; backup seal]
Lock: [locking mechanism; lock-out tool]
Lines: [control and auxiliary line ports]

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review · Page last updated 17 October 2026

Buyer questions

What pressure must a telescoping joint packer hold?

Cooper cites a 200 psi specification with some operators asking 500 psi; API 16F's hydrostatic test steps reach 200 psi. [4] [1]

Why not just make the stroke longer?

Longer barrels exceed rig handling limits; Oil States describes multi-barrel joints instead. [1]

Sources and what still needs a direct check

Sources checked 2026-10-17. All four sources are patent documents from equipment makers, read for the design problems and figures they state.

Still to check yourself

State stroke from the vessel heave analysis.
Match tension rating to the tensioner system.
Fix packer test pressure and energising medium.

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