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Diverter Systems
A diverter closes around the pipe and sends an uncontrolled flow of shallow gas or fluid overboard through large vent lines, instead of shutting the well in. This Category covers diverter housings, diverter assemblies and packers, insert packers, vent and flowline valves, flowline spools and diverter control panels for floating and bottom-supported rigs.
Why a diverter instead of a BOP
Top-hole sections are drilled before the BOP goes on, or through formations too weak to hold shut-in pressure. Closing a BOP on shallow gas there can fracture the formation and broach to the seabed around the conductor. A diverter avoids that. It closes a packer around the pipe and opens a large vent line in the same sequence, so the flow leaves the rig downwind while the well stays open to the vent.
Configurations
- On floating rigs, a diverter housing built into the substructure under the rotary table, with a diverter assembly that latches into it on top of the riser
- On jackups and platforms, a diverter installed on the conductor before the BOP, often with a separate annular-style element
- Insert packers sized for a pipe range, or a full annular element that closes on any size
- Single, dual or selectable vent outlets, so you can pick the downwind side
Key specifications
| Parameter | Why it matters | Typical classes or units |
|---|---|---|
| Housing size | Must fit the rotary table and substructure | in. or mm, by OEM model |
| Working pressure | Far below a BOP's, so the vent must stay open | psi or MPa, by OEM model |
| Vent outlet size | Larger lines cut back-pressure and erosion | Nominal in. or mm |
| Packer type | Insert or annular-style, pipe range covered | Pipe OD range |
| Lower connection | Joins the diverter flex joint or riser | OEM-specific profile |
| Control interlock | Prevents shutting in the well by mistake | Sequence logic in the panel |
Standards and certification
API Standard 64 covers design, installation, maintenance and testing of diverter equipment and replaced the older API RP 64. API 16D covers the diverter control system, including the sequencing. In US waters, 30 CFR 250.433 requires a pressure test of the sealing element and vent valves to at least 200 psi after installation on a surface wellhead. It then calls for an actuation every 24 hours on surface systems and every 7 days on floating rigs, alternating between control stations, plus a flow test of the vent lines.
Failure modes and inspection
The housing bore and packer seal areas wear because pipe passes through on every trip. Packer elements age and tear. Vent and flowline valves stick when not cycled, and vent lines erode and dent where they turn. The most dangerous fault is in the controls. If the packer closes before a vent valve opens, the diverter becomes an undersized BOP.
An inspection should cover dimensional checks of the bore and seal surfaces, magnetic particle testing of the housing load shoulder and latching profile, packer element condition and dates, valve seat tests, and a full sequence test from each panel with the interlock proven.
Documentation
Ask for the last function and pressure test records, the interlock test, packer manufacture dates, the repair history of the housing and assembly, and the outline drawing with the rotary table and riser interfaces. Records of vent line wall thickness surveys add confidence.
Integration
A diverter housing is part of the rig's structure. Its outline, the rotary table bore, the support beams and the flowline and vent routing are all fixed by the rig design. On a floater, the diverter assembly connects through a diverter flex joint to the telescopic joint below, so the lower profile must match. The control panel must fit the rig's hydraulic and air supply.
Refurbishment and the used market
A refurbishment replaces packers, seals and valve trims, re-machines worn seal surfaces where the OEM allows it, and ends in pressure and sequence tests. A used housing or assembly from a sister rig fits best. Spare packers and elements are worth buying unused where the housing model is still common, if their age is known. Well-known marine diverter lines include Vetco Gray and Hydril designs, both now with HMH. The lower connection is covered under flex joints and adapters.
FAQ
Frequently asked questions
What is the difference between a diverter and a BOP?
A diverter routes flow away from the rig through vent lines and is not designed to shut in a well. A BOP closes the well and holds pressure. You use a diverter for shallow gas, before the BOP is installed or where the formation cannot take shut-in pressure.
Which standard covers marine diverter systems?
API Standard 64 covers diverter equipment systems, including design, installation, maintenance and testing, and it replaced API RP 64. The control system that sequences the packer and vent valves falls under API 16D, which also covers BOP controls.
Will a used diverter fit a different rig?
Only if the housing matches the rig's rotary table, substructure supports, flowline routing and riser interface. Diverters are built around one rig design, so compare outline drawings before you buy. Units from sister rigs are the easiest swap.
How often must a diverter be tested?
In US federal waters, 30 CFR 250.433 requires actuation every 24 hours on a surface wellhead and every 7 days on a floating rig. On a surface wellhead, the element and vent valves are also pressure tested to at least 200 psi after installation and at least every 7 days, and vent lines are flow tested.
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