Eleven nitrogen bottles, four spent bladders, and an API 16D 5-year clock with thirty days left.

The intake call was short. KOC had pulled a Koomey Type 80 BOP closing unit off a sour-gas drilling rig in northern Kuwait at 4 years 11 months on the meter. The API 16D 5-year recertification window had thirty days of margin left on it, and the operator wanted the unit "in and out — we have a rig waiting". The skid arrived in our Jebel Ali yard on a low-loader before the recerts file did.

On paper this should have been a recharge-and-stamp. In practice, four of the eleven nitrogen accumulator bladders showed permeation loss above the API 16D 10% / 24 hr ceiling. Six of the eleven SPM (sub-plate-mounted) valves had seat-and-stem packing that had degraded past anything that could be called "in service". One of the two air-hydraulic pumps had a worn diaphragm that was venting 3,000 psi hydraulic back into the rig air supply. The unit had been running on H₂S service for almost five years; nothing on it surprised us, but everything on it had to be touched.

There is a difference between a rebladder and an API 16D 5-year recert. The first is a parts swap. The second is a documented requalification of every closing-unit subsystem against API 16D, witnessed and signed. We told KOC the second was the only path that would survive an audit on a sour-gas well. They cleared the scope inside a working day and we opened the work order.

We stripped and rebladdered all eleven nitrogen accumulators with HNBR-FKM bladder kits in sour-service grade — not the standard NBR replacements that ship with most aftermarket kits. We overhauled all eleven SPM valve assemblies with NACE MR0175 / ISO 15156 seat and stem packing kits, replaced both air-hydraulic pump diaphragms, and recharged each accumulator to the OEM Cameron specification of 1,000 psi N₂ pre-charge. Every nitrogen bottle used in the recharge was logged by batch, fill-station ID and lot number into the recerts file. Eight days on the bench in Bay 3 of the Jebel Ali workshop.

The function test on day 8 ran the complete closing sequence against an API STD 53 simulated BOP load — annular, upper rams, middle rams, lower rams, choke and kill — with closure times measured station-by-station against the API STD 53 ceilings. Everything actuated inside spec. The 5-year recert pack went out with the unit on day 9 and the operator low-loaded it back to Kuwait the same morning.

A rebladder is a parts swap. A 5-year recert is a documented requalification — every bottle, every SPM, every nitrogen lot number, witnessed against API 16D. The line between the two is what an auditor reads when something goes wrong on a sour-gas well.— Yusuf Al Hashimi · Workshop Manager · Jebel Ali

API 16D 5-year recerts on a Koomey closing unit don’t vary much in shape. They vary in what the inspection finds. This one needed all four phases run end-to-end, with no shortcuts on the SPM bank.

Below is the working subset of SOP-OG-019 — our standing procedure for an API 16D 5-year recert on a Koomey-type BOP closing unit. The full revision runs 38 lines; the 23 below are what was ticked off and witnessed on this unit.

Below is what we measured against API 16D and OEM Cameron tolerance on every subsystem of the unit. Four highlighted findings would have failed the 5-year recert witness if the unit had gone out as a recharge-and-stamp.

The unit cleared sign-off on day 8. The KOC drilling supervisor witnessed the closing-sequence test in person, signed the API STD 53 sheet on the bench, and the 5-year API 16D recert stamp went on the unit the same afternoon. Low-loader rolled day 9. Skid was back on the rig site in northern Kuwait inside the operator’s rig-up window. All eleven accumulators, all eleven SPM stations and the air-hydraulic pumps go forward under a single 12-month system warranty against the new recert. Sour-service compliance was reconfirmed against NACE MR0175 / ISO 15156 across every elastomer in the unit.