30 CFR § 250.839
What are the maximum allowable valve closure times and hydraulic bleeding requirements for a direct-hydraulic control system?
July 29, 2020
(a) If you have a direct-hydraulic control system, you must:
(1) Design the subsea control system to meet the valve closure times listed in this section or your approved DWOP; and
(2) Verify the valve closure times upon installation. The District Manager may require you to verify the closure time of the USV(s) through visual authentication by diver or ROV.
(b) You must comply with the maximum allowable valve closure times and hydraulic system bleeding requirements listed in the following table or your approved DWOP:
Valve Closure Timing, Direct-Hydraulic Control System
Open Table
| If you have the following. . . | Your pipeline BSDV must. . . |
Your USV1 must. . . | Your USV2 must. . . | Your alternate isolation valve must. . . | Your surface-controlled SSSV must. . . | Your LP hydraulic system must. . . |
Your HP hydraulic system must. . . |
|---|---|---|---|---|---|---|---|
| (1) Process upset | Close within 45 seconds after sensor activation | [no requirements] | [no requirements] | [no requirements] | [no requirements] | ||
| (2) Flowline PSHL | Close within 45 seconds after sensor activation | Close one or more valves within 2 minutes and 45 seconds after sensor activation. Close the designated USV1 within 20 minutes after sensor activation. | Close within 24 hours after sensor activation | Complete bleed of USV1, USV2, and the AIV within 20 minutes after sensor activation | Complete bleed within 24 hours after sensor activation. | ||
| (3) ESD/TSE (Platform) | Close within 45 seconds after ESD or sensor activation | Close all valves within 20 minutes after ESD or sensor activation. | Close within 60 minutes after ESD or sensor activation | Complete bleed of USV1, USV2, and the AIV within 20 minutes after ESD or sensor activation | Complete bleed within 60 minutes after ESD or sensor activation. | ||
| (4) Subsea ESD (Platform) or BSDV TSE | Close within 45 seconds after ESD or sensor activation | Close one or more valves within 2 minutes and 45 seconds after ESD or sensor activation. Close all tree valves within 10 minutes after ESD or sensor activation. | Close within 10 minutes after ESD or sensor activation | Complete bleed of USV1, USV2, and the AIV within 10 minutes after ESD or sensor activation | Complete bleed within 10 minutes after ESD or sensor activation. | ||
| (5) Subsea ESD (MODU or other type of workover vessel), Dropped object | [no requirements] | Initiate closure immediately. If desired, you may allow for closure of the tree valves immediately prior to closure of the surface-controlled SSSV. | Initiate unrestricted bleed immediately | Initiate unrestricted bleed immediately. | |||
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