Setyr worked example — SEP-2100 Production Separator — Relief Valve Change Isolation Not approved for use. Version 1 · 2026-09-25
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
SEP-2100 Production Separator — Relief Valve Change Isolation
Sour production
Pressure relief valve replacement on a three-phase production separator in sour service. Covers double block and bleed, depressurisation, H2S purge and the protection that must remain in service while the relief path is open.
This is a worked example, not a procedure you can adopt. It describes equipment that does not exist, with illustrative tag numbers.
29 CFR 1910.147(c)(4) requires the employer to develop, document and
utilise energy control procedures specific to their own machines, and (c)(6)
requires the employer to inspect those procedures periodically. Neither duty
can be delegated to a vendor or discharged by this document.
Isolation points
| # | Tag (illustrative) | Type | Disposition | What it does and why | Dwell |
|---|---|---|---|---|---|
| 10 | SEP-2100-INL-1 | Valve | Isolate & lock | Separator inlet block valve, upstream of the double block pair. Caution: A single block on live production is not isolation. The bleed between the pair is what proves the seat. Close and lock. Confirm seat integrity by monitoring pressure between the block pair. | — |
| 20 | SEP-2100-INL-2 | Valve | Isolate & lock | Separator inlet block valve, downstream of the first block. Caution: Both blocks must be locked. Locking one and closing the other leaves an unsecured device in the isolation. Close and lock. | — |
| 30 | SEP-2100-INL-BLD | Bleed | Isolate & lock | Bleed valve between the inlet block pair. Proves the blocks are holding. Caution: This is the verification, not a formality. Pressure recovering at the bleed means production is still reaching the vessel. Open the bleed to the flare header and lock open. A sustained zero reading proves the blocks. A rising pressure means a passing seat. | 300s |
| 40 | SEP-2100-GAS-OUT | Valve | Isolate & lock | Gas outlet block valve to the compression suction header. Caution: Compression suction can pull vessel contents backwards through an unblocked gas outlet. Close and lock. | — |
| 50 | SEP-2100-LIQ-OUT | Valve | Isolate & lock | Liquid outlet block valve to the production header. Caution: The level controller strokes the outlet valve on its own. Isolating the valve without the controller leaves an actuator that will try to move. Close and lock. Confirm the level control valve is also closed and de-energised. | — |
| 60 | SEP-2100-DEPR | Vent | Isolate & lock | Vessel depressurisation valve to the flare header. Caution: Depressurising a sour vessel releases H2S to the flare. Confirm wind direction and that the flare is lit before opening. Open to flare and lock open. Depressurise to atmospheric and hold. Confirm zero at two independent gauges before breaking containment. | 1800s |
| 70 | SEP-2100-DRAIN | Drain | Isolate & lock | Vessel low-point drain to the closed drain system. Caution: Residual sour liquid in the boot remains after gas depressurisation. Gas at zero does not mean the vessel is empty. Open the drain and lock open. Drain to the closed system until flow ceases. | 600s |
| 80 | SEP-2100-N2-PRG | Valve | Isolate & lock | Nitrogen purge connection for sweetening the vessel before entry or hot work. Caution: Purging displaces H2S with an asphyxiant. The atmosphere can be sweet and still not breathable. Purge with nitrogen until H2S readings at the sample point are below the entry threshold on two consecutive tests. | — |
| 90 | SEP-2100-PSV-B | Valve | KEEP ENERGISED | Spare relief path — the standby PSV on the twin-valve arrangement. Caution: Removing the duty relief valve without the standby in service leaves the vessel with no overpressure protection. Do NOT isolate. Confirm the standby PSV is lined up and its inlet block is car-sealed open before removing the duty valve. | — |
| 100 | SEP-2100-ESD | Switch | KEEP ENERGISED | Emergency shutdown valve and its solenoid on the inlet line. Caution: Defeating the ESD to make the job easier removes the last automatic protection on a live inlet. Do NOT isolate. Confirm the ESD remains armed and will close on demand. | — |
| 110 | SEP-2100-H2S-DET | Breaker | KEEP ENERGISED | Fixed H2S detection heads at the separator skid and the personal monitors carried by the crew. Caution: H2S deadens the sense of smell at concentrations well below lethal. Detection is the only warning available. Do NOT isolate. Confirm fixed heads are in service and every crew member has a bump-tested personal monitor. | — |
What your site must supply
- Your own asset and isolation-point tag numbers. The tags shown are illustrative and refer to equipment that does not exist.
- The actual location of every disconnect, valve and vent on your equipment.
- Measured stored-energy magnitudes and the dwell time required to dissipate them.
- Your verification method for each point, and who is authorised to perform it.
- Any additional energy sources present on your equipment and absent here.
Authorship and validation
This example was authored by Setyr for domain validation. It is not derived from any customer's controlled documents. It illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain — it does not certify compliance, which is a property of an employer's programme rather than of any document.