Setyr worked example — GT-1 Geothermal Turbine — Condenser and NCG System Entry Isolation Not approved for use. Version 1 · 2026-09-08
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
GT-1 Geothermal Turbine — Condenser and NCG System Entry Isolation
Geothermal
Condenser entry and non-condensable gas system service on a geothermal steam turbine. Covers steam admission from a header shared with other units, vacuum, turbine overspeed on residual steam, and an H2S-rich NCG stream.
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 | GT-1-GEN | Breaker | Isolate & lock | Generator excitation and the unit main breaker. Caution: A generator connected to a live grid motors the turbine. Racking out is the isolation, not opening the breaker. Open the main breaker, rack out, open and lock the excitation supply. Prove dead at the generator terminals. | — |
| 20 | GT-1-STOP | Valve | Isolate & lock | Turbine stop valve on the steam admission line. Caution: A stop valve alone is a single barrier against a live steam header shared with other units. Close and lock the stop valve. Confirm zero flow at the admission flow element. | — |
| 30 | GT-1-ADM-BLK | Valve | Isolate & lock | Steam admission block valve upstream of the stop valve, forming the second barrier. Caution: Isolating only at the turbine leaves the crew relying on one valve against a header fed by several producing wells. Close and lock. With the stop valve this forms a double block. | — |
| 40 | GT-1-ADM-BLD | Bleed | Isolate & lock | Bleed between the admission block and the stop valve, to the atmospheric silencer. Caution: Geothermal steam carries silica and chlorides that erode valve seats. Passing seats are the norm, not the exception. Open the bleed to the silencer and lock open. A sustained zero proves both valves; rising pressure means one is passing. | 900s |
| 50 | GT-1-VAC-BRK | Vent | Isolate & lock | Condenser vacuum breaker to atmosphere. Caution: A condenser under vacuum holds its manway covers shut with tonnes of force and draws in anything that opens. Open the vacuum breaker and confirm the condenser is at atmospheric on two gauges before opening any manway. | 600s |
| 60 | GT-1-GLAND | Valve | Isolate & lock | Gland sealing steam to the turbine shaft seals. Caution: Gland steam admits into the condenser shell. Isolating it before vacuum is broken pulls air through the seals instead. Close and lock the gland steam valve after vacuum is broken. | 300s |
| 70 | GT-1-TURN | Disconnect | Isolate & lock | Turbine turning gear and rotor. Caution: Residual steam leakage spins a turbine on vacuum alone. A rotor turning slowly in a condenser being entered is a shear hazard. Stop the turning gear, open and lock its disconnect, and confirm the rotor is stationary before condenser entry. | — |
| 80 | GT-1-NCG | Valve | Isolate & lock | Non-condensable gas extraction line to the H2S abatement plant. Caution: The NCG stream is concentrated H2S and CO2. It is the most toxic stream on a geothermal plant. Close and lock the NCG line. Confirm the abatement plant is aware the unit is offline. | — |
| 90 | GT-1-NCG-PRG | Valve | Isolate & lock | Nitrogen purge for the NCG line and the condenser shell before entry. Caution: Purging trades an H2S atmosphere for an asphyxiant one. Neither is breathable and only testing tells them apart. Purge until H2S and CO2 readings are below entry thresholds on two consecutive tests at the manway and at the shell low point. | 1200s |
| 100 | GT-1-CW | Valve | Isolate & lock | Circulating water supply and return to the condenser from the cooling tower. Caution: A cooling tower basin above the condenser floods the shell through an unisolated waterbox. Close and lock both valves, then drain the waterbox. | — |
| 110 | GT-1-COND-DRN | Drain | Isolate & lock | Condenser hotwell drain to the reinjection sump. Caution: Hotwell condensate is hot and carries dissolved H2S that releases as it is disturbed. Open the drain and confirm the hotwell is empty before entry. | 600s |
| 120 | GT-1-H2S-DET | Breaker | KEEP ENERGISED | Fixed H2S detection in the turbine hall and at the condenser manway, plus personal monitors. Caution: A geothermal condenser is the single most concentrated H2S source on the plant. Detection is the entry control. Do NOT isolate. Confirm all heads are in service and personal monitors are bump-tested before entry. | — |
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.