GT-1 Geothermal Turbine — Condenser and NCG System Entry Isolation
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.
How Setyr addresses Geothermal →
It refers to equipment that does not exist and illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain. It is not a document to adopt. Under (c)(4)(i) the employer must develop and document energy control procedures specific to their own machines, and under (c)(6) must inspect them at least annually.
12 points, in sequence
Generator excitation and the unit main breaker.
Method: Open the main breaker, rack out, open and lock the excitation supply. Prove dead at the generator terminals.
Caution: A generator connected to a live grid motors the turbine. Racking out is the isolation, not opening the breaker.
Turbine stop valve on the steam admission line.
Method: Close and lock the stop valve. Confirm zero flow at the admission flow element.
Caution: A stop valve alone is a single barrier against a live steam header shared with other units.
Steam admission block valve upstream of the stop valve, forming the second barrier.
Method: Close and lock. With the stop valve this forms a double block.
Caution: Isolating only at the turbine leaves the crew relying on one valve against a header fed by several producing wells.
Bleed between the admission block and the stop valve, to the atmospheric silencer.
Method: Open the bleed to the silencer and lock open. A sustained zero proves both valves; rising pressure means one is passing.
Caution: Geothermal steam carries silica and chlorides that erode valve seats. Passing seats are the norm, not the exception.
Condenser vacuum breaker to atmosphere.
Method: Open the vacuum breaker and confirm the condenser is at atmospheric on two gauges before opening any manway.
Caution: A condenser under vacuum holds its manway covers shut with tonnes of force and draws in anything that opens.
Gland sealing steam to the turbine shaft seals.
Method: Close and lock the gland steam valve after vacuum is broken.
Caution: Gland steam admits into the condenser shell. Isolating it before vacuum is broken pulls air through the seals instead.
Turbine turning gear and rotor.
Method: Stop the turning gear, open and lock its disconnect, and confirm the rotor is stationary before condenser entry.
Caution: Residual steam leakage spins a turbine on vacuum alone. A rotor turning slowly in a condenser being entered is a shear hazard.
Non-condensable gas extraction line to the H2S abatement plant.
Method: Close and lock the NCG line. Confirm the abatement plant is aware the unit is offline.
Caution: The NCG stream is concentrated H2S and CO2. It is the most toxic stream on a geothermal plant.
Nitrogen purge for the NCG line and the condenser shell before entry.
Method: Purge until H2S and CO2 readings are below entry thresholds on two consecutive tests at the manway and at the shell low point.
Caution: Purging trades an H2S atmosphere for an asphyxiant one. Neither is breathable and only testing tells them apart.
Circulating water supply and return to the condenser from the cooling tower.
Method: Close and lock both valves, then drain the waterbox.
Caution: A cooling tower basin above the condenser floods the shell through an unisolated waterbox.
Condenser hotwell drain to the reinjection sump.
Method: Open the drain and confirm the hotwell is empty before entry.
Caution: Hotwell condensate is hot and carries dissolved H2S that releases as it is disturbed.
Fixed H2S detection in the turbine hall and at the condenser manway, plus personal monitors.
Method: Do NOT isolate. Confirm all heads are in service and personal monitors are bump-tested before entry.
Caution: A geothermal condenser is the single most concentrated H2S source on the plant. Detection is the entry control.
What your site must supply
This example is structurally complete and factually generic. The things below are the things only you can know — and they are exactly what makes a procedure yours.
- 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.
Author this properly, once
Setyr holds procedures like this as living documents — bound to real isolation points, with lock registries, group lockout, person-in-charge custody and periodic review built in.