LS-12 Lift Station — Submersible Pump Pull Isolation
Removing a submersible sewage pump from a wet well. Covers duty and standby pump isolation, discharge check valve backflow, and the confined-space atmosphere over a live wet well that keeps filling during the work.
How Setyr addresses Water & Wastewater →
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.
11 points, in sequence
Bypass pumping connection to keep incoming flow off the wet well during the pull.
Method: Do NOT isolate. Confirm the bypass pump is running and taking the incoming flow before entry.
Caution: Sewage keeps arriving whether or not the station is working. Without bypass the well rises under the crew.
Duty pump motor disconnect at the control panel, 40 hp submersible.
Method: Open, lock, prove dead at the panel load side.
Caution: The pump is 8 m down in effluent and cannot be observed. Absence of noise is not proof it is isolated.
Standby pump motor disconnect.
Method: Open and lock. The standby must be isolated even though it is not the pump being pulled.
Caution: Level controls start the standby automatically when the well rises and the duty pump is unavailable. That is exactly the condition this job creates.
Standby generator and its automatic transfer switch.
Method: Place the generator in OFF and lock the transfer switch out of AUTO.
Caution: An ATS in AUTO restores the station from the generator during a supply interruption, re-energising pumps that were isolated at the utility side only.
Level control panel supply feeding float switches, the level transducer and the autodialler.
Method: Open and lock the control supply after confirming the alternative level alarm is in place.
Caution: Isolating controls stops automatic starts but also stops high-level alarming. Do not leave the well unmonitored.
Inlet channel grinder upstream of the wet well.
Method: Open and lock the grinder disconnect.
Caution: The grinder sits in the same channel the crew reaches into to clear the guide rail.
Duty pump discharge isolation valve on the rising main.
Method: Close and lock the discharge valve before breaking the pump from its guide rail.
Caution: The rising main holds a static head. Lifting a pump without closing discharge drains the main back into the well and over the crew.
Duty pump discharge check valve in the valve chamber.
Method: Confirm the check valve is seated. It is not a lockable isolation device and does not substitute for the discharge valve.
Caution: A check valve is a backflow device. Crews treat it as isolation because it usually holds. It is not, and it is not lockable.
Forced-air ventilation blower into the wet well.
Method: Do NOT isolate. Confirm continuous ventilation for the duration of the entry.
Caution: H2S and methane accumulate in the well headspace. Ventilation is a control, not a convenience.
Continuous atmospheric monitoring at the well head and on each entrant.
Method: Do NOT isolate. Confirm calibration is current and alarms are audible at the surface.
Caution: A wet well is IDLH-capable. Monitoring is the entry control under 1910.146.
Davit and hoist over the wet well used to lift the pump on its guide rail.
Method: Do NOT isolate. Confirm the davit is rated, seated in its socket and the hoist is functional before the lift.
Caution: Isolating the station panel takes the hoist supply with it on this design.
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.