LOT/Advanced/TBT-LOT-010

LOTO for Pumping Stations

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Pumping stations contain multiple energy sources: electrical, hydraulic, pneumatic, gravity, and stored water pressure.
Pumps can start automatically on level control, creating sudden unexpected energisation during maintenance.
Isolation must cover the electrical supply, incoming pipework valves, and non-return valve bypasses.
Gravity flow from upstream can flood the wet well even after pumps are electrically isolated.
Penstock or gate valves on inlet pipes must be closed and locked to prevent gravity inflow.
Residual pressure in pipework and pump casings can cause water release when flanges are broken.
Multi-pump stations require isolating each pump individually plus the common supplies and controls.
The LOTO permit must list every isolation point and be signed by the authorised person before work begins.
Proving dead on electrical systems and confirming zero pressure on pipework are both essential steps.
The Electricity at Work Regulations 1989 and PUWER 1998 require safe isolation before maintenance.

Automatic start risk	Pumps starting automatically on level control have crushed and drowned workers carrying out maintenance in wet wells.
Multiple energy sources	Pumping stations combine electrical, hydraulic, and gravity energy. Missing any single source during LOTO is fatal.
Flooding risk	Gravity inflow from the upstream sewer floods the wet well even with pumps electrically isolated if valves are open.

Don't

Identify every energy source including electrical, gravity flow, and stored pressure.
Isolate incoming flow using penstocks or gate valves and lock them in the closed position.
Isolate each pump electrically and lock off at the starter or distribution board.
Prove dead on all electrical circuits using the three-step test procedure.
Depressurise pipework and confirm zero pressure before breaking any flange joints.
Apply personal locks to every isolation point listed on the LOTO permit.
Brief the maintenance team on all isolation points and the verification procedure.
Monitor wet well levels during maintenance to detect any leakage past valves.
Follow the re-energisation procedure in reverse order with each step verified.
Record all isolation and proving dead results on the LOTO permit.

DON'T rely on electrical isolation alone; pumping stations have gravity flow too.
DON'T assume auto-start systems are disabled just because the control panel is off.
DON'T break flange joints without confirming the pipework is fully depressurised.
DON'T enter the wet well without isolating and locking off incoming flow valves.
DON'T leave isolation valves unlocked where others could inadvertently open them.
DON'T skip the proving dead test on electrical circuits before starting work.
DON'T remove another person's lock from an isolation point under any circumstances.
DON'T assume a single isolation point covers all energy sources in the station.
DON'T re-energise until every person has removed their lock and confirmed clear.
DON'T work on pumps without a completed LOTO permit signed by the authorised person.

See also: LOTO Awareness | Stored Energy Isolation

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