Improving Reliability at Inlet Works

Practical approaches to reducing actuator failures and improving asset availability

Colin Borrows, Head of Sales, AUMA Actuators Limited

At wastewater treatment works, actuated inlet penstocks are among the most critical mechanical assets. As the first control point for incoming flow, failure of either the penstock or actuator can disrupt the treatment process.

Although maintenance often focuses on the actuator, many reliability issues originate at the mechanical interface between the actuator and penstock spindle.

Understanding the thrust base 

The connection between an electric actuator and a rising-spindle penstock is made through the thrust base, which contains bearings, a drive sleeve, grease seals, lubrication points and a drivenut.

The phosphor-bronze drivenut converts rotary movement into the linear motion required to operate the penstock. It is deliberately softer than the stainless-steel spindle, acting as a sacrificial component. Wear is therefore expected, but excessive wear can result in thread slip or loss of engagement.

Preventing premature failure

Thrust bearings are vulnerable if water enters the assembly. Damaged cover tubes or missing end caps can allow rainwater to wash away lubricant, accelerating wear and increasing operating torque.

Rising torque can provide an early indication of bearing deterioration, inadequate lubrication or increasing friction. Regular inspection can therefore help identify problems before failure occurs.

Effective lubrication of both the spindle and drivenut, preventing dirt and water ingress, and maintaining the penstock in good mechanical condition can all extend service life.

Lubrication matters

Lubricating the thrust bearings does not normally lubricate the spindle thread, which usually requires direct application of grease. Where regular maintenance is difficult, automatic lubrication systems can provide an alternative, delivering lubricant to both the thrust bearings and spindle thread.

Routine inspection of the cover tube is equally important in preventing dirt, grit and rainwater from reaching these components.

A condition-based approach

Routine checks should verify lubrication, monitor drivenut wear, inspect the cover tube and review actuator fault logs for repeated torque trips. Inspection frequency should reflect operating frequency and environmental conditions rather than relying solely on fixed intervals.

Modern actuators can also record operating history and fault events, helping maintenance teams identify emerging problems and move towards condition-based maintenance.

Standardising actuator assets can deliver further efficiencies by reducing spare parts inventory, simplifying installation and retrofit projects, and minimising training requirements.

Recognising the drivenut as a consumable component, maintaining lubrication, preventing water ingress and using operational data effectively can help water companies improve reliability, reduce downtime and support more efficient management of critical inlet works infrastructure.

To download a copy of the full White Paper visit auma.co.uk

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