Water lance

A water lance is a water-jet cleaning tool used to remove boiler slag, process build-up or deposits during online cleaning or outages. It may be handheld, semi-automatic or fixed and mechanised. The cleaning action is hydraulic impact, thermal shock or both.

The term overlaps with water cannon, but water cannon usually implies a fixed aimed device for furnace slag, while water lance is broader and can include outage lancing, retractable systems and manual high-pressure cleaning.

Where water lances are used

Water lances are used for outage cleaning of boiler passes, cement preheater build-up, furnace exit slag, superheater or reheater slag, ash deposits in access-limited spaces and some process vessels. Fixed mechanised lances may be used during operation where the design protects the lance and controls water injection.

Manual lancing is labour-intensive and high risk. It can involve confined spaces, elevated platforms, falling deposits, hot surfaces, high-pressure water and poor visibility. Lockout, cooling, ventilation and exclusion zones are therefore central to the work plan.

Design and operating issues

Important parameters include water pressure, nozzle design, standoff distance, jet pattern, lance stiffness, access angle, drainage and how the removed material will leave the vessel. Water introduced into a hot boiler can create rapid steam generation and thermal stress. In process equipment, it can also create slurry handling or wastewater issues.

Lancing is often a recovery method after deposits have already defeated online prevention. If the same area needs repeated manual lancing, the root cause may be fuel chemistry, gas distribution, wall temperature, poor drainage or insufficient online cleaning.

Relationship to sonic horns

Sonic horns can reduce the frequency of water-lancing campaigns where the deposits begin as dry, friable material and can be kept mobile. They cannot replace lancing for hard clinker, fused slag or concrete-like build-up. In Sylio-style planning, water-lance history is useful evidence of where deposits form and how strongly they bond.

Operating context

A water lance is a directed cleaning tool that introduces a water jet through a port or access opening. It may be used online in some furnace services or offline during outages for deposits that require direct hydraulic force. The lance can be simple and manual, or part of a retractable, rotating or automated system. Its effectiveness depends on getting the jet to the deposit at the right distance and angle without damaging tubes, refractory or instruments.

Key variables include water pressure, flow, nozzle pattern, lance stiffness, insertion depth, travel speed, water quality, deposit temperature and the consequence of sudden cooling. In boilers, water can flash to steam and loosen slag, but it can also create thermal shock or wash corrosive species into crevices. In ducts and scrubbers, drainage and containment become more important than thermal shock.

Maintenance and selection

Common problems include worn nozzles, bent lances, leaking valves, blocked strainers, poor port sealing, recoil hazards, damaged refractory and incomplete drainage after cleaning. Safe work requires isolation where appropriate, communication with the control room, exclusion from the jet path and controls for hot water, steam and falling material.

Compared with acoustic cleaning, a water lance is more local and more forceful. It is appropriate when deposits are hard or wet and access is available. Sonic horns are better for frequent preventive cleaning of dry deposits without introducing water. In plant surveys, the choice depends on deposit state, access, damage tolerance and whether the plant can accept the downtime or exposure associated with manual lancing.

Related terms

• Water cannon
• Waterwall
• Manual lancing