If you have experienced problems heating fluids using direct steam heating in your processes, it’s probably caused by steam hammer. It’s loud, unsafe, and violent. And if left unchecked, can disrupt production and damage your system components.
What is Steam Hammer?
Steam hammer occurs when un-condensed steam forms bubbles, and when these bubbles contact a pipe wall or the side of a tank, they collapse and the moving fluid produces a concussive sound. Steam hammer can be very destructive and lead to the following issues:
- Rough heater operation & poor temperature control.
- Reduced wear life of steam injector components and damage to instruments
- Limited range of operation … typically limited to 2:1 turndown
- Steam flashing due to rapid change (drop) in liquid flow rate.
Most operators try to handle it by reducing steam pressure and limiting the process operating range – but this approach doesn’t solve the problem. Slowed steam velocity creates uneven heating and uncondensed steam, and leads to the bubbling that generates aggressive vibration. And limiting the operating range costs money.
Steam condensation rates are tied to steam flow velocity. High steam flow velocity (sonic flow >1000 fps) assures rapid rates of condensation in your process fluid. Maintaining proper steam & liquid pressure differential is critical to assure stable operation. Steam cavitation can occur when sub-sonic (<1000 fps) conditions occur. The most common cause for sub-sonic conditions results when a steam pressure control valve reduces steam pressure to control steam flow.
How to eliminate steam hammer or steam flashing:
• Eliminate use of external modulating steam pressure reducing valve for steam flow control.
• Maintain proper differential between steam & liquid pressure.
• Liquid flow changes should be gradual and should not occur faster than temperature control loop can respond.
• Monitor liquid flow and design appropriate alarm strategies for loss of liquid flow or excessive Hi-temperature conditions.
• Proper steam line design to eliminate excessive condensate.
The most effective solution is a heater with internally modulated steam control, which maintains high steam velocity, while adjusting flow as needed.
ProSonix heaters employ high velocity steam through a modulated jet diffuser opening to eliminate steam hammering. This allows for a much larger operating range and reliably smooth heater operation. These advantages are present even with highly viscous fluids and slurries, and are maintained over time through a self-cleaning design that won’t plug, foul up, or collect mineral scale.