Water hammer, the unexpected release and associated shock wave of high-pressure steam/condensate, can cause injuries or property damage. However, not all employees who work near high-pressure steam/condensate systems realize the hazards associated with such systems.
One of the most important safety principles to remember is that steam and water cannot be safely mixed in a piping system (with the exception of specifically designed systems) without risking condensate-induced water hammer. Never mix steam with water, either by injecting water into a steam system or steam into a system that includes water (condensate).
Here are some primary causes of steam/condensate incidents.
- Condensate systems must be sloped. Improper installation may cause pockets of water to accumulate.
- Inoperative or inadequate trapping in steam lines.
- Cold startup of a steam system
- Improper maintenance and management controls and procedures.
RECOMMENDATIONS FOR SAFE OPERATION
These causes of water hammer and related incidents may be avoided through proper operation and maintenance procedures. All steam systems should be inspected to ensure proper distribution and sizing of cold traps. Steam traps should be located at all low points and inspected frequently for condensate accumulation. Valves that lack properly positioned steam traps should remain open at all times or be removed from the piping system (for sagging) and the piping insulation (for wear).
Before opening valves in steam lines, check for adequate placement and proper operation of steam traps. Fully open bleed valves, using reduced system pressure, to remove any remaining condensate. Activate cold steam piping slowly at reduced pressure and with trap bleed valves continuously open. To prevent possible condensate accumulation, place blowdown valves before and after a vertical rise. In addition, all isolation valves must have bypass systems, though such systems will not prevent water hammer if condensate is present.
Finally, do not “crack open” valves to avoid condensation-induced water hammer; the formation of a condensation-induced water slug can occur at very low condensate flow conditions.
Improperly designed steam/water systems must have problems corrected. Once properly designed systems and operations are in place, maintenance should be the highest priority.
Source: US DOE, Safety and Health Bulletin (Issue 95-1) , Fall 1995.
The tightening of a bolt flange connection is a relatively simple operation, but certain practices must be followed to get a leakproof connection. In boiler rooms across the state, we’ve seen costly pipe and valve replacements caused by water and steam cuts that could have been avoided if the flange had been assembled correctly.
