Leaks in heat exchangers and condensers: the ultrasonic detection method

At a CHP plant, a drop in turbine condenser vacuum or rising make-up water consumption is often written off as the "general condition" of the system. In practice a micro-leak in one or two tubes of the bundle is already eating efficiency and blurring the intervals between overhauls. Dismantling and hydro-testing the whole bundle is expensive. Ultrasound localises the fault far faster.

---

Why tubes leak

Cause	Where it is typical
Erosion / cavitation at the inlet	condensers, oil coolers
Corrosion (chlorides, ammonia)	chemicals, water treatment
Tube vibration in the baffles	large heat exchangers
Mechanical damage during cleaning	after maintenance

A water-to-steam or water-to-oil leak stays masked for a long time, until conductivity or the make-up flow rate rises.

---

The ultrasonic method: two scenarios

1. Unit in place, access to the tube sheet

1. Open the water chamber / water-side cover.
2. Plug or isolate the circuit according to the manufacturer's procedure.
3. Apply compressed air (or nitrogen) to the shell or tube side per the procedure (usually low pressure — around 0.5–2 bar, per the data sheet).
4. Survey the tube sheet with the SDT340 or LEAKChecker: the faulty tube "whistles" in ultrasound.

2. Vacuum condenser in service

Under vacuum on the steam side, air is drawn in through the micro-hole. The SDT airborne sensor picks up the turbulent inflow at flanges, manways and, where accessible, at the tube sheet during a shutdown.

Related leak material: compressed air leaks.

---

Practical advice

1. Mark every "loud" tube with a marker — photograph it for the report.
2. Compare the dBµV level with neighbouring healthy tubes, not with an absolute threshold.
3. After plugging — repeat the survey: the level must drop.
4. For steam traps on the pipework, use a separate TRAPChecker / SDT270 route.

---

Where this is critical in Kazakhstan

• CHP / thermal power plants — turbine condensers, oil coolers, HP/LP feedwater heaters.
• Metals — rolling mill coolers, converter circuits.
• Chemicals — shell-and-tube exchangers on process media.

Application pages: power generation, metallurgy.

---

Relation to other methods

Method	Role
SDT ultrasound	localises the tube / flange
Hydro test	confirms tightness after repair
Chemistry (conductivity)	early "there is a problem" signal
Vibration / ESA on pumps	indirect — rising load on circulation pumps

For circulation and condensate pumps, add Artesis ESA and cavitation diagnostics.

---

Conclusion

An ultrasonic walkdown of the tube sheet is the fastest way to find a faulty tube without guessing across the whole bundle. In a CHP reliability programme it sits alongside steam trap and compressed-air leak audits — see SDT at CHP plants and the 8 pillars of ultrasound.