[ IX Troubleshooting ]
Set up the cleaning water circuit as shown in Figure 3.
Numbers 1 through 4 in the figure indicate the following
items.
1 Container (for cleaning)
2 Pump
3 Submersible pump (placed in the container 1 for
exhaust water)
4 Container for exhaust water (also used to temporarily
drain out cleaning solution when it starts foaming.)
After setting up the cleaning water circuit, place water in
item 1, circulate the water, and check for leaks.
After checking for leaks, replace the circulation water if has
become dirty. If not, the water can be reused for cleaning.
Use as much of it as necessary for cleaning.
1) Make sure that the water inlet pipe has a port for connecting a pipe for chemical cleaning.
Formic acid, citrate, oxalic acid, acetic acid, or phosphate acid diluted to 5% can be used as a cleaning solution to
remove scale.
Do not use hydrochloric acid, sulfuric acid, or nitric acid for cleaning because they are highly corrosive.
2) Make sure that valves are located before the inlet and after the outlet.
3) Connect the pipe for passing the cleaning solution to the inlet/outlet pipe on the gas cooler, fill the plate heat exchanger
with cleaning agent heated to 50-60°C, and then let the solution circulated for two to five hours using a pump.
The time needed to clean depends on the temperature of the cleaning solution or the degree of scaling. Observe the
changes in the color of cleaning solution to determine how long the cleaning solution needs to be circulated.
4) When done cleaning, drain the cleaning solution from the gas cooler, fill the gas cooler with 1-2% sodium hydrate (NaOH)
solution or with bicarbonic acid (NaHCO
cleaning solution.
5) When done, thoroughly rinse inside the gas cooler with clean water.
6) When using a commercially available cleaning solution, make sure that it is not corrosive to stainless steel or copper
beforehand.
7) For details of cleaning, consult the cleaning solution manufacturer.
1) pH (to be measured with a pH tester)
The graph at right shows the relationship between the elapsed
time from the beginning of cleaning and the changes in pH.
Cleaning solution will dissolve scale into the cleaning solution,
which will gradually raise the pH of the cleaning solution.
When the rise in pH begins to slow down (at 90 minutes in the
graph at right), add the cleaning solution so the pH will drop to
0.5.
If the pH rises after the solution is added, keep cleaning to
remove the remaining scale.
If there is no obvious rise in the pH, stop cleaning. Not much
more of scale can be removed.
2) Appearance of the cleaning solution
The cleaning solution is pale yellow at the beginning. When scale is dissolved into the solution, the color may turn to
brown or dark brown. This is normal.
3) Flow rate (to be measured with a water-pressure gauge)
Flow rate will increase as the scale is removed. (A rise in flow rate indicates scale is being removed.)
HWE1517A
Hot water
supply port
) solution, and let the solution circulate for 15 to 20 minutes to neutralize the
3
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Gas cooler inlet
P
2
1
Figure 3 Cleaning water circuit
4.5
4
3.5
3
2.5
0
30
60
Elapsed time (min)
P
3
4
90
120
150
180
GB