During the years we have spent in the Water Treatment business, it has become apparent that many cases of "apparently" dirty boiler come from poor shutdown techniques - not inadequate treatment.

During normal operations, the boiler water chemistry is carefully controlled so that the dissolved/suspended material is conditioned to prevent hard deposits on boiler metal. These dissolved/suspended solids are maintained in suspension by water circulation and the action of the treatment chemicals. When a boiler is shut down or drained, this material (sludge) may settle and bake on tube surfaces; it may become so adherent that mechanical (turbining) chemical cleaning may be required. At worst, there are large piles of sludge in the mud drum and in the lower tube ends which cause the customer and/or boiler inspector to feel that the deposits developed during operation, and thus unjustly criticize the treatment program. Outlined below is a procedure that if followed will minimize the total amount of sludge left behind when a boiler is opened.

Shut-down Procedure

1. Three to five days before a scheduled shut down, increase the blow down by 50%.

• If possible, increase the alkalinity to at least 500 ppm. Go as high as possible without causing foaming or carryover.

• Due to the increased blowdown rate, the feed rate of the scale inhibitor and oxygen scavenger must be increased so as to maintain the normal boiler water residuals.

• If possible, increase the sludge conditioner level in the boiler water by 50 to 100%.

2. During the last twenty-four hours before shut down, decrease the continuous blowdown and increase the manual blowdown.

• Frequent short bottom blows are better than fewer longer blows.

• Generally it is sufficient to hold each mud drum blowdown valve open for about 5-10 seconds every one to two hours.

• Once the load is dropped from the boiler, include the header blowdowns as part of the manual blowdown procedure.

3. When the load is dropped from the boiler, continue bottom blowdowns until boiler is cool and safe to work on.

4. As soon as possible after the boiler is opened, wash down the boiler watersides, preferably with soft water.