You just opened the boiler for inspection and you have scale and now the boiler inspector just recommended acid cleaning the boiler in order to keep your certificate. Now what?
This is becoming a more frequent common trend as insurance companies tend to protect their interest.
The first thing you must address prior to spending any money, is determine why the boiler scaled. These are general rules you should start with:
1) You should always use a softener system on your make-up water. Chemicals should be used with the softener. Chemicals are used as a polisher to remove the minimal calcium or otherwise referred to as hardness that has surpassed the softener. Realistically, a softener will never remove all hardness from your makeup water.
2) Perform daily hardness tests on the softener to ensure it is functioning properly.
3) Perform daily hardness tests to the boiler water. Remember a test is a snap shot of what is happening at that moment of time. There is a number of things that can go wrong causing the softener to malfunction between tests. Performing a test on the boiler water will provide a more general feed back on how the softener perform between tests.
4) If you do have periodic hardness spikes on your boiler water test. Have the softener serviced or replaced. If you have a critical boiler system consider using a dual softener system. The dual system with two softeners in series, where the first softener is automatically regenerated and the second tank is manually regenerated once a month.
5) Have one dedicated maintenance or engineer be fully responsible for boiler testing. Have back up personnel trained to support the leader. From experience, training 3, 5, or 10 or training the entire maintenance to perform testing will rarely work. One person needs to be responsible and held accountable for testing and reporting.
6) Crease log sheets and save your reports. Free templates are available online. The inspector will look for log sheets after seeing scale in the boiler in order to determine if anyone has been performing tests and if the boiler is being ignored.
7) The operator must give the log sheet to a supervisor or engineer for weekly review.
Acid cleaning is expensive if done correctly. Last month a scaled boiler was quoted $24,000 to acid clean a 200 hp boiler. Twenty four 55 gallon drums of sulfonic acid were required to effectively remove all the scale. The boiler inspector with 40 years experience demanded the boiler be acid cleaned to maintain the boiler certificate until the inspector seen the costs. This was a waste recovery boiler so the loss of efficiency was not as important. A more common boiler with 1/8″ scale would have increased energy costs by nearly 20%, so acid cleaning would have be justified.
Instead of acid cleaning the boiler, we proposed the following to the inspector and it was accepted as an alternative plan:
1) Implementation of an acidic polymer. An acidic polymer is used as a gradually way to slowly dissolved the scale. The acid polymer is fed 14 ppm per hardness part in the boiler. For example, if your boiler water has 10 ppm of hardness you should maintain 140 ppm of polymer, The acidic polymer is molybdate traced for ease of testing.
2) We implemented steps 1 through 7 above.