How to Use QEMIDESCAL 977 to Clean Your Boiler

Industrial Boilers
Are you looking for a boiler maintenance solution for your facility? In this blog, we will let you know why you should choose QEMIDESCAL 977 to do the job.


QEMIDESCAL 977 is used to safely and efficiently dissolve tough mineral deposits such as water scale, limescale, calcium, and rust from boilers, chillers, cooling towers, condensers, and heat exchangers.

Perfect for Boiler Maintenance

The efficiency of your facility’s operation depends on boiler maintenance. Over the period of its operation, any boiler accumulates mineral scales inside it. The boiler needs to be cleaned annually because the build-up of deposits may inhibit heat exchange, leading to the boiler’s loss of efficiency. 1/16” thick scale will cause the boiler to use 15% more fuel, 1/8” of scale requires 20% more fuel, and 1/4” of scale increases fuel consumption by 39%.

To prevent your boiler from having increased fuel consumption and reduced efficiency, you should choose QEMIDESCAL 977, which efficiently dissolves harmful deposits. While completing the job, QEMIDESCAL 977 wouldn’t harm the metallurgy or components within your boiler. QEMIDESCAL 977 is non-hazardous to personnel and is biodegradable.

Step-By-Step Guide

The standard QEMIDESCAL 977 cleaning procedure for most common boilers is as follows:

  1. Drain the boiler.
  2. Close the drain valve(s).
  3. Isolate the boiler for circulation by connecting your circulating pump discharge hose to the bottom blow down and connecting the return hose from the boiler to the relief valve on the top of the boiler.
  4. Pump in the recommended quantity of QEMIDESCAL 977 and make up the remaining volume with water until you achieve a return flow and can maintain a steady level in your circulation container.
  5. Circulate the QEMIDESCAL 977 solution for 4-6 hours. The circulation time and quantity will vary with the boiler capacity and the severity of the scaling.
  6. The circulating solution should be tested during the cleaning procedure for residual effectiveness. If the solution expends during the cleaning procedure, more QEMIDESCAL 977 will be required to complete the cleaning. The solution should still have residual effectiveness upon completion of the recommended circulation time.
  7. The boiler can now be drained, flushed thoroughly with water, refilled, and prepared for return to service. The boiler should be free of scale and ready to operate at peak efficiency.

How to Test Circulating Solution

The calcium carbonate spot test is performed by simply having a sample of the circulating solution come into contact with a form of calcium carbonate, which may be a sample of the deposit you are cleaning, a Tums® or Rolaids® tablet, or bare concrete. Observe the reaction of the QEMIDESCAL 977 solution on the calcium carbonate. If foaming and bubbling are observed, the solution is still active. If there is little or no reaction, the solution is expended.

This test should be performed near the end of the recommended circulating time. If, near the end of the recommended cleaning time, the solution has been expended, more QEMIDESCAL 977 will be required to complete the job. However, if the solution is still active at the end of the recommended time, all the scale has been dissolved within the application, and it is ready to be water flushed and returned to service.


At Qemi, our highly experienced staff, representatives, and distributors around the world are committed to helping you find the chemical solutions that deliver optimum value and performance for your specific application. Please contact us today if you have any questions about QEMIDESCAL 977.