In an earlier blog we explained the different fluid tests available and their relevance to identifying system problems, but what about the test results? It is necessary to understand all test results, as well as their meaning, to advise the operator on the appropriate system action.
All the tests are important and no single result is an indication of a single problem. Below we explore the typical problems your thermal fluid system may face and the possible symptoms associated with each one.
Hot expansion tank
The expansion tank on the system should remain below 50°C and maintain a constant head on the system. The expansion tank can become too hot when a vent line has been opened, a relief line is open or that there is simply not enough thermal buffer in the system.
Symptoms include high carbon levels, increased viscosity, increased TAN (Total Acid Number), whilst closed cup flashpoints remain high.
Overheating the fluid
This can happen when the set point has been raised close to the maximum operating temperature of the fluid.
Symptoms include decreased viscosity, low closed cup flash point, lowered open cup flash point and lowered fire point.
This is usually when some refractory has collapsed in the heater chamber, exposing the coil to excessive temperatures and resulting in the fluid hitting or exceeding maximum permissible film temperatures.
This can result in a very low closed cup flash point, rapidly decreased viscosity, reduced open cup flash point, reduced open cup fire point, increased acidity, but no increase in carbon level.
Water build-up within the thermal buffer
Due to condensation over time or a heat exchanger leak, a build-up of water can cause rapid degradation and shortened fluid life. Excessive water levels in the system can result in system problems such as pump cavitation.
Symptoms include increased viscosity, carbon level and TAN; high closed cup flash point, lowering open cup flash point and fire point and high Karl Fischer water content.
Referral to a qualified engineer is required to accurately analyse symptoms and causes.