Boiler Water Tannin for Heritage Steam engines
From the heavily used chartered steam train to the traction engine that only see service at a number of heritage fairs a year, all types of steam locomotive should receive water treatment of some kind. For many this is Tannin and Soda ash and maybe even a polymer sludge conditioner.
The Benefits of these chemicals to steam boilers are as follows:
Tannin has proven itself to be highly effective against oxygen corrosion due to its nature as an oxygen scavenger, by removing the oxygen from the boiler. Due to this, feed tank corrosion cannot set in prolonging the life of the boiler substantially. Additionally Tannin will form a thin corrosion resistant tannate film across the boiler surface. Even when the boiler is not in service and has cooled down, the dosing of Tannin is still a good idea as its effectiveness is not influenced by temperature.
Soda ash or Caustic is also a recommended addition to the treatment of steam engines as this prevents scale by increasing the natural pH of the water from its neutral figure of 7 up to 10.5 or higher. The reason for doing this is to produce different salts from the calcium and magnesium found in the feedwater, caustic chemicals react with the compounds in the water producing salts which form silt instead of dropping out of the boiler water to become scale and baking onto the boilers metal surfaces making the boiler less efficient and even causing damage.
The use of a polymer sludge conditioner can be beneficial due to its ability to keep suspended solids in solutions as over time the concentration of the boiler water with salts and other matter that has been introduced by the incoming water supply can increase, as long as this increases the risks of scale are also increasing. By keeping these suspended solids in solution they can be clumped together and easily removed by blowdown effectively controlling the problem.
Polytan 4F and 4C are products manufactured by Feedwater Limited, these tannin based boiler water treatment chemicals contain a mixture of tannin, alkalinity builder and polymer sludge conditioners eliminating the need to dose several chemicals. For boilers containing Copper, Polytan 4F is recommended as this helps prevent corrosive attack. Polytan is also beneficial compared to other popular steam heritage marketed tannin products because it is highly concentrated containing 4 times the amount of tannin because it has not been watered down due to the fact it is the very same product we use for large industrial boilers on sites across the UK. We do not believe the product should be any different just because it will be used in smaller quantities which is why we also believe our product offers substantial cost savings over other products available to the heritage steam market.
Should be added to the system at an initial dosage rate of 1 litre/ 1000 litres of system water content whenever the system is drained or loses a significant quantity of water then the additional Polytan 4F is typically added at the rate of 100-200ml / 1000 litres of boiler feedwater.
Should be dosed initially at 1:1000, based on the system volume. The ongoing dosages should be made to maintain a tannin reserve of 12-20, and the appropriate pH and alkalinity residuals.
Analysis of your Tannin levels can be performed using our Tannin Titration Reagent Pack