What type of oil is recommended for lubricating three piece low head circulators during service?

The recommended type of oil for lubricating three-piece low head circulators during service is non-detergent (paraffin-based) lightweight oil. This type of oil is specifically formulated to provide the necessary lubrication without the inclusion of detergents, which can lead to excessive foaming and may not provide the proper protection needed for the mechanical components of the circulator.

Non-detergent oils are less likely to cause corrosion and are designed to perform optimally in mechanical applications where specific resistance to oxidation and breakdown is important. Additionally, they maintain their viscosity and lubricity under varying temperature conditions, which is crucial for the reliable operation of circulators.

The other options are less suitable for this application due to various reasons. Detergent-based oils can interfere with the precision workings of the equipment, potentially leading to reduced efficiency and lifespan. Vegetable oils may be too thick or unstable for mechanical lubrication, compromising performance. Heavy-duty grease, while effective in some applications, can be too viscous for circulators and may not adequately flow to provide the necessary lubrication throughout the components. Therefore, non-detergent (paraffin-based) lightweight oil is the preferred choice for this context.