BASIC OPERATION

A. FIXED RODDING DEVICES

This device is normally installed on the base of a reactor, mixer, tank or other vessel with an outlet valve of the straight type such as a ball valve or gate valve. These valves are often preferred due to the lower capital cost and lower maintenance costs compared to piston type or mushroom type flush valves.

The Blackfive Fixed Rodding Device is bolted directly to a Y" piece which in turn is bolted to a main valve fixed directly to the base of a vessel. When it is desired to discharge the contents of the vessel the main valve is opened and the rodding device is used to penetrate up through the ball valve and vessel spigot and well up into the vessel to clear any blockages which may have accumulated above the valve.

These devices are generally used for valves and lines above 2" NB in size with the 3" NB being a very popular size. The photograph below shows a typical assembly.

Operation of the Rodding Device is by slowly turning the handle and lifting to bore out any blockage, similar to the operation of a countersink in engineering. The bored out material drops down as the device penetrates upward. The shaft is highly polished and the gland is of the conventional mechanical type with facilities to adjust to avoid any possibility of leaks. The photograph on the next page shows the detailed shape of the boring head. B. PORTABLE RODDING DEVICES These are generally smaller than the fixed devices and can be transported from position to position to clear blockages all over a plant, mainly but not exclusively on lines of 2" NB or smaller. The principle is the same as for the fixed devices. Designed into the plant in suitable positions adjacent to where blockages may be encountered are valves fitted with male connector nipples and blank caps. To clear a blockage the blank cap is removed, the device is connected via the quick release cam type connectors, the valve is then opened and the Rodding Device is used safely to clear the blockage. When clear and flow has been re-established the rod is withdrawn and the valve carefully closed before disconnecting the portable Rodding Device and replacing the blank cap. Two Portable types are offered:- 1. Without side drain connection. 2. With side drain connection onto which would be fitted a secondary valve for the purposes of ensuring there was no residual pressure prior to disconnection or establishing a flow to drain to assist in the clearance of the blockage.