The purpose of flushing and cleaning lines is to remove loose foreign materials such as dirt, grease, oxide scale, weld deposits, sand and any temporary protective coating, which could cause operational disturbances for the relevant process or service class.
Preparation for flushing
Flushing shall be carried out for piping system specified in Project Procedure. The exception shall be approved by COMPANY. Piping erection and QC inspection is required to be completed and accepted by COMPANY prior to flushing.
Following inline items that can be damaged by dirt, loose scale and debris or items that may trap debris, compromising the effectiveness of flushing shall be removed prior to start of flushing operations. All static and rotating equipment and instrumentation shall be isolated from piping before flushing. Certificate to be provided and quality re-checked every three month.
① Temperature Control valves, Pressure Control valves, Flow Control valves
② Positive displacement meters
③ Turbine meters, Rotameters
④ Fire water spray nozzle
⑤ Pressure Relieving Devices(Rupture discs, Relief valves)
⑥ Orifice plates
⑦ Venturi tubes
⑧ Flame Arrestors
⑨ Check Valve Disc
⑩ Filters(Temporary suction strainer)
⑪ Safety valves(PSV , ESV and etc), Pressure transmitters
⑫ 3-way Valves, Actuated/motorized valves(XV, SDV and etc.), Soft seated valves
An index of all removed items is specified in Project Procedure.
Butterfly valve doesn't need to be removed during flushing operations, however, if any pipe internal impurity or any items found, during line inspection or flushing, COMPANY and QM may request to remove the butterfly valves case by case.
Ball valves shall be in fully open position (or with flappers removed) prior to flushing. In preparation for the flushing activity, ball valves shall be opened during installation of the valve and secured (tied) in the open position, to avoid accidental closure of the valve before flushing.
In case some items are removed for flushing and/or pressure testing, COMPANY may decide to install dummy spools or flexible hose instead. In case dummy spools and flexible hose are used for pressure testing, they shall be suitably pressure rated.
Dumping may be utilized as flushing for the lines which are downward with open end to the sea. Dumping method may be used according to the line arrangements and flushing situations.Min. flushing velocity does not applied by dumping. Dumping method to be approved by COMPANY relevant engineer depending of the line length and route. Quality of water shall be checked and accepted DSME QM and COMPANY representative.