Crude oil is normally stored in tanks, from where it is passed through Columns like Crude Distillation Unit (CDU) and Vacuum Distillation Unit (VDU), Fluid Catalytic Cracking Unit (FCCU), Hydrotreater Catalytic Reforming Unit (HCU) to get end result.
During maintenance in columns,welding, fabrication,riveting job, strip lining, nozzle replacement, trays replacement are carried out, as a result the air inside the column is unhealthy with lot of toxic gases/ fumes and lack of oxygen.
The temperature inside the column because of all the welding work and presence of large number of people(nearly 100-200 at a time) also increases to high levels approximately (48º - 50ºC) with high RH.
Inside the column oxygen level in the air decreases and due to presence of toxic fumes workers cannot work for a long time. They take frequent breaks to go out of the column after small intervals of work .Thus the efficiency of the worker gets affected resulting in delay for completion of job.
Toxic gases can be injurious to the health of workers, engineers & inspection team etc. (can be fatal too).
Productivity of the workers goes down.
Quality of the work inside the column is severely affected resulting in frequent breakdown and more shutdowns are required.
Shutdown period gets extended resulting in huge loss to the refinery (Refinery will loose Crores for single day extension).
Further during night normally condensation takes place resulting in weak and poor welding. Also untreated air during humid months (or in coastal areas) leads to condensation inside the vessel.
Moreover the time frame for the shutdown of these columns is very limited. Hence worker comfort and maintaining the right RH is necessary to reduce any corrosion possibilities as well as removal of moisture inside the column.
The humidity and the temperature inside tanks & columns should be maintained at below 60% RH and temperature between 30ºC - 35ºC.
Presence of moisture between substrate and the paint coat is the reason of occurrence of corrosion. This results in coating and paint failure. To increase the life of coating moisture level needs to be controlled inside the vessel. TDS provides desiccant based dehumidifiers along with other accessories and technical manpower to provide the desired humidity level.
To overcome the high temperature level and affects of toxic gases TDS provides condensing units. The package of condensing units and blowers maintains the temperature between 30ºC ~ 35ºC and also purifies the air by extracting impurities and providing fresh air.