Seawater is used as a cooling agent in condensers and coolers. Intermittent injection of chlorine gas is used to eliminate marine growth. The system is a once through type. The band screens before the suction of the pumps are supposed to eliminate scales and other suspended materials. The band screens are not properly functioning. Cooling water flow is about 2.6 million gallons per hour.
The prescreening and mobile screens are not a sufficient protection for the recirculating water. This is a very common problem. In clean salt water the biological grow in the cooling water pipes is the main problem (mussels, barnacle, algae, etc.). After the life cycle is finished they die and blocking the condenser tubes. To solve this debris problems use self-cleaning Debris Filters (DF) directly installed in front of the waterbox of the heat exchangers.
12. What are some guidelines for designing for liquid and gas velocities in process plant piping?
For normal process plant design liquid pump discharges, look for velocities in the range 5-7 ft/sec. probably not a bad idea to keep design vapor velocities below 125 ft/sec. These guidelines might be applied by an engineering company for design. If you are looking at plant operation, it is common to find velocities in the 9-12 ft/sec range. Erosion problems can also complicate the answer to this question. Erosion is highly dependent on the nature of the fluid. For example, 98% H2SO4 is not corrosive to carbon steel pipe, however it very erosive at “normal design” velocities. Design criteria for 98% H2SO4 might be 0.70 ft/sec MAXIMUM. However, it is also well known that if the same 98% H2SO4 has a little emulsified hydrocarbon, it is substantially less erosive.