A contingency plan should incorporate a number of elements, including:
Expected lead time for delivery, setup and operation. You must do more than merely ascertain that certain equipment can be available at a certain time. After all, just having the equipment on-site does not solve the problem. You need to verify how long it will take to deliver, connect, set up and begin operating the equipment. Some vendors can provide turnkey service; others cannot.
A company that can provide a turnkey service will simplify the process. The chosen emergency provider should be one that keeps all required workers' safety training up to date. If safety training is not kept current, it is likely that at least one additional day of downtime will occur.
Piping. What size piping and how many piping connections are required for the temporary solution? The appropriate valves and flanges should be put in place before the emergency, not after.
Drawings.The drawings should include, at the very least, a plot plan showing the location of all the temporary equipment, including cooling towers, pumps, piping, electrical distribution, transformers, generators and accessories.
Power requirements. The contingency plan should outline power requirements, voltage requirements, power supply source(s), generator requirements and related details.
Equipment availability. Any company providing temporary towers has a limit to its fleet size and might not be able to fulfill a contingency plan at the time of need. Make sure the company you select to be your emergency provider will have enough equipment to support your requirements and/or select an alternate supplier. Check equipment availability periodically, especially in the summer.
Electrical distribution. The plant must spell out how many load centers and how much cable will be required, what electrical classifications must be met and similar details.
Pumps. Will pumps be required? If so, what flow rate and head pressures are needed? Can the same supplier take care of the pumps?
Make-up water. How much make-up water will be needed and what will be its source?
If the contingency is such that a cooling tower constructor will be repairing or rebuilding the permanent cooling tower, special attention should be paid to the placement of the temporary equipment. If access to the primary tower is too restricted, the repair or rebuild could take longer and increase rental and construction costs.
Working with the supplier
Temporary cooling towers can be rented for a period ranging from one day to multiple years. Most suppliers of temporary cooling towers offer significant price reductions based on the length of time the equipment is needed. Rates are usually based on daily, weekly, monthly, four-month, six-month and one-year pricing, so plant operators must communicate the expected duration of use when asking for quotes. Pricing also is dependent on the size of the project and the time of year, as well as the thermal duty, pipe quantity, pump sizes, power source distance and the supplier.
The average space required is approximately 100 square feet per 1,000 gpm. Many designs require minimum distances between each temporary unit to allow proper air inlet; others are more modular and do not. Some units have elevated water basins that allow much of the piping and pumps to be placed underneath the towers to reduce space requirements. CP
Carpenter is a business development manager with Aggreko Process Services, Houston. He has several years of experience in process design, optimization and operations and maintenance in the gas processing, refining and petrochemical industries. Contact him at firstname.lastname@example.org. Childers is manager of Aggreko Cooling Tower Services and has 14 years of experience in cooling tower design, manufacture, construction/installation and project management. He can be contacted at email@example.com.