The improvements include a new central plant building, new chillers, a chilled water storage tank, cooling towers, pumps, air handlers, ducting, and a plant control system. The project gives the firm improved comfort and control, while increasing total system efficiency and economy.
Halliburton provides services and equipment to energy, industrial, and governmental customers. The company operates in two business segments — its Energy Services Group and an Engineering and Construction Group. The Carrollton campus houses major U.S. units of the Energy Services Group, providing a range of services and products to customers for the exploration, development, and production of oil and gas. It serves independent, integrated, and national oil companies.
The Carrollton facility includes 10 buildings ranging in age from 40-plus years to just a few years old. Halliburton’s Real Estate Services group commissioned the Dallas office of a national consulting engineer, Carter & Burgess, to make recommendations for improved chilled water service for the Carrollton campus, along with several other Halliburton sites. The existing chilled water system had developed as the corporate campus had grown since the late 1950s. The plant consisted of five electric centrifugal chillers in three different locations, in sizes from 400 to 700 tons and ranging in age from 12 to 30-plus years.
Problems With The Existing Plant
According to Halliburton facilities engineer Ted Huntington, the existing plant had significant shortcomings. “Over the years we had made efforts to marry the different systems, but that hadn’t really worked very well,” he said. “The systems hadn’t been engineered to work together.” Huntington indicated that there was insufficient system capacity to meet the needs of the growing Carrollton operation.Further, Huntington noted that the immediate impetus for the engineering review was the imminent need to replace two of the older centrifugal chillers. “We felt it was time to take a comprehensive look at the entire system. There were some manufacturing areas that we really wanted to upgrade with cooling services, but we just didn’t have the capacity.”
One of the options that Carter & Burgess was asked to consider was thermal storage to allow Halliburton to avoid heavy electric demand charges and have more capacity for peak summer periods. According to Huntington, this option had been under consideration internally for several years, but the project had been “put on the back burner” because of more pressing needs. With the encouragement of the local power supplier, TXU Utilities, Halliburton decided to take another look at this option.
Project Overview
Working closely with Huntington and Carrollton site energy manager Gene Ballew, Carter & Burgess came up with a comprehensive proposal for an upgrade of the entire comfort system. The recommendation was taken to Halliburton management and approved in its entirety. The project was designed in three stages.The first stage was to develop a dedicated central chilled water plant building to meet the complete chilled water requirement of the campus. TDIndustries of Dallas installed the new central plant building and its related equipment. The plan called for three equal-sized large new chillers. These were to be sized so that any two of them could carry the complete system load.
As part of this phase, the central plant would be equipped with a 1 million-gallon chilled water storage tank to allow the plant to meet a large portion of the daily chiller water requirement with off-peak chiller operation. The storage tank was designed and installed by PDM, a division of Chicago Bridge & Iron, from Houston. Another part of the first phase was a plan to equip the chilled water system with a sophisticated control system to optimize the energy efficiency of the entire operation. The system selected was a Trane Tracer Summit™ chiller plant management system.
Low-Temperature Thermal Storage
A key part of the recommendation from the engineer was to design a primary-secondary chilled water loop system that operated at temperatures much lower than the original plant. Further, the flow rates of condenser water to the cooling tower were designed to be far less than the conventional rate of 3 gallons per ton. This approach — called EarthWise™ design — was designed to reduce the size of necessary system components including chillers, pumps, piping, cooling towers, and terminal equipment. System operating costs can be reduced through the reduction of pumping and tower fan requirements.Because the chilled water is circulated at lower temperatures, the dehumidification function is improved, according to the company. In the case of a storage system such as that at Carrollton, the lower chilled water temperature means greater thermal storage capacity in the same-sized vessel. Where the chilled water previously was circulated at 48 degrees F (9 degrees C) or higher, with the new system the water from storage is 40 degrees F (4 degrees C) or lower.
The three chillers selected for the new plant are Trane CenTraVac™ electric centrifugal machines, Model CVHF, rated at 1,000 tons each. The chillers operate on a 480-VAC service through the site substation. These two-stage machines have the capability to deliver water to the primary/secondary heat exchanger at 37 degrees F (3 degrees C). The chiller plant is designed to allow the future addition of another chiller if needed to meet growing site loads. At the current time, two of the chillers can carry the entire load on a 105 degrees F (41 degrees C) design day.
Normally, the chillers provide chilled water service to the storage tank, which is located adjacent to the plant building. Typically, the chilled water tank can carry the entire cooling load through the noon to 8 p.m. summer peak demand period.
The entire chiller plant operation is controlled by a Trane Tracer Summit chiller plant management system. The chiller plant control system was designed to interface with an older existing control system.
Ballew has been pleased with the ability of the Summit system to provide concise information on system status and thermal storage resources.
This first phase of the project also included installation of a new Marley three-bay cooling tower on an elevated platform adjacent to the chiller plant. The new tower is a high-efficiency design with variable-speed fans.
Also included in this phase was installation of variable-speed pumps on the secondary chilled water loop and on the condenser water loop.
Chilled Water Service
In the second phase, the site’s C-1 Manufacturing Building was converted from a DX cooling application to chilled water. The building is a manufacturing facility and previously had been cooled with rooftop units over 25 years of age. The upgrade included installation of air handlers and a ducted distribution system.The air handlers selected were Trane Modular Climate Changer™ units, typically in the No. 80 size. According to Huntington, standardization of air handlers on a single type and size was emphasized to simplify service and to reduce the number of belts, filters, and other parts to be held in stock.
In a third project phase, older air handlers in the C Building were replaced with new Climate Changer units sized for the lower temperature chilled water now being delivered. Because of the lower water temperature, these could be reduced in size by 20%, reducing both investment and operating costs. According to Huntington, the 47 degrees F (8 degrees C) air from the high ceiling diffusers mixes as it tumbles down to floor level and provides a very comfortable work environment.
A special beneficiary of this project is a tool calibration laboratory where climate control is especially important and where holding stable temperatures had previously been a problem.
In a final project phase, which has not yet been completed, Halliburton plans to change out about half of the air handlers in another building, again to take advantage of the lower temperature chilled water now being delivered.
Halliburton says the objectives of more reliable chilled water service, lower operating costs, and better system control have all been met. As additional areas are equipped with equipment that uses low-temperature chilled water, the system benefits become even more dramatic.
Huntington said, “Now we are in a position to exploit the advantage of the lower temperature water from those new chillers.” As a result of a phased system upgrade, the site has evolved from a mixture of partially interconnected older systems to an optimized network served from an efficient central plant.
Publication date: 01/27/2003
