This paper discusses batching and buffering practices in the Heating, Ventilating, and Air- Conditioning (HVAC) industry based on a literature review and an on-going investigation of mechanical contractors in charge of designing, fabricating, and installing made-to-order ductwork systems. Batching practices affect or create buffers in production systems whether intentional or not. Buffers in production systems may be characterized by location, size, product mix, criticality, etc. Here, the focus is specifically on the location of buffers that result from batching and buffering practices in the production system for duct fabrication and installation. These practices are influenced by organizational issues, production capabilities, labor union regulations, product characteristics, ‘received traditions,’ and local optimization objectives. They are also influenced by the difficulty of forecasting the available capacity and production demand in terms of labor-hours and product mix. A rule of thumb for contractors that perform work in the ceiling space of a building, as is needed for HVAC duct, is “the first one to get in wins.” Therefore, these contractors have to be agile in turning out parts to the construction site in order to avoid major changes in their design, fabrication of parts, or installation sequencing. All these characteristics and influences interact in a dynamic way and thereby contribute to the batching and buffering practices that have become custom and accepted. While these practices may meet local optimization criteria, they also embed a lot of waste in the production system at large. The purpose of this paper is to elucidate current practices so as to promote understanding of the system’s characteristics and development of metrics to optimize system performance at a more global level.
Buffer, batch, inventory, sheet metal, duct work, HVAC system, specialty contracting, mechanical contractor.