Keep the Fire Where it Belongs: Inside the Firetube

Introduction

In the upstream sector of the oil refining process, treaters and separators use firetube heaters to heat production fluid, assist emulsion separation, and keep a process fluid warm and flowing regardless of the ambient temperature (see Figure 1). These vessels, commonly referred to as “heater treaters,” are typically low pressure equipment and are often overlooked with a “set it and forget it” approach.

Firetube heater operation seems simple: burners create heat inside the firetube to keep a fluid, such as oil emulsion, warm on the outside. However, firetubes can be in highly variable service because the duty cycle is often demand-driven, and the demand could be affected by low or high production rates. Alternatively, ambient temperatures can greatly impact demand in environments where there are large temperature swings. For example, in western Canada the ambient temperatures can range from -40°F [-40°C] in winter to +104°F [40°C] in the summer.

Firetubes can fail unpredictably and require repairs and/or replacement. The risk can be as low as a recurring nuisance but can also result in serious incidents such as fires and fatalities. This article explores a few ways that firetubes can fail, including heat-related, cracking-related, and corrosion-related, and practical considerations to prevent problems.