Draft gauge

Modem electronic replacements for the Orsat apparatus include equipment manufactured in the United States by Bacharach, Inc. (www.bacharach-inc.com). This company produces handheld and boxed instruments that can be employed as comprehensive combustion and environmental analyzers, gas burner combustion testers, single gas analyzers, draft gauges, smoke test sets, sling psychrometers, and the like. 

Even when a hood has an integral fan with guaranteed performance, the installer will check the face velocity. For some types of work, laws may require minimum velocities. A highly visible draft gauge should be installed on a hood to inform personnel about its operation. This is especially important where remote or very quiet fans are used. 

DRAFT GAUGE - Instrument used to measure air movement by measuring air pressure differences. 

Reducing air in-leakage in the convective section may correct this problem. Perhaps the convective tube bank is partially plugged on the flue-gas side. A pressure survey with a draft gauge is the first step in identifying the restriction that limits draft. Occasionally, the size of the secondary air registers can be increased. 

Slowly open the stack damper until the draft gauge indicates a small negative pressure (-0.1 in. H2O) at the convective section inlet. 

On one 50,000-B/D crude unit, steps were taken to eliminate air leakage through the furnace skin fuel use subsequently dropped by 6%. To correct excessive draft, one should slowly pinch back on the stack damper until the draft gauge indicates a small negative pressure and open the secondary air registers until the excess air target is reached. 

Draft gauge plugged CO2 in flue gas Fouled convective section Leaks in furnace skin Stuck stack damper Damage to furnace structure Smoke leaks out of convective section... 

Furnace-draft gauge readings can pinpoint restrictions to flow on the flue-gas side of the convective section. Excessive draft at the inlet to the convective section causes cold air to be sucked in and wastes energy (see Chapter 15). 

The damper, which is used to control the draft in the ftirnace, is located in the stack. Adjusting the damper controls the pressure balance within the furnace. The stack height is determined by the draft requirements of the furnace but may be adjusted, Draft gauges are used to check pressure levels. 

Draft gauge This instrument is used to check pressure in a furnace. 

A reformer furnace, shown in Exhibit 7-25, has a penthouse and roof-mounted burners. In addition to platforms and a stairway for regular maintenance and operation, ladders are provided in case of an emergency. Other platforms are for access to peep doors, draft gauges, and piping, as required. 

C, recording pressure gauge i>, indicating pressure gauge E, rate-of-flow controller F, pressure regulator ( , draft gauge H, hand-control valve safety valve ilf, liquid-level control. 

This form of manometer is useful for gas pressures, as for draft gauges. The graduation intervals are commonly 0.01 in of water (0.25 mm of water) with spans up to about 10 in (25 cm). 

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