shovels. william s. otis, of the firm of carmichael, fairbanks and otis, when living in canton,...

SHOVELS

SHOVELSWilliam S. Otis, of the firm of Carmichael, Fairbanks and Otis, when living in Canton, Massachusetts in 1834 and 1835, while his firm was performing grading work for the Boston & Providence Railroad built the first steam excavator – a steam shovel.

OTIS SHOVEL

AN EARLY SHOVEL

SHOVELSFront shovels are used predominately for hard digging above track level and for loading haul units.

Loading of shot rock would be a typical application.

STEP 1: BUCKET SIZEShovels can usually be equipped with different size buckets. Bottom dump buckets are also available.

STEP 1: BUCKET SIZE

Buckets are rated in both heaped and struck capacities.Both PCSA and SAE use a 1:1 angle of repose for evaluating heaped bucket capacity. CECE specifies a 2:1 angle of repose. Heaped Capacity is the rating of interest for Production Estimating.

STEP 2: FILL FACTORThe Fill Factor adjusts Heaped Capacity in lcy based on the type of material being handled.

Table 9.1, page 258

STEP 2: FILL FACTOR

HEAPED BUCKET CAPACITY

FILL FACTOR

= VOLUME (lcy)

STEP 3: CYCLE TIME

There are four elements in the production cycle of a shovel:

1. Load bucket

2. Swing with load

3. Dump load

4. Return swingSee page 260

STEP 3: CYCLE TIME

Height of cut affects shovel production. Optimum height of cut ranges from 30 to 50% of maximum digging height, with the lower percentage being representative of easy-to-load materials, such as loam, sand, or gravel. Table 9.2

STEP 3: CYCLE TIME

Angle of swing affects shovel production. If the angle of swing is increased, the time for a cycle will be increased, whereas if the angle of swing is decreased, the time for a cycle will be decreased. Table 9.2

STEP 3: CYCLE TIME

Ideal production of a shovel is based on operating at a 90° swing and optimum height of cut. The effect of the angle of swing on the production of a shovel is illustrated in Table 9.2.

STEP 4: EFFICIENCY FACTOR

When selecting a minutes per hour efficiency factor visualize the work site and consider: • Materials being handled, bank or

broken

• Size of the shovels’s dumping target,

(large or small)

STEP 5: CLASS of MATERIAL

Production will be in lcy, will need swell factor to adjust to bcy. TABLE 4.3

STEP 6: PRODUCTION

Working mins / hr

Total cycle time (min)

X Heaped Capacity (lcy)

X Fill Factor

X height/swing factor

= Production (lcy/hr)

OTIS STEAM SHOVEL