Regarding hammer crushers (impact crushers with swinging hammers), which statement is correct about rotor orientation and design variants used in industry?

Introduction / Context:
Hammer crushers employ high-speed hammers to break material by impact. There are several configurations used in aggregates, cement, and coal industries. Knowing design variants helps align equipment to duty and material characteristics.

Given Data / Assumptions:

• Industry employs both horizontal-shaft and vertical-shaft impactors (HSI and VSI).
• Hammer mills are sensitive to abrasiveness.
• Top size and product size vary with design and grate settings.

Concept / Approach:
HSI/hammer mills have horizontal rotors; vertical-shaft impactors exist as well. Thus, rotors may be vertical or horizontal. The other statements are too rigid: extremely abrasive feeds cause rapid wear; product size is not a fixed 3 mm; and allowable feed size depends on model (often larger than 50 mm).

Step-by-Step Solution:
List common hammer/impactor orientations in plants.Compare to the given statements about wear, product size, and feed size.Select the orientation statement as correct.

Verification / Alternative check:
Manufacturer literature lists both vertical and horizontal rotor designs, confirming the general statement.

Why Other Options Are Wrong:
Highly abrasive feed: causes severe wear.Fixed 3 mm product: size depends on grate and operating speed.Exact 50 mm limit: not universal; many designs take larger feeds.

Common Pitfalls:
Assuming one universal rotor orientation or single-spec performance limits for all models.

Final Answer:
Rotor shaft carrying hammers can be vertical or horizontal