How to Size a Jaw Crusher: PE and PEX Parameters and Capacity Matching

The jaw crusher is the first machine in a crushing line, and a mistake in sizing it affects every stage downstream — insufficient capacity, abnormal liner wear and idle equipment behind it. After 40 years serving aggregate and mining lines since the 1980s, the lesson at Grand Heavy is that the most common jaw crusher sizing error is not choosing too small, but sizing from the catalogue capacity. This guide gives a workable four-factor sizing method and a capacity derating approach.

图：大美智造破碎装备与耐磨件——颚破是生产线第一台设备，选型影响全线

I. The Four Sizing Factors

Factor 1: maximum feed size decides the feed opening

• Industry rule: the maximum feed size a jaw crusher accepts is roughly feed opening width times 0.8 to 0.85. Working backwards: feed opening width must be at least maximum feed size divided by 0.8;
• Example: if the largest lump on site is 800 mm, the feed opening should be at least 1000 mm;
• Why not 1.0: material needs room to fall and turn. If the largest lump is close to the opening width it will bridge and arch repeatedly, restricting feed, collapsing capacity and in bad cases blocking the machine;
• In practice: size on the largest lump that actually occurs, not on an average or design figure.

Factor 2: material hardness and abrasiveness decide derating and liner material

• Hardness affects capacity: the same jaw crusher may differ by 30 to 40 percent between granite and limestone duty;
• Abrasiveness affects liners: for strongly abrasive material (granite, basalt, iron ore) choose manganese steel or titanium carbide composite jaw plates and budget more for spares;
• Moisture and clay: jaw crushers handle wet, sticky material comparatively well because crushing is by compression, but the feeding stage can still block and needs attention.

Factor 3: required capacity decides the model size (the key step: derate)

• Key insight: the catalogue capacity is an ideal-duty figure — normally medium hardness material, even continuous feed, low moisture and a reasonable size distribution;
• Actual capacity = catalogue capacity times a derating factor, driven by four things: material hardness, feed size distribution, feed evenness and moisture;
• Reference derating ranges (for estimation only; confirm against your duty):

  Material	Reference Factor	Note
  Soft to medium, such as limestone	times 0.9 to 1.0	Close to catalogue
  Medium hardness	times 0.8 to 0.9	Slight derating
  Hard rock such as granite	times 0.6 to 0.8	Clear derating
  Strongly abrasive hard rock such as basalt	times 0.5 to 0.7	Largest derating

• Sizing rule: catalogue capacity times derating factor must be at least the required capacity. If it falls short, step up one model size.

Factor 4: product size decides the discharge range and whether a second stage is needed

• A jaw crusher reduction ratio is typically 4 to 6, so it is a primary crusher;
• If fine product is required, the jaw crusher handles primary crushing only and a second stage is essential (cone or impact crusher);
• Common mistake: closing the discharge setting tightly to produce fines and avoid buying a second machine — the result is collapsed capacity, faster liner wear and a higher unit cost.

Choosing between PE and PEX

One line to remember: PE for large lumps in primary crushing, PEX for finer output and higher reduction — do not use PEX as a primary crusher and do not expect PE to produce fines.

II. A Field Lesson: A Jaw Crusher Sized from the Catalogue Delivered Sixty Percent

A granite quarry built a new crushing line and sized the jaw crusher directly against the catalogue capacity to match the required output — on paper there was ample margin, even a little spare.

After commissioning the problem appeared: actual capacity was only about sixty percent of the catalogue figure. The whole line was throttled by the first stage, and the cone crusher and screens downstream were permanently underfed. The plant initially suspected the equipment.

Rather than discuss equipment first, we ran three checks:

• 1. Feed size distribution: on-site measurement showed the largest feed lump was close to 0.95 times the feed opening width, well outside the 0.8 to 0.85 safe band. Large lumps were bridging and arching repeatedly and feed was intermittent;
• 2. Material hardness: the line crushed granite, a hard rock, but sizing had been done against the catalogue figure quoted for medium hardness with no derating applied at all;
• 3. Feed method: material was tipped straight from trucks with no feeder. Feed came in surges and stops, so the crushing chamber ran full one moment and idle the next — during idle time there is no output while the liners keep wearing.

The root cause was clear: the equipment was fine, but sizing had ignored the real duty and the jaw crusher had never been given a proper feed.

Three corrective actions followed:

• 1. Control the top feed size: a grizzly or pre-screen was added upstream to keep the largest feed below 0.8 times the feed opening width;
• 2. Install a vibrating feeder: giving even, continuous and controllable feed so the chamber runs steadily full;
• 3. Re-baseline the capacity expectation and reset the discharge setting: a realistic target for granite duty, with the discharge setting at a sensible position rather than chasing the catalogue figure.

Capacity recovered to near expectation afterwards, and liner wear became noticeably more even because the chamber no longer ran idle.

The rule: size from the real duty with derating, never from the catalogue capacity; half of a jaw crusher capacity is decided by how it is fed.

图：选型现场给料粒度测量——进料口宽度须≥最大给料粒度÷0.8，按现场实际最大块度定

III. Jaw Crusher Sizing Reference Table (Save This)

Five questions to answer before sizing

Related reading: jaw crusher versus impact crusher, the jaw plate buying guide, jaw plate breakage causes, aggregate line configuration and titanium carbide composite versus manganese jaw plates.

IV. Insider Gotchas

• Sizing from catalogue capacity: the most frequent jaw crusher sizing error. Catalogue figures assume ideal duty, so hard rock must be derated or the line will underperform;
• Sizing the feed opening at 0.95 to 1.0 times the largest lump: it looks like full utilisation but causes bridging and restricted feed, so capacity falls rather than rises. The safe band is 0.8 to 0.85;
• Ignoring hardness derating: granite and limestone on the same model can differ by more than 30 percent. Sizing for soft rock and feeding hard rock will fall short;
• No feeder: tipping straight from trucks gives uneven feed and an idle chamber — capacity is lost while liners keep wearing, a double waste;
• Closing the discharge to make fines: with a reduction ratio of only 4 to 6 this collapses capacity and accelerates wear, raising unit cost;
• Mixing PE and PEX roles: using PEX as a primary crusher (small opening, prone to blocking) or expecting fines from PE are both misapplications;
• No margin on motor power: on hard rock a minimum-rating motor can stall, start badly or overheat, and retrofitting later costs more.

V. When a Jaw Crusher Is Not the Right Choice

• Soft material and a strict product shape requirement: an impact crusher gives cubical product and suits high grade aggregates better;
• Single-pass reduction to simplify the flowsheet: for medium hard material such as limestone a hammer crusher can do it in one pass and remove the second stage;
• Secondary or tertiary crushing of medium hard and harder rock: a cone crusher uses interparticle compression for better efficiency and shape;
• Very fine product such as manufactured sand: a jaw crusher cannot deliver it; that belongs to a second or third stage or a sand making machine;
• Frequent relocation: choose a mobile jaw crushing plant instead of a stationary unit with foundations.

Three actions: 1. Set the feed opening from the largest lump actually seen (divided by 0.8); 2. Check capacity with a hardness derating factor rather than the catalogue figure; 3. Give the jaw crusher a feeder so the chamber runs steadily full.

FAQ

• Q: How do we determine the maximum feed size for a jaw crusher? A: Work from feed opening width at least maximum feed size divided by 0.8 (safe band 0.8 to 0.85). Use the largest lump actually seen on site, not a design or average figure. Sizing at 0.95 to 1.0 causes bridging and restricted feed.
• Q: Why did a jaw crusher sized from the catalogue fail to reach capacity? A: Because catalogue capacity is an ideal-duty figure (medium hardness, even feed, low moisture). Actual capacity equals catalogue capacity times a derating factor, which on hard rock can be only 0.6 to 0.8. The correct approach is to derate and still meet the requirement, otherwise step up a model size.
• Q: How do we choose between PE and PEX? A: PE is for primary crushing (deep chamber, large opening and discharge) as the first stage handling large rock; PEX is for fine crushing (shallow chamber, higher reduction ratio) as a second stage on small to medium lines. Do not use PEX as a primary crusher.
• Q: Can we close the discharge setting to get finer product? A: Not advisable. A jaw crusher reduction ratio is only about 4 to 6, so it is a primary machine. Closing the setting sharply collapses capacity and accelerates liner wear, raising unit cost. If fines are needed, add a second stage (cone or impact crusher).
• Q: Is a feeder really necessary? A: Strongly recommended. Tipping directly from trucks means the chamber runs full one moment and idle the next — during idle time there is no output while liners keep wearing. A feeder keeps the chamber steadily full and is the highest value option on the list.
• Q: What jaw plate material suits hard rock? A: For strongly abrasive material (granite, basalt, iron ore) choose manganese steel or titanium carbide composite jaw plates. Composite plates last clearly longer in high abrasion duty, but the choice should be checked against a cost-per-tonne calculation. See titanium carbide composite versus manganese jaw plates.
• Q: Can Grand Heavy supply complete machines and line solutions? A: Yes. Grand Heavy supplies crushing, grinding and screening machines as well as complete solutions covering line configuration, equipment sizing and wear part matching, with sizing calculations for your duty. See also aggregate line configuration.

VI. Final Verdict

Jaw crusher sizing comes down to one phrase: size from the real duty with derating, never from the catalogue capacity. Three disciplines: 1. feed opening width at least maximum feed size divided by 0.8; 2. capacity checked with a hardness derating factor (hard rock times 0.6 to 0.8); 3. a feeder is essential so the chamber runs steadily full. The jaw crusher is the first machine in the line, and if it is sized wrongly everything downstream suffers. Foshan Grand Heavy Trading Co., Ltd. has built mining equipment and wear casting expertise for 40+ years, holds 20+ patents, partners with Central South University and Guangdong University of Technology, and is certified as a National High-Tech Enterprise [To be added: certificate number]. We serve CNBM, Conch Cement and clients across 6 overseas markets with 24-hour response from Guangzhou, Foshan and Changsha. Send us your material, largest lump size and capacity requirement and we will run a sizing calculation.

Grand Heavy — Size from the real duty with derating, never from the catalogue!