A spring is a flexible machine element that deforms under an applied force, returns to its original shape when the force is removed, and can store energy. Springs perform many tasks, such as damping vibration, applying force, cushioning impact, holding parts in position and providing protection under overload. In crushing and screening equipment they are used in critical applications such as jaw crusher tension springs, cone crusher safety springs, vibrating screen suspension springs and impact crusher apron springs.
In this guide we take a comprehensive look at spring types and their properties, spring materials, spring rate and selection criteria, spring failures and spring applications on mining equipment.
Spring Types
| Spring Type | How It Works | Typical Use |
|---|---|---|
| Helical compression spring | Applies force when compressed | Screen suspension, crusher tension and safety systems, valves |
| Helical extension spring | Pulls back when stretched; hooks at the ends | Return mechanisms |
| Torsion spring | Works against a turning moment | Covers, latches, hinges |
| Disc spring (Belleville washer) | Conical disc; small footprint, high force | Maintaining bolt preload, brakes, heavily loaded compact applications |
| Leaf spring | Stacked leaf plates | Vehicle suspensions |
| Conical spring | Coil diameter varies | Where short length and progressive stiffness are needed |
| Wave spring | Wavy flat wire; short length | Bearing preload |
| Rubber springs and buffers | Elastomer; high damping | Screen suspension, motor mounts |
| Air spring (air bag) | Works with compressed air | Some screen and vehicle suspensions |
Basic Spring Properties
- Spring rate (spring constant, k): The force the spring produces per unit of deflection (N/mm). A stiff spring has a high rate.
- Wire diameter (d): The larger it is, the stiffer the spring.
- Mean coil diameter (D): The larger it is, the softer the spring.
- Number of active coils (n): The more coils, the softer the spring.
- Free length and solid length: The unloaded length and the fully compressed length.
- End type: Closed and ground ends let compression springs seat squarely.
The rate of a helical compression spring is roughly proportional to the fourth power of the wire diameter and inversely proportional to the cube of the coil diameter and to the number of active coils. A small change in wire diameter therefore changes spring stiffness greatly. This is why stating these dimensions exactly matters when ordering replacement springs.
Spring Materials
| Material | Property |
|---|---|
| High-carbon spring steels | Economical, general purpose |
| Alloy spring steels (Cr-V, Si-Cr, etc.) | High strength and fatigue resistance; heavy duty |
| Stainless spring steels | Corrosion resistance |
| Rubber and polyurethane | High damping, quiet running |
For heavy-duty springs, heat treatment, shot peening and corrosion protection (paint, coating) significantly increase fatigue life.
Springs on Crushing and Screening Equipment
Jaw Crusher Tension Springs
In jaw crushers, tension rods and springs pull the lower end of the pitman towards the toggle plate, keeping the parts in constant contact. If a spring breaks, the toggle plate can come out of its seat, causing knocking and damage. Tension spring preload must be kept at the manufacturer’s value. For details see our tension rods and springs guide.
Cone Crusher Safety Springs
Some cone crusher designs (especially spring cone crushers) have many heavy springs holding the upper frame down on the lower frame. When uncrushable material enters, the springs compress, letting the upper frame lift and the object pass. A broken or fatigued spring makes the setting unstable and lets the frame move. For hydraulic protection systems see our hydraulic cylinders guide.
Impact Crusher Apron Springs
In impact crushers, the aprons are held in position by spring packs and retract when uncrushable material arrives. If spring preload is low the apron vibrates; if it is too high the protective function is weakened. For details see our apron adjustment system guide.
Vibrating Screen Springs
Vibrating screens sit on the support frame on helical steel springs or rubber buffers. The springs let the screen vibrate freely while reducing the vibration transmitted to the frame and building. A broken spring makes the screen run askew and irregularly, causing side plate cracks and bearing problems. Screen springs should be replaced as a set. For details see our vibrating screen spare parts guide.
Vibrating Feeders and Roll Crushers
Vibrating feeders also run on springs; in roll crushers, spring packs maintain the roll gap and provide protection (roll crusher guide).
Spring Failures and Their Causes
| Failure | Possible Cause | Prevention |
|---|---|---|
| Fatigue fracture | Variable load, surface damage, corrosion | Suitable material, shot peening, coating |
| Set (loss of length) | Overstressing, high temperature | Correct spring selection, preload control |
| Corrosion | Moisture, water, chemicals | Protective coating, stainless material |
| Buckling | Long, slender compression springs | Guide rod or sleeve |
| End damage | Ends not seating squarely | Ground ends, correct spring seat |
Points to Watch When Replacing Springs
- Compressed springs store a great deal of energy; use suitable tools and take safety precautions when removing and fitting them.
- Screen and cone crusher springs should be replaced as a set.
- The new spring’s wire diameter, outside diameter, free length and number of coils must match the old one.
- Spring seats and guide parts should also be checked.
- Record preload or length measurements after fitting.
Frequently Asked Questions
What types of spring are there?
The main types are helical compression, extension and torsion springs, disc springs, leaf springs, conical springs, wave springs, and rubber and air springs.
What does spring rate depend on?
It depends on the material’s shear modulus, wire diameter, coil diameter and number of active coils.
Why should screen springs be replaced as a set?
Because new and old springs differ in stiffness and length, replacing a single spring upsets load distribution and can make the screen run askew.
How can spring breakage be prevented?
Through correct sizing, suitable materials and surface treatments, corrosion protection and regular inspection.
Information Needed to Order Springs
| Information | Explanation |
|---|---|
| Wire diameter (d) | The thickness of the spring wire |
| Outside or inside diameter | According to the seat or guide the spring fits |
| Free length | Unloaded length |
| Total and active number of coils | Determines spring stiffness |
| Coil direction | Right- or left-hand; important for nested springs |
| End type | Closed and ground, open, etc. |
| Material and surface protection | Spring steel type, paint or coating |
| Working load or spring rate | If known |
For nested spring sets (a second spring inside the first), the dimensions of both springs must be stated separately.
Factors Affecting Spring Prices
- Wire diameter and total wire length (weight),
- Material (alloy spring steels cost more),
- Surface treatments such as heat treatment and shot peening,
- End grinding and precision dimensional requirements,
- Order quantity (production in sets is more economical).
Glossary
- Spring rate: Force per unit of deflection.
- Preload: The initial compression given to a spring on assembly.
- Solid length: The length at which the spring is fully compressed.
- Set: Permanent loss of spring length over time.
- Shot peening: A process that increases fatigue life by inducing compressive stress in the spring surface.
More Questions
How are springs classified among machine elements?
By type of load, into compression, extension and torsion springs; by shape, into helical, disc, leaf, conical and wave springs.
Rubber spring or steel spring?
Rubber springs give better damping and quieter running; steel springs offer more predictable stiffness and long life. The choice depends on the screen design.
CSP Mühendislik Support
CSP Mühendislik supplies jaw crusher tension springs, cone crusher safety springs, impact crusher apron springs and vibrating screen suspension springs. See our crusher spare parts page for crusher springs, our vibrating screen spare parts page for screen springs and our feeder spare parts page for feeders.
