Pit Bottom Buffers in Mine Winding Shafts – Purpose, Design & DGMS Safety Provisions

🧾 DETAILED NOTES

1️⃣ Introduction

In mine winding systems, pit bottom buffers are vital safety devices installed at the bottom of winding shafts to absorb the impact energy of a descending cage or skip if it overshoots the normal landing. According to Regulation 88 of the Metalliferous Mines Regulations, 1961 (MMR) and DGMS guidelines, every winding shaft must be equipped with a suitable buffer system to minimize mechanical shock and prevent damage to men, material, and winding gear.

2️⃣ Purpose of Pit Bottom Buffers

To absorb kinetic energy in case of overwinding.
To prevent cage or skip damage.
To safeguard winding ropes from excessive strain.
To prevent fatal injuries to persons in the cage.
To ensure operational safety and compliance with DGMS standards.

3️⃣ Types of Pit Bottom Buffers

Spring Buffers: Made of helical steel springs. Common in shallow or moderate-depth shafts.
Hydraulic Buffers: Filled with oil or fluid for energy absorption. Used in deep shafts with heavy loads. Provide controlled deceleration.
Rubber or Composite Buffers: Suitable for auxiliary winding or small skips. Low-cost and maintenance-free.

4️⃣ DGMS & Statutory Provisions

Provision	Description
Reg. 88 (MMR, 1961)	Every winding shaft must have a suitable device to prevent overwind impacts.
Reg. 91 (MMR, 1961)	Specifications for winding arrangements and protection against overwind.
DGMS Circular (Tech)	Specifies buffer testing and approval standards before installation.
Testing Interval	Every 12 months or after major overhaul.

5️⃣ Design and Construction Requirements

Designed to absorb 150% of maximum kinetic energy of descending cage.
Must return to normal position after impact.
Located directly below cage landing platform.
Constructed on firm foundation or concrete bed.
Free from water accumulation and corrosion.
Periodically inspected by Mechanical Engineer.

6️⃣ Maintenance and Testing

Monthly inspection by competent engineer.
Oil level check (for hydraulic type).
Spring tension test (for mechanical type).
Visual inspection for cracks, corrosion, or misalignment.
Record maintained in Form 10 (Mechanical Log Book).

7️⃣ Case Example (DGMS Incident Report)

In a manganese mine, a skip overshot due to winding brake failure. The hydraulic buffer absorbed most of the impact energy, preventing total damage. DGMS inquiry revealed the importance of maintaining oil levels and ensuring annual testing under Regulation 88.

⚙️ QUICK ONE-LINERS (Revision Points)

Reg. 88 of MMR 1961 → Pit bottom buffers.
Used to absorb impact energy from overwinding.
Two common types: spring & hydraulic.
Installed directly below cage landing.
Absorbs up to 150% of impact load.
Mandatory inspection every month.
Tested annually under DGMS supervision.
Prevents damage to cage, rope, and drum.
Hydraulic buffer uses oil for energy absorption.
Records maintained in Mechanical Log Book.

🧮 DESCRIPTIVE MODEL QUESTION

Q. Explain the purpose, types, and maintenance requirements of pit bottom buffers in MN-winding shafts as per DGMS and MMR 1961.

Answer:
Pit bottom buffers are devices installed at the bottom of winding shafts to absorb energy during overwinding or rope failure. Under Regulation 88 of MMR 1961, these buffers are mandatory for all winding installations. Types include spring, hydraulic, and rubber buffers. Hydraulic types are preferred for deep shafts due to smoother energy absorption. Regular maintenance includes monthly inspection, oil checks, and annual testing. DGMS-approved designs must be used to ensure operational safety and legal compliance.

🧩 25 DGMS-Based MCQs (Dynamic Answers – A–E)

Q1. Pit bottom buffers are provided in:

Solution: Buffers are safety devices for winding shafts (vertical transport).

Q2. The main purpose of pit bottom buffer is:

Solution: Their primary function is to absorb the kinetic energy of a falling/overshooting cage.

Q3. Regulation dealing with pit bottom buffers:

Solution: Regulation 88 of MMR 1961 specifically mandates these devices in shafts.

Q4. The energy absorption capacity of pit bottom buffer should be:

Solution: They must be designed to handle 150% of the maximum kinetic energy to ensure a high safety factor.

Q5. Which type of buffer uses oil for damping?

Solution: Hydraulic buffers use the principle of fluid (oil) displacement to absorb and dissipate energy.

Q6. Pit bottom buffers prevent:

Solution: They act as cushions to prevent a hard, damaging impact (mechanical shock) at the shaft bottom.

Q7. Common buffer used in shallow shafts:

Solution: Spring buffers are mechanically simpler and cost-effective, making them suitable for lower loads/speeds in shallow shafts.

Q8. Buffers should be tested at least once every:

Solution: Annual (12-monthly) testing is a standard requirement for such critical safety devices.

Q9. Oil leakage in hydraulic buffer leads to:

Solution: Loss of hydraulic fluid means the buffer cannot absorb the design energy, leading to a loss of efficiency.

Q10. Pit bottom buffer is installed:

Solution: They are placed at the very bottom of the shaft, directly under the cage's normal stopping position.

Q11. Which DGMS document governs buffer testing?

Solution: Technical Circulars are issued by DGMS to provide specific guidelines on testing and standards for equipment.

Q12. Buffers help prevent:

Solution: They are specifically designed to safely stop the cage in case it travels too far down (overwind).

Q13. Material used in mechanical buffer:

Solution: Mechanical buffers primarily use large helical steel springs to absorb energy.

Q14. Inspection of pit bottom buffer is done by:

Solution: As a critical mechanical device, it must be inspected by a competent Mechanical Engineer.

Q15. Buffer records are kept in:

Solution: Form 10 (or equivalent log book) is used for recording inspections of winding machinery, including buffers.

Q16. Which buffer type offers smooth deceleration?

Solution: Hydraulic buffers dissipate energy at a controlled rate, providing smoother stopping compared to the recoil of a spring.

Q17. Failure of buffer can lead to:

Solution: Without a buffer, an overwind would result in the cage crashing into the shaft bottom.

Q18. Buffer inspection frequency (minimum):

Solution: A detailed inspection by a competent engineer is required at least once every month.

Q19. DGMS recommends re-testing after:

Solution: After any major repair or component replacement, the buffer must be re-tested to ensure it functions correctly.

Q20. Pit bottom buffers reduce:

Solution: They are designed to absorb kinetic energy, thereby reducing the final impact force on the cage and shaft bottom.

Q21. Hydraulic buffer filled with:

Solution: Specially engineered hydraulic oil/fluid is used as the medium for energy dissipation.

Q22. In deep shafts, preferred buffer is:

Solution: Hydraulic buffers are more effective at safely handling the higher kinetic energies involved in deep shafts.

Q23. Pit bottom buffer must be:

Solution: Buffers must be securely fixed to a solid foundation to effectively absorb impact.

Q24. Purpose of foundation in buffer installation:

Solution: A firm foundation ensures the buffer remains stable and correctly aligned to receive the cage.

Q25. Overshoot of cage may lead to:

Solution: If the cage overshoots (travels too far down), its first point of contact will be the pit bottom buffer.

🔗 INTERNAL LINKS

Related Topic	Read More On...
Winding Safety	DGMS Mining Management & Safety Notes (MMR 1961)
MMR 1961	Metalliferous Mines Regulations 1961 - Chapter 1
Accident Investigation	Accident Investigation & Legal Framework
DGMS Syllabus	DGMS Exam Syllabus 2025 - CMR & MMR Guide

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Pit Bottom Buffers in Mine Winding Shafts – Purpose, Design & DGMS Safety Provisions

🧾 DETAILED NOTES

1️⃣ Introduction

2️⃣ Purpose of Pit Bottom Buffers

3️⃣ Types of Pit Bottom Buffers

4️⃣ DGMS & Statutory Provisions

5️⃣ Design and Construction Requirements

6️⃣ Maintenance and Testing

7️⃣ Case Example (DGMS Incident Report)

⚙️ QUICK ONE-LINERS (Revision Points)

🧮 DESCRIPTIVE MODEL QUESTION

🧩 25 DGMS-Based MCQs (Dynamic Answers – A–E)

🔗 INTERNAL LINKS

🎯 Prepare for DGMS Winding Safety Questions!

OUR COURSES View More

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Pit Bottom Buffers in Mine Winding Shafts – Purpose, Design & DGMS Safety Provisions

🧾 DETAILED NOTES

1️⃣ Introduction

2️⃣ Purpose of Pit Bottom Buffers

3️⃣ Types of Pit Bottom Buffers

4️⃣ DGMS & Statutory Provisions

5️⃣ Design and Construction Requirements

6️⃣ Maintenance and Testing

7️⃣ Case Example (DGMS Incident Report)

⚙️ QUICK ONE-LINERS (Revision Points)

🧮 DESCRIPTIVE MODEL QUESTION

🧩 25 DGMS-Based MCQs (Dynamic Answers – A–E)

🔗 INTERNAL LINKS

🎯 Prepare for DGMS Winding Safety Questions!

OUR COURSES View More

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