Knocker Housing

I. Functions and Roles of Knocker Housing

1. Protective barrier.

Knocker Housing provides physical protection for the internal pistons, springs and shaft parts to prevent underground high pressure, mud erosion and mechanical collision.

It isolates the external harsh environment to ensure the stable operation of the internal hydraulic oil system and mechanical structure.

2. Structural support.

Knocker Housing can fix the positions of internal components to ensure that parts such as pistons and springs remain precisely centered during reciprocating motion.

The Knocker Housing, in conjunction with the upper and lower joints, forms a complete shock force transmission path.

3. Energy transfer.

As the main medium for transmitting the impact force, the Knocker Housing transfers the energy released by the internal energy storage components to the drill string or tool string.

It withstands and transmits an impact force of up to tens of tons at the moment of the shock.

II. Key Characteristic Requirements of Knocker Housing

• High yield strength (≥600MPa), resistant to deformation.

• Good impact toughness (≥50J/cm²), preventing brittle fracture.

• Knocker Housing has excellent fatigue resistance and can withstand long-term periodic loads.

• The inner surface is highly smooth, reducing frictional resistance.

III. Roles in the Working Principle of Knocker Housing

The Knocker Housing plays multiple roles in the drilling jar's working cycle:

1. Energy storage stage.

When the drill string gets stuck and the cable is lifted, the shock shaft moves inside the shock housing.

The Knocker Housing bears the huge pressure generated by the compression of the internal spring (or disc spring assembly).

The hydraulic oil flows in a special chamber within the vibrating shell, providing damping and pressure balance.

2. Shock release stage.

When the set unlocking force value is reached, the locking mechanism releases.

The spring rapidly releases energy, driving the shock hammer to move upward.

The Knocker Housing transmits the impact force to the drill string, loosening the clamping point.

The fit accuracy between the inner wall of the knocker housing and the piston/shock hammer directly affects the energy transmission efficiency.

3. Reset stage.

After the shock, the hydraulic system and spring assembly inside the  knocker housing assist in the reset of the shock shaft.

The shock-absorbing structure alleviates the reaction force and protects the shock-struck shell from damage itself.

Apply anti-biting agent to the key mating surfaces to facilitate disassembly next time.

Although the drilling jar knocker housing is called the "outer shell", it is the "soul" of the drilling jar. Its performance directly determines the reliability and service life of the drilling jar. Only by choosing the appropriate material, maintaining and servicing it carefully, and conducting regular inspections can we ensure that the knocker housing always remains a "steel body" in the extreme downhole environment, providing a solid guarantee for oil and gas exploration and development.