Hydraulic Snubbers

     The hydraulic snubber is a standard 3000 psi hydraulic cylinder with a built-in fluid reservoir. The fluid is ported through the end blocks to a manifold which in turn directs the flow through a valve block. The valve block contains two regulating valves with bleed grooves. The connection of the manifold to the reservoir and the valve block to the manifold utilize ethylene propylene “O” ring seals.

    In operation, the piston rod will extend or retract at a velocity less than the lockup velocity.  When shock, vibration or sway tends to increase the rate of displacement of the piston rod beyond the lockup velocity, the regulating valves close and the unit limits the velocity.  The resistive capacity of the unit transfers the force to the structure and reduces the possibility of overstressing the pipe or associated equipment connections.

    The function of the bleed grooves is to control the velocity after lockup. For prolonged thrust, the bleed grooves are eliminated and the unit becomes a rigid strut during lockup.

Recommended Service:  For absorbing thrust associated with the release of blow off valves which may cause immediate or accumulative damage to piping or equipment.  For use with piping subjected to shock, sway or vibration caused by earthquake, water hammer, or other transient forces.

Codes and Standards:  Hydraulic snubbers are manufactured in conformance with government and industry codes where applicable.  Among theses are ‘Federal Specification WW-H-171E, Manufacturers Standardization Society MSS-SP-58, and American National Standards Institute Code for pressure piping ANSI B31.1.

How to Size:

1. Select a figure number and bore size which will accommodate the maximum required loading (tension and compression), movement and dimensional requirements.  The stroke of the unit should be greater than or equal to the anticipated minimum movement plus 20%.
2. Adjust the "L5 (COLD)" dimension such that 50% of the anticipated movement will be expired, when the unit reaches the mid-stroke position.
3. For Fig. E385 assembly, add the appropriate “F” dimension to the adjusted "L5 (COLD)" dimension to establish the “C-C (COLD)” dimension.   Refer to the Snubber Compression Chart and insure the compression load is less than or equal to that specified at “C-C (MIN)”.  Add the appropriate takeout of the pipe attachment (dimension “K” for a pipe clamp) and structural attachment (dimension “L3” for a rear bracket) to obtain the required distance from structure (back of rear bracket) to center of pipe.
4. For Fig. E390 assembly, determine the distance from the structure (back of rear bracket) to center of pipe.  Subtract the appropriate takeout of the pipe attachment (dimension “K” for a pipe clamp) and structural attachment (dimension “L3” for a rear bracket) to obtain the “C-C (COLD)” dimension.  Refer to the Snubber Compression Chart and correlate the “C-C (COLD)” dimension with the compression load to verify the correct bore size had been selected.  Calculate the required “L4” dimension that accommodates the adjusted “L5 (COLD)” and “C-C (COLD)” dimensions. Insure the “L4” dimension is greater than or equal to the “L4 (MIN)” dimension specified in the table.

Features:  

• Offers little resistance to normal thermal movement
• Compact – furnished as a complete functional unit
• Can be used in compression or tension
• Has a built-in reservoir with a transparent window for viewing of fluid level
• No external piping – unit is complete manifold
• Hydraulic fluid is nonflammable
• All units have special fluid and seals suitable for installation in radiation areas.

Optional Features:  An external reservoir for remote mounting can be added for inaccessible locations.  Pressure relief valve blocks and corrosion resistant assembles are also available.  Contact AAA Technology & Specialties Co. Inc., for ordering instructions.

2 Types and 2 Sizes

Select size below
Fig 385a	size 3/4" to 3 1/4" Short
Fig 385b	size 4" to 10" Short
Fig 390a	size 3/4" to 3 1/4"
Fig 390b	size 4" to 10"