Hydraulics: Understanding Rams and Cylinders

Questions and Answers

What is the primary purpose of Hurst lift cylinders?

To lift heavy vehicles using air pressure

To lift heavy loads using hydraulic power (correct)

To provide stability during building construction

To operate solely with hand pumps

What should be checked during the visual inspection of hydraulic rescue tools?

Electrical connections for power

Existence and stability of the handle (correct)

Battery charge status

Fuel levels in the engine

Which pressure system allows Hurst lift cylinders to handle a maximum capacity of over 141,500 lbs?

10,000 psi system (correct)

2,500 psi system

7,500 psi system

5,000 psi system

Why is it recommended to receive proper training before using Hurst lift cylinders?

To ensure safe and effective operation Signup and view all the answers

In the context of hydraulic tool maintenance, which actions should be avoided?

Using pure oil on cutter blades Signup and view all the answers

What is the main function of shoring within the fire service?

To minimize hazards and provide stability Signup and view all the answers

What should be done if hydraulic tool couplings are found to be dirty?

Clean them with soap and warm water Signup and view all the answers

What should be the outcome of operational checks on hydraulic tools?

Tools should not leak hydraulic fluid Signup and view all the answers

What is a common application scenario where Hurst lift cylinders might be particularly useful?

Lifting heavy objects in tight spaces Signup and view all the answers

What does proper maintenance of hydraulic rescue tools involve after use?

Using a clean towel to wipe them down Signup and view all the answers

What is the primary difference in force application between pushing and pulling with rams?

Pushing force is significantly greater than pulling force due to reduced surface area. Signup and view all the answers

During the NFPA 1936 testing procedure, how is the spreading force of a ram measured?

At 3 uniformly spaced intervals from fully retracted to 95% extended. Signup and view all the answers

What is the primary advantage of a telescoping ram over regular rams?

It provides increased stroke length while keeping a small retracted storage size. Signup and view all the answers

What happens to the pushing capacity of a two-stage telescoping ram as it extends?

The capacity decreases as the second stage engages due to reduced surface area. Signup and view all the answers

Which of the following statements accurately describes double acting hydraulic cylinders used in rams?

They apply more force when pushing compared to pulling. Signup and view all the answers

What is the function of attachments for rams?

To provide additional functionality such as gripping or cutting. Signup and view all the answers

Which is a limitation of the telescoping ram design?

It cannot achieve maximum force during the second stage of extension. Signup and view all the answers

How does the design of rams compare to spreaders regarding their operation?

Rams apply linear force only using the piston rod. Signup and view all the answers

What is the maximum height to width ratio for a box crib made from lumber to ensure stability?

3:1 Signup and view all the answers

What is the main consideration when constructing a box crib to enhance stability?

Limiting the height to width ratio Signup and view all the answers

What minimum overlap is required at the corners when stacking cribbing layers?

4 inches Signup and view all the answers

How is the load carrying capacity of a point of contact calculated?

Multiplying surface area by bearing stress Signup and view all the answers

What is the bearing stress used in calculations for Douglas Fir and Southern Pine lumber?

500 psi Signup and view all the answers

What is the load carrying capacity of a 4x4 point of contact?

6,000 lbs Signup and view all the answers

How many points of contact does a 2 by 2 box crib have?

4 Signup and view all the answers

If a box crib is constructed using 6x6 lumber, what is the load carrying capacity of a 3 by 3 configuration?

135,000 lbs Signup and view all the answers

What should a box crib be built upon if it is not on a solid base?

A solid platform Signup and view all the answers

What should be avoided to ensure a balanced construction of a box crib?

Building an asymmetrical design Signup and view all the answers

What is the function of the double funnel approach in shoring?

To distribute the load across a wider area. Signup and view all the answers

Which characteristic of wood makes it suitable for emergency shoring?

It provides audible warning signs when overloaded. Signup and view all the answers

When loading wood parallel to the grain, what is a potential failure mode?

Sudden buckling due to increased stress. Signup and view all the answers

What is the maximum allowable bearing stress of Southern Pine loading parallel to the grain?

650 psi Signup and view all the answers

What is a significant disadvantage of using Oak for shoring compared to Douglas Fir?

Oak can splinter, weakening its integrity. Signup and view all the answers

What can be inferred about the importance of growth rings in evaluating wood for cribbing?

A minimum of 8 growth rings per inch is required for optimal strength. Signup and view all the answers

In shoring, what is the primary reason for creating a box crib from smaller wood pieces?

To ensure a stable foundation that supports the load effectively. Signup and view all the answers

What would indicate that wood shoring material is being overloaded?

Audible groaning sounds and visible crushing. Signup and view all the answers

Which of these species is NOT commonly used for emergency shoring?

Maple Signup and view all the answers

What is a challenge faced when shoring with very large pieces of wood?

They are difficult to transport in emergency situations. Signup and view all the answers

What is the primary purpose of raker shoring in rescue operations?

To provide horizontal stabilization for loads Signup and view all the answers

Which materials can be used to construct raker shoring?

Either wood or mechanical struts Signup and view all the answers

In what scenario is elaborate raker shore construction typically utilized?

In structural collapse situations Signup and view all the answers

What is crucial for personnel using mechanical struts in rescue operations?

Mastery of construction, setup, use, and capacities Signup and view all the answers

What type of operation does the vehicle tie-back represent within the context of raker shoring?

An example of day-to-day rescue operations involving rakers Signup and view all the answers

What is a significant limitation of inverted step chocks?

The top section being wider can cause instability. Signup and view all the answers

Which feature is crucial for a proper wedge set assembly?

Maintaining maximum surface contact. Signup and view all the answers

What is the primary purpose of shims in cribbing?

To change the load distribution angles. Signup and view all the answers

What should be avoided when using under driven wedges?

Using them without structural support. Signup and view all the answers

How does the design strength of a 6x6 wooden post shore compare to a 4x4 post shore?

The 6x6 post shore supports more weight. Signup and view all the answers

What is an important consideration when adjusting the height of vertical wooden post shores?

Incorporating lateral bracing for longer posts. Signup and view all the answers

What is a key benefit of using mechanical struts as opposed to wooden post shores?

They allow for quick and easy height adjustment. Signup and view all the answers

What is a critical aspect of stable step chocks?

Uniform step dimensions with five points of contact. Signup and view all the answers

What does the term 'Full Driven' refer to in the context of wedges?

Wedges driven together completely. Signup and view all the answers

What failings can occur if a wedge set is under driven?

Improper force generation. Signup and view all the answers

What is the maximum recommended height-to-width ratio for a box crib with one point of contact?

1:1 Signup and view all the answers

Which configuration of a box crib generally provides the most stability?

Four points of contact Signup and view all the answers

What should the height-to-width ratio be limited to when a box crib has two points of contact?

1.5:1 Signup and view all the answers

When constructing a slopped box crib, what must the shims match in dimensional size?

The cribbing used Signup and view all the answers

What is the primary purpose of using step chocks in stabilization?

To redirect the force to the ground Signup and view all the answers

What risk is associated with stacking more than two pieces of cribbing in the same direction?

Increased lateral instability Signup and view all the answers

How should the load path be managed in a slopped box crib?

It should be contained within the footprint of the crib. Signup and view all the answers

What is the preferred length-to-height ratio for a step chock to achieve optimal load stabilization?

4:1 Signup and view all the answers

In what circumstances can step chocks be positioned inverted?

When they don’t pose a trip hazard Signup and view all the answers

What is directly affected by the number of points of contact under a load in a box crib?

The lateral stability of the crib Signup and view all the answers

Study Notes

Hydraulic Rams

Rams apply linear force using only the piston rod, unlike spreaders with pivoting arms.
Available in various lengths to suit different applications.
Some rams include double acting hydraulic cylinders for both pushing and pulling forces, with maximum force during pushing.
Pulling force is typically 50% of pushing force due to reduced surface area on the piston.
Attachable accessories enhance ram functionality, providing grips, cutting, or piercing capabilities.
Extensions can increase the range of rams.
NFPA 1936 testing measures spreading force at three intervals between retracted position and 95% extended position to determine forces (HSF, LSF, HPF, LPF).

Telescoping Rams

Feature a 2-stage telescoping action for extended stroke length while minimizing storage size.
Maximum pushing capacity occurs during the first extension stage, with reduced capacity in the second stage due to less surface area.
Designed solely for pushing and undergo NFPA compliance testing.

Hurst Lift Cylinders

Specialized hydraulic rescue tools, powered by a hydraulic system rather than a hand pump.
Operating at 5,000 psi allows lifting capacities over 96,000 lbs.; at 10,000 psi, capacities exceed 141,500 lbs.
Ideal for narrow spaces where high-pressure air bags cannot fit (e.g., under rail and METRO cars).
Available in 2- and 3-piston models with various attachments.
Usage requires proper training due to operational complexity compared to standard rescue tools.

Tool Maintenance and Inspection

Daily inspections of hydraulic rescue tools are essential, checking for leaks, handle stability, and blade condition.
Operational checks include ensuring the control valve's functionality and tool movement with attention to unusual noises or leaks.
Post-use clean tools with a towel, if necessary, using a damp cloth with mild cleaner; avoid lubricating cutting blades.
Inspect hydraulic pumps and hoses for damage before operation, ensuring couplings are clean and fluid levels in reservoirs are proper; follow manufacturer guidelines for fluids.

Shoring Principles

Shoring provides temporary support to structures during emergency incidents, enhancing stability for rescuers and victims.
Uses a double funnel principle to collect, transfer, and distribute loads effectively.

Wood Construction and Capacity

Wood shoring offers overload warning signals through audible groaning as it crushes under stress.
Commonly used softwoods like Douglas Fir and Southern Pine are preferred for their characteristics.
Allowable bearing stresses for Douglas Fir: 650 psi parallel to grain and 500 psi perpendicular to grain.

Cribbing Techniques

Box cribbing stacks smaller wood pieces to create supportive structures, resembling "Lincoln Logs."
Maximum height-to-width ratio is 3:1, but should be reduced to 2:1 when dealing with unstable objects.
Recommended height limits are 4 feet for 4x4s and 6 feet for 6x6s; overlapped corners help prevent splits.

Load Carrying Capacity Calculations

Capacity of contact points is determined by surface area times bearing stress; thus, a 4x4 supports about 6,000 lbs. and 6x6 supports about 15,000 lbs.
Box crib capacity is calculated by combining the capacities of individual contact points.

Step Chocks and Shims

Step chocks function as portable cribbing, with a 4:1 length-to-height ratio for effective load stabilization.
Shims are triangular pieces that help fill voids and adjust angles, while wedge sets create mechanical advantage for lifting.

General Considerations for Stability

Crib complex structures should maintain stability with a maximum of two crib pieces stacked in the same direction to minimize rolling risks.
Understanding load distribution and lateral stability is crucial during cribbing and shoring operations.### Wedge Set Marrying
Full Driven Wedges: Considered the best option for stability.
Over Driven Wedges: Acceptable if there is adequate overhang.
Under Driven Wedges: Not recommended as they are undesirable for stability.

Vertical Post Shoring

Vertical post shores can supplement or replace cribbing for stabilization.
Takes up less space than box cribbing and supports greater heights.
Constructed with a header, post, and footer, aligning with the double funnel principle for load stabilization.
All components must be connected to form a complete system for efficient stabilization.
Wedge sets, preferably made of 2x4s, are used to adjust post heights.
Length restrictions are in place to prevent buckling, and lateral bracing is required for longer posts.
Design Strengths:
- 4x4 post: Maximum strength of 8,000 lbs, length up to 8 feet.
- 6x6 post: Maximum strength of 20,000 lbs, length up to 12 feet.

Mechanical Struts

Several manufacturers produce aluminum mechanical struts that replace wooden post shores.
Mechanical struts offer quick height adjustments but also lose strength with increased length due to buckling.
Always follow manufacturer guidelines for load limits when utilizing mechanical shores.

Raker Shoring

Raker shores stabilize loads against horizontal movement.
Can be made from either wood or mechanical struts, often used in structural collapse scenarios.
Regular operations may still require rakers, such as the vehicle tie-back.
Mastery of construction, setup, use, and capacities of the specific rakers used on apparatus is crucial for rescue personnel.

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Description

This quiz explores the mechanics of hydraulic rams and double acting cylinders. It covers their functionality, differences between pushing and pulling forces, and practical applications. Test your knowledge on hydraulic systems and their components.