Hydraulic torque wrenches are indispensable in industrial bolting applications, facilitating the application of high torque levels surpassing 600 ft. lbs. While manual clicker wrenches can reach up to 1000 ft. lbs., their usage is notably arduous. Conversely, power tools offer enhanced ease for assemblers, resulting in superior precision and repeatability.
The operation of hydraulic tools hinges on a hydraulic pump, often referred to as a "power pack," which transmits high-pressure hydraulic force via a hydraulic hose to achieve the desired torque result. Proper calibration of the hydraulic pump enables accurate torque setting adjustments, with the option for pneumatic (air-driven) or electric power to drive the pump.
The torque range of hydraulic torque tools spans from a minimum of 100 ft. lbs. to a maximum of 120,000 ft. lbs., contingent upon the capacity and dimensions of the hydraulic equipment. Notably effective on substantial bolts measuring 1 inch in diameter or larger, hydraulic torque wrenches offer unparalleled utility. In this post, we will explore the mechanism of hydraulic torque wrenches, starting from the power source— the pumps— and to the tools themselves.
The Hydraulic Pump also Known as The Power Pack
A standard pump can generate pressures of up to 10,000 PSI, enabling torque setting adjustments on the hydraulic wrench. Most pumps are compatible with all major tool brands.
Pumps are available in electric or air-driven types, with pneumatic hydraulic pumps commonly used in hydrocarbon processing. However, using an electric pump for certain bolting applications may need a Hot Work Permit due to electrical considerations.
In all hydraulic torque wrench setups, a hose links the hydraulic pump to the wrench itself. The hose connections, known as couplers, are designed to prevent wrong attachment—requiring proper matching of male/female attachments to connect. Consequently, connecting the hose to the pump is simple and intuitive.
Hydraulic Hose That Must BePaid Attention To
Once the pump is activated, you will adjust the pressure to correspond with the target torque value indicated on the calibration sheet. The hose is connected to the hydraulic tool via what's known as the uni-swivel. It's worth noting that the uni-swivel can withstand pressures of up to 10,000 PSI.
It is important to note that the Hydraulic hoses must be rated for a 4:1 hydraulic pressure, meaning they should be rated for at least 40,000 psi. There are settings for advancing or retracting. The advance setting fills the piston with hydraulic fluid, subsequently moving the piston forward to exert pressure on the drive pawls. As a result, the drive pawls rotate, causing the nut to turn.
Also, before using the hose, carefully examine hydraulic hoses for any signs of damage or punctures. If the pressurized liquid were to leak through a hole, the ensuing stream could inflict serious injuries such as severed fingers or deep lacerations.
Square Drive Bolting Tools
The square drive bolting tool stands as the predominant hydraulic torque wrench in industrial bolting. Available in various sizes including ½”, ¾“, 1″, 1 ½”, and 2 ½”, each size determines the maximum torque output achievable with these tools.
Practical experience demonstrates that square drives excel in breakout tasks due to their sturdiness and simpler construction compared to low-profile wrenches, resulting in reduced susceptibility to breakage.
A square drive tool's reaction arm is positioned further from the flange, owing to the impact socket and square drive, which renders square drives more challenging to use for assembly compared to low-profile hydraulic torque wrenches.
Low Profile Bolting Tools: An Assembler Favorite
Low-profile hydraulic wrenches comprise two components: a powerhead and a link. What distinguishes low profiles is the link, as each set of links is tailored to fit a specific nut size. Changing the link involves removing the link pin and replacing it with a differently-sized link.
Low-profile wrenches range from 2,000 ft. lbs. upwards to 4,000, 8,000, 16,000, and beyond. Each wrench size requires a corresponding link, meaning multiple links may be necessary for a 2,000 ft. lb. version, multiple links for the 4,000 ft. lb. version, and so forth. Links for different models of tools are not interchangeable.
True to their name, low profiles excel in situations with limited clearance. The reaction point for a low profile is positioned directly against the adjacent nut. Consequently, the low-profile wrench is often favored by assemblers due to its ease of use compared to a square drive.
Hydraulic Torque Wrench Safety
Given the high-pressure fluid and the immensely powerful mechanical reaction arms involved, the potential for injury due to improper use of hydraulic equipment wrenches is significant. TorcStark strongly advises that any site using hydraulic tools undergo comprehensive training in safe operation and usage beforehand.
Before usage, it's crucial to depressurize the hydraulic hose. When storing hydraulic hoses, arrange them in a circular configuration wrapped end to end, avoiding screwing the ends on one side together. Any sign of steel braiding bins, cracks, burns, or kinks on a hose indicates it should not be used.
Another important safety measure for all hydraulic torque wrenches involves pinch points resulting from reaction points. According to the laws of physics, every action has an equal and opposite reaction. In bolting, this implies that if an assembler applies 1000 ft. lbs. of force to a bolt, the reaction arm exerts the same force on the adjacent nut. It's imperative to avoid getting any part of the body caught between these metal components.
There are two primary designs for hydraulic tools: those equipped with holding pawls and those without. Holding pawls enables the tool to ratchet without requiring a wind-up on the fastener. However, the holding pawl may become entangled with the fastener over time, making it challenging to remove the flange.
In such instances, it is crucial not to resort to using a hammer on the tool. Instead, power up the tool through the hydraulic pump and depress the holding pawl to release the hydraulic tool.
Hydraulic Torque Wrench Maintenance
An essential aspect of maintaining hydraulic torque wrenches involves monitoring the seals, as they are often the first components to deteriorate. If you notice milky or contaminated oil in your hydraulic pump, laden with water, dirt, or grime, these impurities will traverse along with the hydraulic fluid through your tool, potentially causing damage to the seals.
Another critical maintenance consideration pertains to the hydraulic hoses. The couplers on these hoses frequently accumulate grime and other debris. Unfortunately, individuals may resort to using channel locks or pipe wrenches to tighten these couplers, which can lead to damage over time. It is advisable to clean the fittings after each use to avoid this, as using channel locks can eventually deteriorate and ruin the couplers.
Should you need to replace a fitting, it is imperative to adhere to the requirements specified by the hydraulic hose manufacturer. While hydraulic pumps typically do not require maintenance in the field, they may occasionally need troubleshooting. Air-driven hydraulic pumps are typically equipped with a Filter Lubricator Regulator (FLR). Before operating your tool, ensure to drain any accumulated water, grime, or debris from the FLR's bottom nozzle. Allowing such contaminants to pass through the FLR into the hose risks damaging the air motor.
The FLR features a sight glass to monitor oil input. Verify that the oiler is dispensing one drop of oil every 10 seconds. This lubricates the air motor, preventing it from binding. Adjusting the oiler to dispense oil more frequently may lead to oil leakage, while insufficient oiling can cause pump binding, needing eventual pump replacement.
We strongly recommend contacting the torque wrench manufacturer for guidance. They typically offer safe use and operation courses, along with troubleshooting assistance, as each manufacturing and model type may have unique characteristics and requirements for individual parts.
Following any maintenance on a hydraulic torque wrench, recalibration is essential. It is also necessary to reapply grease to both the drive pawls and the side plates to ensure smooth movement and prevent binding or galling.
Calibration: Timing and Requirements
Calibrating a hydraulic torque wrench involves two important components:
- The hydraulic torque wrench.
- The gauge on the hydraulic pump.
Both these elements should undergo calibration at least once every 12 months. After calibration, it's essential to generate a new torque chart. This updated chart becomes the reference for your crews when using the tool thereafter. Always verify the serial number and date to ensure the correct calibration chart matches the tool in question.
