Hydraulic Torque Wrench Pressure Chart: Accurate Torque-To-Pressure Guide

How Hydraulic Torque Wrenches Convert Pressure to Torque

Hydraulic Torque Wrenches use a simple linear formula: Torque (T) = K × Pressure (P). The K-factor is a constant unique to each wrench model and serial number. This number tells you how much torque you get from any pressure input.

Pressure Chart in Action

Look at the RTX-4 model with a 10,000 psi pump and class 1 gauge. At 1,000 PSI, you get 150 ft-lbs (203 Nm). Bump it up to 5,000 PSI, and output jumps to 750 ft-lbs (1,016 Nm). Max pump pressure of 10,000 PSI gives you 1,500 ft-lbs (2,033 Nm). The relationship stays linear across the full range.

Standard industrial pumps run up to 10,000 PSI max. High-pressure hoses handle this safely. They’re rated at 40,000 PSI. That’s a 4:1 safety margin. You adjust pump pressure to hit your target torque using the chart for your tool’s serial number.

Tool Capacity Ranges

Hydraulic torque wrench systems cover huge torque ranges:

• Minimum capacity: 100 ft-lbs for small bolts

• Maximum capacity: 120,000 ft-lbs for heavy industrial fasteners over 1-inch diameter

• RT/RTX Square drive models: 75–71,169 Nm range

• RTX direct-drive hex models: 346–43,108 Nm output

Calibration Protocol

Calibrate your wrench and pump gauge every 12 months. No exceptions. Each calibration creates a new torque chart for your tool. Check the serial number and calibration date before use. They must match your equipment.

Setting Pressure

Follow this sequence:

1. Find your required torque from engineering specs (ft-lbs or Nm)

2. Locate the matching value on your calibrated pressure chart

3. Set the pump gauge to the PSI or BAR reading shown

4. Activate the piston and check for smooth, even advancement speed

Don’t guess between chart values. Don’t use generic tables. MXTD-Series tools from TorcStark and HYTORC models each have their own K-factors. Each one needs its own calibration data for accurate conversion.

Hi-Force TWH Series Pressure-Torque Charts

Hi-Force offers five TWH Series models. Capacity ranges from 2,625 to 48,181 Nm. All models work at 700 bar (10,000 psi) maximum pressure. Pick your model based on hex size and torque specs from your drawings.

Model Selection by Capacity

TWH-27N works with fasteners from 1.1/16″ to 2.3/8″ (24–60 mm). Output reaches 2,700 Nm. TWH-54N fits 1.7/8″–3.1/8″ hex sizes. Maximum torque hits 5,372 Nm. TWH-120N delivers 9,900 Nm for 2.3/16″–3.7/8″ fasteners. TWH-430N tackles large industrial bolts at 5″–6.7/8″ (130–175 mm). This one delivers 48,181 Nm.

Reading the Pressure Charts

You get two chart formats from Hi-Force. Nm/Bar works for metric jobs. Lbf.ft/PSI covers imperial specs. Conversion stays linear across the full operating range.

TWH-27N pressure readings (24–46 mm hex link):
– 600 Lbf.ft = 2,630 PSI
– 700 Lbf.ft = 3,068 PSI

TWH-54N metric example (38–65 mm hex link):
– 300 Nm = 2,587 Bar
– 500 Nm = 4,312 Bar
– 700 Nm = 6,037 Bar

TWH-120N imperial range (50–80 mm hex link):
– Pressure span: 4,000–9,000 PSI
– Torque output: 4,000–9,000 Lbf.ft

TWH-430N settings (130–175 mm hex link):
– 200 Nm = 13,766 Bar
– 400 Nm = 27,532 Bar
– 600 Nm = 41,298 Bar

Chart Application

Start by matching bolt size to the hex link range. Find your target torque value next. The pressure reading shows where to set your pump gauge. Metric charts run from 50–700 bar. Each hydraulic torque wrench has its own serial number and calibration sheet. Match the chart to your tool’s ID number.

HYTORC Stealth Series Pressure Chart Breakdown

HYTORC Stealth models operate at a fixed maximum of 10,000 PSI (700 kg/cm²). Your hydraulic hoses, pumps, and gauges must all meet this pressure rating. Six models cover the full industrial torque range. Each model handles different drive sizes and fastener jobs.

Model Range and Specifications

STEALTH-2 delivers 377–2,534 Nm (278–1,869 ft-lbs) through a 19 mm drive. This compact unit works for precision work and light industrial fasteners.

STEALTH-4 outputs 819–5,450 Nm (603–4,020 ft-lbs) with a 27 mm drive. This model fits mid-range jobs and standard production bolting.

STEALTH-8 generates 1,625–10,823 Nm (1,198–7,980 ft-lbs) via 46 mm drive. Maintenance teams use this for heavy machinery installation.

STEALTH-14 produces 2,854–19,324 Nm (2,104–14,255 ft-lbs) through 55 mm drive. Large structural bolts need this power level. Critical joint work demands it too.

STEALTH-22 reaches 4,406–29,654 Nm (3,250–21,875 ft-lbs) with 70 mm drive. Wind turbine work needs this output. Mining equipment maintenance uses it too.

STEALTH-36 tops out at 6,665–47,083 Nm (4,917–34,722 ft-lbs). No drive size specification appears for this model. It handles the biggest industrial fasteners in oil and gas jobs.

Pressure-Torque Conversion Data

STEALTH-2 chart runs from 1,500 to 10,000 PSI. At 3,000 PSI, you get 575 ft-lbs (779 Nm). Jump to 7,000 PSI for 1,311 ft-lbs (1,777 Nm). Maximum pressure delivers the full 1,869 ft-lbs.

STEALTH-4 readings show wider gaps. 1,500 PSI produces 603 ft-lbs (817 Nm). The 5,000 PSI mark hits 1,994 ft-lbs (2,703 Nm). Full capacity needs the complete 10,000 PSI input.

STEALTH-8 scale shows a straight line pattern. Starting at 1,500 PSI gives 1,198 ft-lbs (1,625 Nm). Half pressure (5,000 PSI) yields 3,994 ft-lbs (5,417 Nm). Maximum torque needs maximum pressure. No shortcuts here.

Each pressure chart includes PSI, Bar, ft-lbs, Nm, and Kgm conversions. This multi-unit format stops calculation errors during field work. Match your spec units right to the chart values.

Tritorc TSL/THL Pressure Calculation Method

Tritorc uses a simple proportional formula. No guesswork needed. The calculation works the same across all TSL and THL models. You divide your target torque by the tool’s maximum capacity, then times it by 700 bar.

The Core Formula

Pressure (Bar) = (700 × Desired Torque) ÷ Maximum Tool Torque

Every Tritorc hydraulic torque wrench runs at 700 bar (10,000 PSI) maximum pressure. The minimum operating pressure sits at 70 bar (1,000 PSI). This 10:1 ratio gives you precise control across the full torque range.

Real-World Calculation

Take a TSL-3 with 4,520 Nm maximum capacity. You need 1,160 Nm for your job. Run the numbers: (700 × 1,160) ÷ 4,520 = 179.64 bar. Round to 180 bar on your pump gauge. Done.

The relationship stays linear. Double your torque target? Your pressure requirement doubles too. No complex curves or adjustment factors needed.

TSL and THL Series Specifications

TSL models span 112 to 69,427 Nm (81–50,300 ft-lbs). Ten different tools cover this range. Bolt compatibility runs from 19 to 175 mm. Square drives measure 19.05 to 63.5 mm (0.75–2.50 inches).

THL series delivers 273 to 51,909 Nm (201–38,286 ft-lbs). These tools handle the same 19–175 mm bolt range. Hex cassette systems let you change sockets fast between different fastener sizes.

Accuracy and Friction Variables

Tritorc guarantees ±3% accuracy during torquing operations. This tolerance holds across the full pressure range with proper calibration schedules.

Bolt surface condition affects your torque calculations. Use these friction coefficients:

• μ = 0.10 for lubricated threads

• μ = 0.15 for semi-lubricated jobs

• μ = 0.20 for dry fasteners

Use these values for calculating preload requirements. Your engineering specs should show which coefficient matches your assembly conditions.

Unit Conversion Reference

Convert between measurement systems with these factors:

Pressure conversions:
– 1 bar = 14.50377 PSI
– 1 PSI = 0.06894757 bar

Torque conversions:
– 1 Nm = 0.738 ft-lbs
– 1 ft-lb = 1.355818 Nm

Keep these numbers handy for mixed-unit specifications or international project requirements.

Atlas Copco RT/RTX Series Setup Guide

Atlas Copco RT and RTX models need specific connection steps and pressure settings before you start. The setup differs from other hydraulic torque wrench brands. This is due to unique F.R.L. systems and ratchet link designs.

Initial System Connections

Air-powered pumps need air hoses with minimum 3/4-inch internal diameter. Install a Filter Regulator Lubricator (F.R.L.) unit between your air source and pump. Fill the oil bowl through the top cap. Use the control knob to adjust air admission. The F.R.L. has seven key parts: oil filler cap, oil reservoir bowl, air pressure adjustment knob, automatic water drain port, condensation collection bowl, air flow on/off lever, and oil lubricator adjustment screw.

Check your hydraulic reservoir oil level before connecting lines. Electric pump users should find the nearest power outlet first. Connect air, hydraulic, and electrical lines one by one. Make sure your power source is stable before moving forward.

RTX Low Clearance Assembly

Push the ratchet mechanism all the way inward before mounting. Hook the powerhead onto the ratchet link. Secure both parts with the link pin. The fixed pin aligns mounting holes on its own. The driving stroke turns the hex ratchet toward the shroud front. This direction is the same across all RTX models.

Position the RTX wrench on your target nut. The ratchet hex must engage all the way in. Partial engagement causes slippage and torque loss. Place the reaction block against a fixed object. Adjacent nuts or flange edges work best as reaction points.

Pressure Adjustment Protocol

Turn the pump ON. Hold the advance switch or button. Rotate the “T” handle clockwise while watching your pressure chart gauge. Don’t turn the handle counterclockwise to lower pressure. Release pressure all the way, then re-advance to 4,000 PSI. This stops hydraulic shock and gauge damage.

Working pressure tops out at 4,000 PSI for standard jobs. After setting your target pressure, turn the pump OFF. Tighten the knurled lock nut under the “T” handle to stop drift during use.

Operating Cycle Sequence

Push the remote advance button. The rear cylinder pushes the tool to the reaction point. Keep holding as the socket and ratchet move together. The fastener turns during this stroke. Release the button. The cylinder pulls back on its own. You’ll hear a “click” as the ratchet resets. Repeat cycles until you hit your target torque reading.

Pre-Operation Safety Checks

Release all system pressure before you disconnect hoses. Push the black solenoid button and check the gauge reads zero. Don’t remove couplings under pressure. Hydraulic fluid spray causes injuries. Bleed the system by running one advance cycle. This clears trapped air pockets that hurt torque accuracy.

Atlas Copco guarantees ±3% accuracy and ±1% repeatability with these setup steps. Tighten all hydraulic fittings by hand. This stops leaks after pressure release.

Ratchet Link Specifications

RTX series uses swap-out ratchet links for different hex sizes:

• 3 1/8″ reduces to 2″ (Part #4222 2138 22)

• 2 3/4″ reduces to 1 5/8″ (Part #4222 2134 17)

• 2 3/4″ reduces to 1 13/16″ (Part #4222 2134 20)

• 50mm reduces to 19mm (Part #4222 2138 28)

RT-series models use standard square drives. Use impact-rated sockets only. Regular sockets crack under hydraulic pressure cycles.

Pressure Chart Reading Best Practices

Your pressure gauge accuracy controls torque output precision. Operating pressure stays between 25% and 75% of the gauge’s full-scale range. A 50 BAR working pressure needs a 0–100 BAR gauge. Systems with pressure pulsation need more headroom. Keep maximum operating pressure under 50% of full scale. This stops needle bounce and reading errors.

Pre-Reading Verification Steps

Check the pointer position before connecting hoses. The needle rests on zero. Any offset? Your gauge needs new calibration or replacement. Pick a measurement range that matches your expected pressure value. A 10,000 PSI pump shouldn’t use a 15,000 PSI gauge. Too-large ranges cut reading accuracy.

Check which unit your pressure chart uses. BAR, PSI, and MPa conversions cause frequent mistakes. Write down the unit each time you record a value. Many gauges show dual scales—red markings for BAR, black for PSI. Check which scale matches your torque specs before starting work.

Accuracy Class Requirements

EN 837 Class ratings define gauge precision. Class 0.25 offers tighter tolerances than Class 1.0. Critical bolting jobs need accuracy class between 0.1 and 0.25. Lower class numbers mean smaller measurement variation. A Class 1.6 gauge on a 0–250 BAR scale shows 10 BAR increments between small markings. Pointer readings between marks need ±5 BAR estimation.

Physical Reading Technique

Read from a direct, front-facing angle with your eye level aligned to the dial face. Side or overhead viewing creates parallax errors. This alignment makes the difference between spec compliance and rejected joints. Pick dial sizes large enough for easy viewing from your normal working distance.

Gauge range equals twice your operating pressure. Position the dial so mid-scale aligns near the 12 o’clock position. This gives you maximum resolution in your working pressure range.

Environmental Factors

Check fluid characteristics before connecting pressure systems. Corrosive fluids, thick oils, or slurry materials need specific gauge types. Vibration, extreme temperatures, and deep-sea conditions all affect measurement stability. Install dampeners or protective housings where conditions exceed standard gauge ratings.

Calibration Protocol

Compare gauge readings against a calibrated reference standard at multiple pressure points. Dead weight testers or precision pressure controllers work as reference devices. Record differences between your gauge and the reference standard. Use correction factors if differences exceed specified tolerances. Accredited calibration labs issue certificates that document results and adjustments. Follow manufacturer calibration schedules—12 months for industrial torque applications.

Common Reading Errors to Avoid

• Mixing up measurement units between BAR, PSI, and MPa

• Operating beyond 75% of gauge full-scale capacity

• Reading from non-parallel viewing angles

• Using low accuracy class for critical fasteners

• Skipping zero-point check before each job sequence

Check Your Wrench’s Pressure Chart

Every hydraulic torque wrench ships with its own pressure chart. This chart links to the tool’s serial number and last calibration date. You can’t swap charts between brands. You can’t even swap them between identical model numbers. Each tool’s K-factor changes a bit based on internal parts, seal wear, and piston shape differences.

Check Your Chart Before Use

Before your first torque cycle, match these three items: tool serial number, calibration certificate date, and chart issue date. They must match perfectly. A mismatch means your conversion data is wrong. Check the calibration sticker on your wrench body. Compare it to the chart header. Dates differ by more than 12 months? Stop work. Schedule recalibration.

Digital pressure charts from makers include built-in codes. Scan the QR code on Hi-Force charts with their mobile app. The system checks if your chart is real. It also warns you about expired calibration windows. HYTORC’s online portal checks serial numbers against their calibration records. Atlas Copco gives you PDFs with encrypted checksums.

Check Multiple Tools the Right Way

Labs with multiple identical wrenches need separate chart sets for each unit. Three HYTORC STEALTH-4 wrenches? You need three separate records. The serial number tells you which chart to use—not the model name. Factory tests show K-factor changes up to 2.8% between same-model units straight from production.

Document these steps for each tool:

• Run comparison tests with calibrated torque sensors

• Record actual output against chart predictions at 25%, 50%, and 75% pressure points

• Calculate deviation: (Measured Torque – Chart Torque) ÷ Chart Torque × 100

• Flag tools with deviation beyond ±3% for quick recalibration

Double-Check Your Accuracy

Use reference torque sensors to check chart accuracy during setup. Mount a calibrated sensor between the wrench and reaction arm. Set pump pressure to mid-range chart values. Compare sensor readings to chart predictions. Good variance stays within ±3% for industrial work and ±1% for critical joints.

Tritorc says test at least three pressure points: low-range (1,500 PSI), mid-range (5,500 PSI), and high-range (9,500 PSI). Record all readings. Calculate average deviation across the range. Testing just one point misses drift at pressure extremes.

Write Down Your Results

Create records showing the link between maker specs and actual field results. Include date, technician name, weather conditions, and test equipment serial numbers. Note any gaps between predicted and measured torque values. Explain fixes you made for bad results.

Lab directors must approve your check steps before clinical use—or for industrial work, before production bolting starts. Technical supervisors review results and confirm they’re good. Staff must take part. Maker reps can help but can’t complete the check on their own without your team.

Watch Out for Chart Changes

Any change from maker specs cancels the original pressure chart. Changed hydraulic fluid thickness, aftermarket seals, or non-standard temps need full validation—not just a check. Validation adds tests for sensitivity, precision, and broader performance traits beyond basic accuracy checks.

Weather changes need reverification too. Temperature shifts beyond 5°C (9°F) from calibration conditions affect fluid thickness and pressure readings. Moving tools between climate-controlled shops and outdoor sites changes your baseline data.

Conclusion

Mastering your hydraulic torque wrench pressure chart goes beyond reading numbers. You need to ensure every critical joint meets exact specs. This prevents equipment damage and safety incidents. Working with Hi-Force TWH, HYTORC Stealth, Tritorc TSL/THL, or Atlas Copco RT/RTX series tools? The pressure-to-torque relationship is your precision roadmap for perfect bolt tensioning.

Three pillars matter for pressure chart mastery. First, understand your specific manufacturer’s calibration data. Second, cross-reference tool model specs against actual job requirements. Third, verify chart accuracy through regular calibration checks. Even a 5% pressure variance can cause major torque differences in high-stakes applications.

Before your next critical project, locate your tool’s specific pressure chart. Verify its calibration date. Run a test on non-critical fasteners first. Your bolt integrity depends on this. So does the safety of everyone downstream. Precision matters, so guesswork doesn’t belong in your toolkit.

Ready to optimize your torque operations? Bookmark your manufacturer’s pressure charts. Schedule your next tool calibration today.