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  • In mining and slurry pipelines, correct flange bolt torque is essential for safe, leak-free hose performance.

    Unlike rigid steel pipe, mining hose contains rubber components that compress during tightening. This means bolt tension can reduce after the first pass, requiring multiple tightening cycles to achieve the correct final clamp load.

    Step 1: Confirm the Connection Type

    These torque values are intended for bolting a rubber beaded end mining hose to a flat steel flange face.

    It is also important to understand that every application is different. Pressure, end construction, hose application, bolt grade, can all influence the final torque required.

    The values below should therefore be used as a general installation guide only.

    Step 2: Select the Starting Torque

    • Pressure Rating

      150 PSI / 10 Bar 300 PSI / 20 Bar 450 PSI / 30 Bar

    • Recommended Starting Torque

      80 Nm 100 Nm 200 Nm

    Please note the above torque values do not apply to different connection styles such as rubber-to-rubber joints, fixed flanges, flanged coupling or Victaulic ends. For these styles different procedures may apply.

    Step 3: Check Hose and Flange Alignment Before tightening, make sure:

    • Hose ID is aligned with the pipe ID
    • Flange faces are square
    • The hose is not twisted
    • Bolts are not being used to pull pipework into position

      • Unchanged:

    Poor alignment can cause leaks even when the bolts are torqued correctly.

    Flange Alignment Before tightening
    Figure 3.1

    Step 4: Fit Bolts and Hand Tighten

    Install all bolts, nuts, and washers.

    Hand tighten first so the flange faces pull together evenly.

    Do not fully tighten one bolt at a time.

    Fit Bolts and Hand Tighten
    Figure 4.1

    Step 5: Torque in a Star Pattern

    Tighten bolts in a star pattern to apply even pressure across the rubber bead.

    For an 8 bolt flange the sequence will look like the above diagram

    Torque in a Star Pattern
    Figure 5.1

    Step 6: Complete Minimum 3 Torque Passes

    Because rubber absorbs pressure and settles under load, bolts must be gone over at least three times at full load.

    Recommended method:

    Pass Torque
    Pass 1 75% of target torque
    Pass 2 100% of target torque
    Pass 3 100% of target torque
    Pass 4 100% of target torque
    Complete Minimum
    Figure 6.1

    Step 7: Inspect for Leaks

    Once the hose is installed and pressurised, inspect the flange joint for leaks.

    Check for:

    • Weeping around the flange
    • Uneven compression
    • Inspect for Leaks
    Figure 7.1

    Step 8: Increase Torque Only if Required

    If the hose continues to leak after the correct torque procedure:

    • Increase torque in 20 Nm increments
    • Retorque using the star pattern
    • Go around the flange evenly
    • Recheck for leaks after each increase

    It is critical to increase torque in small increments. Over torquing can distort the flange or backing ring causing premature wear or failure.

    Step 9: Final Check

    Before putting the hose into full service, confirm:

    • All bolts have been torqued evenly
    • There are no leaks
    • The hose is not under twist or strain
    • Supports are correctly positioned

    Correct bolt torque, alignment, and installation procedure are critical to achieving safe and reliable mining hose performance.