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UBC International Training Fund

PresentsPresents

Tensioning

The following material is intended to make you aware

of the currently acceptable and recognized methods of

performing the tasks described in this presentation.

However, every possible application of these methods

cannot be foreseen and the following material is not

designed to cover every potential application. Therefore,

you must always follow all current procedures and safety

regulations whenever you perform any of the tasks

discussed in this presentation.

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WE SAID BEFORE -

THERE ARE TWO COMMON WAYS TO PRE-LOADA BOLT OR STUD:

1. TORQUE

2. TENSIONING

NOW THAT WE KNOW SOMETHING ABOUT TORQUELET’S DISCUSS TENSIONING

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TENSIONING

TENSIONING = STRETCH THE BOLT,

LET IT SPRING BACK

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TENSIONING

1. HEAT

3 WAYS TO TENSION

2. HYDRAULIC TENSIONERS

3. MECHANICAL TENSIONERS

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TENSIONING

TENSIONING WITH HEAT

Gas Bolt HeaterGas Bolt Heater

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Objectives

• Correctly setup a gas bolt heater

• Properly adjust oxy-acetylene flame

• Correctly adjust air flow

• Safely operate a gas bolt heater

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Design

• Heating causes a bolt to grow in length

• Relieves tension on bolt

• Gas Bolt Heater is machined from solid Stainless Steel

• A single bolt heater can be adapted to fit most bolt sizes by changing the heating tube diameter and length

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Operation• Select a heating tube that is 1/8” smaller than the

hole in the bolt and approximately 3” shorter than the depth of the hole

• Install heating tube in bolt heater• Use stainless steel reducing bushing for smaller

heating tubes• Use high temperature thread compound• Tighten hand tight• Connect air line to bolt heater• Air pressure should be between 50-100 PSI

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• Set oxygen pressure to 14 PSI

• Set Acetylene pressure to 7 PSI

• Use Victor #5-W gas welding tip

• Always use check valves

• Adjust flame to obtain a carburizing flame– Carburizing flame has an acetylene feather

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• Insert bolt heater into bolt• Purge bolt cavity with air• Turn air valve off• Insert welding tip into gas bolt heater• Gradually open air valve approximately 1/8 turn• Observe color of heating tube through vent holes

in gas bolt heater• Maintain a cherry red color by adjusting air valve

– More air is cooler– Less air is hotter

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• For proper operation a balance of pressure must be maintained between welding tip and heating chamber back pressure

• Excess back pressure will result in welding tip back-fire

• If back-fire occurs, close acetylene valve, remove welding tip from bolt heater, purge bolt cavity with air, and restart heating process

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TENSIONING

TENSIONING WITH HEAT

(INDUCTION)

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TENSIONING

TENSIONING WITH HEAT

CON’S:•HOT•SLOW•INACCURATE•HARD ON STUDS•MUST HAVE HOLE•ROUGH ON GASKETS

PRO’S:•MINIMUM MUSCLE

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TENSIONING

1. HEAT

3 WAYS TO TENSION

2. HYDRAULIC TENSIONERS

3. MECHANICAL TENSIONERS

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TENSIONING

HYDRAULIC TENSIONERS

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TENSIONING

HYDRAULIC TENSIONERS

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VARIOUS TYPE OF HYDRAULIC TENSIONERS

TOP CONNECTCYLINDER

SIDE CONNECTCYLINDER

HYDRAULICNUT

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TENSIONING

1. HEAT

3 WAYS TO TENSION

2. HYDRAULIC TENSIONERS

3. MECHANICAL TENSIONERS

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JACK SCREW TYPE

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TORQUING THE JACK SCREWS

•MULTIPLIES WORK •TAKES FOREVER

•TINY LOAD POINTS •CAN’T CHECK RESULTS

The EndThe End