‘Squirter®’ Direct Tension Indicators

ST

RU

CT

UR

AL

‘Squirters®’

‘Squirter®’ DTI’s

‘Squirters®’ are special direct tension indicators with fl exible silicone embedded in the depressions under the indicator protrusions. Fit them under a nut face washer under the nut and tighten the assembly until after the orange silicone appears in volume from most of the DTI’s squirt locations, stop tightening and that’s all there is to it.

Saves erector timeTensioning is achieved quickly because the operator can see when to stop and move on.

Shank tension achieved accuratelyTension control not torque control. Tension is consistent.

Easier and better than part-turn methodYou don’t have to remember to stop turning at 1/2 or 3/4 turn. No match marking necessary

Easier and better than torque controlYou don’t have to establish and then check torque resistance of bolts daily, for each lot or when wrench conditions change.

Works with all bolt lengthsEven when the bolts are extremely short or long, ‘Squirter®’ DTI’s show when the correct tension has been achieved.

‘Squirter®’ DTI performanceThe performance requirements of the ‘Squirter®’ DTI’s comply fully with the requirements of BS 7644 Part 1 Grade 1 suitable for use with BS 4395 Part 1 HSFG fastener assemblies.

The use of ‘Squirter®’ DTI’s has enabled bolting, inspection and approval on the Dubai International Airport project to be carried out in record time.

The first 8000 tons of the new prestigeous terminal building used standard DTI’s, but when Cleveland Bridge commenced work on a new phase they began to use ‘Squirter®’ DTI’s. Now several hundred thousand ‘Squirters®’ later there is no going back.

Three levels of inspection exist on this project, by Cleveland Bridge, an outside inspection company and the owner’s consultant, DAR. Despite this, Cleveland Bridge reported that the visual confirmation offered by ‘Squirter®’ DTI’s had enabled site staff to finish a joint, have it inspected and move on quickly, without any call-backs.

��������������� � � � � � � � � �

������������������������������������������

‘Squirter®’ DTI’s were developed in the USA by Applied Bolting Technology Products Inc and are being manufactured and distributed in the UK and Europe by Cooper and Turner Limited. Squirter DTI’s and Squirter DTI are registered trade marks of Applied Bolting Technology Products Inc.

Case Study

Hole Sizes

‘Squirter®’ DTI’s must be used over normal clearance holes, as specified in BS4604. A ‘Squirter®’ DTI will not function correctly if placed directly over an over-size or slotted hole. (Please call for further advice)

Calculation of Bolt Lengths

The calculation of HSFG bolt lengths required for ‘Squirter®’ DTI’s is identical to that for other DTI’s. The grip length i.e. the total thickness of the members to be bolted together, should be added to the length shown in Table 3. The figure shown in the table allows for the thickness of the ‘Squirter®’ DTI, the thickness of one flat round washer or one nut face washer, the nut and sufficient bolt protrusion through the nut. If the length obtained is between bolt lengths, the total length is rounded off to the next longer.

*Each ‘Squirter®’ has one squirt location for every protrusion. The number of squirts should be at least equal to the number of protrusions on the ‘Squirter®’ less one. For instance a five protrusion ‘Squirter®’ DTI should squirt out in at least four places.

Shank Tension

When installed in accordance with these instructions the shank tension achieved will not be less than the minimum specified in BS4604 Part 1 for BS4395 Part 1 HSFG bolts. (see Table 1)

Description

The performance requirements of ‘Squirter®’ DTI’s comply fully with the requirements of BS7644 Part 1 Grade 1 suitable for use with BS4395 Part 1 HSFG fastener assemblies ‘Squirter®’ DTI’s are supplied in a mechanically galvanized finish in accordance with ASTM B695 Class 50, this finish is totally compatible with the high temperature hot dip galvanized ‘Galvaspin’ finish or zinc electroplated finish applied to the HSFG bolts and nuts.

‘Squirter®’ DTI’s can be used like a conventional DTI and fitted under the bolt head but the greatest benefit from using ‘Squirter®’ DTI’s is achieved when they are fitted under the nut where the wrench operator can monitor the tightening directly. To use them in this location, simply fit them under a nut face washer under the nut and tighten the assembly until after the orange silicone appears in volume from most of the DTI’s squirt locations*. Stop tightening and that’s all there is to it.

‘Squirter®’ DTI’s

Nominal Diameter

Minimum Shank Tension (kN)

M16 92.1

M20 144

M22 177

M24 207

M27 234

M30 286

M36 418Table 1

Average Indicator Gaps (mm)

Indicator Position Max Average Gap

Under nut face washer under nut, when nut is rotated

0.25

Under bolt head, when nut is rotated

0.40

Table 2

Nominal Diameter

Additional to grip length to give bolt length required for use with ‘Squirter®’

DTI (mm)

M16 29

M20 33

M22 37

M24 39

M27 42

M30 45

M36 51Table 3

closed sufficiently at the intended squirt appearance. Inspectors will then be able to tell at a glance which of the bolts has been tensioned correctly. Occasional checks with a feeler gauge may be carried out (see table 4).

Calibration and Installation Procedure

Before commencing installation, ‘Squirter®’ DTI’s must be calibrated by checking the ‘Squirter®’ DTI gap with a feeler gauge in the projects structural steelwork. (see Table 2) ‘Squirter®’ DTI’s have circumferential indentations spaced equally around the outside circumference, corresponding to and in alignment with each feeler gauge entry space to indicate where the feeler gauge must be inserted.

‘Squirter®’ Position – Under nut face washer under nut, tightened by rotation of the nut.

Tighten the assembly and verify suffucient compression with a 0.25mm feeler gauge. (see Table 2)

Insufficient compression has occured when the feeler gauge can be inserted in more than half the ‘Squirter®’

DTI gaps. If this happens, tighten the assembly a little more and repeat verification.

When the feeler gauge can not be inserted in half the ‘Squirter®’ DTI gaps (see Table 4), you have sufficient compression, note the squirt volume & appearance and repeat this two or three more times at the beginning of work. Erectors will quickly get a feel for how much squirt volume indicates correct tension.

‘Squirter®’ Position – Under bolt head, tightened by rotation of the nut.

Tightening procedure generally as for under nut fitting but check gap with a 0.40mm feeler gauge. (See Table 2)

Snug tighten the joint

Always snug tighten an array of ‘Squirter®’ DTI assemblies in a joint before final tightening. Starting from the middle of the joint, tighten the assemblies in a staggered pattern working outwards and partially tighten without any or much silicone showing. Don’t fully compress the ‘Squirter®’ DTI on the snug (first) pass. After snug tightening there should be no (or very little) silicone showing.

Finally tighten the joint

Tighten the ‘Squirter®’ DTI assemblies, in the same pattern as for snug tightening until after the orange silicone appears in volume from most of the ‘Squirters®’ squirt locations. Don’t stop tightening until the squirt volume and appearance is just like it was in the calibration exercise. Then stop tightening.

Inspection

Observe the ‘Squirter®’ DTI’s calibration procedure at the beginning of the project. Ensure the DTI gap has been

NominalDiameter

Number of indicator

protrusions

Minimum number of

feeler gauge refusals

M16 4 2

M20 5 3

M22 5 3

M24 5 3

M27 6 3

M30 7 4

M36 8 4Table 4

Stage 1:Loose

Stage 2:Snug

Stage 3: Tight