ML20210C918

Rev 0 to Calculation/Problem M-68, Qualification of Diamond Cored Bolt Holes

ML20210C918
Person / Time
Site:	Comanche Peak
Issue date:	02/02/1987
From:	ABB IMPELL CORP. (FORMERLY IMPELL CORP.)
To:
Shared Package
ML20210C645	List: ML20210C729 ML20210C803 ML20210C891 ML20210C918 ML20210C936 ML20210C970 ML20210C995 ML20210D006 ML20210D012 ML20210D030 ML20210D060 ML20210D066 ML20210D075 ML20210D087 ML20210D100 ML20210D135 ML20210D152 ML20210D165 ML20210D244 TXX-6352, Forwards Revised Documents Addressing Generic Technical Issues for Cable Tray Hangers
References
0210-041, 210-41, M-68, NUDOCS 8705060361
Download: ML20210C918 (3)

Text

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1 CALCULATION / PROBLEM COVER SHEET O'

v Calculation / Problem No: M(e6

Title:

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1.0 INTRODUCTION

$ The Comanche Peak Steam Electric Station specification EI-20 for installation of Hilti drilled-in bolts (Reference 1) allows the renoval of an existing Hilti anchor by core drilling a hole around the existing i

anchor and then installing the next larger anchor in the core drilled j hol e. The issue develops in that Hilti does not guarantee the bolt allowables when the holes were drilled with anything other than Hilti

. masonry carbide bits. There is a concern that due to the difference in hole contour and size the Hilti bolt may not develop the full capacity.

Our review of the installation procedure indicates that Hilti bolts installed in core drilled holes in accordance with the Reference 1 will be able to develop the required capacities.

2.0 Standard Hilti Installation Pr-dura e

• • 1 The Hilti installation procedure calls for a hole of the same~nomiristi.

diameter as the bolt to be drilled with a Hilti masonry carbide bit.' The hole that is formed with this bit is irregular in shape but sized so as to j provide a finn fit for the bolt. The Hilti bolt is then driven into the hole f ar enough to allow at least six threads to be below the fixture.

Hilti bolts are then tightened using a turn-of-thenut method. By turning -

the nut 3 to 4 revolutions a load slightly above the working load allowable is achieved. The anchorage is locked in place by the wedges 1

being forced against the side of the bolt hole as the tappered cone at the j end of the bolt is drawn up, i

l 3.0 TUGCD $TANDARD INSTALLATIDh Mt0EI11RE FOR HILTI B(LTS The TUGCo procedure calls for the drilling of holes using Hilti carbide bits.in comp 11anos with Hilti requirements. The bolt is then driven into the.shole and torquod to spectf fed torque level. This torque value is baasd en tests conducted by Hilti at the TUGCo Site. The TUGCo installation procedure limits the amount that the bolt may be pulled out

ofDthe hole during torquing to one nut thickness. One nut thickness is slightly more than the 3-4 turns recommended by Hiltt. However, there i

appears to be sufficient bolt end cone to allow a one nut pull out without slipping past the wedges.

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j 4.0 TUGG3 HILTI RDLAEMNT FROGDURE The TUGCo installation specification for Hilti bolts allows for the replacement of an existing Hilti bolt using a diamond core bit of the same nominal outside diameter as the replacement expansion bolt. Once the new hole has been made the bolt is then installed in accordance with a regular 4 TUGCo proceduro. It should be noted that a core drilled hole is generally round in shape and may be.slightly larger than that drilled with a Hilti carbide masonry bit. The installation of the replacement bolt is then 3

done with the same procedure as for the original bolts. This means that

the torque limits specified in the TUGCo procedure must be achtwed and d

the increase in bolt projection must be limited to the one nut thickness value specified in the installation specification for bolts installed in ,

carbide bit drilled holes.

5.0 Q)NCLUSION S The Hilti anchors are essentially a pro stressed connection in that the

! torquing done during installation pre loads the bolt and assuresfthattthe

! working load capacity has been achtwed. When a bolt is installedfinia, i dimond core drilled hole the hole size may deviate from that required to achieve maxima capacity. However, the requirement for the same bolt torque in the core drill hole as in the carbide bit drilled hole should assure that the required preload has been achtwed. The I fmitation on ,

i bolt pullout during setting must still be maintained for the diamond core j drilled hole installation.

Based on the torque and pullout limits it can be concluded that the bolt will have the required preload and capacity and that the wedges will have i the same amount of margin against slip through as the bolts in the carbide

! bit drilled hole. The requirment to achtwo the mintam torque 1wel and the limitation of bolt pullout during setting is considered adequate to assure that the Hilti expansion anchor will achtwo an acceptable capacity in the dimond core drilled hole.

i 6.0 EMBRE1 ,

.we +

1. :" Installation of Hilti Drilled In- Bolts," Proadure No. EI-20,

,Resision g, dated 12/16/5.

l 2. 'Wilti Architects and Engineers Anchor and Fastener Design Manual," ,

l 1984.

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Impell Instruction PI-ll. " Cable Tray System Analysis and Qualification Closcout" Rev. 2 (Replace Reference 45, Complete PI)

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