Steel - Storage and Handling

Hello..

Generally, greater care is required in storing and handling stainless steel than carbon steel to avoid damaging the surface finish (especially for bright annealed or polished finishes) and to avoid contamination by carbon steel and iron.

Storage and handling procedures should be agreed between the relevant parties to the contract in advance of any fabrication and in sufficient detail to accommodate any special requirements. The procedures should cover, for instance, the following items:

• The steel should be inspected immediately after delivery for any surface damage.
• The steel may have a protective plastic or other coating. This should be left on as long as possible, removing it just before final fabrication. The protective covering should be called for in the procurement document if it is required (e.g. for bright annealed finishes).
• Storage in salt-laden humid atmospheres should be avoided. Storage racks should not have carbon steel rubbing surfaces and should, therefore, be protected by wooden, rubber or plastic battens or sheaths. Sheets and plates should preferably be stacked vertically; horizontally stacked sheets may get walked on with a risk of iron contamination and surface damage.
• Carbon steel lifting tackle, e.g. chains, hooks, and cleats should be avoided. Again, the use of isolating materials, or the use of suction cups, will prevent iron pick-up. The forks of fork lift trucks should also be protected.
• Contact with chemicals including undue amounts of oils and greases (which may stain some finishes) should be avoided.
• Ideally, segregated fabrication areas for carbon steel and stainless steel should be used. Only tools dedicated to stainless steel should be employed (this particularly applies to grinding wheels and wire brushes). Note that wire brushes and wire wool should be of stainless steel and generally in a grade that is equivalent in terms of corrosion resistance (e.g. do not use ferritic stainless steel brushes on austenitic stainless steel).
• As a precaution during fabrication and erection, it is advisable to ensure that any sharp burrs formed during shearing operations are removed.
• Consideration should be given to any requirements needed in protecting the finished fabrication during transportation.

Thats all for today..see u next articles.

Nondestructive Testing with Bruker Handheld XRF Analyzers

Non-destructive testing or NDT – also called non destructive examination (NDE), nondestructive inspection (NDI), and non-destructive evaluation (NDE)  – with Bruker handheld XRF analyzers can be achieved in seconds or minutes for a broad variety of applications.  By contrast, other elemental analysis techniques, such as OES (Optical Emission Spectrometry) leave a spark mark on the alloys being analyzed; and ICP (Inductively Coupled Plasma) analysis or AA (Atomic Absorption) analysis are destructive to the sample.  Handheld XRF allows you to perform completely nondestructive testing on practically any material.

When it is crucial that materials not be marred in any way yet elemental analysis is required, nondestructive testing with handheld XRF guns make it possible for many manufacturers, retailers, distributors and consultants to remain compliant with regulations:

• Art Conservation and Restoration
• Consumer Products/H.R.4040 with the (S1 TITAN) XRF Gun
• Lead in Apparel with the S1 TITAN
• TPCH- Toxics in Packaging Clearing House Laws
• ASTM F-963 - The Mandatory Toy Standard
• RoHS- Restriction of Hazardous Substances
• Prop 65- Lead restricted from all products sold in CA
• Jewelry Evaluation - Precious Metals, Gold, Silver
• PMI Analysis
• Positive Materials Identification in Aerospace Alloys
• QA/QC for Alloys

There are also applications in industries where nondestructive testing is not required yet it makes life a lot easier if the sample is not destroyed and can be confirmed with back up analysis in a laboratory:

• Soil Remediation
• Mining Exploration

Whether you are striving to comply with regulations or conducting elemental analysis where nondestructive testing is necessary for optimum efficiency, handheld XRF analyzers from Bruker can get the job done, quickly, effectively and nondestructively.

Analysis and Design of the Fastener

Analysis and retrofitting design of the fastener group for the spreader                 

                                         bar of SM3 disassembly 

Background:

      Try to re-use (or to modify) the existing Mino project spreader bar for SM3

      disassembly project. the capacity of the spreader bar for SM3 project is:

               Overall load P_t = 9.4 tons with span distance L_s = 201 in

               

Applicable codes:

      ASME B30.20; “Below – the – Hook Lifting Devices”

      ASD, AISC 9^th edition

     

References:

      ME – 397459

      ME – 397426

      MD – 397452

      “Steel Structures Design and Behavior” by C. Salmon & J. Johnson, 3^rd edition

Assumptions:

      Slip critical  connection, single shear

     

Figure 1 of  page 1 is showing that when the applying load P is eccentric to the centroid of the bolt group, this physical configuration is the actual design of the spread bar using for sm3 project.

  

                

Where:

       P = 9,400 lbs, applying load

       L = 47.625 in

       Location A is the geometrical centroid of the bolt group, 6  bolts are located as

       showing in Figure 1. currently, it is assuming: A325, ¾ - 10, UNC

       n = 6

       per Table I –D, part 4 of ASD,  R_av = 7.51 kip (allowable shear load)

Find out the local properties of the fastener group:

      ∑x² =  4 (4)² = 64 in²

         ∑y²  = 6 (2)² = 24 in²

      ∑x² +  ∑y²    = 88 in²

The primary shear load R_v of each bolt subject to the applying load P:

     R_v = P/n = 9,400 lbs / 6

          = 1,567 lbs ↓

The secondary torsional shear load of the bolt subject to the moment PL:

   To pick the bolt of the most right top one as showing in figure 1,

Where: R_x = PLy ÷ (∑x² +  ∑y²)

                  = (9,400 lbs) x (47.625 in) x (2 in) ÷ 88 in²

                  = 10,174 lbs. →

             R_y =  PLx ÷ (∑x² +  ∑y²)

                  =  (9,400 lbs) x (47.625 in) x (4 in) ÷ 88 in²

                  =  20,349 lbs ↓

The resultant force applying to the most right top bolt:

             R = [(R_v + R_y)² + R_x² ]^1/2            

                 = [(1,567 + 20,349)² + (10,174)² ]^1/2  lbs

                 = 23,259 lbs > R_av = 7.51 kip

It is necessary to look for:

      a. Different specifications of the fastener with the same fastener group.      

      b. Another pattern of the fastener group

A.Different specification of the fastener with the same fastener group:

     A1. If using 6 bolts with A325, 1 3/8”- 6 UNC,*   

       then R_av = 25.2 ksi > R = 23.26 ksi,

 *:  The hole ctr. to hole ctr. distance L_e = 4.0 in < 3d = 4.13 in

    A2. If using same fastener group with bolt of A490, 1 ¼”- 7, UNC,

 then R_av = 25.8 ksi > R = 23.26 ksi (per Table I-D, part 4 of ASD, 9^th edition)

 where: L_e = 4.0 in > 3d = 3.75 in

B. Modify the current pattern of the fastener group:

    Figure 2 on page 3 is the new fastener group with adding additional 10 fasteners to

           the original group, it can be found the new properties of the fastener group:

      ∑x² =  (4 (4)² + 4 (2)² + 6 (6)²) in²

                   = (64 + 16 + 216) in²

             = 296 in²

      ∑y²  = (6(2)² + 8(3.375)²) in²

                    = 115 in²          

                             

          ∑x² +  ∑y²    = (296 + 115) in²

                                   = 411 in²

              Also n = 16

The primary shear load R_v of each bolt subject to the applying load P:

     R_v = P/n = 9,400 lbs / 16

          = 588 lbs ↓

The secondary torsional shear load of the bolt subject to the moment PL,

To pick the bolt of the most right top one as denoted as bolt A of Figure 2:

Where: R_x = PLy ÷ (∑x² +  ∑y²)

                  = (9,400 lbs) x (47.625 in) x (3.375 in) ÷ 411 in²

                  = 3,677 lbs. →

             R_y =  PLx ÷ (∑x² +  ∑y²)

                  =  (9,400 lbs) x (47.625 in) x (6 in) ÷ 411 in²

                  =  6,536 lbs ↓

The resultant force R applying to the most right top bolt A:

             R = [(R_v + R_y)² + R_x² ]^1/2            

                 = [(588 + 6,536)² + (3,677)² ]^1/2  lbs

                 = 8,017 lbs > R_av = 7.51 kip

If the bolt material change to ASTM A490, then  R_av = 9.28 kip

             R = 8.017 kip < R_av = 9.28 kip

Since only 2 bolts of the fastener group will experience shear load of R ~ 8.017 kip, all the rest bolt shear load is less than 7.51 kip, so there are two choices:

1.      The most top right and bottom right bolts use A490, the rest bolts use A325. (3/4 – 10,  UNC.)

2.      Or all of them use A490 bolts (3/4 – 10, UNC)

The conclusions:

There are two ways to modify the current fastener group to meet the new design criteria of spreader bar for SM3 disassembly:

1.      Using (6) A490 high strength structural bolts with spec. of 1¼ - 7, UNC (original is ¾ -10, UNC), or

2.      Using (16) A490 high strength structural bolts with spec. of ¾ -10, UNC.