tips march03

8/12/2019 Tips March03

1/25

TIPS FOR HEAVY LIFTINGAND

RIGGING ENGINEERINGPosted March 2003

This section contains tips and recommendations on heavy lifting and rigging engineering. I am a firmbeliever that the better we communicate lessons learned, unique ideas and good rigging practices toothers, the safer the rigging industry will become. The material presented here has served me wellduring the years I worked as a Crane Operator, Rigging Superintendent and Rigging Engineer. Readersare encouraged to submit tips, suggestions, comments, recommendations, or requests for moreinformation about a certain item. Credit for tips or recommendations submitted will be given unlessinstructed not to. I reserve editorial rights on what material will be used.

The following topics have been address so far. Others will be added as time allows or on specialrequest. The topics under CRANES and RIGGING ENGINEERING are in alphabetical order but theitems with in a topic are not. New items will be added to the bottom of a particular topic.

TABLE OF CONTENTSCRANES

INSPECTION:MAINTENANCE:OPERATION:

RIGGING ENGINEERINGATTACHMENT DESIGN:CRANE SET UP:CRANE STUDIES:DEADMEN:

GROUND BEARING PRESSURE:HOOKS:LIFTING:MODELS:TAILING A VERTICAL VESSEL:TRANSPORTATION:WORK HABITS:

CRANES

INSPECTION:

1. CRANE INSPECTION AND LOAD TEST PROCEDURE FORCONVENTIONAL CRAWLER AND TRUCK CRANES

Every crane should be subjected to two types of inspections:a. A maintenance inspectionb. A safety and operational inspection

The maintenance inspection is geared more to preventative maintenance and identifying thoseitems requiring repairs that will prevent the crane from being in a like new condition or fromoperating correctly, such as oxidized or cracking paint, sheet metal damage, track pad wear, track

Pgina 1 de 25TIPS FOR HEAVY LIFTING AND RIGGING ENGINEERING

16-10-2013http://www.maximumreach.com/Tips_March03.htm


2/25

roller wear, rubber tire wear, oil levels, oil changes, etc. The Equipment Superintendent or hisrepresentative usually performs this inspection.

The safety and operational inspection, on the other hand is more concerned with identifyingthose items that will either stop a lift during the middle of an operation such as a worn sheavebearing that could freezes to it's shaft or those items that could possibly lead to a componentfailure and an accident such as a hoist line with broken wires or a bent boom lacing. For

example, this inspection would not be as concerned with tire wear because all lifts are required totake place on outriggers. However, excessive tire wear would be noted on the inspection report.

Both inspections can be and sometimes are done by the same inspection party, but this procedureis geared to the safety and operational inspection and assumes that someone else will completethe maintenance inspection.

Cranes should be visually inspected by "a qualified person". A qualified person being someonewho by virtue of his education and experience is knowledgeable about cranes, crane maintenanceand rigging operations.

Cranes should be inspected per the crane manufactures recommendations and riggingprocedures. This means that the crane must be assembled with components specified by themanufacture and using his assembly procedures.

Cranes should be visually inspected per good rigging practices and Industry standards.

Listed below are the most important items to inspect on a conventional crawler or truck craneand some wear tolerances:a. Boom suspension line and end attachment devices.

1. Check for broken, worn or crushed wire on the boom drum itself with the boom inthe horizontal and in the vertical at minimum radius where the heavy loads aremore likely to occur. Replace per ASME B30.5 or local standard.

2. Check for lack of lubrication and indications of rust.3. Elongation of the pin holes in the end attachment devices such as open wedge

sockets and swage sockets should not be more than 1/8 " (3 mm). If the pins willnot turn freely, then it is an indication that the pin hole has elongated 1/8" (3 mm)or more.

b. Hoist line and end attachment device. Same criteria as 1 abovec. Boom pendants and swage fittings. Same criteria as 1 above

1. Broken wires will most usually occur right at the end of the swaged socket ratherthan in the body of the pendant itself.

2. Boom pendants should be opened up with a marlinspike and checked for properlubrication and/or rust between the strands and the core.

d. Boom sections.1. Cordsa. Must be straight within a tolerance of 1/8" in 10'b. Must be free from cuts, nicks and rust. A cut of 1/16" (1.5 mm) or more is

cause for rejectionc. Must not be repaired by anyone other than the manufactured. Must have the correct material for the connecting pins or bolts

2. Lacingsa. Must be straight within a tolerance of 1/8" in 5'b. Must be free from dings or gouges




3/25

c. Must be made of material approved by the manufacturee. Welds must be free of cracks and rustf. Lacings and their welds must be replaced/repaired only by a factory

certified welder and procedure

Note: If there is any question in the inspectors mind whether a boom section meets therequirements listed above, he should contact the Crane Manufacture for a clarification.

As the Crane Inspector, do not place your self in a position where you are approving aninspection item that may well be a safety hazard. Qualified help is available.

e. Sheaves.1. Groves. The radius of the support area must not be less than 1/16" smaller than

the wire rope diameter to prevent pinching the wire rope, and must not be greaterthan 1/16" in order to provide 135 degrees of support for the wire rope

2. Flanges must be continuous and free from structural damage3. Shafts, bearings and pins. The sheaves must roll freely by hand and have less

than 1/16" play between the shaft and the bearing. If there is more play than the1/16", disassemble the sheave or sheave nest and check the bearings and pin.Replace either the bearings or pin (or both) as required

f. Brakes and hoist clutches.1. A single part line with a load equal to the full safe working load of the hoist linewill test the adjustment and the capacity of the brakes and the hoist clutches.

g. Hooks (for the load block and the overhaul ball on the jib)1. Hooks should be inspected and tested per ASME B30.10

It is recommended that the crane inspector take a systematic approach to inspecting cranes anddo it the same way every time. For example,a. Start the inspection by having the boom laid down in the horizontal with the boom tip and

jib tip on the ground.b. Start at the right side of the crane and inspect the hoist lines, boom, jib and pendants out

to the boom or jib point.

c. Inspect the load block and the overhaul ball.d. Inspect the left side of the boom, pendants and hoist lines back to the crane.e. Inspect the hoist wire on the boom drum and the hoist drums for:

1. Wear, crushing, lubrication, etc2. Spooling

f. Inspect the gantry and boom stops.g. Inspect the counterweight.h. Inspect the brake drums and lining.i. Inspect the tracks and the car body.j. Have the boom raised until it is at minimum radius and check the boom kick out

mechanism. Do not lower the load block or overhaul ball at this time.

k. Inspect the hoist wire on the boom drum with the boom at minimum radius.l. Inspect the hoist wire on the hoist drums as the load block and over haul ball are lower tothe ground. Check to make sure there is a minimum of 5 wraps on each drum when theyare at ground level.

m. All deficiencies must be corrected at this point before going on to the next step .n. Lower the boom to about 50 degrees.o. Perform a long radius load test per the load test procedure a listed below

LOAD TEST




4/25

It is recommended that load test "a" be performed for each routine crane inspection and eachtime the crane has been assembled. Load test "b" should be performed to verify any structuralmodifications, repairs, and changes to the configuration of the crane. The load tests should beconducted using certified or verifiable weights. The crane should be set up on crane mats or on afirm surface for the load tests. These should also be full functional tests as the crane should bechecked to see that it will walk, swing, hoist up, hoist down, hold the load, boom up, and boomdown with a 100 % load, and to check all safety devices such as the vertical limit switches on the

hoist lines, the load moment kick out and the weight indicator, if applicable.

"a" A long radius load test (with the boom at approximately 50 degrees above horizontal)using test weights equal to 100 % of the applicable capacity chart at the radius beingused.

"b" A minimum or short radius load test using weights equal to 100 % of the applicablecapacity chart at the radius being used.

After each load test, the boom and boom support system (including the gantry back legs, etc), allwire rope and end terminations, and load blocks should again be thoroughly inspected for signs

of structural deformation. Freshly cracked paint is a good indicator of deformation.

MAINTENANCE:1. Adjustment of brake bands, clutch bands, etc should always be done according to the

manufacturers recommendations in the operators manual. The results of an adjustment are toocritical to guess at how to make them.

An example is the time I was assigned to a bridge project running a 60-ton Lima truck crane.The previous operator on the Lima had told me that it wouldnt boom up with a heavy load so Iinspected the boom hoist clutch but, without an operators manual, I couldnt tell if it wasadjusted correctly or not. We first poured the footings and then started setting large gang formsto construct the piers. As we were setting the large gang forms on the first pier, I boomed them

carefully out into place so that I wouldnt have to boom back up with the load. After all of theforms were set and the concrete crew started pouring them with a pump, I took the boom hoistclutch out, filed off the layer of grim on the lining and cleaned up the inside of the drum withsolvent. I figured that this would take care of the boom problem. But, when we were ready tostrip the pier and the carpenters hooked me up to the first heavy form, I couldnt boom it up. Thenewly filed hoist clutch lining just slipped and squealed, so I had to resort to my trusty operatorskit and throw some powdered resin between the lining and the drum. I was able to boom up allof the gang forms from the first pier and boom them back out into place on the second pier.

I then took the boom hoist clutch out and took it to the maintenance shop and had it relined withthe recommended lining. I figured that I now had the problem solved, but when I tried to boom

up with the first heavy gang form from the second pier, the clutch acted the same way as before.So, again I resorted to powdered resin. After we set the forms for the third pier, I went to themaster mechanic in the home office maintenance shop and asked him if he had a copy of theoperators manual for the 60-ton Lima. He copied the pages on the adjustment of the boom hoistclutch for me and off I went to check the actual adjustment.

As I was going through the adjustment check, everything checked out pretty well until I came tothe adjustment for the return spring on the rod for the air can. The adjustment in the book calledfor the spring to be tightened until it was say 3 long. In measuring it, I found that it wastightened until it was only 1.5 long. As soon as I saw this I knew that the return spring was




5/25

tightened so tight that it was overcoming most of the force from the air can that was required to seat thehoist clutch lining. The spring should have been just tight enough to keep the lining fromdragging on the drum. I made the correct adjustment and waited with anticipation as thecarpenters hooked me up to the first gang form. I engage the boom hoist clutch at low throttleand with out any slipping or squealing, the crane slowly boomed the form up out of the hole.This made a believer out of me; always make adjustments per the operators manual.

2. A lead crane operator should operate every crane on a project every two weeks or at leastmonthly to confirm that the crane is in adjustment. Many times, inexperienced operators do notrealize if a crane is getting out or is actually out of adjustment. Cranes being out of adjustmentfor the work involved can lead to a mishap or accident, i.e. when using a crane for a period oftime doing regular hook work and then using it to make a heavy lift without tightening up thebrake bands, hoist clutches, etc.

OPERATION:

1. How to still a load:Some crane operators go through their whole working careers without learning how to properlystop the motion of the hook or load after the crane has stopped swinging or booming. They seem

content to let it swing freely or until someone grabs a hold of the load and stops it for them. It isthe sign of a good crane operator when he knows how to control his load at all times. Especiallywhen it is quite easy to do so.

For example, a crane operator is pouring concrete. The operation includes picking up the bucketfull of concrete at the mixer truck and swinging it 90 degrees counterclockwise to the pour area.If he swings slowly, then the bucket will stay pretty well under the hook during the circularjourney and he can spot the bucket in front of the dump man with little or no residual swinging inany direction (assuming his pick up point and dump point are at the same radius).

Most concrete pours need to be completed as fast as possible, so typically the crane operatorpicks up the bucket and swings as fast as he possibly can. A one-drum operator only performs

one crane function at a time, i.e. hoists, then swings, then booms, then lowers the bucket, etc. Agood operator will perform several functions at the same time, including hoisting, swinging andbooming.

Therefore, as the operator in this example is a multi-drum operator, he will start hoisting thebucket and swinging at the same time. This results in the boom tip leading the bucket by severalfeet during take off. As he increases his swinging speed, the boom tip will lead the bucket evenmore. He will swing as fast as he can with out causing the bucket to swing out away from thecrane due to the centrifugal force. Just before he reaches the end of the swing arc, he willreverse his swing clutches and slow the swinging of the crane until the momentum of theconcrete bucket brings it under the boom tip. As the bucket approaches the dump man, the

operator applies more pressure to the right swing clutch to stop the bucket (the right swing clutchis actually slipping against drum flange as the crane is still swinging left). At this point, theboom tip is several feet behind the bucket. As soon as the bucket is stopped in front of the dumpman, the operator reverses the swing clutches and swings the boom tip quickly to the left overthe bucket and it is stilled, i.e. it does not move side ways in relation to the boom.

If it swings in and out at this point due to excess centrifugal force, the operator merely waits untilit reaches the end of its swing arc in toward the crane and quickly booms up, bringing the tip ofthe boom over the bucket and again it is stilledin this direction. If the operator can see that heactually needs to boom down somewhat for the bucket to be in the correct position for the dump




6/25

man, he would wait for the bucket to reach the end of its swing arc away from the crane and thenboom down over the bucket. Again, this will stop any swinging to or away from the crane. Aseveryone in rigging knows, the center of gravity of any load wants to hang under the boom tip.In this example, when the bucket is hanging under the boom tip, it cant swing with out ahorizontal force of some kind acting on it.

If the dump point is at a larger radius than the pick up point, the operator will have to boom

down during or at the end of the 90-degree swing arc. This can make stillingthe bucket eventrickier, but the operator would stillthe bucket using the same procedure as above.

If the pouring operation is being made in the blind, the signalman has to be the operators eyes.He will have to anticipate the crane functions needed and give signals, either by radio or byhand, to the operator in time for him to make them happen smoothly and safely. Operations arealways done slower in the blind. When ever possible, the operation should be set up so that theoperator can see the load at all times.

Some operators use a suck line when pouring concrete. A suck line is a hoist line running fairlyhorizontal from the front drum on the crane out thru fairleads to a connector link located just

above the hook. This prevents the bucket from moving away from the crane and allows theoperator to swing at a much faster speed. At the end of the swing cycle, he only has to stillthebucket in one direction, which is side ways to the boom. A suck line also lets the operator changethe radius of the bucket almost instantaneously. He can start at the mixer truck with a low boomangle and the bucket at say a 30 radius and during the swing arc let out on his suck line so thatwith in a second, the bucket is at a 50 radius. He does this function with his feet so he can addone more function to his multi-function list. In fact, if he is coordinated enough and his brakesare smooth enough, he can actually let out on the suck line and the hoist line at the same timeand let the bucket sail freely thru the air. The tricky part is braking smooth enough so that hedoesnt flip concrete out of the bucket. Using a suck line to pour concrete can increase thequantity poured by at least 50%. To use a suck line effectively, the crane must be located highenough that the suck line clears all obstructions during swinging, i.e., forms, vertical embedded

rebar, etc.2. Swing operation for a standard lattice boom crane, crawler or truck crane:

All of the gears, sprockets, and shafts mounted on the equipment deck of the crane are called thedraw works. The horizontal reverse clutches located in the draw works are used to swing thecrane. Refer to the sketch below for the location of these clutches. The internal expandingbands (swing clutches) are not shown for clarity and only the clutch drums are shown connectedto shaft No. 3. Shaft No. 3 is actually hollow and is made up of two sections. One section isconnected to pinion gear I and a clutch drum and the other section connects to pinion gearJand the other clutch drum. These two sections of shaft only rotate when the crane swings. Asecond shaft is connected to sprocket C and runs thru both sections of shaft No. 3. The swingclutches are also connected to this second shaft. This means that this shaft and both swing

clutches are rotating whenever the draw works are turning.

If the crane operator wants to swing to the left, he would move the swing lever until the leftswing clutch starts to bear against and slip on the drum flange closest to sprocket C. He wouldcontinue to apply more pressure on the left swing clutch until less slippage occurres and the leftclutch drum starts to rotate, which in turn rotates pinion gear I and on down thru the powertrain until the swing pinion R starts the crane swinging to the left. Note, as pinion gear I isturning counterclockwise, pinion gear J is turning clockwise. As the crane starts to swingfaster, the operator would only keep enough pressure on the left swing clutch to keep the craneswinging at the speed he want to maintain. Note, that very seldom, does the operator actually




7/25

apply enough pressure on a swing clutch to lock it to the drum flange. Most of the time, theswing clutches slip against the drum flanges to get the desired swing action. If he centers theswing lever, neither swing clutch is in contact with a drum flange and the crane would then justbe coastingon its own. To stop the crane from swinging left, the operator would move theswing lever in the opposite direction and apply enough pressure with the right swing clutch untilit slowly brings the crane to a stop. If the operator then wants to swing to the right, he wouldcontinue keeping pressure with the right swing clutch until the crane starts to slowly swing right.

The main purpose of the above narrative is to show that swinging a crane is accomplished byplaying one swing clutch against the other by slipping them against the appropriate drum flange.The swing clutches are never applied hard enough to stop the crane suddenly as this would sideload the boom, rather the crane is always brought to a gentle stop before reversing it in theopposite direction.

Hydraulic cranes do not have horizontal reverse clutches; instead they swing by means ofhydraulic swing motors hooked directly to swing pinions similar to R. Some hydraulic cranesare set up so that they will coast when the swing lever is centered. Most hydraulic cranes willnot coast and to swing, the operator meters oil thru the hydraulic motors one way or the other.When the operator stops metering oil thru the hydraulic motors, they stops turning. Therefore,

he has to be very gentle as he stops the flow of oil to the motors to keep from side loading theboom.




8/25

RIGGING ENGINEERING

ATTACHMENT DESIGN:

1. A safety factor of 1.8 is recommended for lifting attachment design. By using this factor and




9/25

using the AISC allowables for stresses, the design will conform to ASME B30.20, Below the hooklifting devices.

2. Lug design for any lifting attachment must conform to AISCs Part 5, specifications and codes,sections on pin-connected plates and eyebars.

3. A minimum safety factor of 1.25 should be used in analyzing vessel shell, skirt and baseringstresses due to lifting forces.

4. The allowable bending stress used in analyzing the above vessel stresses should not

exceed .75*Fy.5. In some cases, it is easier to initially draw a design to scale and show it the way it is supposed to

look or fit up, and then go back and check it mathematically to ensure that it will work.6. The design of some lifting attachments, especially like a long spreader bar, should be limited by

the amount of deflection involved and not just the stresses involved. A long spreader bar can bedesigned so that it is structurally sound but have visible deflection at the middle. In order tohave the erection crew feel comfortable with using the bar, the design should limit the deflectionso that it cannot be seen, even though the stresses may be very low.

7. Over the years, in checking spreader bars designed with lugs top and bottom, it has been foundthat in most cases the designers do not understand how to design them with the least amount ofbending, and the field is even worse in using them. And yet, most of the spreader bars in use to

day by the average contractor is this type of bar. This type of bar is show in the sketch below.

To illustrate how critical the design is, take the example of an 18" dia x 32 STD wall pipespreader bar with the CG of the load at the center of the bar. The top lugs are not centered overthe bottom lugs but are each 171.34 from the CG while each bottom lug is 180 from the CG.The centerline of the top lugs is 15 from the centerline of the bar. With these dimensions, andwith the top slings at a 60 degree angle with the horizontal, the line of force from the slingsintersects the centerline of the bar exactly over the bottom lugs. Therefore, the bar will havezero bending from the influence of the slings. This bar will carry a 600 kip load based on acombined unity stress check of 1.0. If slings at 55 degrees are used, this bar will only handle a325 kip load. If slings at 70 degrees are used, this bar will only handle a 440 kip load.

If the top lifting lugs were originally located directly over the bottom lifting lugs, and with theslings at 60 degrees, this bar will only handle a 155 kip load.

Therefore, it can be seen that if this type of bar is used, that it should be designed for zeromoment due to the influence of the slings, and a sling angle of 60 degrees is recommended.Using the bar with slings that produce sling angles greater or lesser than 60 degrees should bedone only after a through design check has been made. As a last comment, the top lugs shouldnever be located directly over the bottom lugs if the design is to achieve maximum capacity ofthe spreader bar.




10/25

CRANE SET UP:

1. Crane Leveling Procedurea. Layout the crane mats on the lift pad constructed per the steps in the lift pad construction.b. Walk the crane upon the mats and if possible, swing the counterweight around several




11/25

times.c. Using a four-foot carpenters level, check the level in both the longitudinal and transverse

directions. Check the transverse direction by placing the carpenters level on themachinery deck between the boom foot pins. The bubble in the carpenters level should befairly well centered between the marks, and not more than 1/8 out of level.

d. If the crane is out of level more than 1/8 in four feet, walk the crane back off the matsand place plywood under the track areas as required.

e. Walk the crane back upon the mats and recheck the level.2. Crane Lift Pad Construction

In general, the lift pad under the crane mats should be constructed to the following requirements:a. A levelness of in 30 ft.b. The lift pad should extend 3 feet outside the crane mats in all directions.c. Any down slopes connected to the lift pad should be at a 2:1 (Horizontal: Vertical) slope

or flatter.d. The lift pad should be constructed so that it is well drained.e. The lift pad should be constructed to the required soil bearing capacity.

3. Crane MatsIt is recommended that crane mats be used under the tracks of the crane for the following

conditions:a. When the soil bearing pressure under the crane tracks exceeds the allowable soil bearingpressure.

b. When the load is greater than 75 % of the lifting capacity of the lift crane, even if theallowable soil bearing pressure is greater than the actual soil bearing pressure under thetracks.

c. When the load is greater than 60 % of the lifting capacity of the tail crane, even if theallowable soil bearing pressure is greater than the actual soil bearing pressure under thetracks.

4. The top layer of crane mats should be laid out perpendicular to the crane tracks.5. The crane mats should be placed as close to each other as possible. Do not leave gaps between

the crane mats and then fill the gaps with gravel.

6. The effective length of the crane mats extending past the ends of the tracks must be used indetermining the crane mat requirements for the lift. Consult a Rigging Engineer if necessary.

7. Crane mats or wooden blocking used under the floats of truck cranes should have an area that isat least four times larger than the area of the floats. This mat area should be used over soil orconcrete. For cranes larger than 100 tons, a soil bearing study should be made to ensure that thecorrect area of crane mats is used for the allowable soil bearing of the lift pad. This is especiallytrue for capacity lifts.

8. Blocking tumblers.To correctly block the idler tumblers (the front tumblers), steel plate or hardwood blockingshould be placed directly under the centerline of the idler tumblers and in a thicknessrecommended by the crane manufacturer. See the Manitowoc Engineering sketch below

showing the correct location for blocking. The thickness of the blocking should range fromabout 1/2" to 1-3/8", depending on the crane manufacturer. The blocking width should be amaximum of 24" so it will not extend back under the front rollers. The length of the blockingshould be equal to the width of the shoes + 12" (for a 6" extension either side of the track).

The following procedure should be used to block the idler tumblers:a. Lay crane mats transverse to the tracks.b. Walk the crane upon the mats until it is within the set radius for the liftc. Set the travel locks on the craned. Walk the crane back against the travel lockse. Check the radius to make sure the crane is still within the set radius




12/25


13/25

CRANE STUDIES:

1. When doing a preliminary crane study, especially for a heavy lift, the following guidelinesshould be followed:




14/25

a. Use a maximum of 80% of lifting capacity chart for the crane being considered.Equipment to be erected has a habit of getting larger and heavier as it is being fabricatedin the shop. Using 80% will provide some reserve capacity, just in case of growth.

b. In the elevation view of the crane study, use two (2) feet of clearance between the bottomof the boom and the spreader bar, the load, etc.

c. In the elevation view of the crane study, use five (5) feet of vertical clearance between thebottom of the load and the anchor bolts or support structure.

Using the design parameters above will provide some reserve capacity and clearances as theactual weight and size of the load and the plot plan are being finalized.

2. Design parameters for final design of an Engineered lift:a. In general, use a maximum of 95% of the lifting capacity chart of the crane. For a lift to

be made at 100% of the lifting capacity chart, the following factors must be considered:1. The weight of the load must be know to +/- .5 %2. The soil bearing pressure from the lift must be lower than the allowable soil

bearing of the soil under the crane mats or concrete lift pad.3. The crane must be set up solid and level.4. The weather conditions must be clear and calm.5. The lift must be made very slowly without any impact.

b. Use a minimum of one (1) foot of clearance between the boom and spreader bar, load,etc.c. Use a minimum of three (3) feet of vertical clearance between the bottom of the load and

the anchor bolts or support structure.

DEADMEN:1. Buried deadmen should be used when every possible as they are much safer than deadmen used

on top of the ground. For example, using a coefficient of friction between concrete and dry soilfor sliding can quickly be reduced to a coefficient of friction some where between concrete andice if the weather turns cold or rainy. Also, an impact loading can move a deadman when itexceeds the sliding safety factor. If properly designed and backfilled, a buried deadman shouldnever move more than an 1/8 to .

2. Example of a deadman design:a. Maximum tension in the guywire = 76 kipsb. Slope of the guywire = 20 degreesc. Use a safety factor = 1.5d. Use a line of action of the guywire force through the center of pressuree. Use 350-lbs/cu ft for equivalent fluid density (EFD) from the soils reportf. Fp = force from the passive earth pressure acting at 1/3 of the way from the base of the

triangleg. Water table is at grade.h. Fb = buoyancy force

i. Neglect the one-foot of over burdenj. Neglect sliding friction between the deadman and the groundk. Neglect negative pressure on the bottom and back face of the deadmanl. Assume a deadman 8 wide (w) x 8 high (h) x 11 long (L)

Refer to the sketch below:




15/25

R = 76* 1.5 = 114 kips

V = 38.99 kips

H = 107.12 kips

E = 8/3 = 2.67

Check horizontal movement (sliding):

Resisting force Fp = EFD*L*h^2/2 = (350 lbs/ft 3)*11*8^2/2 =123.20 kips

123.20 kips > 107.12 kips GOOD

Check up lift:

Up lift force = V + Fb = 38.99 kips + 8*8*11*62.40 lbs/ft^3 = 82.92 kips

Resisting concrete weight CW = 8*8*11*150 lbs/ft^3 = 105.60 kips

105.60 kips > 82.82 kips GOOD

Check overturning at point A:

Overturning moment = (Fb + V)*w/2 + H*E == 82.92*4 + 107.12*2.67 = 617.69 kip-ft

Resisting moment = Fp*E + 105.60*w/2 = 123.30*2.67 + 105.60*4 = 751.61 kips

751.61 kip-ft > 617.69 kip-ft GOOD

Summary:

The 8wide x 8 high x 11 long deadman is adequate for a guyline tension of 76 kipswhere the water table is at grade or ground level.

GROUND BEARING PRESSURE:

1. Ground bearing capacity boils down to a matter of how much settlement can be tolerated for alift and/or how much money it takes to make the risk acceptable, i.e. if you wanted to beextremely safe, a reinforced concrete lift pad complete with piles could be constructed at a hugecost. As an alternative, the lift pad could be constructed of crushed rock overlaid with cranemats at a much cheaper cost. The reinforced concrete pad could be design to have negligible




16/25

settlement and the crushed rock and crane mat pad could be designed for acceptable settlements ofsay .5. If the lift was directly over the front of the crane so that both tracks settled .5, then thesettlement would not be a problem as the boom would not be side loaded. If the lift includedpicking and swinging 90 degrees, and the .5 of settlement followed the lift around, again thesettlement would not be a problem.

The problem with settlement is when it is differential settlement. This causes side loading on the

boom and also impairs the smooth operation of the crane by having to swing up hill, etc.Therefore, in most cases, the lift pad has to be designed so that differential settlement is minimal.This doesnt mean using reinforced concrete lift pads either. It can usually be done withimproving the strength of the lift pad with crushed rock or limestone and using crane mats overit.

If the ground bearing capacity of the lift pad is slightly below the ground bearing pressure causedby the lift, a failure of the soil will not occur, just settlement. For example, consider a lift with aground bearing pressure of 5,000 psf being made on a lift pad with a ground bearing capacity ofsay 4,000 psf. In this case, the lift pad will settle until it picks up the required bearing area tosupport 5,000 psf and then the settlement will stop. This is usually what happens and nobody

realizes that the settlement has taken place, even if it causes some differential settlement withsome side loading of the boom. That is unless it settles far enough to cause an accident.

So, in summation, ground-bearing capacity is really a matter of how much settlement can betolerated and if any differential settlement can be allowed.

2. Figure 10-4 below shows some bearing values that can be used as guidelines when estimating thebearing strength of a lift pad or the surrounding soil. Be very conservative in using the table, i.e.if the lift pad and the subsoil are made of firm sandy gravel; choose class 6 with a bearing valueof 8,000 psf instead of class 5 with 10,000 psf. Whenever in doubt or for a very critical lift,dont guess. Have the owner provide an allowable ground bearing capacity for the lift pad or subsoil.




17/25

HOOKS:

1. Load block hooks up to and including 250 ton capacity, should be completely disassembled fromthe load blocks, thoroughly inspected, and repaired as required to bring them and any component




18/25

parts back to a like new condition. This should be done at least every five years.2. Overhaul ball hooks should be completely disassembled from the overhaul balls, thoroughly

inspected, and repaired as required to bring them and any component parts back to a like newcondition. This should be done at least every other year.

3. FOR ENGINEERED LIFTS ONLY, Crosby now allows three (3) slings and four (4) slings to becollected in the bowl of a Crosby Shank Hook with the following restrictions: (Refer to thesketch below for a graphic illustration of the sling configurations)

a. All legs must be collected within 30 degrees either side of the centerline of the hook bowlas illustrated in Figure 1 and 2 of the sketch.

b. For Three (3) Leg Slings:1. The vertical plane * of the hook should be parallel with the plane of the sheaves2. The horizontal sling angle of the legs must be 60 degrees or greater3. The single leg must be on the point side, and the double legs on the backside of

the hook throat4. The sum of the vertical components must not exceed the WLL of the system

and/or the hook5. The included angle between the sling legs must be 120 degrees as shown in the

top view of Figure 1

c. For Four (4) Leg Slings:1. All legs must be loaded equally with symmetrical angles about the verticalcenterline of the hook

2. The sum of the vertical components must not exceed the WLL of the system orthe hook

3. The horizontal sling angle of the legs must be 60 degrees or greaterd. All other loading conditions must be analyzed by a qualified person, and the WLL

reduced such that the combined hook shank stresses (bending & tensile) do not exceedthe original shank tensile stress at the rated WLL

* The vertical plane bisects the hook through the centerline of the shank and point




19/25




20/25


21/25

required.p. Instruct the operator to leave the house swing brake and/or lock off during lifting.q. When working with crawler cranes, added safety can be obtained by making all lifts over

the front of the tracks with the tumblers blocked. As the crane takes the weight of theload, a qualified person, either the crane oiler or rigger, should constantly monitor thetrack rollers on the counterweight side of the crane. If daylight occurs between thebottom of the rollers and the top of the track shoes, or settlement occurs under the load

side of the tracks, the lift should be stopped and the lift conditions checked as tippingmay be starting

r. A qualified person, either the crane oiler or rigger should constantly monitor theoutriggers as the truck crane takes the load. If daylight occurs between the top of theoutrigger beams and the outrigger housing on the counterweight side of the crane orsettlement occurs under the outriggers on the load side of the crane, the lift should bestopped and the lift conditions checked as tipping may be starting.

s. A qualified person, either the crane oiler or rigger should constantly monitor the positionof the load block during the lift by standing directly behind the lattice boom crane andlooking through the center of the boom, or by standing behind and sighting on both sidesof a hydraulic crane boom. If the load block is not centered in the boom, the lift should be

stopped and lift conditions checked as the boom is being side loaded.t. Whenever possible, make a dry run with the load just clearing the ground. Swing theload over the side, for example, and boom it out into a clear area to the actual set radius.Check the stability of the crane at the set radius, boom the load into minimum radius,swing to the set angle over the rear of the crane, boom out and set the load.

u. Do not make any lift in winds that exceed the manufacturers recommendations.v. If the crane is working at minimum radius, boom down before releasing all the load

weight. Failure to do so will result in bent boom stops and/or a bent boom as the stretchcomes out of the boom pendants.

The above list is not all-inclusive, but contains the most important elements needed to make asafe lift. The rigging supervisor and the rigging crew should also follow all good riggingpractices and industry standards.

MODELS:1. Models are very useful for determining how a load will react during lifting. The model doesnt

have to look exactly like the load being lifted; it only needs to be to some scale with the weight,the location of the lifting points and the location of the center of gravity in proportion to theactual load.

A photo of a model of Quiz No. 1 is shown below. Note that all that was required was a two footpiece of wood, two pieces of bicycle chain and sprockets, a 1.5 nipple, a bolt, a nut, somewashers and some string.




22/25

TAILING A VERTICAL VESSEL:

1. For maximum safety during a tailing operation, the boom on the tail crane should be as short aspossible. Many contractors try to get multi-use out of a crane, without changing the boom. Thesmall expense of shortening the boom for a tailing operation and then lengthen it again is worththe added safety achieved.

2. Do not use a jib on the tail crane during a tailing operation. It is hard to keep the jib mast or thejib itself from interfering with platforms, etc.

3. Vertical vessels that do not have tail lugs for up ending will have to be erected using a tail sling(s). There is some risk in this operation if the tail sling is not rigged properly around the skirt orbottom of the vessel. The correct procedure is:a. Refer to the sketch at the bottom of this item and select the recommended timber

blocking size for the diameter of the vessel being erected, i.e. for a 4' diameter vessel, usefour- 4" x 4" x 6' hard wood blocks.

b. Position the four blocks on the skirt of the vessel as shown and secure them with twotirfors or come-alongs.

c. Attach the tail sling to the hook on the tail crane.d. Center the hook and tail sling over the vessel about 2' from the base plate.e. Wrap the tail sling around the skirt and connect it as shown with the appropriate shackle.f. Before tightening up the tail sling, rotate the sling (clockwise as viewed on the sketch)

around the skirt about 6". This will move the shackle off center and force it and the slingto bite down on to the timbers as the sling is being tightened up.

g. Snug up on the tail sling. If the tail sling is not centered over the vessel, slack off on thesling and repeat step f.




23/25

h. Hammer the shackle down as far as it will go until it rests on the timbers.i. Slowly hoist until the crane has about 50 % of the tail load. If the sling and shackle are

snug down against the timbers and the sling is centered over the skirt, the bottom of thevessel is ready to be lifted.

Note! If the sling and shackle are snug down against the timbers, it is nearly impossible for thesling to slip or ride up as the vessel is being up ended. In order for the sling to ride up on the

skirt, the circumferential length of the sling around the skirt would have to increase. Under load,this is impossible. The friction between the sling /wood and the skirt provides a resisting forcethat is greater than necessary to prevent slippage of the sling.




24/25

4. Do not tail a vessel by placing a choker on a cone section. The sling will slip to the smalldiameter of the cone during lifting, possibly damaging the sling and/or flange.




25/25

TRANSPORTATION:

1. Transportation drawings should show the stability of the trailer and load for both tipping andstructural. Calculations should be furnished that back up the above information. Allowabletipping should be calculated on a 5:1 safety factor. This is applicable to platform trailers andlowboys.

2. Transportation drawings for platform trailers should show how the hydraulic cylinders are

plumbed, i.e., in a three-point suspension or in a four-point suspension.

WORK HABITS:1. Work habits that have served me well during my career:

a. Carrying a notebook and keeping a to dolist. Prioritizing it dailyb. Carrying a small tape measure and a piece of soap stone to the fieldc. Keeping only one design job on my desk at a timed. Breaking each job down and getting the long term items started first, so the job will come

together as efficiently as possiblee. Always starting work on time. You can start work early, you can stay late, but people

will always know if you are running late

f. Knowing that hindsight is always 20-20. Learning from my mistakes and then movingon, not dwelling on the mistakesg. Keeping my employees from making the big mistakes, but letting them make the little

ones by themselves, so they can learn and progressh. Letting my employees know that if anything goes wrong, I will take the blame and when

things go well, everybody will share the crediti. Being loyal to the company and being honest. Never accepting more than a dinner from

a Vendorj. Being passionate about by work. I never had a day that I didnt enjoy going to work.


tips march03

Documents