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Published bySherman White Modified over 8 years ago
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Blocking
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56.14211a
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56.14211b
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56.14211c
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56.14211e
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Program Policy Manual Specifically requires blocking of raised components to prevent “free & uncontrolled descent” in event of failure of system holding up raised component
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Chocking Chock vehicle before raising equipment Chock on downhill side
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Chocking Use two chock points due to increased weight & pressure generated by lifting & forcing vehicle weight back onto tires opposite of lift
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Chocking Disconnect starter devices to assure equipment is not moved & that parking brakes set
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Cribbing
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4-Point Contact Maintain 4 points of contact with solid surface at all times Example: front right frame blocked with all other tires on ground
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4-Point Contact Most jack accidents occur when individuals lift objects from center point creating an unstable situation Slight movements cause load unbalance especially using jacks with a small contact surface
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Tires on firm ground Frame blocked with cribbing
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4-Point Contact When 4 point contact cannot be maintained due to type of lift, such as lifting arms and loader buckets, need minimum of 2 contact points to maintain load stability
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Empty bucket rotated forward & hydraulic pressure relieved Post Improper pipe support Lock pins or props
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Cribbing Strength Crib capacity determined by contact area where overlying timbers contact one another Two rows of 4-point cribs can be replaced with one row of 9- point cribs without loss of support capacity
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4-Point
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9-Point
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Use 9-point cribbing for very heavy loads
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Cribbing Have safety factor of 4 Guard against natural tendency to underrate load Place on firm level foundation to evenly distribute & balance load Should not be secured in permanent fashion
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Cribbing Construction Various loads cause wood compression & slight movement in wood Assembled at time of use so proper sizing & placement considered Use hardwood
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Securing Wood Together May cause fractures or cracks along wood grain leading to crib failure Does not allow for horizontal expansion or compression without causing fractures
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Aspect Ratio H W Maintain aspect ratio between 2.5 and 5.0. Remember 26 + 3 rule. Timber lengths increase by 3” for each additional foot of crib height, starting with 26-inch timbers at 5’ height Aspect Ratio = H/W
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Wood Posts Avoid using posts for blocking unless post fitted with top cap & base plate Top caps & base plates help stabilize & distribute load Top caps 1.5 times & base plates 2 times post diameter
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Wood Posts Use hardwood Top cap & base plate thickness' vary depending on weight supported Weights over 1800 lbs can damage top caps unless properly positioned
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Wood Posts No longer than 36” due to load instability or swaying Calculate vertical weights carefully Squarely set to achieve proper load stability Even end cuts on posts
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Top Plate Base Plate Weak area when over 1800 pounds
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Maximum load identified on jack Base plates on unstable ground
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Industrial rated floor jack meeting ASME/ANSI requirements Constructed differently than those purchased at Wal-Mart
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Porta power, electric & hydraulic type lifting devices
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Light vehicle jacks designed to work with manufacturer recommended lifting points
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Jack Stands Preferred to be purchased from certified sources However… if we build ’em Before building a jack stand, it is advised that they are designed with following criteria in mind
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Building Jack Stands Substantial construction. Designed for intended weight & environment Have 4:1 safety factor Design approved by an engineer Assembled by competent welder
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Building Jack Stands Constructed from suitable materials that can withstand weights & pressures Load tested prior to service work to assure structural integrity Clearly labeled with load rating
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Top Plate Base Plate Center Support Post Gussets increase strength Use 4 on each support
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If no top plate, use blocking material to prevent slippage & assure adequate contact surface
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Make sure load rating clearly identified on stand side
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Rotational Engine Stand
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Sawhorse constructed from schedule 80 pipe & 4” I Beam
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Locking Dump Bed
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block or pin articulation joints
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Pin Lock Device
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You Make The Call
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Blocking Guidelines Park equipment on flat stable ground Set parking brake & chock Know weight of equipment Use cribbing of appropriate size & type for equipment weight
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Inspect For: Cracks Oil or grease buildup Nails, screws etc. Bent plates & supports Bent or missing lock pins Charred Never paint or stain
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Guidelines Maintain 4-point contact on equipment & 2-point contact on attached implements & hydraulic devices Block or pin articulation points to prevent movement when in raised position
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Guidelines Tagout & disconnect batteries on blocked equipment to prevent starting When repairing articulation points, use pin or securely block both sides of articulation point
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Guidelines Require appropriate training by competent person prior to work Consult manufacturers operations manual for recommended block points
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