Blocking

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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

Chocking Chock vehicle before raising equipment Chock on downhill side

Chocking Use two chock points due to increased weight & pressure generated by lifting & forcing vehicle weight back onto tires opposite of lift

Chocking Disconnect starter devices to assure equipment is not moved & that parking brakes set

Cribbing

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

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

Tires on firm ground Frame blocked with cribbing

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

Empty bucket rotated forward & hydraulic pressure relieved Post Improper pipe support Lock pins or props

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

4-Point

9-Point

Use 9-point cribbing for very heavy loads

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

Cribbing Construction Various loads cause wood compression & slight movement in wood Assembled at time of use so proper sizing & placement considered Use hardwood

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

Aspect Ratio H W Maintain aspect ratio between 2.5 and 5.0. Remember 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

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

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

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

Top Plate Base Plate Weak area when over 1800 pounds

Maximum load identified on jack Base plates on unstable ground

Industrial rated floor jack meeting ASME/ANSI requirements Constructed differently than those purchased at Wal-Mart

Porta power, electric & hydraulic type lifting devices

Light vehicle jacks designed to work with manufacturer recommended lifting points

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

Building Jack Stands Substantial construction. Designed for intended weight & environment Have 4:1 safety factor Design approved by an engineer Assembled by competent welder

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

Top Plate Base Plate Center Support Post Gussets increase strength Use 4 on each support

If no top plate, use blocking material to prevent slippage & assure adequate contact surface

Make sure load rating clearly identified on stand side

Rotational Engine Stand

Sawhorse constructed from schedule 80 pipe & 4” I Beam

Locking Dump Bed

block or pin articulation joints

Pin Lock Device

You Make The Call

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

Inspect For: Cracks Oil or grease buildup Nails, screws etc. Bent plates & supports Bent or missing lock pins Charred Never paint or stain

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

Guidelines Tagout & disconnect batteries on blocked equipment to prevent starting When repairing articulation points, use pin or securely block both sides of articulation point

Guidelines Require appropriate training by competent person prior to work Consult manufacturers operations manual for recommended block points