1.
What is rigging technology?
Rigging is the process of
using hoists, ropes, pulley, slings, jacks and cranes for lifting, lowering or
shifting the heavy objects.
2.
Who is rigger?
A person who
leads or carries out the rigging process.
3. What are the various rigging elements used in power plant?
- Synthetic
and wire ropes
- Slings
- Chain
hoist/chain block
- Pulley
block
- Screw
and hydraulic jacks
- Crane
- Winch
machine
- EOT
cranes
- Derricks…etc.
4.
Write a short note on rigging plan.
In order to ensure the
safety of workers and the equipment involved, any operation involving the use
of a lifting item to lift items must be planned thoroughly before being carried
out.
Rigging Plan Involves:
1. Determination of Task and
Job Site Requirements:
a. What is to be lifted?
b. Who is the in charge
person?
c. What are the job site
requirements?
d. What type of lift?
Ordinary
Lift: Involve the use
of basic hoisting equipment directly above the load. The load must also have
certified lifting points to relatively easy to sling. It is repetitive in
nature.
Critical
Lift: Involves
lifting objects in congested space, heavy objects, high susceptibility to
damage and precision.
Pre-Engineered
Lift: Involves use of
tooling, fixtures, sketches, analyses, and written procedures for handling.
2. Characterization of Load:
It involves weight and
center of gravity judgment of an object to be lifted
There are
mainly two types of loads that are generally handled:
Symmetrical Load: Spare, square and rectangular type
loads. These have center of gravity (C.G) at their center, so it will be very
easy to handle such objects.
Asymmetrical
Load: An object with
an off-center C.G due to the object’s irregular shape and/or composition. These
objects are difficult to handle as their C.G lies out of center.
3. Selecting the Proper
Rigging Element:
After characterizing the
load, proper rigging elements are selected.
Examples:
- For
lifting only, chain blocks and slings are selected.
- For
lifting and shifting: Cranes.
- For lifting
precision objects, lifting belts are selected instead of wire ropes and slings.
5.
What is the safe working load of 25 mm Nylon rope?
Safe working load (SWL) of
Nylon rope = D X D = 25 X 25 = 625 kgs.
Where D is the diameter of
rope in mm.
6.
What is the smallest size of nylon rope used for lifting?
Smallest size of nylon
rope used for lifting is 12 mm.
7.
What is the material of composition of wire ropes and slings?
MOC of wire ropes and
sling is Steel of grade 80.
8.
What is the smallest size of wire rope used for lifting?
Minimum size of steel wire
rope for handling loads is 5 mm.
9.
How do you calculate the safe working load of steel wire ropes and slings?
SWL of wire ropes slings =
8 X D X D, Where D is the
diameter of sling in inches.
10. What are the different hitches of slings/ropes? And what is the relation between sling angle & angle factor?
Vertical
Hitch:
In vertical hitch SWL = Capacity
of the rope/sling.
Choker
Hitch:
In choker hitch, SWL = Sling
capacity X 80%. i.e. sling lifting capacity will reduce by 20% of its rated
capacity.
Basket
Hitch:
In basket hitch, SWL of
Sling = Sling capacity X 140%, i.e. sling lifting capacity increases by 40% of
its rated capacity.
Relation between sling angle & its angle factor
As the sling angle decreases to the horizontal then the angle factor increases.That is for lower sling angles to the horizontal the capacity of the slings reduces.
it is maximum at 90 degree angle & minimum at 30 degree angle.Hence it is recommended that slings are not loaded at ange below < 30 degree
11.
What are the different slings used in power plant rigging?
Types of Slings:
- Eye/Eye
type
- Eye
thimble
- Thimble/Thimble
12. What are the pre-use checks to be done on Nylon and wire
ropes?
- Check
its manufacturer name plate details and ensure lifting load capacity.
- Check
for strand damages; discard if more than 10% of strands are damaged.
- Check
for strand frying.
- Check
for rope knotting.
- Check
for overloaded rope (Rope which was overloaded in previous lifts should not be
used for lifting at its rated SWL).
- Check
for reduction in rope diameter, wear out should be less than 10%.
- Should
not have exposed temperature more than 65 and 95 °C for synthetic and wire
ropes respectively for long time.
- Check
for corrosion/rusting of wire rope.
- Check
for any scoring or abrasion marks on wire rope.
- Check for wire
end attachments damages.
13.
How do you calculate the SWL of Chain block?
SWL = 80 X 0.4 X D2
Where D is diameter of
load chain link.
14.
What are the safe checks carried out on chain block?
Following are the
inspection checks carried out on chain blocks:
- Check
tightness of block’s nut bolts.
- Check
gearing system is well operating and its lubrication.
- Check
hook of block as per hook check list.
- Check
load chain links for elongation and wear out.
- Link
10% size less than its original diameter is discarded.
- Check
for unauthorized welding and cutting marks on chain hoist.
- Check whether
chain is in contact with acid or alkali for long time.
15.
What are the safe checks carried out on hooks used for lifting?
Inspection checks of hooks:
- Check
for manufacturer identification numbers.
- Check
for cracks, nicks etc.
- Check
for unauthorized welding and grinding.
- Check
for increase in throat area (not to exceed more than 5%).
- Check
for wear out (not to exceed more than 10%).
- Check
twist from plane of un bent hook.
16.
What are the different types of eye bolts used in lifting?
Straight and shoulder type
eye bolts are generally used for lifting applications.
17.
What is the function of turn buckle?
Turn buckles are used for
leveling and distributing the loads.
18.
List down the safe checks carried out before moving/shifting heavy jobs.
Following are the check
points for moving/shifting heavy jobs by cranes, forklifts or Hydras:
Trained
operator
- Weight
to be lifted
- CG
of load
- Lift
points
- Crane
capacity
- Crane
length, speed and boom maximum height
- Environmental
parameter’s like wind velocity, visibility and temperature
- Travel
route clearance
- Travel
floor capacity
19. What
is the allowable wind speed during rigging?
It
should be less than 9 meter per second
20. What do you mean by tandem lifting?
Rigging plan
where two cranes are used for lifting a single object
21. What are the different types of cranes
used in rigging?
- Mobile crane
- Tower crane
- Gantry crane
22. What is the allowable speed of wind
while working at height?
It is around
10.3 meter per second
23. What are the different synthetic web
slings?
Synthetic web
slings are made of Nylons & Polyesters
24. How do you decide the capacity of the
web sling?
It can be
decided by its width
25. What are the advantages of Synthetic
web slings over other slings?
- Flexible & can adjust as per required shape.
- Minimize
twisting and spinning.
- Do not rust and
are non-sparking.
- Are elastic and
stretch. Nylon has 6% & Polyester has 3% stretching capacity
Read articles related to power plant maintenance
Also read Tools & Tackles used in power plant 
