Question No. 51
What are various temporary closures for
lines?
Answer:
Line blind valve, line blind, spectacle plate, double block and bleed,
blind flanges replacing a removable spool.
Question No. 52
Why horizontal displacement is specified in data-sheet? What will you do if the angle due to displacement is more than 4
degree?
Answer:
For bottom mounted springs it is mentioned to avoid large spring bending by
frictional force and displacement. So that additional measures can be taken to
lower frictional force by providing PTFE/graphite slide plate.
For top
mounted spring hangers horizontal displacement is mentioned to check angularity
of 4 degree to reduce transmission of horizontal force to piping systems as
spring hangers are designed to take the vertical load only.
If angle
becomes more than 4 degree due to large horizontal movement then install the
spring hanger in a offset position so that after movement the angle becomes
less than 4 degree.
Question No. 53
Which spring will you select for your
system: Spring with low stiffness or higher stiffness and why?
Answer:
Springs with lower stiffness provides less load variation for same travel.
So this spring is a better choice than a spring hanger with higher stiffness.
Question No. 54
What do you mean by Stress? What are the
types of Stresses that are generated in a Piping?
Answer:
Whenever a force is applied to any object it applies a reaction force
against the deformation by that force. That reaction force per unit area is the
measure for the generated stress.
There has to
be an external force to create stress. In a piping system there are various
reasons for the generation of stress like Piping Weight, Internal and External
pressure, Change in temperature, Seismic and Wind forces, PSV reaction force
etc.
The stresses
generated in a piping system are as follows:
- Axial Stresses
- Tangential or Hoop stress
- Longitudinal Stress
- Radial Stress
- Expansion Stress
- Stress due to occasional events like Seismic and Wind effects.
Question No. 55
What factors to consider for site
selection?
Answer:
District classification, Transportation facilities, Manpower availability,
industrial infrastructure, community infrastructure, availability of raw water,
effluent disposal, availability of power, availability of industrial gas, site
size and nature, ecology and pollution.
Question No. 56
Why Stress Analysis is required?
Answer:
Ensure reliability and safety of working by
- Limiting Stresses (sustained, expansion, hydro-test, occasional) within code allowable.
- Limiting nozzle load and moments connected to equipment (Pump/Vessel/Heat Exchanger etc) within allowable values.
- Reducing damaging effects of dynamic loads.
- Avoiding leakage at joints.
- Limiting sagging and displacements within allowable limits.
- Avoiding high loads on supporting structures.
Question No. 57
What is the difference between Stress and
Pressure?
Answer:
Stress is generated because of internal resistance force. Pressure is
generated because of external force.
Pressure can
be a cause to generate stress.
Question No. 58
Where jacked screwed flange is used?
Answer:
For spectacle discs, one flange is jacked screw flange. This flange has two
jacked screws 180 degree apart which are used to create sufficient space
between flange for easy removal and placement of line blind or spectacle blind.
Question No. 59
What is double block and bleed?
Answer:
Two valves with bleed ring in between with a bleed valve connected to the
hole of bleed ring.
Question No. 60
Where blind flange is used?
Answer:
It is used with view to future expansion of the piping system, or for
cleaning, inspection etc.
Question No. 61
What are crude oil ranges?
Answer:
Crude oil BP Range: 100F-1400F, lightest material: below 100F, Heavier
materials- upto 800F, Residue above 800F.
Question No. 62
What is batch shell process?
Answer:
feed, heat, condense, heat more, condense, low quality.
Question No. 63
What are types of towers?
Answer:
Stripper, Vacuum tower, trayed, packed towers.
Question No. 64
What is chimney tray?
Answer:
It’s a solid plate with central chimney section, used at draw-off sections
of the tower.
Question No. 65
What factors to consider while setting
tower elevation?
Answer:
NPSH, Operator access, Maintenance access, Minimum clearance, re-boiler
type , common area, type of support, Tower dimensions, type of head, bottom
outlet size, foundation details, minimum clearances.
Question No. 66
How to located tower maintenance access
nozzles?
Answer:
At bottom, top and intermediate sections of tower, must not be at the
down-comer section of tower and in front of internal piping.
Question No. 67
How to located feed nozzle?
Answer:
Must be oriented in specific area of tray by means of internal piping.
Question No. 68
What are the steps in selection of valve?
Answer: What to handle, liquid,
gas or powder, fluid nature, function, construction material, disc type, stem
type, how to operate, bonnet type, body ends, delivery time, cost, warranty.
Question No. 69
What are functions of valves?
Answer: Isolation, regulation,
non-return and special purposes.
Question No. 70
What are isolating valves?
Answer: Gate, ball, plug,
piston, diaphragm, butterfly, pinch.
Question No. 71
What are regulation valves?
Answer: Globe, needle,
butterfly, diaphragm, piston, pinch.
Question No. 72
What are non-return valves?
Answer: check valve.
Question No. 73
What are special valves?
Answer: multi-port, flush
bottom, float, foot, pressure relief, breather.
Question No. 74
What materials are used for construction of
valves?
Answer: Cast iron, bronze, gun
metal, carbon steel, stainless steel, alloy carbon steel, polypropylene and
other plastics, special alloys.
Question No. 75
What is trim?
Answer: Trim is composed of
stem, seat surfaces, back seat bushing and other small internal parts that
normally contact the surface fluid.