PE 5

• Packed tower


  The most suitable gas-liquid contacting device involving highly corrosive fluids
• Film coefficients for gases vs liquids. At equal mass velocities, the values for gases are generally lower than that for liquids
• Ultimate stress


  The ratio of the largest load in a test to the original cross-sectional area of the test specimen
• Wall thickness of thin cylindrical shell with hemispherical ends more than that of the spherical ends
• Rupture disc

  An accessory provided in chemical equipment for relieving excess pressure
• Characteristics of a vertical short tube evaporator (Calendria type)

  • Tube dia of 2.5-7.5 cms, tube length of 75-200 cms and cylindrical drum dia of 1-6 metres are normally used
  • Area of central downtake is equal to 40 to 100% of total cross-sectional area of the surrounding tube
  • Liquor is inside the tube while the steam is outside the tube
• Tube pitch


  The shortest centre to centre distance between the adjacent tubes in a shell and tube heat exchanger
• Reinforcement of shell openings greater than 5 cms for a storage tank

  Preventing the local overstressing of the shell around the opening
• Minimum tube pitch for shell and tube heat exchangers

  About 1.25 times the outside diameter of the tube
• Liquid redistribution in a packed tower

  Should be done every 6 metres or 2.5-3.0 times the column diameter, whichever is lower
• Slope of countercurrent flow rotary drier

  0 to 0.08 meter/metre
• Maximum size of saddle packing (e.g., berl and intralox saddles)

  1/15th of the column diameter
• Minimum baffle height in a shell and tube heat exchanger

  Twice the impeller diameter
• Optimum inside pipe diameter for turbulent flow (NRe > 2100) of low viscosity fluid (μ > 20cp) in steel pipes

  Di, opt = 3.9 Q0.45 ρ0.13
• Margin (minimum distance from the centre of the rivet hole to the nearest edge of the plate)

  1.5 d
• Normal range of velocity of water in pipes is 1-2 m/s
• Baffle shape that does not fall in the category of transverse baffle

  Flat plate extending across the wall
• A certain pressure vessel manufacturer's approach of always providing a reinforcing pad extending up to double the diameter of the opening and of the same material and thickness as that of the shell wall leads to safe design irrespective of the shape of the vessel
• Diamond riveted joint


  The number of rivets decreases from the innermost row to the outermost row
• Cladding/lining thickness for large process vessels operating under extreme temperature and pressure conditions

  10 to 20 percent of the total thickness
• Heat transfer coefficient for a horizontal condenser vs vertical condenser

  About 3 times
• wrong statement pertaining to the design of the distillation column.

  A. Generally, a skirt clearance of 0.5" to 1.5' is recommended to prevent plugging

  of the slots by residue build up.

  B. The purpose of the slot is to disperse the gas into the liquid in the form of small

  bubbles.

  C. If sufficient slot area is not provided, the gas may pass through the skirt

  clearance.

  D. None of these.
• Longitudinal stress induced in a thin walled cylindrical vessel under internal pressure

  pd / 4 t
• Buckling tendency of compression members

  Always in the direction of the least radius of gyration
• Shell plate thickness for plain carbon steel butt welded joints

  ≤ 3.8 cms
• Average velocity in the tubes of a 1-4 heat exchanger vs 1-1 heat exchanger

  4 times
• Hoop (circumferential) stress induced in a thin walled 'Horton Sphere' used for the storage of liquid ammonia under pressure

  ρD / 2t
• When one of the fluids is highly corrosive and has fouling tendency, it should preferably flow inside the tube for its easier internal cleaning
• Flow that achieves maximum plate efficiency

  Cross flow
• LMTD correction factor (FT)

  The ratio of true temperature difference to the LMTD
• Minimum value of ligament (clearance between two tubes in a shell and tube heat exchanger)

  One fourth the outside diameter of the tube, but in no case less than 4.5 mm
• Length to diameter ratio and number of transfer units (NTU) for economic operation of rotary dryers

  Length to diameter ratio varies from 4 to 10, and NTU varies from 1.5-2.5
• Peclet number = 0

  Represents complete back mixing
• Point 'A' on the stress-strain diagram for low carbon steel/mild steel

  Elastic limit
• Typical static submergence for bubble cap plate column operating at atmospheric pressure

  Around 0.5"
• Length of straight rectangular weir used on cross-flow trays

  0.6-0.8 times the column diameter
• Slope of the operating line in the rectifying section of a distillation column

  Less than 1
• Factors affecting stage efficiency for packed tower

  • Type and size of packing
  • Fluid rates and fluid properties
  • Operating pressure and column diameter
• Le/D for couplings and unions would be negligible
• Removable connection of tubes to tube sheet is called ferrule