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    Pressure Vessels, Glass Vessels and Glass-lined Vessels

    Springer International Publishing Switzerland 2015K. Golwalkar, Process Equipment Procurement in the Chemical and Related Industries, DOI 10.1007/978-3-319-12078-2_7


    Pressure vessels are very important process equipment. Their typical applications include the manufacture of ammonia, liquid sulphur trioxide (by boiling of oleums), nitrogen and oxygen (cryogenic, PSA and membrane processes), processing of pe-troleum, waste heat recovery boilers, etc.

    Incorrect specifications can lead to serious accidents. Hence, the following in-formation should be given to and discussed with designer and fabricator before ordering procurement.

    7.1 Considerations for Procurement of Pressure Vessels

    Intended use: reactor, condenser, heat exchanger, boiler, air receiver Intermittent or continuous use Volumetric capacity (working volume and some empty space at the top) Normal operating weight of the vessel: up to the overflow nozzle Maximum weight when completely filled Agitated/un-agitated Will the vessel be a fired or an unfired one? This is extremely important for

    statutory regulations. The purchaser should treat (from safety point of view) any process unit likely to develop pressure due to heating, reaction, choking of exit gas pipes, closure of valves of outlet pipes, failure of cooling medium, etc. as a fired pressure vessel. All precautions regarding designing, MOC, construction, testing, erection, commissioning, operation and maintenance should be taken

    Properties and composition of material to be handled: toxic/inflammable/explo-sion limits/boiling point/density/viscosity/erosive/corrosive

    pH, density, melting and boiling points of material to be handled Reactions, heat evolution, rise in pressure when reactants are added at a normal

    rate. However, the maximum rate of additions should also be considered for de-sign

    Corrosive/inflammable/explosive nature of material

  • 78 7 Pressure Vessels, Glass Vessels and Glass-lined Vessels

    Possibility of condensation of reactants into solids at low temperature, this may choke inlet/outlet nozzles

    Operating pressures: normal and maximum; future increases Operating temperatures: minimum, maximum and possible shock loads due to

    sudden development of higher rates of reactions, which may cause high tempera-tures

    Frequency of pressurisation/depressurisation during use of the vessel Is the vessel stationary or transported regularly during use (product tanker)? Installation location: indoor/outdoor, height from the ground Installation position: horizontal/vertical Will the pressure vessel be heated or cooled (internally/externally)?

    7.1.1 Arrangements

    Safety valves and rupture discs Nozzles for vent, safety valves, pressure and temperature indicators For heating/cooling (to be decided by the design engineer appointed by pur-

    chaser): whether jacket or external limpet coils (for external reinforcement) or internal coils (difficult to clean and replace) are required

    Nozzles for level indicator, sight and light glasses, sampling points, inlet of reac-tants and exit of products, entry for agitator shaft, thermo wells for temperature indicators

    Connecting pipes to nozzles and their orientations for incoming and outgoing materials; draining out the vessel. External pipes can cause bending of loads or mechanical stress if not supported independently outside

    Manholes for inspection and maintenance (whether bolted or welded cover plates are to be used is decided by the design engineer as per maximum pressure inside vessels)

    7.1.2 External Fittings

    Earth connection Lifting lugs and support legs External heating/cooling jacket or limpet coils Drain valves, vent valve and pressure taps Anchors/cleats for external insulation Shaft seals: whether ordinary glands, water-cooled glands (for lower pressure

    only) or mechanical seals to be useddepends on operating conditions, nature of material inside the vessel (inflammable or toxic)

  • 797.1 Considerations for Procurement of Pressure Vessels

    7.1.3 Factors for Deciding Wall Thickness of Pressure Vessels

    Radius of the vessel Internal/external pressure Vacuum (can cause inward collapse of vessel walls) Expected weightempty/full vessel (due to choked exit/closed valves) Additional loads possible due to fittings, valves, connected pipes, shock loads

    from compressors, wind loads, etc. Additional safety margin and corrosion allowance for material of vessel Allowance (as safety margins) for corrosion, severity of operating conditions

    and nature of fluid (dangerous/inflammable)

    7.1.4 Heads for Pressure Vessels

    Purchaser should obtain approval for the pressure vessels design, welding joints, electrodes, etc. from a statutory authority before placing fabricationorder to vendor

    Flat head for low pressures, up to 5 kg/cm2 Torispherical head for pressures up to 15 kg/cm2 Ellipsoidal head generally for pressures 1525 kg/cm2 Hemispherical head generally used above 25 kg/cm2

    7.1.5 General Considerations for Design and Fabrication

    Various design and fabrication codes such as American Society of Mech Engi-neers (ASME) Sec. VIII Div. I and II, Tubular Exchangers Manf. Association (TEMA), American Society of Testing Materials (ASTM), ASME Sec. II A/B/C/D, Indian Boiler Regulations (IBR), Indian Standards (IS) should generally be followed. Any deviation from standards/codes must be with a mutual written agreement between fabricator and purchaser

    Approval for design, drawing, fabrication methods, welders qualification, etc. should be obtained from a statutory authority before purchaser places order for fabrication to vendor

    Approval for all drawings should be obtained by the purchaser or his consultant before fabrication commences

    Radiography (100 %) of all welded joints MOC of welding rods used for fabrication

    No statutory provision must be violated.

    Actual corrosion allowance should never be less than the design value in the final drawing for fabrication

    Supporting pad plates (weep holes for pad plates) and position/details of lifting lugs

  • 80 7 Pressure Vessels, Glass Vessels and Glass-lined Vessels

    External insulation and painting should be done only after completion of all tests at vendors shop and re-tests at site (after erection)

    External reinforcement in the form of flats or angle irons External enclosures (to prevent flying off of debris in case of explosions) may

    be erected at site. The vessel should preferably be installed away from human activity

    Welding by direct current sets only Connected pipelines with expansion bellows so that no stress is created on the

    nozzles due to expansion and contraction of pressure vessels due to temperature changes or any other reason

    7.1.6 Materials of Construction

    General considerations

    Certification for tensile strength Corrosion resistance at conditions against chemicals handled MOC: should not be adversely affected during fabrication, cutting/welding High-impact resistance, especially for vessels in low temperatures Pressure vessels should be fabricated from standard-sized sheets available in

    market as virgin material. They should not be fabricated from recovered material (used for some other vessels earlier or obtained from ship-breaking yards)

    Purchaser should specify MOC for reactants and products under maximum pressure and temperature

    MOC Ordinary mild steel (e.g. I.S.2062 or its international equivalent) should not be allowed. Certification for MOC must be obtained. Samples of MOC must be tested in approved laboratories.

    Some common MOCs

    Carbon steel: IS 2002 Grade A, ASTM A 560, SA-516, A-179 Carbonmanganese steel Carbonmolybdenum steel Chromiummolybdenum steel Chromiummolybdenumvanadium steel Chromiumnickel stainless steel Duplex steel, super duplex steel Non-ferrous alloys of Ni, Cu, Al, Ti

    Temperature limitations of materials of construction

    Carbon steel for non-corrosive service: up to 500 C Stainless steel (1825 % Cr; 820 % Ni; 0.050.2 % C): corrosive conditions, up

    to 650 C. Also, 0.03 % low carbon stainless steel Clad steel (carbon steel with cladding of stainless steel)

  • 817.1 Considerations for Procurement of Pressure Vessels

    Nickel alloys: Monel for marine/organic service Inconel: for dairy/food processing service Brass: up to 200 C Carbonmolybdenum steel: up to 550 C Chromiummolybdenum steel: up to 650 C

    MOC that can be used after test of corrosion resistance

    SS-304: 18 % Cr, 8 % Ni SS-316: 1618 % Cr, 1114 % Ni, 2 % Mo SS-317: 3 % Mo min SS-316 L and SS-317 L: carbon should be less than 0.03 % SS-321 has added Ti

    7.1.7 Fabrication Drawings

    General arrangement drawing and installation in key plan Completion of mechanical design as per codes: thickness of wall, flanges and

    nozzles, selection of proper material of construction Preliminary drawings should show shell thickness, tie rods, reinforcements at

    nozzles, corrosion allowance, details of welded joints, design and test pressure, radiography/electrode specifications

    Should be reviewed by all concerned along with comments, suggestions Fabrication drawings should contain comments by consultants and shop floor

    senior engineers for suggested changes or waiving off of requirements (some fittings or nozzles may not be required)

    Permission should be obtained from statutory authorities for these changes. The final approved fabrication drawings must have signatures of all concerned par-ties

    Generally, six hard copies may be prepared of the original: a master copy and copies for designer, plant head, fabri


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