Horizontal Tanks (HT)
Horizontal vessels are commonly used as settling drums, surge tanks, reactors and distillate drums. A settling drum is used for phase separation between two immiscible liquids. The L/D ratio of a settling drum is normally four. A surge tank or surge drum is used to maintain a constant flowrate of liquid to a downstream piece of equipment when the flowrate of liquid from the upstream piece of equipment is fluctuating. The fluctuations in flow rate are absorbed by the surge drum by allowing the liquid level in this drum to rise and fall. Horizontal drums are frequently filled with catalyst and used as reactors. Placing catalyst in horizontal vessels allows shallow bed depths and large cross-sectional areas. A typical example of horizontal vessels being used as reactors is the Claus reactor. A distillate or reflux drum provides space for overhead condensables from a distillation column to separate from vapors. Surge drums and distillate drums are normally vertical.
If there is settleable water in the feed to these vessels, however, the vessel is erected with a water pot.
The horizontal vessel is a pressure vessel fabricated according to the rules of the specified code (i.e., Section VIII Division 1 of the ASME Code) and erected in the horizontal position. Although the horizontal vessel may be supported by lugs in an open steel structure, the more usual arrangement is for the vessel to be erected at grade and supported by a pair of saddles.
Cylindrical, pressure/vacuum, code design and construction, includes heads, single wall (base material, clad/lined), saddles/ lugs, nozzles and manholes.
Multi-Wall Vessel:
of individual, thin, heat-shrunk cylinders (maximum 2 INCHES [50 MM] thick) heat shrunk, pressure vacuum design and construction according to user-designated design code standard.
This item is a horizontal process vessel, the total wall thickness of which is made up of individual cylinders. Each individual cylinder is no more than two inches thick. The composite is made as follows. A cylinder is fabricated with a diameter slightly larger than the innermost cylinder. This cylinder is expanded thermally, slipped over the inner cylinder and as it cools, a tight shrink fit is obtained.
This procedure is repeated until the total wall thickness is built up.
Application Symbol: Defines vessel function and related
piping/instrumentation model. Default: *blank*
blank – Standard continuous process vessel
BATCH – Batch process vessel
STORAGE – Storage vessel
RECVR – Receiver
KO – Knock-out drum
Shell Material: For clad plate, specify the backing plate material.
(Cladding is defined below.) See Chapter 28 for materials.
Default: *A 515*.
Capacity: Enter either capacity or diameter and length.
Diameter: Enter either capacity or diameter and length.
Vessel T-T Length: Enter either capacity or diameter and length.
Design Press. – Gauge: If pressure and vacuum entered, design is for worst case. Default: *15* PSIG [*100* KPA].
Design Vacuum – Gauge: If pressure and vacuum entered,
design is for worst case. Default: pressure.
Design Temperature: Default: 650 DEG F [340 DEG C] ferrous
material; 250 DEG F [120 DEG C] other material.
Operating Temp.: Default: design temperature.
Cladding Material: See Chapter 28; for cladding materials.
Manhole Diameter: Max: 48 INCHES [1,200 MM];
Default: *18* INCHES [*450* MM]
Number of Manholes: Default: *1*.
% All. for Internals: Specify an allowance for internals as a percent of basic vessel weight. Default: *0.0*.
Diameter of Drip Leg: Drip leg (boot) diameter and length must be specified if required.
Length of Drip Leg: Drip leg (boot) diameter and length must be specified if required.
Base Mat’l Thickness: Base material thickness including corrosion allowance.
Corrosion Allowance: Default: 0.125 INCHES [3 MM] for CS, 0.0 for other materials.
Weld Efficiency %: 50 – 100; ASME/JIS codes only, where
allowed for thin wall vessels; Default: Area Basis.
Stress Relief: Default: See Area Design Basis.
CODE – Provide stress relief if code requires
YES – Provide stress relief
NO – No stress relief required
Cladding Thickness: Default: 1.125 INCHES [3 MM] if cladding
material is specified; otherwise 0.0.
Stiff’g Ring Spacing: Default stiffeners designed for vacuum
only, enter 0.0 if not required.
Head Type Symbol:
ELLIP – 2:1 ellipsoidal
HEMI – Hemispherical
TORI – Torispherical (ASME)
No. Body Flange Sets: Number of sets (pairs) of body flanges of
same diameter as vessel.
Diameter Option: Defines desired diameter as ID or OD;
Default – see Area Design Basis.
OD – Outside diameter
ID – Inside diameter
Horizontal Vessels:
Horizontal pressure/vacuum drum. 
The capacity excludes the volume of the heads. If both the vessel dimensions and capacity are specified, the system-calculated capacity must agree with the specified capacity to within plus or minus 10% to avoid an error condition. To secure desired vessel
size, specify the diameter and height directly. A value must be specified if vessel diameter and/or vessel height (or length) are not specified. If vessel diameter and height (or length) are
specified, the vessel volume is calculated from these dimensions.
If only vessel capacity is specified, a straight side length-to-diameter ratio is chosen by the system, considering cost and practicability.
(Default ratio is 2:1.)
Application Symbol: Defines vessel function and related
piping/instrumentation model. Default: *blank*
blank – Standard continuous process vessel
BATCH – Batch process vessel
STORAGE – Storage vessel
RECVR – Receiver
KO – Knock-out drum
Shell Material: For clad plate, specify the backing plate material.
(Cladding is defined below.) See Chapter 28 for materials.
Default: *A 515*.
Capacity: Enter either capacity or diameter and length. The
capacity excludes the volume of the heads.
If both the vessel dimensions and capacity are specified, the system-calculated capacity must agree with the specified capacity to within plus or minus 10% to avoid an error condition.
To secure desired vessel size, specify the diameter and height directly.
A value must be specified if vessel diameter and/or vessel height (or length) are not specified. If vessel diameter and height (or length) are specified, the vessel volume is calculated from these dimensions.
If only vessel capacity is specified, a straight side length-to-diameter ratio is chosen by the system, considering
cost and practicability.
Diameter: Enter either capacity or diameter and length.
A value must be specified if vessel capacity is not specified. If both capacity and height (or length) are specified, the diameter is calculated from these values.
Vessel T-T Length: Enter either capacity or diameter and length.
A value must be specified if vessel capacity is not specified. If both vessel capacity and diameter are specified, the height (or length) is calculated from these values.
Design Press. – Gauge: If pressure and vacuum entered, design is for worst case; Default: *15* PSIG [*100* KPA] pressure.
Design Vacuum – Gauge: If pressure and vacuum entered, design is for worst case. Default: pressure.
Design Temperature: Default: 650 DEG F [340 DEG C] ferrous
material; 250 DEG F [120 DEG C] other material.
Operating Temp.: Default: design temperature. The operating temperature is used in the calculation of piping and insulation thickness.
Manhole Diameter: Max: 48 INCHES [1,200 MM];
Default: *18* INCHES [*450* MM].
Number of Manholes: Default: *1*.
% All. for Internals: Specify an allowance for internals as a percent of basic vessel weight. Default: *0.0*. This value
adjusts vessel weight and cost accordingly.
Diameter of Drip Leg: Drip leg (boot) diameter and length must be specified if required.
Length of Drip Leg: Drip leg (boot) diameter and length must be specified if required.
Base Material Thickness: Base material thickness including corrosion allowance.
Corrosion Allowance: Default: 0.125 INCHES [3 MM] for CS, 0.0 for other materials.
Weld Efficiency %: ASME/JIS codes only, where allowed for thin wall vessel; Default: Area Basis. Range: 50 – 100.
Stress Relief: Default: See Area Design Basis.
CODE – Provide stress relief if code requires
YES – Provide stress relief
NO – No stress relief required
Cladding Thickness: Default: 0.125 INCHES [3 MM] if cladding material is specified, otherwise: 0.0.
Stiff’g Ring Spacing: Default stiffeners designed for vacuum only, enter 0.0 if not required.
Head Type Symbol: If no value is specified, the system selects the torispherical type and calculates its thickness. If the head is thicker than the vessel shell, the system selects the 2:1 ellipsoidal type head thickness. If the head is still thicker than the shell, the system selects the hemispherical type head.
ELLIP – 2:1 elliposidal
HEMI – Hemispherical
TORI – Torispherical (ASME)
No. Body Flange Sets: Number of sets (pairs) of body flanges of same diameter as vessel.
Diameter Option: Defines desired diameter as ID or OD;
Default – see Area Design Basis.
OD – Outside diameter
ID – Inside diameter.
Vertical Tanks (VT)
Vertical process vessels are typically used as either surge drums or knock out drums. When used as surge drums, they act like shock absorbers, maintaining a constant flowrate of liquid out of the vessel regardless of the flowrate into it. If liquid flows in faster than the constant rate it flows out, the vessel fills with liquid. If liquid flows in slower than the constant rate it is removed, then the liquid level drops. The liquid level is constantly fluctuating in order to absorb these variations in flow and maintain a constant flowrate out. When a vertical process vessel is used as a knock out drum, a mixture of gas and liquid flows into the vessel and this mixture is separated into its gas and liquid components within the vessel. The gas then flows out the top of the vessel and the liquid flows out the bottom.
Vertical process vessels, as their name indicates, are erected in the vertical position. They are cylindrical in shape with each end capped by a domed cover called a head. The length to diameter ratio of a vertical vessel is typically 3:1.
Typically, vertical process vessels hold less than 5000 GALLONS.
Vertical tanks include: process, storage applications liquid, gas, solid processing and storage; pressure/vacuum code design for process and certain storage vessel types; includes heads, single wall, saddles, lugs, nozzles, manholes, legs or skirt, base ring, davits where applicable.
Pressure/Vacuum Service
Cylindrical vertical pressure/vacuum vessel.
Use minus pressure for vacuum design.
Application Symbol: Defines vessel function and related
piping/instrumentation model. Default: *blank*
blank – Standard continuous process vessel
BATCH – Batch process vessel
STORAGE – Storage vessel
RECVR – Receiver
KO – Knock-out drum
Shell Material: For clad plate, specify the backing plate material.
materials. Default: *A 515*.
Capacity: Enter either capacity or diameter and height.
The capacity excludes the volume of the heads. If both the vessel dimensions and capacity are specified, the system
calculated capacity must agree with the specified capacity to within plus or minus 10% to avoid an error condition. To secure desired vessel size, specify the diameter and height directly.
A value must be specified if vessel diameter and/or vessel height (or length) are not specified. If vessel diameter and height (or length) are specified, the vessel volume is calculated from these dimensions. (Default is 2:1.)
If only vessel capacity is specified, a straight side length-to-diameter ratio is chosen by the system, considering
cost and practicability.
Diameter: Enter either capacity or diameter and height.
A value must be specified if vessel capacity is not specified. If both vessel capacity and height (or length) are specified, the diameter is calculated from these values. If both vessel capacity and diameter are specified, the height (or length) is calculated from these values.
Vessel T-T Height: Enter either capacity or diameter and height.
