Definition and selection of design temperature and pressure prg.gg.gen.0001

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Form code: MDT.GG.QUA.0508 Sht. 01/Rev. 1.94 File code: Normal.dot Data file: PRG_GG_GEN_0001_R0_E.doc
CONFIDENTIAL document. Sole property of Snamprogetti. Not to be shown to Third parties or used for purposes other than those for which it has been sent.
DESIGN CRITERIA
DEFINITION AND SELECTION
OF
DESIGN TEMPERATURE AND PRESSURE
PRG.GG.GEN.0001
Rev. 0
May 1994
Ex PRG.PR.VES.2 - Rev. 2 - June 1989

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Rev. 0 Date May 1994
Sheet 2 (19)
C O N T E N T S
1. GENERAL 3
1.1 Scope and field of application 3
1.2 References 3
2. INTRODUCTION 4
2.1 Overview 4
2.2 Definitions 4
3. GENERAL CRITERIA 6
3.1 Design temperature 6
3.2 Design pressure 7
3.3 Criteria for determination of MDMT 8
4. SPECIAL CONSIDERATIONS 10
4.1 Columns 10
4.2 Reactors 10
4.3 Furnaces 10
4.4 Heat exchanger 11
4.5 Pumps (and downstream equipment) 12
4.6 Compressors and fans (and downstream equipment) 13
4.7 Hold-up/storage vessels containing special fluids 13
4.8 Complex circuits 14
4.9 Storage tanks 14
4.10 Steam turbines/steam outlet pipes 15
5. GUIDE TO DETERMINING DESIGN TEMPERATURE AND PRESSURE 16
5.1 Introduction 16
5.2 Equipment design temperature and pressure 16
5.3 Piping design temperature and pressure 19

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1. GENERAL
1.1 Scope and field of application
The purpose of the present document is to set the general criteria for determining the design
temperature and pressure of equipment and piping.
The field of application is that of oil and chemical plants.
In relation to specific design requirements where greater temperature and pressure values are
required, the criteria can be modified, checking however the repercussions on the safety and
cost effectiveness of the plant.
In addition to the criteria contained in this document, the design engineer must also consider all
the special requirements contained in national and international codes and standards (e.g.
ASME Boiler and Pressure Vessel Code) that are applicable to the various pieces of equipment
and plant sections.
1.2 References
OPR.MO.XE.5011 Process engineering for primary oil and chemical systems
PRG.GG.NRM.0001 Guide to metric (SI) unit of measurement
ASME, Sect. VIII, Div. 1
API RP 521 Guide for Pressure-Relieving and Depressurizing Systems

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2. INTRODUCTION
2.1 Overview
The design temperature and pressure affect the safety, reliability and cost effectiveness of a
plant.
In determining the design temperature and pressure, all possible and foreseeable operating
conditions to which equipment or piping might be subjected to must be considered, including
those relating to starting-up, shutdown and changes in supply, products, operating severity, etc.
When equipment or piping are subjected to more stringent temperature and/or pressure
conditions with respect to normal operating conditions, these must be specified as alternative
design conditions.
For example, higher temperatures than those of normal operation can be reached during the
regeneration of a reactor’s catalyst, but at a lower pressure.
The design temperature and pressure affect the selection of materials and are used for
calculating the thickness of the walls of equipment and piping.
The design temperature and pressure also significantly affect the cost of equipment and piping
and therefore must not be set unjustifiably high, especially in correspondence with changes in
rating or material.
In particular, with fluids containing hydrogen an unjustifiably high temperature can require for
more expensive materials that are not strictly necessary.
Design temperature and pressure are also used to determine the rating of the nozzle flanges for
equipment and piping.
2.2 Definitions
2.2.1 Operating temperature (OPT)
The temperature of the process fluid in the equipment or piping during normal operation.
2.2.2 Maximum operating temperature (MXOT)
The maximum temperature the process fluid reaches inside equipment or piping in conditions
that vary from those of normal operation, i.e. during start-up and shutdown, for process control
and flexibility needs, and when heated up to the maximum ambient temperature or "sunshine
temperature".
2.2.3 Minimum operating temperature (MNOT)
The minimum temperature the process fluid reaches in equipment or piping in conditions that
vary from those of normal operation, i.e. during start-up and shutdown, as a result of predictable
faults and for process control and flexibility needs.

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2.2.4 Design temperature (DT)
The minimum/maximum temperature of the fluid that represents the most demanding condition
for the equipment or piping, considering simultaneous temperature and pressure conditions.
The design temperature is used together with the design pressure to determine the mechanical
dimensions of the vessel.
2.2.5 Minimum Metal Temperature (MMT) e Minimum Design Metal Temperature (MDMT)
The Minimum Metal Temperature is the minimum operating temperature the walls of the
equipment can reach.
The minimum operating temperature, conditions that deviate from normal conditions due to
operating faults, self-cooling, minimum ambient temperature and any other source of cooling
must be considered when setting the Minimum Metal Temperature.
The material of the equipment and piping shall be selected to avoid fragility at the Minimum
Design Metal Temperature (MDMT) and at the corresponding pressure.
2.2.6 Operating pressure (OPP)
The gage pressure at which equipment or piping works during normal operation.
2.2.7 Maximum/minimum operating pressure (MXOP/MNOP)
The gage pressure at which equipment or piping works under conditions that deviate from
normal operating conditions, i.e. during starting-up and shutdown, as a result of predictable
faults and for process control and flexibility needs.
2.2.8 Design pressure (DP)
The maximum gage pressure (minimum in the case of vacuum operation) at the top of a piece
of equipment or piping. It is used to determine the mechanical dimensions of a piece of
equipment or piping at the design temperature.
2.2.9 Maximum admissible operating pressure (MAWP)
The maximum gage pressure admissible at the top of a vessel, or in piping, under operating
conditions at a fixed temperature.
It is calculated on the basis of the actual thickness of the equipment, less the corrosion
allowance.
This thickness may be greater than the minimum thickness required by the design pressure
and, consequently, the maximum admissible operating pressure is either equal to or greater
than the design pressure.
The pressure safety valve (PSV) installed to protect the equipment can be recalibrated on the
basis of the MAWP.

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3. GENERAL CRITERIA
3.1 Design temperature
3.1.1 Determination of design temperature
The design temperature is determined in the following manner:
• For operating temperatures below -29°C, both the minimum design temperature, which is
equal to the minimum operating temperature, and the maximum design temperature,
determined as described below, must be specified.
• For maximum operating temperatures between -29°C and 343°C, the design temperature is
equal to the maximum operating temperature plus 30°C, but not less than the maximum
ambient temperature defined for the project.
• For maximum operating temperatures above 343°C, the design temperature is equal to the
maximum operating temperature plus 15°C.
3.1.2 Additional considerations
3.1.2.1 Minimum Design Metal Temperature (MDMT)
According to ASME standards (ASME Sect. VIII, Rev. 1, UG-20, b), in addition to the design
temperature, the Minimum Design Metal Temperature and the corresponding pressure (> 0.1
MPa) must also be specified.
See section 3.3 for the criteria to use in determining the MDMT.
3.1.2.2 With regards to the system downstream of the condenser only (composed of separator, pump
and possible compressor), in certain special cases, the design temperature can be set with the
minimum equal to the maximum condenser inlet operating temperature.
3.1.2.3 In distillation columns with a reboiler, the maximum operating temperature of the column bottom
is set to the operating temperature of the steam leaving the reboiler. The design temperature is
then determined in consequence.
3.1.2.4 When piping is traced or jacketed with steam, the design temperature is taken as the greater of
the temperature calculated as above and that calculated in the following manner:
• Jacketed lines (or lines traced using heat-conducting cement): the design temperature is
equal to the condensation temperature of steam at the design pressure of the steam used in
the jacket.
• Steam-traced lines: the design temperature is equal to 70% of the condensation temperature
of the steam at the design pressure of the steam used in the tracing.
3.1.2.5 In vessels internally concrete-sprayed for heat insulation, the design metal temperature is
usually set to 343°C, even though it has been shown in experiments that with an internal
concrete lining, the temperature of the metal varies from 120°C to 200°C, depending on the
operating temperature, the environmental conditions and the characteristics of the lining.
This is to take into account possible seepage of hot gases through the concrete layer for various
reasons that give rise to hot spots on the metal.

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3.1.2.6 For flanges of uninsulated equipment or piping, the design temperature can be assumed as
equal to 90% of the maximum fluid temperature.
Where this is the case, a note should be added to the equipment datasheet specifying that the
flanges must not be insulated.
3.1.2.7 For pressurized vessels with a design pressure not greater than 0.35 MPa, the design
temperature shall be specified as at least 120°C.
3.1.2.8 For reboilers/heat exchangers that use steam as the heating fluid, the design temperature on
the steam side shall be specified as equal to the steam saturation temperature at the design
pressure or equal to the design temperature of the steam system.
3.1.2.9 For steam generators that use a process fluid as the heating fluid, the design temperature on
the steam side, shall be specified as equal to the steam saturation temperature at the design
pressure.
3.2 Design pressure
3.2.1 Determination of design pressure
The design pressure, for pressurized equipment, is determined in the following manner:
• For operating pressures below atmospheric pressure, it is necessary to specify the minimum
design pressure as absolute vacuum, the maximum design pressure equal to 0.18 MPa (or
0.35 MPa if the safety valve installed for equipment protection has a blow-down discharge)
and the external pressure equal to the atmospheric pressure of the area where the
equipment will be installed.
• For operating pressures between atmospheric pressure and a gage pressure of 1.8 MPa, the
design pressure is the greater of 0.18 MPa (or 0.35 MPa if the safety valve installed for
equipment protection has a blow-down discharge) and the value obtained by adding 0.18
MPa to the maximum operating gage pressure.
• For operating gage pressures between 1.8 MPa and 4 MPa, the design pressure is equal to
110% of the maximum operating gage pressure.
• For operating gage pressures between 4 MPa and 8 MPa, the design pressure is the value
obtained by adding 0.4 MPa to the maximum operating gage pressure.
• For operating gage pressures above 8 MPa, the design pressure is equal to 105% of the
maximum operating gage pressure.
For equipment directly open to the atmosphere (e.g. chemical vessels and similar), the design
pressure shall be specified as "Atm.".
In addition, no calculation code shall be indicated.

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3.2.2 Additional considerations
3.2.2.1 For systems containing propylene or ethylene, the vapor pressure of which varies significantly
over the operating temperature range, the general rule is not valid. A sufficient margin must be
provided beyond the operating pressure such that minimal changes in the operating
temperature do not trigger the opening of the safety valve.
As a rule, the design pressure is set equal to 120% of the operating gage pressure.
3.2.2.2 The absolute vacuum design condition (and corresponding temperature) must be specified for
all equipment that normally operates under vacuum or that can operate under vacuum when
starting up, for discharge operations, during emergency stops and for regeneration.
The same condition shall be specified for vessels and heat exchangers that normally operate
liquid-full and which can be shut off and thus made to go under vacuum for cooling, and for
columns and the connected vessels that can go under vacuum due to the effect of heat loss
(amine regeneration column and acid water stripper, for example).
The absolute vacuum design condition shall not be specified for vessels for which the possibility
of going under vacuum is only related to steam purging.
3.3 Criteria for determination of MDMT
Determination of the MDMT requires a detailed study of all possible low temperatures and
corresponding pressures.
Possible operating errors and the possibility of installing safety devices that counteract or
prevent these errors must be taken into account.
The possibility that certain gases may cause a temperature drop in the case of adiabatic
depressurization must be given special consideration.
3.3.1 The possibility of the project-defined minimum ambient temperature coinciding with the design
pressure must be considered for vessels without insulation.
3.3.2 The MDMT for vessels containing fluids having a vapor pressure greater than the atmospheric
pressure at the minimum ambient temperature is determined in the following manner:
• The minimum temperature (MMT) is calculated via a series of successive isentropic flashes,
starting from the initial pressure (design pressure) up to the final pressure (atmospheric
pressure), establishing the MDMT for vessels containing liquefied gases; the fact that the
thus-determined MDMT will coincide with a lower pressure shall be taken into account.
The MDMT will then be set 50°C higher than the above-calculated MMT, as long as:
- the highest "primary local membrane stress" at the MMT does not exceed 50 N/mm2
- the equipment cannot be repressurized while it is still cold
• For safety reasons, the MDMT shall not be more than 0°C if the volume of LPG contained in
the vessel is equal or greater than 5 m3.
3.3.3 When a vessel contains high-pressure gas, the fact that very low temperatures can be reached
when the gas expands adiabatically must be considered.
In consequence, the formation of a liquid phase due to the effect of retrograde condensation can
also occur, such that the vessel is in the condition of containing a liquefied gas, for which the
criteria of the previous section are applicable.

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3.3.4 For safety reasons, equipment containing lethal substances in quantities equal or greater than
300 kg shall have an MDMT of not more than 0°C.

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4. SPECIAL CONSIDERATIONS
Certain special guidelines that supplement the general criteria and rules that deviate from them,
are provided below.
4.1 Columns
4.1.1 Distillation columns with side streams
4.1.1.1. Maximum operating temperature
In multi-product columns, in the zone between the extraction plates of two side streams the
offtake temperature of the heaviest fraction is taken as the maximum operating temperature for
the zone.
For the zone between the extraction plate of the last side stream and the column bottom, the
temperature of the fluid feeding the column or, in the case of a column with reboiler, the reboiler
outlet temperature is taken as the maximum operating temperature for the zone.
4.1.2 Steam sidestream strippers on an atmospheric or vacuum column
The inlet temperature of the fluid to be stripped is taken as the maximum operating temperature.
4.1.2.2. Design pressure
This is assumed to be the same value set for the main column to which the stripper is
connected.
4.1.3 Absorption and fractionating columns
For the zone between the top tray and the feed tray, the temperature corresponding to the feed
tray is taken as the maximum operating temperature.
For the zone between the feed tray and the column bottom, the temperature of the column
bottom is taken.
4.2 Reactors
The temperature and pressure conditions for possible regeneration of the catalyst must be
specified.
4.3 Furnaces
4.3.1 Maximum operating temperature
The inlet and outlet temperatures of the process fluid under planned normal operating
conditions must be specified.
In addition, in the case of non-linear vaporization, temperature-enthalpy and pressure-enthalpy
diagrams for evaluating the temperature trend of the fluid in the furnace coil must be attached.

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4.3.2 Design temperature
4.3.2.1. Design temperature of process fluid
The design temperature of the process fluid coincides with the high-temperature trip value
provided for by Italian regulations (see Collection F, ANCC).
It is defined, according to the type of furnace, as follows:
• maximum operating temperature plus 15°C for preheating ovens (topping/vacuum distillation,
desulphurization, reboiler furnaces, etc.).
• maximum operating temperature plus 5°C for thermal cracking/reaction furnaces (visbreaker,
coking, etc.).
In the case of decoking operations, the maximum operating temperature should not be
considered for the purposes of determining the design temperature.
4.3.2.2. Design temperature of coil
This is defined after the thermodynamic calculation for the furnace, on the basis of the process
fluid’s design temperature as defined above.
4.3.3 Design pressure
If a control or shut-off valve is installed upstream of the furnace, the value of the PSV set
pressure for protecting the equipment downstream, increased by 120% of the pressure drop
between the furnace entrance and the PSV, is taken as the design pressure.
If, the control or shut-off valve is installed downstream of the furnace, the design pressure shall
be equal to that of the vessel that is upstream of the furnace or the design pressure of the feed
pump.
In the case of licensed plants (and therefore calculated according to API RP 551, constant-
thickness coil, sized with decreasing design pressures corresponding to increasing
temperatures), but subjected to ANCC regulations, Collection F, if the Licensee’s design is
maintained, crossovers must be provided between one section and another with a shut-off
pressure switch (1 out of 2 logic), calibrated to the individual design pressures of the various coil
sections.
4.4 Heat exchanger
4.4.1 General
A different design temperature and pressure should be specified for both the pipe side and the
shell side.
In the case of multi-body heat exchangers, the possibility of specifying separate design
temperatures for each body based on the calculated operating temperatures should be
evaluated.
This may also allow separate choice of materials (n.b. to be chosen on the basis of the
maximum operating temperature).

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4.4.2 Design temperature
The inlet temperature of the hot fluid and the outlet temperature of the cold fluid are taken into
account when calculating the design temperature on both sides.
As the heat exchanger is pressurized equipment, the MDMT must also be defined.
The following must be considered:
• The position of a heat exchanger must be taken into account when defining its design
pressure:
- When the heat exchanger is installed upstream of a control or shut-off valve, the design
pressure on the side where the valve is installed is the same as that of the equipment
upstream of the heat exchanger or, if on the delivery of a centrifugal pump, the pressure is
calculated as in subsection 4.5.1.1.
- When the heat exchanger is installed downstream of a control or shut-off valve, the
design pressure on the side where the valve is installed is given by the set pressure of the
PSV for protecting the equipment downstream plus 120% of the permitted pressure drop
between the equipment downstream and the inlet of the heat exchanger under normal
operating conditions, increased by any static head.
• In the case of heat exchangers that can be shut off, the design pressure on the low pressure
side shall be set equal to 2/3 of the design pressure on the high pressure side. The possibility
exists of exceeding 110% of the above-defined design pressure due to heat exchanger tube
rupture.
The position in relation to other connected equipment must be considered. For example, the
2/3 rule will not be followed in the case of reboilers when the lower pressure side is
connected to the column, as the piping and connected equipment have sufficient capacity to
absorb possible losses due to pipes breaking without increases in pressure.
Instead, water coolants with water-side shut-off on both inlet and outlet, for example, shall
follow the 2/3 rule.
The rating of piping shall consider the thus-determined design condition from and up to the
shut-off valves.
4.5 Pumps (and downstream equipment)
4.5.1.1. Centrifugal pumps
The design pressure for equipment and piping on the delivery side of a pump is equal to the
maximum delivery gage pressure and is calculated by adding the maximum head of the pump
(normally the shutoff head) to the maximum suction pressure. The shutoff head is that with the
impeller installed and at the specified density and number of revs.
If data for the purchased pump is not available, the pump’s maximum head is assumed to be
120% of the head under design capacity conditions.

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For vertical pumps, which reach values of 130÷140% on shut-off, the value to specify must be
carefully evaluated.
4.5.1.2. Reciprocating and rotary pumps
The design pressure for equipment and piping on the delivery side of a pump is calculated as
115% of the discharge gage pressure, or as a minimum, the discharge gage pressure plus 0.18
MPa.
4.6 Compressors and fans (and downstream equipment)
4.6.1 Maximum operating temperature
The maximum operating temperature is the temperature of the fluid on the compressor delivery
side, initially calculated by the process engineer.
The "correct" value is provided by the manufacturer of the compressor.
4.6.2 Temporary operating conditions
Temporary conditions that can occur during alternative plant operation must be specified.
For example, during regeneration in catalytic units, the characteristics of the compressed fluid
are different from normal process characteristics, which could entail different and more difficult
temperature and pressure conditions.
4.6.3 Design conditions
The maximum delivery operating conditions are considered when setting the design conditions
for fans. The design temperature and pressure shall be set equal to the maximum operating
temperature or pressure indicated by the Manufacturer.
4.7 Hold-up/storage vessels containing special fluids
4.7.1 Fluids to be considered
The fluids for which the following considerations are applicable are:
• NaOH solutions
• NH3 solutions
• Corrosion inhibitors
• Demulsifiers
• MEA
• DEA
• TEL
4.7.2 Operating pressure
The operating pressure shall be determined as follows:

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• Atmospheric pressure if the vessel contains non-volatile fluids (a non-volatile fluid is defined
as a fluid that has an absolute vapor pressure of less than 0.07 MPa at the maximum
operating temperature or at the project-defined maximum ambient temperature).
• Vapor pressure corresponding to the maximum operating temperature for volatile fluids.
• Vapor pressure of fluid at the project-defined maximum ambient temperature for TEL.
The design pressure is consequently determined in the following manner:
• Atmospheric pressure for non-volatile fluids.
• Vapor gage pressure corresponding to the design temperature for volatile fluids.
• Absolute vacuum for TEL.
4.8 Complex circuits
If a control or shut-off valve is installed downstream of the vessel, then the design pressure
must be the same as that of the vessel located upstream or equal to the design pressure of the
feed pump.
If the control or shut-off valve is installed upstream of the vessel, the design pressure shall be
calculated as the sum of the set pressure of the PSV for protecting the vessel located
downstream of the one under consideration, plus 120% of the pressure drop of the circuit
connecting the two vessels under normal running conditions, increased by any static head.
The possibility of planning graduated design pressures for the various pieces of equipment must
be evaluated, for example, in high-pressure and temperature reaction circuits.
For a clearer understanding, please see the examples in section 5.
4.9 Storage tanks
The following cases can be identified for storage tanks:
4.9.1.1 Storage tanks without blanketing gas
In this case, the design pressure at the top of the tank is equal to the atmospheric pressure .

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4.9.1.2 Storage tanks with blanketing gas and water seal with of less than 0.1 m
In this case, the design pressure at the top of the tank is equal to 1.42 kPa. .
4.9.1.3 Storage tanks with blanketing gas and water seal of more than 0.1 m and less than 0.4 m
In this case, the design pressure at the top of the tank is equal to 4.90 kPa
4.10 Steam turbines/steam outlet pipes
When setting the design temperature of outlet pipes from steam turbines, special care should be
taken in considering the start-up or low-speed conditions (due to lower efficiency, the steam
could be particularly superheated).
In all cases, the manufacturer’s recommendations must be taken into account.

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5. GUIDE TO DETERMINING DESIGN TEMPERATURE AND PRESSURE
5.1 Introduction
Two examples of determining the design temperature and pressure for equipment and piping
using the guidelines of the present design criteria document are provided below.
5.2 Equipment design temperature and pressure
Tables 5.2.a. and 5.2.b. list the operating temperature and pressure conditions for the
configurations shown in Figs 5.2.a. and 5.2.b respectively.
The design temperatures and pressures, calculated according to the criteria in sections 3 and 4,
are also provided for each piece of equipment.
Table 5.2.a. – Equipment design temperature and pressure (see Fig. 5.2.a.)
Equipment Operating Conditions Design Conditions
Pressure Temperature
Surge Drum Pressure 0.15 MPa (ga) 0.35 MPa (ga) 76°C
Temperature 96°C
Charge pump Suction pressure 0.18 MPa (ga) 1.40 MPa (ga) 76°C
Delivery pressure 1.02 MPa (ga)
Max. suction press. 0.39 MPa (ga)
Charge heat Pipe side 46/101°C 1.40 MPa (ga) 131°C
exchanger Shell side 128/75°C 0.85 MPa (ga) 158°C
Column Head pressure 0.67 MPa (ga) 1.40 MPa (ga) 158°C
Head/bottom temp. 113/124°C
Condenser Pressure 0.67 MPa (ga) 0.85 MPa (ga) 143°C
Temperature 113/60°C
Receiver Pressure 0.62 MPa (ga) 0.85 MPa (ga) 113°C
Temperature 60°C
Reflux pump Suction pressure 0.64 MPa (ga) 1.23 MPa (ga) 113°C
Delivery pressure 0.93 MPa (ga)
Max. suction press. 0.88 MPa (ga)
Coolant Product Pipe side 30/40°C 0.82 MPa (ga) 70°C
Shell side 60/40°C 1.23 MPa (ga) 90°C
Reboiler Pipe side 175/175°C 1.20 MPa (ga) 192°C
Shell side 124/128°C 0.85 MPa (ga) 158°C
Notes:
1) Steam to reboiler: 0.80 MPa (ga), saturated, design pressure 1.20 MPa (ga)
2) Steam tracing: 0.55 MPa (ga), condensation temperature 156°C

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Table 5.2.b. - Equipment design temperature and pressure (see Fig. 5.2.b.)
Design Conditions
Equipment Operating Conditions International Italy
Pressure Temp Pressure Temp
Charge pump Suction pressure 0.57 MPa (ga) 8.04 MPa (ga) 76°C 8.04 MPa (ga) 76°C
Delivery press. 6.60 MPa (ga)
Max. suct. press. 0.80 MPa (ga)
Charge/effl. Pipe side: press. 5.48MPa (ga) 5.96 MPa (ga) 400°C 7.01 MPa (ga) 400°C
heat exchanger temp. 370/128°C
Shell side: press. 6.27MPa (ga) 6.90 MPa (ga) 338°C 7.01 MPa (ga) 338°C
temp. 46/308°C
Charge oven Inlet pressure 6.09 MPa (ga) 6.69 MPa (ga) 360°C 7.01 MPa (ga) 360°C
Temp. 308/355°C
Reactor Inlet pressure 5.60 MPa (ga) 6.10 MPa (ga) 400°C 7.01 MPa (ga) 400°C
Temp. 355/370°C
Rx. effl. cond. Inlet pressure 5.25 MPa (ga) 5.68 MPa (ga) 161°C 7.01 MPa (ga) 161°C
Temp. 131/55°C
Trim Condenser Pipe side: press. 0.50MPa (ga) 3.73 MPa (ga) 68°C 4.67 MPa (ga) 68°C
temp. 30/38°C
Shell side: press. 5.18MPa (ga) 5.60 MPa (ga) 131°C 7.01 MPa (ga) 131°C
temp. 55/38°C
H.P. separator Pressure 5.10 MPa (ga) 5.50 MPa (ga) 131°C 5.00 MPa (ga) 131°C
L.P. separator Pressure 0.70 MPa (ga) 0.88 MPa (ga) 68°C 0.88 MPa (ga) 68°C
Recycle compr. Suction pressure 5.05 MPa (ga) 7.01 MPa (ga) 131°C 7.01 MPa (ga) 131°C
Suction pressure 6.36 MPa (ga)
Delivery temp. 52°C
M/U compr. Delivery press. 5.30 MPa (ga) 5.70 MPa (ga) 125°C 5.70 MPa (ga) 125°C
Delivery press. 95°C
Note:
1) In the case of plants constructed in Italy, a safety valve set at 7.0 MPa (ga) and sized for the
total liquid flow must be installed on the liquid charge.
No shut-off valve shall be installed between the above-mentioned PSV and the high pressure
separator.
2) Alternatively, all equipment up to and including the reactor can be designed for a pressure of
7.01 MPa (ga) and the downstream equipment can be designed for graduated pressures as
shown in the table (International), on condition that:
• no shut-off valve is installed between the reactor and high pressure separator.
• an attestation (signed by an engineer who is a member of the society of engineers) is
presented to ISPESL, in which it is stated that “in any eventuality the Δp between the
equipment and the PSV (set pressure 5.5 MPa (ga) cannot exceed the value of .....".
If, for example, the equipment in question is the reactor effluent condenser, the maximum
Δp will be 0.18 MPa.

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Fig. 5.2.a.
Fig. 5.2.b.

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5.3 Piping design temperature and pressure
The criterion for determining the design temperatures and pressures for piping for the
configuration shown in Fig. 5.2.a. is summarized in the following table.
Table 5.3.a. - Design temperature and pressure for Fig. 5.2.a.
Segment Design Pressure Design Temperature
A d/s DP 0.35 MPa (ga) OPT+30°C 76°C
B u/s DP+St.Head 0.39 MPa (ga) OPT+30°C 76°C
C Pump DP 1.40 MPa (ga) OPT+30°C 76°C
D Pump DP 1.40 MPa (ga) OPT+30°C 131°C
E d/s DP+St.Head 0.92 MPa (ga) OPT+30°C 131°C
F u/s DP 0.85 MPa (ga) OPT+30°C 143°C
G u/s DP 0.85 MPa (ga) OPT+30°C 143°C
H u/s DP+St.Head 0.88 MPa (ga) OPT+30°C 143°C
I Pump DP 1.23 MPa (ga) OPT+30°C 90°C
J u/s DP+St.Head 0.88 MPa (ga) OPT+30°C 90°C
K u/s DP 0.88 MPa (ga) OPT+30°C 90°C
L d/s DP+St.Head 0.95 MPa (ga) OPT+30°C 90°C
M u/s DP 0.85 MPa (ga) 70% st.tr.temp. 109°C
N d/s DP+110% Op 0.60 MPa (ga) 70% st.tr.temp. 109°C
O u/s DP+St.Head 0.89 MPa (ga) OPT+30°C 154°C
P u/s DP 0.85 MPa (ga) OPT+30°C 158°C
Q u/s DP+St.Head 0.85 MPa (ga) OPT+30°C 128°C
R u/s DP 0.85 MPa (ga) OPT+30°C 105°C
S u/s DP+St.Head 0.90 MPa (ga) OPT+30°C 70°C
Legend:
d/s = downstream
u/s = upstream
St. Head = static head
Revision Memorandum
May 1994 First issue

Definition and selection of design temperature and pressure prg.gg.gen.0001

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Definition and selection of design temperature and pressure prg.gg.gen.0001