Sheet
1 of 13
Job Job No. No. : SC-2 SC-225 252 2
Hydraulic Basis
Dual Feed Ethylene Cracker Project(ONGC)
Hydraulic Basis
Project Name : Dual Feed Ethylene Cracker Project(ONGC)
Client : OPaL Dahej, Gujarat, India Job No : SC-2252
0
Mar.5 '09
Preliminary
KHG
SMJ
ICP
REV.
DATE
DESCRIPTION
MADE BY
CHK'D BY
APP'D BY
Process team Rev. 0
. General The Hydraulic Calculation Basis is intended to describe a criteria to determine a pipe size and differential pressure of pump, compressor and control valve and flow regime analysis of two phase flow for Dual Feed Ethylene Cracker & Associated Units Project in Dahej, Gujarat, India. Hydraulic calculation is to select the optimum line size within the available pressure drop. This document will be developed throughout the detail engineering phase of the project if necessary. 1. Contents of the internal documentation after calculation 1) Documentation Summary (or similar), 2) Calculations sketch with Pressure Drop Summary Sheet (last v alid revision) and Pressure drop calculations (last valid revisions), 3) Estimated isometrics (last revision), 4) Supporting data, written communications, and 5) Old revisions of all documents, calculations, etc. 2. Initial Line size for hydraulic calculation Line size and suction vessel elevation in proposal P&ID will be used for HYTOS initial input. 3. Required material for calculation 1) Preliminary calculation Material balance with fluid dynamic properties for several operation cases VDB stream data sheet Utility balance P&ID Plot plan Process data sheet B/L condition list Piping Material Specification 2) Isometric drawing 3) Process Flow Diagram 4. Calculation Tool HYTOS to be used for calculation of pump loop and control valve loop. In house line sizing program to be used for Simple single phase line sizing (utility service) 5. Consideration 1. Compressor loop, cracked gas loop and pump suction lines to be calculated using isometric drawing. Linde K value (resistance coefficient) in Attachment #3 can be considered for optimizing the line size with the approval of manager. 2.If VDB stream datasheet is available as MS Access or Excel format, using simple data extraction program, make easy input the process data into HYTOS. 3. If the process data is not available until calculation, use the reference data from experienced project(ex. TASNEE) 4. The hydraulic result shall be always checked with that of reference project ex perienced(ex. TASNEE) before confirm or report to manager, especially the comment's from Linde shall be checked. 5. During initial hydraulic calculation or line sizing, if the calculation result is in the marginal area against criteria, take conservative position. ( ex. calc result velocity 2m/s - 2", criteria : 2.1m/s -> take 3" for design) 6. After initial calculation finishes, the process datasheet for rotating will be prepared and it will be revised according to calculation result with newly available information. 7. KEEP hydraulic calculation status summary list. 8. If required, the result to be checked based on the criteria of licensor(Linde). 9. design margin : Linde's M/B case vs. owner's design margin -> to be discussed and decided 6. Complete process datasheet based on calculation result 1. Basically for Pump datasheet, Input the calculation result of one max case without margin, but round off at one decimal. 2. Basically for c/v datasheet, Input the calculation result of max/n or/min without margin, but round off at one decimal. 2/13
Process team Rev. 0
. Criteria for Hydraulic Calculation 1. Basis of Flow Rate It is under confirmation with Owner and final basis to be informed later.
▶ Pump Hydraulics calculation for Pump spec. preparation and suction/discharge line sizing The one maximum case will be calculated for Pump spec. preparation. 1) Suction line(for NPSHa and line sizing) Rated flow of operating + minimum flow of a spare pump(if vendor data not available, 25% of rated flow to be considered) ( Suggested by Proposal tech. document sec 3.13.2.15) * ITB 2830-8110-PD-0003 sec.10 - End of curve flow for calculation of NPSH. - Allow for spare pump start up where applicable - 110% margin for sizing of suction line 2) Discharge line An additional margin is not considered to the flow rate for maximum case shown on the stream data. Column reflux line shall be sized with the maximum flow rate plus 20% margin, which is indicated on pump data sheet. ( ITB 2830-8110-PD-0003 sec.10) ▶ Flowrate engineering margin for line sizing Refrigeration circuit : 102% of heat and mass balance to allow for efficiency deviation Cooling water, heating media and fuel gas lines
: 110% margin on heat and mass balance
Gravity flow lines
: 110% margin on heat and mass balance
Other lines
: Nor margin. Use next commercially available line size
2. Equation of Frictional Pressure Drop Calculation
▶ Liquid line size is designed with Darcy's equation 2 * Friction factor 4f*L mℓ ΔPfL = If Re＜ 2000, f = 16 / Re D 2ρℓ where,
If Re ＞ 4000, calculated with Chen's equation
f : friction factor L : line length, m D : inside diameter, m 2
mℓ : liquid flux, kg/m s ρℓ : liquid density, kg/m
3
ε : roughness factor, m
▶ Vapor Line size is designed with c ompressible isothermal flow equation
M 2RT where,
2
2 2 (Pa -Pb )
-
G gc
ln
ρa ρb
2
=
G f ΔL 2gcr H
f : friction factor G : mass velocity gc : Newton's-law proportionality factor L : length M : molecular weight r H : hydraulic radius of conduit R : gas constant
▶ For two-phase flow, the line size will be designed with a program developed by SECL which show the similar output calculated by PIPE-3 of HTFS in pressure drop, velocity and flow regime analysis. - Two phase velocity should be below than erosion velocity. - The following flow patterns should be avoided as shown below.
→ Slug and plug flows (intermittent flows) for horizontal piping → Churn and plug flows (bubbly slug) for vertical upwards flow → Oscillary flow for vertical downwards flow
3/13
Process team Rev. 0
3. Velocity/pressure drop per 100m Criteria for Line Sizing . Basically, follow the criteria of ONGC( Refer to attachment 1 and 2), however the licensor's( Refer to attachment 5) will be used as supplement for special case. In order to ensure the carry over of the coke particles, the decoking line should be sized so that the decoking gas reaches a velocity as close as possible to 70 m/sec during the decoking step under which the maximum volume flow is present (maximal velocity= 75 m/sec for discontinuous flow). Detailed instruction to be provided by Linde. 4. Inside Diameter of Pipe According to the Project Piping Material Specification 5. Roughness 0.00015 m for carbon steel and 0 m for stainless steel Cracked gas line, where a roughness of 1.0 mm should be considered 6. Equivalent Length
▶ In general, the equivalent length is estimated by multiply a factor to the straight length, including vertical or horizontal line from plot plan considering fittings and valves in lines for preliminary hydraulic calculation for initial calculation because ISO drawings for hydraulics are not available. - For Lines in process unit,
equivalent length = straight length x 3
- For interconnecting lines on the pipe rack,
equivalent length = straight length x 1.5
▶ For the critical lines such as compressor loop, big line size, pump suction and low pressure system, preliminary isometric drawing should be used for equivalent length estimation. ▶ For final hydraulic calculation, the equivalent length is calculated with straight length plus equivalent length corresponding to pipe fittings and valves based on the ISO drawing for hydraulics when it is available.
7. Pressure Drop of Equipment and In-line Element Equipment
In-line Instrument
Heat exchanger
allowable ΔP on data sheet
Orifice
0.14
Filter (Cartridge)
ΔP on data sheet. If not available, 0.7 bar
Venturi (liquid)
0.1
Line Mixer
ΔP on data sheet. If not available, 0.5 bar
Venturi (vapor)
0.03
Others
Positive displacement
0.7
0.04 bar for Y, T type
Turbine, Magnetic, Mass
0.5
0.1 bar for bucket type
Vortex
0.3
Filter at inlet of brazed Al H/Ex
0.01 bar @ max. flow
Rotameter
0.2
Metering station
0.5 bar (not applicable for this project)
Target meter
1.0
Strainer
4/13
Process team Rev. 0 8. Determination of Control Valve
ΔP
There are two cases, control valve included in pump loop and control valve which is not included in pump loop. 1) Control valve included in pump loop : Besides the calculation for pump spec. preparation, another two cases, normal and minimum of M/B, should be done with fixed pump head of pump spec. in order to determine a control valve's ΔP for Max, Nor and Min. At each case, the pressure drop through in-line equipment/instrument will be reduced according to flow rate's square ratio. Control valve ΔP shall be determined as greater figure of the followings, for each calculation(2830-8110-PD-0002, sec 4.10). - Minimum 0.7 bar (for vapor, 0.1) - 8 % of pump discharge (or 10% of discharge vessel pressure) 2
- [(1.1135 x (max. flow/nor. flow)) - 1] x Δpfriction - 33% of Δpfriction ( or 25% total friction drop) 2) Control valve not-included in pump loop : Three calculations will be done in order to determine a control valve ΔP, following cases are considered. Case 1
Case 2
Case 3
Max (M/B)
Nor (M/B)
Min (M/B)
Equipment press. at starting point
Min
Nor
Max
Equipment press. at destination point
Max
Nor
Min
Control valve flowrate
Min
Nor
Max
case
For maximum, normal and minimum case, the flow rate, pressure and physical properties are given consistently by the stream data in different cases. At each case, the pressure drop through in-line equipment/instrument will be reduced according to flow rate's square ratio. Control valves should be designed to be approximately 70% open at normal flow rates. Maximum opening under all operating cases shall not exceed 90%. 9. Pump Shutoff Pressure (2830-8110-PD-0002, sec 4.11.2.7) For centrifugal pumps for a single consistent case, Maximum Design Pressure = Maximum Differential Pressure + Maximum Suction Pressure Where: Maximum Suction Pressure = Suction Vessel Design Press.(or, Relief Valve set Press.) + Vessel Suction Head @ HLL Maximum Differential Pressure = F x Net Differential Pressure(@ Rated capacity) Where F is:- • 1.25 for motor driven pumps / • 1.38 for turbine driven or variable speed pumps Note: Calculation is based on maximum operating S.G. / Level information can be referred to Datasheet. For reciprocating pumps, these should be provided with discharge relief valves, the pressure of which should be set to avoid the pump over-pres surizing any system into which it discharges. 10. Pump NPSH, Low Liquid Level in Suction Vessel & Pump centerline (2830-8110-PD-0002, sec 4.8.1.3) In order to avoid the possibility of cavitation and vibration in centrifugal pump, the size of pump suction pipe and elevation of suction vessel shall be decided considering NPSHa is greater than NPSHr by pump manufacturer plus a safety factor as below. NPSHa ≥ NPSHr + 1.0 m (safety factor) up to design capa. for boiling, dissolved gases, foaming another liquids NPSHa ≥ NPSHr + 2.0 m (safety factor) up to design capa. for BFW pumps of initial stage, it can be reduced with vendor data and ISO dwg. Liquid level in suction vessel and pump centerline shall be considered as follows, refer to datasheet for level inform. ; - Tangent line in vertical vessel - Bottom line in horizontal vessel - LLL in Tanks - Pump impeller center line for horizontal pump - Pump suction nozzle center line for vertical pump The following elevation for pump center line shall be assumed untill vendor information is available M3/h
Centerline elevation
up to 45
0.76 m
45 -225
0.91 m
225-2270
1.07 m
(+ 0.3 m)
2270-4540
1.37 m
(+ 0.3 m) 5/13
Process team Rev. 0
Attachment #1
Recommended High limit for Line Sizing (2830-8110-PD-0002, sec 4.9.1) 1. Liquid Flow The guidelines cover most normal situations for systems within unit battery limits, but they may not be applicable for all cases. For critical services and long headers, the total pressure drop in the system must be checked to ensure the system meets the design pressure balance, whether or not individual process lines meet the pressure drop and velocity criteria given here. This standard may not apply to critical services, such as slurry lines or high pressure piping, for which reference should be made to additional standards. 1) Pump Suction Lines (1) DelP/100m bar (approx.)
Velocity m/s
Bubble point Fluids
0.113
0.91
Sub-cooled Fulids
0.453
2.44
Bubble point Fluids
0.113
1.83
Sub-cooled Fulids
0.453
3.66
Item
Remark
Pipe Dia. -8" and less
Pipe Dia. Greater than 8"
Note 1. Pump suct. line dia. should normally not be more than two (2) standard line sizes larger than the pump suction
2) Pump Discharge Lines (Line sizing is a trade-off between piping installation costs and operating costs.) Materal Type Flow rate
Carbon Steel (bar/100m)
Alloy (bar/100m)
0
-
60 m3/h
0.6 - 2
1.4 - 3.5
60
-
160 m3/h
0.3 - 1.6
0.9 - 2.5
0.2 - 0.9
0.5 - 1.6
DelP/100m bar (approx.)
Velocity m/s
Liquid Transfer Line
0.339
3.66
Cooling Water Line
0.339
3.66
-
0.61
Reboiler Trap-out lines (2)
0.068
1.52
Reboiler Return lines
0.068
-
+ 160 m3/h
3) Other liquid lines Item
Steam Condensate Lines (1)
Remark
Line size to be confirmed by Mech. (thermal rating) Line size to be confirmed by Mech.(thermal rating)
Note 1. Or as required by system pressure balance. Note 2. Standard tower draw-off rates should be referred to (see Section 5.1.2). For liquid lines with orifice plates, if the liquid velocity is too high, swaged-up meter runs may be required. Velocities for lines containing orifice plates shall be limited to: 2” and over < 3.4 m/s Except 14” and over Sch. 80 < 3.1 m/s In cases where higher velocities are essential the Instrument Group should be consulted.
6/13
Process team Rev. 0
Attachment #2
Recommended High limit for Line Sizing (2830-8110-PD-0002, sec 4.9.1) 2. Vapor The guidelines cover most normal situations for sy stems within unit battery limits, but they may not be applicable for all cases. For critical services and long headers, the total pressure drop in the system must be checked to ensure the system meets the design pressure balance, whether or not individual process lines meet the pressure drop and velocity criteria given here. For long vapour lines, s uch as flare headers or vacuum transfer lines, when the ΔP > 10% P, a compressible flow calculation procedure should be adopted. 1) Hydrocarbon Lines Item
DelP/100m bar (approx.)
Velocity m/s
0.07 bara or less
0.01
122/√ρ (2)
0.5 bara or less
0.03
0.5 to 3.5 barg
0.11
3.5 to 10 barg
0.34
10 to 35 barg
0.68
Over 35 barg
1.13 (1)
Remark
Note 1. 0.5 % of pressure level Note 2 ρ = gas density, kg/m3
2) Steam Lines ( < 100 m length ) Item
DelP/100m bar (approx.)
0.07 bara or less
0.01
0.5 bara or less
0.05
0.5 to 3.5 barg
0.11
3.5 to 10 barg
0.34
10 to 35 barg
0.68
Over 35 barg
1.13 (1)
Note 1. 0.5 % of pressure level
7/13
Velocity m/s
Remark
Process team Rev. 0
Attachment #3 Linde K value In this attachment Resistance Coefficients which can be employed for a preliminary sizing of the lines are supplied. The actual coefficients for the different pipe fittings, valves, filters, etc, should be determined by SECL according to the piping components (type, quality, etc) to be used for this specific job (once the manufacturers information is available), and to the Piping Specifications. When a decision is met concerning the suppliers of piping material for the various pipe classes, it is advisable to develop a summary of Resistance Coefficients to be used for the pressure drop calculations. This summary can have the form as supplied in this attachment, and its level of detail / accuracy should be determined according to the following criteria: - Expected savings by the use of a more accurate coefficient, - Cost (time required) of determining an accurate coefficient, - Pipe class and line size, - Purpose of the calculation (e.g. normally the "real" or greater coefficient is to be used for line sizing, but the "real" or smaller coefficient should be used when searching for the maximum possible flow through a line for example), - Number and type of piping components in the line, and the proportion of pressure loss originated by them in relation to the total pressure loss, - Total pressure loss available, and - Accuracy of the pipe routing considered for the calculation.
a) Resistance coefficients for 90 deg smooth bends: Pipe size D ≤ 3"
Roughnes
3" < D " 0.3
D > 16"
≤
0.15 mm
0.4
0.1 mm
0.38
0.29
0.25
1 mm
0.8
0.5
0.33
0.25
Remarks: The above figures are based on the following: - Reynolds number greater than 100000 (for lower Reynolds numbers the K value increases rapidly). - Relation r/D = 1.5 b) Resistance coefficients for 45 deg smooth bends: The Resistance Coefficients are about 65 % of the coefficients for 90 deg smooth bends. c) General Resistance Coefficients: Piping component
Resistance Coefficient
90 deg segmental bend
0.35
Pipe entrance
1.5
Pipe exit
1
Y-strainer / T-strainer
7
Pot-type strainer
4
Gate valve Butterfly valve
0.2 ND 2" to 8"
0.76
ND 8" to 14"
0.49
ND 16" to 24"
0.33
Ball valve
0.1
Control valve
6
Disk check valve
5
Check valves
7
8/13
Process team Rev. 0
d) Expansion pieces: Note: in the following Resistance Coefficients only the friction portion is considered.
9/13
Process team Rev. 0
e) Reduction pieces: Note: in the following Resistance Coefficients the friction loss and the loss due to the pressure head variations are considered. The coefficient K1 is referred to D1.
10/13
Process team Rev. 0
f)
T-pieces:
The Resistance Coefficients are expressed as a function of the relation of flows Ga / Gz. (same line sizes at z, d & a)
11/13
Process team Rev. 0
Attachment #4
Recommendation for Line Sizing (2830-8110-PD-0002, sec 4.9.2.2) Tower Draw-Off Line Sizing Liquid from a tower tray is aerated to some extent depending on the foaminess of the gas-liquid mixture. The recommended method for sizing draw offs employs the following criteria: -The depth of the draw-off pan to be 1 – 1½ times the nozzle diameter. The minimum allowable depth is 200mm. - Allowable velocity may vary from 0.7 m/s to 1.2 m/s depending on the nozzle size (See Attachment 1 –Capacities of Side- an Draw-off Nozzles). - The nozzle is to be swaged down to a line size which will not exceed 0.1 bar/100m pressure drop. The swage is to occur at a point in elevation 1.2m below the nozzle draw-off. Only lines 0.2m and larger are to be swaged down, small lines will be maintained at nozzle size to the pump or first exchanger (See Attachment 2 - ‘Typical Swaged Lines After Side-pan Draw-off Nozzle’).
12/13
Process team Rev. 0
Attachment #5
Velocity Criteria for Line Sizing (By Linde) Liquid General Naphtha Boiler Feed Water Steam Condensate Process Water Cooling Water Caustic (NaOH) Methanol Corrosion Inhibitor Polymerization Inhibitor Fuel Oil Luburication Oil Quenching Oil Gasoline Liquid C2, C3 & C4 Slope piping to pits
Lined Pipes (Rubber-, Cement-, Asphalt-)
Suction Side, m/s 0.5 ~ 1.0 0.5 0.5 0.5 0.7
~ ~ ~ ~
1.0 0.8 0.8 1.5
0.8 ~ 1.2 0.5 ~ 0.8 0.5 ~ 0.8 0.5 ~ 0.8 0.7 ~ 1.0 0.5 ~ 0.8 0.5 ~ 0.8 0.7 ~ 1.0 0.7 ~ 1.0 0.3 upto ND 80 0.4 from ND 100 upto 200 0.7 upwards ND 250 upto 1.8
Discharge Side. m/s Remark 1.0 ~ 3.0 1.5 2.0 1.0 ~ 3.0 1.5 ~ 3.0 1.5 ~ 3.0 2.5 upto ND 300 3.0 from ND 400 1.0 ~ 2.0 1.0 ~ 1.5 1.0 ~ 1.5 1.0 ~ 1.5 1.5 ~ 2.0 1.0 ~ 1.5 1.0 ~ 1.8 1.0 ~ 1.8 1.0 ~ 2.0 * * : below 1 m/s when at boiling point
Velocity, m/s 20 ~ 40 20 ~ 50 20 ~ 40 upto ND 300 40 ~ 50 from ND 300 15 ~ 25
Remark
Gas Nitrogen Fuel Gas Sour Gas H2 rich Gas Instrument Air Plant Air Max. velocity at inlet of Silencer Decoking Gas
Velocity, m/s 15 ~ 25 5 ~ 25 5 ~ 25 below 50 15 ~ 25 15 ~ 25 0.6 Mach 30 ~ 65
Remark
Gas in general, according to process pressure upto 3 3~7 7 ~ 15 15 ~ 28 28 ~ 34
Velocity, m/s 14 ~ 40 12 ~ 35 10 ~ 30 8 ~ 18 4 ~ 10
Remark
Steam VHP steam HP steam MP steam LP steam
Special Cases
Nitrogen as purge gas in the Flare System: min. velocity=0.03m/sec Inlet of process steam traps: max. velocity = 0.5 m/sec
13/13
