Cloud you please anyone help me to calculations of natural pipe line size.Please find the attached steam velocity criteria at different pressures, is it applicable for natural gas pipe line sizing calculations? • • Generally gases consider maximum velocity 30 m/sec for pipe line sizing calculations, is it applicable applicable for all gases? for different pressures? is it available similar kind of velocity chart for natural gas also? Natural gas conditions and properties: Molar Flow : 35 MMscfd (35680 kg/hr) Molecular Weight :20.43 Operating Pressure Barg: 75 Operating Temperature Deg C : 50 Density :68.62 kg/m3 Viscosity:0.014 Cp Compressiblity factor:0.8261 Thanks, Best Regards, A pipeline system needs to consider not only the velocity but also the pressure drop in the pipeline. This is specifically true when we are talking of long distance sales gas (natural gas) transmission pipelines and the required pressure at the terminal end of the pipeline governs the line size along with the velocity. Velocity of 30 m/s is obviously very high. There are also considerations related to erosion due to high velocities which need to be taken into account. Companies like "Shell" recommend that gas velocities in transportation of natural gas through long-distance pipelines should be in the range of 5-10 m/s for continous operation and a maximum up to 20 m/s for intermittent operation. The normal sizing procedure for gas transmission pipelines is to assume a line size and check the pressure drop and velocity for the assumed line size using equations for singlephase gas pipeline equations such as the AGA (American Gas Association), Weymouth, Panhandle A and Panhandle B. A very detailed excel workbook including all the above mentioned equations, calculation of flow or pressure drop based on these equations and calculation of erosion velocity is available at the online store of "Cheresources" at the following link: ORSOK P-001 SIZING OF GAS LINES (Page 12-13) When sizing gas lines the sizing criteria will be a compromise between the maximum velocity and allowable pressure drop . %n most transmission pipelines recommended gas velocity is 40 . α. $. 2006. Elsevier. by S Mokhatab. -s a rule of thump" pipe erosion begins when velocit! e..50 and 5.50% of the erosional velocity. J G Speight.1 . Following notes are from "Handbook of Natural Gas Transmission and Processing".6.421.6 .83 psi/mile. %n s!stems with &'( as low as )*( +" velocit! should be limited to 50 ft/s or lower" for it is difficult to inhibit &'( corrosion at higher velocities. Section 11. As a rule of thumb the velocity should be kept below: V = 175 X (1/ )^0.43 Where. . Most cost effective gas pipelines should have a pressure drop between 3. ! is the maximum velocity of gas to avoid noise in m"s and ρ is the density of gas in kg"m#.#. gas velocity shall not exceed limits which may create noise or vibrations problems. )ee attached NORSOK Standard P-001 $egards )hivshankar AttachedFiles 1. pages 418 .ceeds the value of &//012(3 in ft/s" where 3 4 gas densit! (in lb/ft3 and & 4 empirical constant (in lb/s/ft( (starting erosional velocit! . However for those pipelines (short ones in which pressure drop is of secondar! importance" the pipe could be si#ed on fluid velocit! onl!. W A Poe. $efer %able &:$ecommended pressure drop for operating pressure in '($)(* )%A'+A$+) on page .Design Considerations on sales gas pipelines.Line Sizing Criteria. subsection 11. When dP is not critical: Velocity is 60 m/s (or the lowest value) When dP is critical: dP is set depending on the operating pressure.Maximum velocities In lines where pressure drop is not critical. -s a rule of thump" pipe erosion begins to occur when the velocit! of flow e. Norsok Standard gives much higher velocities for pressures higher than about 15 barg (approaching starting erosional velocities for C=200). If operating pressure of the gas were 0. &4)00 in most cases. "Handbook of Natural Gas Transmission and Processing" gives a method to specify max allowable gas velocity. 3. α. .2 A flat allowable max velocity at low operating pressures (60 m/s per Norsok standard) seems reasonable to apply in the case of NG pipe line. . I can say that post No 7. low is represented by the orange line of the diagram.Line Sizing Criteria). According to above.4 . Recommended gas velocities should report corresponding operating pressure. %n most cases" & is taAen to be )00. with no polyethylene pipes ). in function of operating pressure. The lower the pressure the higher the max allowable velocity.xls" estimates starting erosional velocities.1 What is considered as starting erosional velocity in normal NG pipe lines.uation ())*(( (<eggs" )987 = >e 4 &/3?0. Not having access to API 14E. or C=200 in the formula (in lb/s/ft2)? C=100 when there may be condensate. However" -6% 16 )78 ()987 suggested a value of &4)00 for a continuous service and )(5 for a noncontinuous service. Recommended gas velocities are considered as 50% of corresponding erosional velocities. the high one to C=200 per API 14E. The low erosional velocity corresponds to C=100. For lower pressures it gives a flat value of 60 m/s. There is no mention of two phase flow in this subsection. reflects the writing of "Handbook of Natural Gas Transmission and Processing" . %n addition & 4 )50 to (00 ma! be used for continuous" non corrosive or corrosion controlled services without solid particles present.3 Any other comment on the above or the "NGvel.5. Attached "NGvel. allowable max gas velocity would be 64 . allowable max gas velocity under the conditions specified by cnu879 would be 7. Questions to promote clarification of the matter. 3.14. -6% 16 )78 ()987 suggested &4)00 for continuous and )(5 for non continuous service. versus 28. for either the NG described by cnu879 or pure methane at 15 oC. %n addition" it suggests that values of & from )50 to (00 ma! be used for continuous" noncorropsive or corrosion controlled .127 m/s. high by the red line. 3.4 m/s given by Norsok Standard. 2. Can you confirm applicability and recommend flat value? The Handbook of Natural Gas does not seem to mention something similar. β." (00( . recommended velocities are quite low for high pressure pipe lines.7 m/s.xls"? 4. or corrosion? How is it that the gas contains solid particles? 3. Reasonable. para 1. versus 60 m/s per Norsok Standard. Exact wording of the relevant point is as below: :%n most pipelines" the recommended value for the gas velocit! in the transmission pipelines is normall! 70 to 50+ of the erosional velocit! (Mohitpour et al. per API 14E ? Shall we use C=100. refer to the links below. since density decreases with pressure (yet density * estim max allowable velocity decreases with pressure). Note: For additional info that could be useful. γ.6.ceeds the value given b! 8. depending on conditions. as explained there. Recommended max allowable velocities by Norsok Standard P-001 are also presented for comparison (green line on diagram). Indeed.2 barg (which could more or less occur in a city distribution network.1 (Sales Gas Transmission .5 ())*(( where >c is erosional flow velocit!" ft/sec@ 3 is densit! of the gas" lb/ft3@ and & is empirical constant. subsection 11. In order to estimate NG allowable velocities in long distance pipelines.e. Temperature variations are thus minimized. 3. please clarify). understood as any gas line (if not. 5. but what happens in practice? 5. Clarifications on this point would be welcomed.2 (even assuming two phase). dry gas always). Assumption of condensation could explain the low recommended velocities (say 10 m/s) in high pressure pipelines. I think we need answers to the following (after consideration of the above). how can we specify max allowable velocity in function of actual density or other parameters? Objective is to have a guide for allowable velocity at various operating conditions. It refers to two phase flow in "flowlines and pipelines". since increasing velocity of gas (without liquids or solids) will create rather noise / vibrations than erosion. even if gas is initially without condensates.2 How could we interpret / comment on relevant text of "Handbook of Natural Gas Transmission and Processing" (para 1)? 5. 5. pipeline operators have also defined limits for "liquefiable HCs" in pipelines and these figures are quite low.3 of post No 7? Long-Distance Sales Gas Transmission pipelines have water specifications of a maximum of 7 lb per MMSCF as required in the United States . As long as the temperature in the pipeline is above its cricondentherm value. or 3.1 For a gas introduced "dry" to the pipeline. Most long-distance pipelines for sales gas run buried. will it usually "create" condensates (water / hydrocarbons) somewhere or not? Water and hydrocarbon dew points may suggest "not". Influence of solids on erosional velocity is estimated by API 14E for two phase flow. 2. even if quantity of formed condensates is minimum.cheresources. not in the Pressure Reducing (and metering) stations.services if no solid particles are present:. Similar to the water content specification for gas transmission lines.1a. The previous limitation "allowable gas velocity = 40 . so allowable velocity should be based on erosion velocity.com/invision/topic/10801-c-factor-in-the-erosional-velocity-eqnas-per-api-rp-14e/ proposes higher values for C to be used in the erosional velocity formula. In most cases the HC dewpoint of sales gas is below -20°C. Erosion in gases is accepted to be due to entrained liquids or solids.3 Any response to point 3. 4. hydrocarbon condensation is ruled out irrespective of the pressure.50% of erosional velocity" is understood to concern long distance pipelines only. Water is a strict no-no in gas transmission lines since it can cause corrosion as well as slugging due to water accumulation. If not (i. Casual changes of gas composition can also result in condensates. Probably some condensation of hydrocarbons / water is quite possible in long distance pipelines. Again dropout of hydrocarbons is detrimental to the operation of the pipeline since it can cause slugging and can lead to increased pressure drop thus disrupting the pipeline operation. So probability of water has to be ruled out. what about same influence for gas without any condensate? 5. http://www. Besides it could explain difference to allowable velocity per Norsok standard (for pressures higher than ~ 15 barg). We speak here of condensates formed in the pipeline. So once again the probability of some condensation of hydrocarbons in a sales gas transmission pipeline is ruled out. For a reference to allowable "water content" and "liquefiable HCs" in gas transmission lines in North America refer the link below: . at least in usual case concerning condensates. It is improbable that authors of "Handbook of Natural Gas Transmission and Processing" misinterpret API 14E. In Canada it is <= 5 lb per MMSCF. pipeline terrain. A point raised in post #9 says about pressure reducing stations. This is based on experience of companies like Shell and considers a variety of factors such as pressure drop. I am now clear about when to use Weymouth. Panhandle A & B and Spitz glass equations to calculate single phase gas velocity along with erosion velocity for long distance transmission of natural gas. v=Q/A where: v = velocity Q = flow rate A = cross-sectional area of the pipeline The presentation you have provided has no name for the author. Shashi Menon's book fails to consider that erosion is a factor related to the metallurgy of the pipeline for evaluating "C" factors in the erosion velocity equation. I have myself proposed in post #6. "C" value of 100 as provided in Menon's book is far too conservative and not practical in today's context when production economics need to be carefully evaluated from gas-condensate wells. Pressure reducing stations are required only at the terminal or consumer end of the pipeline. When I mention gas-condensate wells it is gas and condensate as a 2-phase fluid. TGNET is a single-phase gas pipeline simulator and is not meant for 2-phase flow which reiterates the fact that sales gas pipeline needs to be modelled as single-phase and not 2-phase. hanks for interesting discussion. Another important point to note for all new design engineers who have just been introduced to pipeline hydraulics is that a lot of natural gas pipeline hydraulic simulation is done using TGNET software from PIPELINE STUDIO. E.Bulk velocity at any cross-section of the pipeline is nothing but the flow rate @ operating pressure / temperature divided by the cross-sectional area of the pipe. erosion/corrosion. Shashi Menon's book "Gas Pipeline Hydraulics" whose reference is given in the presentation does talk about erosional velocity and there is no denying the fact that erosion velocity is a factor to be considered.e. periodic maintenance and the life-cycle cost of the pipeline. operational flexibility. . The pressure at the start point and the terminal point i. and not sales gas. that long-distance sales gas transmission pipleines should not have velocities exceeding 10 m/s. However. Gas transmission pipelines do not have pressure reducing sations along the pipeline terrain. the point is that E. It is obvious that the "C" factor cannot be the same for carbon-steel and stainless steel. instead they generally have pressure booster stations using booster compressors due to unamanageable pressure drops in long distances of the pipeline. the required pressure drop along with the velocity plays a major role in determining the pipeline diameter. 7 psia and 60 ° F) T = Operating Temperature ° R P = Operating presssure.. I don't know how this equation is derived ? and erosional velocity is given as v(e) = C/ Where. Q: !or a gas introduced "dry" to the pipeline# will it usually "create" condensates (water / hydrocar$ons) somewhere or not% &ater and hydrocar$on dew points may suggest "not"# $ut what happens in practice% A: . Engineering just does not work on the theory of probability. psia Z = Gas compressibility factor However. "Sales Gas Pipeline Part I". For solids-free fluids where corrosion is not anticipated or when corrosion is controlled by inhibition or by employing corrosion resistant alloys.imately *rom the . "'rosional velocity( )igher velocities will cause erosion o* the pipe interior over a long period o* time. v(e) = Fluid erosional velocity (ft/s) C = Empirical Constant = Gas Density (lbs/ft3) For solids-free fluids values of c = 100 for continuous service and c = 125 for intermittent service are conservative.. +he upper limit o* the gas velocity is usually calculated appro. v = 60*Z*Q*T / d^2* P Where. Comments : Post No 9 clearly indicates this is a question. inches Q = Gas flow rate MMscfd (at 14. Questions were asked by kkala in post No 9 and replies given by ankur2061 in post No 10 and other. section "Single Phase Gas flow". not a statement.zip" attached to post No 11 by Shivshankar. Nevertheless they do not make an insult to kkala. -Following is taken from "New Folder(4). Comments are by kkala. Also there is an inference that copying from a book does not make it entirely true and one has to do an in depth study of the subject before coming to any conclusions. values of c = 150 to 200 may be used for continuous service: values up to 250 have been used successfully for intermittent service. 1. Mentioned derogating hints have no place in an engineering forum.The conclusion is that sales gas transmission has to be treated as a single-phase flow and not as a "probable" two-phase flow. v = Gas velocity (ft/s) d = Pipe inside diameter. lessening its reliability.In API 14E the gas velocities may be calculated using following derived equation. Regards Below are notes on sales gas pipeline sizing. from 70 barg downswards. Allowable max velocity (initially specified) does not seem to depend on allowable ∆P per unit length. One would expect gradually higher allowable velocities as operating pressure goes lower e. On what pressure this velocity refers to? Clarification would be welcomed. I have heard of NG liquids formed along the pipeline and of slug catchers. Advice on this point appreciated. a flat allowable max velocity is anticipated at low pressures (like in Norsok std). Q: If not (i.9 is usually considered clean". /00/012+(3g (l$m/*t4)).2 (even assuming two phase). according to answer 1. dry gas always).g.. too. (*t/s) . while allowable max velocity is actually higher? 4. where allowable max velocity is specified by noise. some water or condensate may be present. This concept seems to predict the low allowable velocities at high pressures (say 70 barg). potential corrosion. at least in usual case concerning condensates. A: gas velocities in transportation of natural gas through long-distance pipelines should be in the range of 5. an acceptable operational velocity is 50% of the above". not a flat 10 m/s. Comments : Placing the question to the forum. A pipeline with E greater than 0... Usually. otherwise how could these velocities be explained? Or these 10 m/s correspond to optimum ∆P/unit lenth. Some solids may be also present.. -Text from Shivshankar attachment complies with 50% erosional velocity for sales gas pipelines. Q: How could we interpret / comment on relevant text of "Handbook of Natural Gas Transmission and Processing"? A: .*ollowing e-uation( Vma.. 3.. does API 14E specify a flat max allowable velocity at low pressures? (no mention of it so far). Q: Any response to point 3. For two phase flow.3 of post No 7? Commenton 3.g. Therefore the gas flow rate must be multiplied by an efficiency factor (E). 2. Comments : Above evidently concerns sales gas pipelines without any condensate in it (dry gas). . yet these cases can represent non normal operation (e.An explanation why dry gas allowable velocity is so low at high operating pressures would be also useful.there is an inference that copying from a book does not make it entirely true and one has to do an in depth study of the subject before coming to any conclusions. post No7: Answer is pending. &ong-distance sales gas transmission pipelines should not have velocities e#ceeding ! m"s. para 4). so that allowable velocity could be estimated for any operating condition. even for single phase gas flow. "Pipeline efficiency: In Practice.! m"s for continuous operation and a ma#imum up to $! m"s for intermittent operation.e. could have hopefully made things clearer. or 3. vibration results.. % would not design a long-distance natural gas transmission pipe line for a velocity of more than ! m"s normally. Concerning dry gas. This is based on e#perience of companies like 'hell and considers a variety of factors such as pressure drop( erosion"corrosion( pipeline terrain( operational fle#ibility( periodic maintenance and the lifecycle cost of the pipeline.2. change in composition spec) resulting in lower gas flow rate. . Erosion is understood not to affect a dry gas pipeline without solids (post No 9. how can we specify max allowable velocity in function of actual density or other parameters? Objective is to have a guide for allowable velocity at various operating conditions. Economics affect allowable (frictional) ∆P per unit length and may dictate a lower velocity.. 3. One of the most comprehensive documents related to erosion know to me is by "BP Amoco" titled "Erosion Guidelines" which provides some values on "C" factors. Post No 7 is anticipated to be applicable for these multiphase flows (allowable velocity = 50% of erosional) with the revised values of C. . . post No 7. 17 welcomed (numerous. Ankur. Regards."Handbook of Natural Gas Transmission and Processing". 9. Chapter 3. notes that flow is often multiphase in the raw gas transmission lines from wells (different to sales gas pipelines). General comments on posts 7.Commenton 3. Below is what they list out for the "C" factor for various materials and flow conditions: CS: a) "C" = 135 if nominally solids free (solids less than 1 pound of solid per thousand barrel of liquid) b) "C" = 200 or Ve = 65. Can you confirm or advise accordingly? ot much research has been done in this area.6 ft/s whichever is lower if totally solids free 13Cr Steel: "C" = 300 if nominally solids free DSS: "C" = 350 if nominally solids free Single Phase Liquid Flow: CS: "C" = 250 (under CO2 corrosion and no corrosion inhibition) 13%Cr Steel: "C" = 300 DSS: "C" = 450 if nominally solids free Hope this helps. if possible).