“Alignment Checking” this term is quite familiar to piping engineers and all construction engineers. During piping installation at the construction site, it is expected that the equipment flange should match perfectly (aligned) with the piping flange so that during bolting no problem occurs.
But achieving that perfect alignment is very difficult. If this alignment for rotary equipment is not proper then there may be several problems in the future during operation which may lead to vibration of equipment/piping system or in some situations equipment failure.
American Petroleum Institute code API RP 686 provides the data for acceptable deviation from the ideal perfect alignment. As per the code if the vertical and horizontal deviation of the piping flange and rotary equipment flange centerline is within 1.5 mm and parallelism (rotation) is within 0.0573 degrees then the alignment is accepted otherwise means to be devised to bring the deviation within those values.
While performing stress analysis of rotary equipment connected piping systems in Caesar II we can very easily ensure this limitation. The following write-up will describe the step-by-step method of doing the same.
Alignment check of nozzle flange shall be performed for all Rotating Equipment like Centrifugal Compressor, Steam Turbine, Centrifugal Pumps, Gear Pumps, etc as per the following procedure.
Alignment checking using Caesar II
Ensure the correct weight of the pipe (with proper thickness), Support weight (dummy pipe), Weight of valves, flanges, and any in-line items.
Consider Insulation density carefully (equivalent insulation density to be correctly fed with insulation & cladding weight, Check insulation on dummies for cold insulated lines).
Model all branch piping (like drip legs etc.) greater than 2 inches.
Discuss with a piping lead engineer the requirement of any maintenance flanges (Normally for steam turbine or centrifugal connected lines the maintenance flange is recommended) and include it if required.
Minimize the sustained load on the equipment nozzle as much as possible during the static analysis run of the Caesar model.
Normal industry practice is to analyze the Alignment checking in a separate file. So rename the static file as Filename_Alignment.C2
Make the equipment nozzle anchor flexible or remove the displacement if the anchor was not modeled. You can delete the equipment also if required.
Wherever spring support is used, define spring rate and cold load in case of variable effort spring & Constant effort support load in case of constant effort spring.
After performing the above create one additional load case in Caesar II as mentioned below:
WNC+H SUS System with spring hanger WNC SUS System without spring hanger
Set the spring hanger as “As designed”.(Two load cases can be generated for spring As designed and rigid condition)
Fig. 1: WNC Checking in Caesar II for Rotary Equipment
Now run the analysis and check the displacements of the nozzle at the above-mentioned load case (WNC or WNC+H, as applicable) and limit them within below mentioned values:
Vertical deflection (Normally DY): +/- 1.5 mm Horizontal displacement (sqrt sum of DX and DZ): +/- 1.5 mm Parallelism (sqrt sum of RX and RZ): 0.0573 degrees.
In case, the above limitations are not met then re-analyze by readjusting the spring and other supports and do the simulation.
Few Notes for Pump Alignment Checking
An alignment check is to be performed for both inlet and outlet lines.
An alignment check must be performed with the spring under both “As designed” and in “locked” condition.
To avoid small misalignment in the vertical direction first support from the rotary equipment nozzle is used either spring support or adjustable type support.
For top nozzles, the advantage of the equipment can be taken (with approval from the client) as the equipment flange will support the piping flange during alignment.
Pump installation with proper methodology is an important activity. Improper pump installation could lead to vibration issues during pump operation. In this article, we will explore the pump installation best practices and pump installation checklists to reduce vibration problems.
What is Pump Installation?
Pump installation can be defined as the procedures or steps required to employ in the placement, alteration, and preparation for the operation of the pump without difficulty. Pump installation refers to the process of setting up and placing a pump system in its intended location, ensuring it is properly connected to the necessary components, and making it ready for operation. The goal of pump installation is to ensure that the pump operates efficiently, safely, and reliably in its intended application. Proper installation is essential to prevent issues such as leaks, vibrations, misalignment, and premature wear, which can lead to pump failure and reduced performance.
Steps for Pump Installation
Installing a pump correctly is essential for its efficient and safe operation. The actual pump installation steps may vary slightly depending on the types and models of pumps. However, in general, the following steps can be followed:
Step 1: Read the instruction manual thoroughly to understand any specific requirements and guidelines.
Step 2: Use a rigid, strong, and stable pump foundation. It should be level, secure, and clean of debris.
Step 3: Install the pump base on the foundation.
Step 4: In the next step, install the pump and the driver on the baseplate.
Step 5: Add oil to the proper level in the bearing housings
Step 6: Check initial pump alignment.
Step 7: Connect the suction and discharge piping.
Step 8: Complete a second alignment check, and readjust piping as needed. For long-term operation, proper alignment is critical.
Step 9: Perform a rotational check of the driver by disengaging the coupling element.
Step 10: Verify that the pump settings are correct.
Step 11: Install all ancillary equipment; coupling, and/or insert.
Step 12: Perform a pre-startup check, valves, electrical connections, etc., and prime the pump
Step 13: Recheck the pump alignment to ensure that fluid weight in the piping is not causing a misalignment.
Step 14: Start the pumping unit and verify that the pump is delivering the desired flow rate and pressure by checking pressures, flows, temperature, and other indicators.
Step 15: If there is any problem, make the necessary adjustments and rerun the pump.
Checklist for Pump Installation
Normally, organizations prepare a pump installation checklist to ensure that all relevant points are taken care of to ascertain the proper working of the pump. Most of such points are normally mentioned in detail in the pump operating manual provided by the pump manufacturer. Those points in the shorter form are listed in the pump installation checklists so that nothing is missed during actual installation time.
A pump installation checklist and best practices will ensure that major checkpoints are taken care of without missing any important considerations. The pump installation checklist is a document that lists in order of preference the considerations one must follow during the installation process. The checklist is usually grouped into various parts like:
Pump Pre-installation checklist
Pump Installation checklist
Pump Start-up checklist, etc
For the proper functioning of the centrifugal pumps in any plant, the following points need to be taken care of while installing.
Checking the site before the pump installation
The engineer should perform the following checks before the pump installation:
Make sure the foundation concrete is of sufficient strength.
Only place the pump set on a foundation whose concrete has been set firmly.
Only place the pump set on a horizontal and level surface.
Refer to the weights given in the Pump general arrangement (GA) drawing.
All structural work required must have been prepared in accordance with the dimensions stated in the outline drawing/general arrangement drawing.
Improper pump installation in potentially explosive atmospheres
Pumps required to operate in explosive atmospheres should ensure the following pump installation checks
Comply with the applicable local explosion protection regulations.
Observe the information in the datasheet and on the nameplates of the pump and motor.
Installing the pump assembly
Always install the pump set in a horizontal position to ensure proper self-venting of the pump. Refer to Fig. 1:
Fig. 1: Figure showing the foundation of the pump
Position the pump on the foundation and use a spirit level to align the shaft and discharge nozzle. Permissible deviation: 0.2 mm/m. If required, use shims (2) to adjust the height. Fit shims between the baseplate/foundation frame and the foundation itself; always insert them to the left and right of the foundation bolts and in close proximity to these bolts.
For a bolt-to-bolt clearance > 800 mm, insert additional shims halfway between the adjoining holes. All shims must lie perfectly flush.
Insert the foundation bolts (4) into the holes provided. Use concrete to set the foundation bolts (4) into the foundation. Wait until the concrete has been set firmly and then align the baseplate. Tighten the foundation bolts (4) evenly and firmly.
Grout the baseplate using low-shrinkage concrete with standard particle size and a water/concrete ratio of ≤ 0.5.
Produce flowability with the help of a solvent.
For low-noise operation, the pump set can be mounted on vibration dampers upon confirmation by the manufacturer. In this case, only fasten the flexible elements at the baseplate after the piping has been connected.
Expansion joints can be fitted between the pump and the suction/discharge line.
Observe the permissible forces and moments at the pump nozzles and Take appropriate measures to compensate for the thermal expansion of the piping.
Check and ensure that the suction lift line/suction headline has been laid with a rising/downward slope towards the pump.
The nominal diameters of the pipelines are at least equal to the nominal diameters of the pump nozzles.
To prevent excessive pressure losses, adapters to larger diameters have a diffuser angle of approximately 8°.
Thoroughly clean, flush, and blow through all vessels, pipelines, and connections (especially of new installations). Before installing the pump in the piping, remove the flange covers on the suction and discharge nozzles of the pump.
Use a filter with laid-in wire mesh (mesh width 0.5 mm, wire diameter 0.25 mm) of corrosion-resistant material. Use a filter three times the diameter of the piping. Conical filters have proved suitable.
The volute casing and casing/discharge cover take on the same temperature as the fluid handled.
Make sure the space between the casing cover/discharge cover and the bearing cover is sufficiently vented. Never close or cover the perforation of the bearing bracket guards. Never insulate the casing cover and the bearing bracket.
Make sure that the coupling is correctly aligned at all times. Always check the coupling after the pump has been installed and connected to the piping. Also, check the coupling of pump sets supplied with the pump and motor mounted on the same baseplate. Refer to Fig. 2.
Fig. 2: Checking the spacer-type coupling with a dial gauge
Mark the installation position of the coupling by dotting marks (balancing condition).
Remove the coupling spacer. While the pump’s coupling is disengaged, also check the direction of rotation.
Check the alignment of the coupling halves with a dial gauge (see Fig. 2). Admissible run-out of coupling face (axial) maximum 0.1 mm. Admissible radial deviation, measured over the complete circumference, maximum 0.2 mm.
After having installed the pump set and connected the piping, check the coupling alignment and, if required, re-align the pump set (with the motor). Any differences in shaft center height between the pump and the motor are compensated by means of shims.
Check the coupling alignment.
Unscrew the hexagon head bolts at the motor. Insert shims underneath the motor feet until the difference in shaft center height has been compensated. Refer to Fig. 3.
Fig. 3: Pump Set with Shim
Re-tighten the hexagon head bolts. Check that the coupling and shaft can easily be rotated by hand.
Always operate the pump set with a coupling guard. If the customer specifically requests not to include a coupling guard in the Vendor’s delivery, then the operator must supply one! Observe all relevant regulations for selecting a coupling guard.
Reinstall the coupling guard and step guard, if any. Check the distance between the coupling and the coupling guard. The coupling guard must not touch the coupling.
Check the available mains voltage against the data on the motor nameplate.
Select an appropriate start-up method. Change the motor’s direction of rotation to match that of the pump.
Observe the manufacturer’s product literature supplied with the motor. Never check the direction of rotation by starting up the unfilled pump set. Separate the pump from the motor to check the direction of rotation.
Never insert your hands or any other objects into the pump. Check that the inside of the pump is free from any foreign objects.
The correct direction of rotation of the motor and pump is in the clockwise direction (seen from the motor end). If the direction of rotation is incorrect, check the connection of the motor and the switchgear, if any.
Overall, the pump installation should consider safety as the topmost priority.
GRP / GRE / FRP / HDPE piping modeling in START-PROF is as easy as for steel piping. Your job is only to select the appropriate code and choose the material. That’s all!
Difference between GRE/GRP/FRP and Steel
The main differences between GRP / GRE / FRP piping to steel piping are:
The material is orthotropic. The stress values in axial as well as hoop direction need to be considered during analysis. Mechanical properties needed for analysis differ from steel piping: Ea – Elasticity modulus in the axial direction, Eh – Elasticity modulus in the hoop direction, G – Shear modulus, vh/a – Poisson ratio hoop/axial, va/h – Poisson ratio axial/hoop. Material properties are different for each vendor, so please ask the manufacturer for the values needed for stress analysis in the database.
Linear expansion for GRP / GRE / FRP piping is much greater than for steel piping. Pressure elongation is significant (Bourdon effect), and thermal expansion is also great. Due to uneven heating of pipe wall thickness, the real thermal expansion is lower than thermal expansion for the full temperature range. To consider this piping behavior thermal expansion is multiplied by the temperature range factor which is usually considered 0.85.
A long-term failure envelope is used instead of single allowable stress. See the material database for more details. Allowable stresses depend on load type factor f2, temperature factor A1, chemical resistance factor A2, and fatigue factor A3. A different envelope is used for pipes and fittings.
Modeling of GRP / GRE / FRP / Reinforced HDPE Piping using PASS/Start-Prof
To model GRP / GRE / FRP piping choose ISO 14692 code. This code is also suitable for modeling reinforced HDPE or other plastic piping:
Selecting the piping code for Analysis
Then select material from the database:
Selecting the Material Database
That’s all. All other job is the same as steel piping.
The material Database contains all material properties. If there’s no material you need in the database, please ask your vendor to fill the table and add it to the database manually. Future pipe industries and NOV already provided needed data and it is included in the START-PROF database.
Sample Failure Envelope for GRE/GRP/FRP
All load cases for the ISO 14692 code will be created automatically. Just draw piping. After analysis, you get results according to ISO 14692 code.
Output Results after Analysis
Also, we did a job for the vendor of MRPP pipes to add material properties into the START-PROF database for 50-year service life, and now START-PROF is used for stress analysis of MRPP piping.
MRPP – an HDPE pipe, reinforced by a rigid steel carcass made of a welded wire.
MRPP Pipes
Stress Analysis Methodology
The complete video explaining the stress analysis methodology using Start/Prof is given below for your quick reference.
Online Video Course of FRP/GRP/GRE Pipeline Stress Analysis using Caesar II
If you are interested in learning FRP/GRE/GRP Piping Stress Analysis using Caesar II software, you can have a look at the following online video course
A rigid Strut is a dynamic restraint that is used specifically to reduce dynamic loads. They act as compression as well as tension element. Struts can also be a good alternative to the normal piping guide supports. The strut assembly consists of two rods joined by a structural steel member. They are selected from the vendor catalog considering the maximum load that has to be restrained.
Rigid Struts are used to provide a rigid connection between the piping and supporting structure. Using their pivot connection, rigid struts allow a small angular displacement in the range of (+/-) 7 degrees. This allows a little pipe thermal movement in a singular direction.
Refer to my earlier post “A Brief Description of Sway Brace, Strut and Snubber ” for the basics of working and the uses of Rigid Struts. This article will explain the step-by-step methods for modeling the Rigid strut using the software Caesar II.
Rigid Strut Modeling in Caesar II
The steps involved in Strut modeling are as follows:
1. Find out the direction in which restriction of movement is required (Assume X direction) and the location of the strut installation. For reducing thermal loads to be carried by rigid struts it is preferable to choose thermal null points if feasible.
2. Double-click on the restraints checkbox in the Caesar spreadsheet and model restraint X with a 0 mm gap and with no friction. Keep the stiffness K1 box blank.
3. Run Caesar Analysis and found out the force in that node.
4. Enter into any catalog (like C&P, Lisega, PTP, Anvil, Binder, etc) and select the appropriate rigid strut depending on that force (For your reference strut selection table has been reproduced in Fig. 1 from C&P Catalogue).
5. Obtain the stiffness value for the strut from the catalog and enter this value in restraint stiffness (K1) which u left blank in the initial stage.
6. Run the analysis to obtain results.
Fig. 1: Strut Selection Table from C&P Catalogue
Typical Application of Rigid Strut
Rigid Struts are used in Turbine and Compressor connected lines near the nozzle connections to take advantage of very little friction. Otherwise, struts can be used as a substitute for guide supports where the steel structure is not available for using standard guides.
Rigid Strut Ordering Information
Rigid struts are usually made of carbon steel. While selecting a rigid strut, its load-carrying capability must be checked from the manufacturer catalog. The important ordering information is:
Winterization Systems are required in refineries, petrochemical plants, and similar plants to protect equipment and piping against solidifying or coagulation of contents. Winterization in processing plants is normally achieved by using Steam Tracing, Steam Jacketing, Electrical Tracing, or Process Heating. This article will highlight the requirements for the basic design of the Winterization System.
Data Required for Winterization System Design
The data to be used for the design of winterization should be obtained from, but not limited to, the following documents ;
Winterization for process fluids shall be considered in all circumstances, appropriately for the fluids and local ambient conditions.
Winterization of water and steam condensate piping
The following table gives criteria for the requirement of winterization
Fig. 1: Criteria for Winterization Requirement
Winterization of Process Piping
Basic Principle:
Process piping where the pour point or solidifying point of the internal fluid is higher than the lowest ambient temperature shall be winterized. Unless otherwise specified, the fluid temperature shall be maintained above the solidifying point or at least 10°C above the pour point.
For liquid sulfur lines, steam jacket piping or electric heat tracing shall be applied to maintain the fluid temperature between 118 °C and 158°C.
For highly viscous fluids such as asphalt and bitumen, the fluid temperature shall be maintained, applying steam tracer piping or steam jacket piping, at temperatures exceeding the pour point +10°C or temperatures giving a kinetic viscosity of 300 CST (Allowable maximum viscosity during the use of centrifugal pumps) or lower, whichever is higher.
Appropriate measures to prevent fluids from temperature drop are taken for piping in which fluids are always flowing (on-stream) while the plant is being operated. The necessity of winterization, therefore, should be studied for the case where the plant stops operating.
Tank yards have many items of piping, in which fluids are not always flowing (not on-stream). Care should be taken on this point.
Winterization Requirements for Liquid Lines
The following winterization requirements should be applied to the liquid lines containing a fluid that has a higher pour point or solidifying point than the lowest ambient temperature.
(1) Winterization Philosophy for Lines always on-stream:
(a) Bare pipelines, in which the liquid is likely to coagulate within about 12 hours after the liquid stops flowing, should be hot insulated.
(b) Hot-insulated lines, in which the liquid is likely to coagulate within about 12 hours after the liquid stops flowing, should be steam traced, even though the liquid operating temperature is high.
(2) Winterization Philosophy for Lines not always on-stream (liquid-filled lines):
Every size of piping should be steam traced and hot insulated regardless of liquid temperatures.
The same criteria should also be applied to the following lines.
Vents and drains provided for the line should, in principle, be hot insulated; the requirement of steam tracing should be according to the line conditions.
(3) Winterization requirements for Lines not always on-stream (usually empty)
Such lines should be sloped so as not to form pockets and should also be provided with steam purge connections to completely empty the inside; otherwise, they should be only hot insulated.
(4) Other requirements for Winterization
Lines, in which highly viscous fluids such as heavy fuel oil flow, should be steam traced.
Caustic solution and amine solution lines should be steam traced when the freezing point of the solution is higher than the lowest ambient temperature.
Steam tracing of caustic and amine solution lines should be provided with insulating spacers to prevent alkali embrittlement.
Winterization Requirements for Vapor Lines Saturated with Steam
(1) Winterization for Lines always on-stream
(a) The upstream side of the lines of orifice plates or control valves, in which steam could possibly condense, should be hot insulated. The amount of condensate generated from the gas line has to be calculated by estimating the temperature drop and consequent partial pressure decrease of steam.
(b) Lines, in which freezing of condensed water is likely to cause trouble with continuous operation, should be steam traced.
(c) Lines are properly sloped so as not to accumulate condensate.
(d) Lines in which ice or hydrate can be possibly formed on depressuring should be steam traced.
(2) Winterization for Lines not always on-stream
Piping should preferably be free draining. The following items should be steam traced.
– Instruments (such as LG, LT, PG, and lead pipes of PT)
– Bypass lines for control valves
– Inlet line of a relief valve. In some cases, lines should only be hot insulated depending on pipe size and length, considering heat loss.
Winterization Requirements for Vapor Lines with Higher Dew Point Fluid
The following requirements should be applied to the vapor lines containing fluid that has a dew point higher than the lowest ambient temperature.
(1) Lines always on-stream
(a) The upstream side of the lines of orifice plates or control valves, in which vapor could possibly condense, should be hot insulated.
(b) Lines, in which condensate is likely to solidify or is corrosive, should be steam traced.
(c) Lines, in which condensate is likely to freeze or coagulate due to depressurization during shutdown operation, should be steam traced.
(d) Piping should preferably be free draining.
(e) Pockets where condensate accumulates, which may have adverse effects on the indications of instruments (such as PG, and lead pipes of PT), should be steam traced.
(f) Lines, which are likely to have adverse effects on continuous operation due to the condensing of the fluid, should be hot insulated.
(2) Lines not always on-stream
Fig. 2: Typical example of a steam tracing system
Winterization of Utility Piping
Water Piping-Main pipes should, in principle, be buried below the freezing depth. Aboveground piping or underground piping buried above the freezing depth should comply with the requirements of “Winterization of Process Piping”.
Described below are precautions, in particular, for water piping.
Piping of 2″ or less should be heat traced and hot insulated.
For piping of 3″ or larger, which is always on-stream, measures should be established to ensure that water flow is not interrupted, as far as possible. Along with this, temperature drops in winter have to be calculated, and the piping should be hot-insulated for freeze-proofing as necessary.
Piping, which is not always on stream, should be heat traced and hot insulated.
A circulation line should be provided at the terminal of each header so as not to stop flowing.
For pump coolers, water should also be circulated into spare stand-by pumps in order to minimize freezing trouble.
Winterization for Air and Nitrogen Piping
Special attention should be paid to the following.
Instrument air and nitrogen contain little moisture. Instrument air and nitrogen piping, therefore, are not required to be hot insulated; such piping should be constructed of materials for low-temperature services considering the lowest ambient temperature.
When plant air is dry, plant air piping may be bare. When it is not dry, it should be steam traced and insulated.
Winterization for Steam Piping
Attention should be paid, in particular, to the following items.
Steam traps should be installed in lines where condensate is likely to accumulate such as pockets or control valve bypass lines.
Even for the lines not frequently used, a steam trap should be installed at the inlet of each block valve to prevent freezing
Winterization for Steam Condensate Piping
1½” or smaller steam condensate piping should be heat traced and hot insulated.
2″ or larger steam condensate piping, which is always on-stream during plant operation, should be hot insulated.
2″ or larger steam condensate piping, which suffers from the intermittent flow of condensate accumulation for long periods of time, should be heat traced and hot insulated.
Winterization of Equipment
(1) Equipment requiring winterization:
(a) Equipment containing water and where water accumulates for a long period of time, such as separators, flash drums, and receiver boots, from which water has to be removed.
(b) Equipment containing fluids with a high pour point, high solidifying point, or high viscosity, will cause coagulation or hard-to-flow conditions.
(c) Equipment that is likely to have adverse effects on the entire unit, due to the partial condensation of hydrocarbons in gas, such as fuel gas drums.
(d) Equipment handling chemicals, such as caustic soda solution drums and inhibitor drums.
(2) Winterization of static equipment:
(a) Of towers, vessels, and heat exchangers, those handling fluids that may freeze should be provided with a drain valve at a position allowing the fluids to be drained completely during the suspension of plant operation.
(b) Parts of vessels (boots, etc.) that come into contact with water, nozzles, valves, and piping should be heat traced and hot insulated.
(c) No winterization is required for the equipment which can be heated by internal or external heating coils or similar facilities, even if the equipment contains liquid during plant shutdown.
(3) Winterization of air-cooled heat exchangers:
(a) Winterization of air-cooled heat exchangers should be subject to the requirements of API standard 632.
(b) Louvers should be installed to prevent excessive cooling when the inside tube skin temperature in winter decreases to lower than the freezing point or pour point of the fluid passing through the tube.
(c) For air-cooled heat exchangers handling heavy oils with a high pour point or viscosity, steam coils should be provided to prevent the plugging of tubes due to excessive cooling. The use of a hot-air circulation system may be considered necessary.
Data on the consumption of steam by air-cooled heat exchanger steam coils should be obtained from the manufacturer, together with the criteria for use.
Operation Mode Change
Winterization is studied per season, in view of energy saving, and is incorporated in piping design. Such cases are increasingly common.
(1) Winterization for water or moisture freezing prevention:
Heat tracing should not be done during seasons in which the lowest temperature is above 0°C.
Experience shows that when the temperature falls to about −5°C, water freezes, and bare piping, therefore, breaks at pockets.
(2) Winterization to maintain process fluid temperature higher than its pour point/solidifying point:
Heat tracing may be suspended per season according to the pour/solidifying points of the process fluid.
The heat tracing of the equipment and piping handling process fluids with 10°C or lower pour point may be suspended during seasons in which the lowest temperature exceeds 15°C. Seasons may be divided into two groups, for example, the summer season and the winter season, in view of the complexity of the operation.
Selection of Heat Tracing Method for Winterization
Heat tracing (Fig 2) for winterization should be steam tracing, as a rule. Electric tracing may be applied for the winterization of equipment and piping located away from the steam supply source or located in positions to which it is difficult to supply steam. Also, where the fluid is required to be maintained at 200°C or higher, electric tracing may be considered. Where steam cannot be used because of the properties of the internal fluids, hot water tracing may be applied.
Stress Analysis of HDPE, PE-RT, PP-H, PP-R, PVC-C, PVDF Piping
The main features of HDPE piping and other plastic piping related to steel piping are:
The allowable stress of plastic piping is dependent on service life and temperature. The equation is. The A, B, G, and J factors are stored in the Start-Prof material database
In some cases, swelling elongation due to a chemical reaction with the product should be considered. The swelling strain should be specified in the pipe properties
Linear expansion for plastic piping is much greater than for steel piping and caused by the Bourdon effect, thermal expansion, and swelling elongation
Pressure elongation of plastic piping is significant (Bourdon effect), and thermal expansion is also great.
Unlike steel piping, Young’s modulus (creep modulus) for plastic piping depends on service life. For higher service life – the lower creep modulus is used. The support loads, displacements, etc. are calculated at 100 minutes of creep modulus. The seismic analysis was performed using a 0.1-hour creep modulus.
In operating conditions, the average creep modulus is used (average between installation and operating temperature)
Allowable stress for plastic piping depends on the chemical resistance factor, laying condition factor, safety factor, and joint strength factor
The wall thickness check is performed only for straight pipes and not performed for fittings
Modeling of HDPE pipe in Start-Prof
To model HDPE piping or other plastic piping choose GOST 32388 code:
Choosing the Piping Code
Then create a pipe and choose the appropriate material from the database:
Selecting the Pipe Material
In an additional pipe, properties specify the chemical resistance factor (usually 1.0), Joint strength factor (0.4-1.0), and Laying conditions factor (0.8 for buried piping, 0.9 for underground piping in concrete channels, 1.0 for above-ground piping). The temperature range is multiplied by this factor. It considers the nonlinear distribution of temperature across the wall thickness. For plastic piping recommended value is 1.0 and for fiberglass piping 0.85 for fluid and 0.8 for gas if no other information is available.
The swelling strain is used for a chemical swelling elongation. It is the same as temperature elongation but caused by the chemical reaction between the pipe material and the product.
Allowable Stress Values
That’s all. All other job is the same as steel piping.
The Database contains all material properties. If there’s no material you need in the database, you can add its properties manually.
Adding the properties in Material Database
All load cases for analysis will be created automatically. After analysis, you get results according to the code.
Analysis Results
Videos for HDPE Piping Stress Analysis in START-PROF
