IPE-TM-510 Hydraulics
Piping Equivalent Length Guidelines
IPE-TM-510-08
1. Purpose
This procedure provides guidelines for setting equivalent lengths for piping in the Inflection Point Engineering Hydraulics Program.
2. Background
The Inflection Point Engineering Hydraulics Program determines the dynamic pressure drop for a line segment by multiplying the calculated pressure drop per equivalent foot of length by the total equivalent length. The equivalent length is either directly entered by the user as a total or it is calculated as a function of the pipe diameter using equation constants provided by the end user. This procedure provides suggestions for what constants should be entered for various line services.
Equivalent lengths are calculated using the following formula:
Where: "A" constant is the minimum straight length of the piping run.
"B" constant is the cumulative equivalent length factors for the "fittings" composing the piping run.
"C" constant is an additional straight length factor representing that larger plants with larger lines take up more plot area and therefore have longer piping runs.
Input “A”, “B” and pipe inside diameter as feet.
3. Guidelines for A, B, and C Constants
Suggested equivalent length constants for various services are:
TYPE SERVICE A* B C
1 Pump or Compressor, Suction or Discharge 50 450 50
2 Gravity Circulation S&T Reboiler, Inlet or Outlet 25 120 20
3 Typical Run 50 250 25
4 Short Run 10 60 10
5 Close Couple 5 - -
6 Fired Htr Reboiler, Inlet/Outlet See Procedure
7 Vertical Thermosiphon Reboiler, Inlet/Outlet See Procedure IPE-TM-510-02 App. B
- * Add 400 to the "A" constant for all process lines coming from and going to battery limits. This is to account for the pressure drop in between the two process units since they are a long distance apart.
- * Add 100 to the "A" constant for lines coming from and going to Fired Heaters.
- * Add delta elevation to the "A" constant for lines connecting equipment whose delta elevations are greater than about 20 feet. An example of this might be the line from a reflux control valve to the top tray of a fractionator. This is done automatically by the Inflection Point Engineering Hydraulics Program.
3.1 Notes
- The listed types are gross simplifications of the issue of detailed piping layout. Use of these "standard" types does not replace the need for critical review of piping lengths.
- These types when applied to a series of line segments constituting a complex piping run (e.g. vessel / splitter / pump / splitter / flow meter / control valve / exchanger / vessel) may be questionable for some or even many of the individual segments. However, it is expected that the piping run's overall equivalent length is representative of a contractor's typical layout and suitable for Inflection Point Engineering's general hydraulic purposes.
- Services such as reactor section piping will usually have recommended equivalent length guidelines that are technology specific.
4. Guidelines for Application of the Service Types
4.1 Pump or Compressor, Suction or Discharge Service
Only use this set of constants for either the last pipe segment just upstream or the first pipe segment just downstream of the pump or compressor. This service has a "B" constant that is representative of the configurations listed in Section 6.
Compressor Discharge pipe segments would generally have lower "B" constants but higher "A" constants than given for this service type. However, for simplicity and with the expectation that the end result will be satisfactory, it has been suggested that this service type also be employed for Compressor Discharge services.
4.2 Gravity Circulation S&T Reboiler, Inlet or Outlet Service
Only use this set of constants for either the last pipe segment just upstream or the first pipe segment just downstream of the exchanger. This service has a "B" constant that allows for a pipe entrance and 5 tees or 4 tees and a pipe exit.
If the exchanger has a TEMA "J" shell and the pipe segment branches to each nozzle have been explicitly defined, then the pipe segment connecting to the branches would use this service while the branches themselves should use the “Short Run” service constants.
4.3 Typical Run Service
Use this set of constants for most pipe segments connecting items of equipment. This service should be used for pipe segments between a flow element and control valve. This service has a "B" constant that allows for a number of elbows plus typical combinations of through or cross tees, reducers, meter runs, and gate valves.
4.4 Short Run Service
Use this set of constants for pipe segments connecting items of equipment wherein one could assume that the items are close together, or wherein one end of the segment is a pipe tee (split or mix). This service has a "B" constant that allows for either a few elbows, or a cross tee, or limited combinations of through tees, elbows, pipe entrances, and gate valves. Examples of application:
- The segment connecting two exchangers in related services like a fractionator's feed/bottoms exchanger followed by a bottoms cooler
- The segment connecting a condensate flow meter to the outlet of a steam service exchanger
- The segment from a fractionator to the tee where the net bottoms splits off from the material to a reboiler
4.5 Close Couple Service
Use this set of constants for pipe segments connecting two pipe tees or a pipe tee that one could assume is right at the connecting item of equipment. This service has only a straight length element.
5. Typical Fittings Counts
5.1 Service: Pump Suction
EQUIVALENT NUMBER
"FITTING" LENGTH OF TOTAL
TYPE PER FITTING FITTINGS LENGTH
Elbow 20 8 160
Tee (cross) 60 1 60
Reducer 15 1 15
Pipe Entrance (projecting) 65 1 65
Strainer 150 1 150
Gate Valve 10 1 10
TOTAL “B” Constant => 460
5.2 Service: Pump Discharge
EQUIVALENT NUMBER
"FITTING" LENGTH OF TOTAL
TYPE PER FITTING FITTINGS LENGTH
Elbow 20 10 200
Tee (cross) 60 1 60
Increaser 25 1 25
Check Valve 100 1 100
Gate Valve 10 1 10
Meter Run 30 1 30
TOTAL “B” Constant => 425
5.3 Service: Centrifugal Compressor Suction
EQUIVALENT NUMBER
"FITTING" LENGTH OF TOTAL
TYPE PER FITTING FITTINGS LENGTH
Elbow 20 8 160
Pipe Entrance 45 1 45
Strainer 150 1 150
Butterfly Valve 45 1 45
Gate Valve 10 1 10
TOTAL “B” Constant => 410
5.4 Service: Reciprocating Compressor Suction
EQUIVALENT NUMBER
"FITTING" LENGTH OF TOTAL
TYPE PER FITTING FITTINGS LENGTH
Elbow 20 8 160
Tee (cross) 60 1 60
Pipe Entrance 45 1 45
Strainer 150 1 150
Plug Valve 20 2 40
TOTAL “B” Constant => 455
6. Schematic Example
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