stress & support

7/29/2019 Stress & Support

1/23

STRESS ANALYSIS

&PIPE SUPPORTS


2/23

- The layout and design of piping and its supporting elements shall bedirected toward preventing following:

1. Piping stresses in excess of those permitted in code

2. Excessive thrusts and moments on the connected equipments

3. Excessive piping sag

4. Excessive interference with thermal expansion and contraction in piping

SUPPORTS


3/23

How to decide the support

location ?


4/23

How to decide the type

support ?


5/23

- Mainly four types of supports are available.

1. Simple resting.2. Guide

3. Axial Restrain

4. Anchor - Again some more supports are available.

1. Spring Constant and Variable Support

2. Hanger Supports.


6/23


7/23


8/23


9/23

STRESS ANALYSIS


10/23

1

BASIC REQUIREMENTS

- Piping system shall have sufficient flexibility to prevent thermalexpansion or contraction or movements of piping supports andterminals from causing

1. Failure of piping or supports from overstress.

2. Detrimental stresses in piping or in connected equipment (pumpand turbines etc.) resulting from excessive thrusts and moments in

the piping.


11/23

1

When Analysis Required?Or

Which system need to beanalyzed?


12/23

1

Types of Stresses

&

Allowable Limits as per Code


13/23

1

Stresses in Pipe

- Hoop stress or Circumferential stress due to Internal pressure.

- Longitudinal stress due to Internal pressure and weight.

- Thermal stress due to temperature gradient.

Allowable Stresses

- Hoop stress Allowable stress as per table A-1

- Longitudinal stress

Allowable stress as per table A-1

- Thermal stress Thermal stress range S A as defined in the code.


14/23

1

Thermal stress range S A

SA = f (1.25 Sc + 0.25 Sh)

Where,

f stress range reduction factor from table 302.3.5

Sc basic allowable stress at minimum metal temperatureexpected during the displacement cycle under analysis.

Sh basic allowable stress at maximum metal temperature

expected during the displacement cycle under analysis.


15/23

1

Hydrostatic stress

Allowable stress during hydro testing is 1.33 Sc because at hydrotest we are testing the system to withstand near the Yield.


16/23

1

Load on Equipment Nozzles


17/23

1

Sample Calculation

Force coming on end Nozzle.

Carbon steel pipe of 600mm OD with 10mm thickness at a temperatureof 300 c.

E = 26.85 Msi ( 1.888 x 10 4 kg/mm2) from ASME B 31.3 Table C6

Thermal expansion = 3.625 x 10 -3 mm/mm (from Table C1)

A = pi / 4 x (600 2 580 2) = 18535.4 mm2

P = 18535.4 x 1.888 x 10 4 x 3.625 x 10 -3

= 1269 tons


18/23

1

Allowable Nozzle Loading

1. WRC 107/297 for Equipments.

2. API 610 for Pumps.

3. NEMA 23 for Turbines (National Electrical Manufacturers

Association).

4. API 617, 619 for Compressors.

5. API 596 for Air Coolers.


19/23

1

Failures

1. Catastrophic Failure

2. Fatigue Failure

Static Analysis

1. Sustained Condition

2. Expansion Condition


20/23

2

Means of providing Flexibility


21/23

2

Caesar Application for Analysis


22/23

2


23/23

2

Thank You

stress & support

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