Week 11 Challenge

Week 11 Challenge Solutions

1. Friction load determination

A pipe carrying LNG rests on the shoe having vertical force of 125 kN. Calculate the Friction load on the axis. Also find the friction force, if TEFLON pad is used between shoe and pipe support.

Procedure:

Friction factor on Piping:

Materials	Friction factor
Steel to Steel	0.3
Teflon to Steel	0.1

(A) When Steel pipe is resting on steel:

Friction force in longitudinal dire

ction = Friction factor x Gravity load = 0.3 * 125 = 37.5 kN

Friction force in transverse direction = 10% of piping operation load = 0.1 * 125 = 12.5 kN

(B) When Steel pipe is resting on Teflon:

Friction force in longitudinal direction = Friction factor x Gravity load = 0.1 * 125 = 12.5 kN

Friction force in transverse direction = 10% of piping operation load = 0.1 * 125 = 12.5 kN

2. Support Types

Identify the type of support as Spring, Guyed, Stop or Semi Anchor (Guyed + Rest + Stop ) or Rigid Strut from following images.

Solution:

Figure 1:

• Spring Support: It permits the pipe to move in the vertical direction

Figure 2:

• Rigid Support: Allow small angular displacement and thermal movement.

Figure 3:

• Stop support: Restrains the movement of pipe in the axial direction but allow the pipe movement in the lateral direction

Figure 4:

• Semi Anchor Support: Restrict the pipes to move in axial as well as transverse directions.

Figure 5:

• Guyed support: Restrains the lateral movement in two directions therefore also limits the rotational movement of pipe but permits axial movement of the pipe

Figure 6:

• Anchor Support: It does not permit the pipe to move in any direction thus movement in all 6 degrees of freedom is restricted.

3. Design of a pipe rack

Design a typical pipe rack bent in oil plant. The pipe rack configuration shall be as shown in Figure 1 and the plan layout as shown in Figure 2.

Given,

Height of Column = 9 m

Height of First tier = 6 m

Height of Second tier = 7.5 m

Height of Third tier = 9 m

Width of Pipe Rack = 7.5 m (C/C of Column in width of pipe rack)

Span of each Bay = 6 m

Number of bays = 7

Top tier of pipe rack has 3 number of cable trays each 150 mm wide

Second tier of pipe rack has 4 pipes, one of 24 " dia and one of 12 " dia, remaining two pipes are of dia 8"

First tier of pipe rack has 6 pipes, one of 18 " dia and remaining 5 pipes are of dia smaller than 8"

Procedure:

Following Loads are to be assigned:

1) Structural Dead Load:

Load due to weight of Structure excluding weight of pipe

2) Operating Dead Load:

Weight of pipe, fluid in it and insulation.

UDL of 1.9 kN/m² is assumed for pipe of dia 8".

Point load is considered at appropriate location for pipe larger than 8" dia pipes which will be reported by Piping Engineer.

3) Empty Dead Load:

Weight of empty pipe without fluid in it but including insulation, it is assumed as 60% of operating load.

4) Test Dead Load:

In case test medium in pipe is not known, water with density of 1000 Kg/m³ is considered as test medium so generally test load is same as operating dead load.

5) Cable Tray Load:

UDL of 1 kN/m is considered

Dead Load Calculation:

Lets assume Selfweight as 1.1 factor. Where 10% is extra for connections.

Operating Load Calculation:

Weight of Pipe upto 8" = 1.9 kN/m²

Load acting on deck slab = 1.9 x 6 = 11.4 kN/m

For 12" dia pipes,

Operating weight = 79.7 + 72.2 + 16.3 = 168.2 kg/m = 1.682 kN/m

Load on slab = 1.682 x 6 = 10.09 kN

For 18" dia pipes,

Operating weight = 105.1 + 150.8 + 21.6 = 277.5 kg/m = 2.775 kN/m

Load on slab = 2.775 x 6 = 16.65 kN

For 24" dia pipes,

Operating weight = 140.9 + 273.9 + 27.6 = 442.4 kg/m = 4.424 kN/m

Load on slab = 4.424 x 6 = 26.54 kN

Empty Dead load - 60 % of operating load = 0.6 * 11.4 = 6.84 kN/m

Test Dead load = Operating load = 11.4 kN/m

Cable tray load = 1 kN/m

Now create nodes for the structure

Add beams to connect the nodes

Use translational report to repeat the frames

Now apply the loadings to the model

Structure Dead load:

Operating load for 8" pipe:

Operating load for 12" pipe:

Assuming the 12" pipe to be placed at 2.5m from the column

Edit d1= 2.5m

Operating load for 24" pipe:

Assuming 24" pipe to be at the centre

Operating load for 18" pipe:

Assuming 18" pipe to be at 2.8m from the column

Empty pipe load:

Test dead load:

Cable tray load:

Assign parameters as shown

Now run the analysis