DESIGN OF EQUIPMENT FOUNDATIONS

DESIGN OF EQUIPMENT FOUNDATIONS

WAQAS RIAZ 08-NOV-2007

INDUSTRIAL EQUIPMENTS: • • • •

HORIZONTAL VESSELS VERTICAL VESSELS PACKAGE EQUIPMENTS MACHINERY EQUIPMENTS

HORIZONTAL VESSELS: • • • •

General Overview Foundation Type & Shape Design Data Loads Applied to Pedestal

HORIZONTAL VESSELS: General Overview:• Horizontal Vessels mainly Includes Heat Exchangers & Drums. Foundation Type is similar for both of them. • A heat exchanger is a device used to transfer heat from one fluid to another while preventing the two from intermingling. • The three main types are  Shell & Tube HE’s  Air-cooled HE’s  Plate HE’s

Plate HE’s

Air-cooled HE’s

S/T HE

Plate HE

HORIZONTAL VESSELS: Foundation Type & Shape:• Reinforced spread foundations or pile foundations shall be used. • The plane shape of foundation footings and pedestals shall be generally rectangular. • A foundation shall have footings equivalent to the number of saddles of each equipment and will be connected to each other as necessary using a footing (grade) beam.

HORIZONTAL VESSELS: • The widths (a &b) of a pedestals shall, in principle, be greater than:  250 mm  125 mm from the center of an equipment anchor bolt  25 mm from each side of a equipment base plate.

• With regard to the relation between the footing beam and pedestals: β ≤ 60o If β > 60o, Two tie-beams shall be provided. • Minimum Edge Distance i.e. lp, should be 100 mm. Stacked HE's

HORIZONTAL VESSELS: • Where the height (hp) of the pedestal is 1500 mm or larger, corbels shall de considered.

HORIZONTAL VESSELS: •

Regarding Pile Arrangement, for the number and layout of piles, one of the cases shown in figure shall be applied.

CASE 1

CASE 2

CASE 3

CASE 4

2

3

4

5

xZp

2L

3L

4L

5L

yZp

4F

4F

8F

8F

No. Of Piles (n) Section Modulus of Pile group

HORIZONTAL VESSELS: Design Data:1.

2.

WEIGHT: The following weights given in the loading data shall be used as equipment weight: Empty weight Wem Operating weight Wop Test Weight Wt Tube bundle weight Wb DIMENSIONS: Equipment Data Sheet

HORIZONTAL VESSELS: Loads Applied to the Pedestal:1.

VERTICAL LOAD (P): Equipment weight applied to pedestal shall be allocated to each pedestal in proportion to the amount of eccentricity (e) in the axial direction. • • •

Empty Load : Pem = Wem (1/2+e/L) Operation Load : Pop = Wop (1/2+e/L) Test Load : Pt = Wt (1/2+e/L)

HORIZONTAL VESSELS: Loads Applied to the Pedestal:2.

HORIZONTAL LOAD IN AXIAL DIRECTION (Hx): a)

EARTHQUAKE FORCE (Ex) Earthquakes shall be assumed to take place during only operation. Earthquake force shall be calculated by multiplying weight by an earthquake coefficient (k).

Ex = k/2 Wop If thermal resistance force i.e. µWop is less than Ex, then all the Earthquake force equal to kWop shall be applied to fix side only. Where µ is the friction coefficient. kWop Ex FE

kWop

Ex SE

Thermal Force > Ex

kWop FE

SE

Thermal Force < Ex

HORIZONTAL VESSELS: Loads Applied to the Pedestal:b) TUBE BUNDLE PULLING FORCE (Fb) Tube bundle pulling forces are loads occurring solely in the case of heat exchangers. Under the empty weight, maintenance of tube bundles is carried out.

Fb = 1/2 Wb (JGC recommendation) Fb = 1.5/2 Wb (Aramco recommendation) If frictional resistance force i.e. µWem is less than Fb, then all the bundle pulling force equal to Wb/1.5Wb shall be applied to fix side only. Where µ is the friction coefficient. Wb Fb FE

Wb

Fb SE

Frictional Force > Ex

Wb FE

SE

Frictional Force < Ex

HORIZONTAL VESSELS: Loads Applied to the Pedestal:c)

THERMAL STRESS (Th) Thermal stress occurs during operation and is applied to pedestal surface. Thermal stress shall be obtained by multiplying vertical operation weight by a friction coefficient (µ).

Th = µ Pop Typical Coefficients of friction are as follows: • • •

No Slide plate (Steel support on concrete) Steel Slide Plate (Steel on steel) 0.30 Teflon Slide Plate* – –

•

0.50

Bearing Pressure 100 psi and below0.10 Bearing Pressure above 100 psi 0.06

Laborite Slide Plate* 0.10 * Values should be verified against Project specifications.

HORIZONTAL VESSELS: Loads Applied to the Pedestal:3.

HORIZONTAL LOAD IN TRANSVERSE DIRECTION (Hy): Horizontal force applied in the direction perpendicular to the axis of equipment shall be horizontal loads during occurrence of Earthquakes/Wind. These loads shall be allocated to each pedestal in proportion to the amount of eccentricity in the Axial direction.

HORIZONTAL VESSELS: Loads Applied to the Pedestal:4. •

•

MOMENTS Moment arm for moments working on pedestal surfaces due to horizontal forces applied in axial and transverse direction is “h” . However, for bundle pulling force, moment arm is the “hmax”.

HORIZONTAL VESSELS: Foundation Design:•

•

Using the Loads on the Pedestal, foundation stability and foundation design can be performed using general understanding of the foundations. Stability checks includes : – – –

Soil/Pile Bearing Sliding Check Overturning Check

VERTICAL VESSELS: • Vertical Vessels mainly includes: – Process Columns – Vertical Drums (3-Legged Vessels) • Reinforced Concrete foundations with a spread footing or piling. • Mostly for Vertical Drums block type foundations are preferred. • For Process Columns, configuration of the pedestal and footing shall be as follows: – dp or l ≤ 2.0 m : Rectangular – dp or l > 2.0 m : Octagonal

VERTICAL VESSELS: •

Following loads on the foundation shall be considered based on the loading data: – Weight during Operation Wop – Weight during water test Wt – Empty Weight Wem – Horizontal Load H – Overturning Moment M M=H.h

Data Sheet

PACKAGE EQUIPMENTS: • • • •

Package Equipments are the one in which only governing load is the DEAD LOAD. No significant vibrations are imparted. Foundations for Package Equipment are referred as SKID FOUNDATIONS. Skid Foundations are only checked for the Stability. Weight Check, rebar volume check and thickness check is not required for package equipments.

MACHINERY EQUIPMENTS: • • • •

General Overview Foundation Type & Shape Static Design Loads Static Design

MACHINERY EQUIPMENTS: General Overview:•

Reciprocating Machinery Machinery with reciprocating masses as major moving parts. This machinery should be supported as close to grade elevation as possible directly on rigid block.

MACHINERY EQUIPMENTS: General Overview:• Rotating Machinery Machinery with rotating masses as major parts. This machinery may be supported on a rigid block or on an elevated structure.

MACHINERY EQUIPMENTS: Foundation Type & Shape:1. Foundation Type • • •

Foundations for these equipments are referred as Machine Foundations. Reinforced Concrete Spread or Pile Foundations are recommended. Machine Foundations are grouped as follows:

MACHINERY EQUIPMENTS: Foundation Type & Shape:2.

Foundation Shape

• •

Block foundations should be rectangular. Thickness of the rigid block for machinery shall not be less than:0.60 + L/30 where L (in meters) is the length or breadth. Where two or more machines are on a common foundation, L shall be the greater of : – The breadth of the common foundation. – Then length of the longest segment assigned to any one machine.

MACHINERY EQUIPMENTS: Static Design Loads:• In addition to the Dead Load of Machine following loads should be considered for static design:– Vertical impact of 50% of the dead weight of the machine and base plate. – A lateral force of 25% of the weight of each machine including its base plate applied normal to its shaft at a point midway between its end supports. – A longitudinal force of 25% of the weight of each machine and its base plate applied along the shaft axis. – Lateral and longitudinal forces shall not be considered to act concurrently. – Seismic Loads should also be considered in accordance with project specifications.

MACHINERY EQUIPMENTS: Static Design:• Weight Check – For Reciprocating Machines: Weight of Rigid Block should be 3 - 5 times the weight of Machine. Weight of Pile Cap should be 2.5 – 4 times the weight of Machine. – For Rotating Machines: Weight of Rigid Block should be 2 - 3 times the weight of Machine. Weight of Pile Cap should be 1.5 – 2.5 times the weight of Machine.

• Stability Check – Rigid block should be check against Soil Bearing, Sliding & Overturning. – However, for spread footings 50% reduction in allowable soil pressure should be considered.

MACHINERY EQUIPMENTS: Static Design:• Rebar Volume Check The effects of shrinkage and thermal expansion shall be taken into account to prevent cracking. The minimum quantity of reinforcement in concrete shall be 30 kg/m3 for rigid blocks.

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