design criteria for all pumps

8/4/2019 Design Criteria for All Pumps

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The following data are extracted from the same reference book:

I. DESIGN CRITERIA FOR ALL PUMPS

b. WITH CAST IRON OR ALUMINUM NOZZLES AND CASINGS ALUMINUM PUMPFORCE, MOMENT AND STRESS LIMITATIONS

The following criteria shall apply for pumps with 4-in. discharge nozzles or smaller(suction nozzles may be larger). The forces contained herein are considered

minimum criteria and should be adjusted where the vendor has experimental or testdata permitting larger reactions.

Suctions and discharge nozzles shall be designed to withstand forces and momentsfrom the thermal expansion or contraction of piping. Piping reactions shall be

computed in conformance with ANSI B31.3 : Petroleum Refinery Piping, Section 319,"Code for Pressure Piping", and shall be designed within the limiting criteria set by

this standard. The modulus of elasticity shall be adjusted for the operatingtemperature condition.

Each nozzle shall be capable of withstanding forces from external pipingdetermined by the following formulas :

For suction nozzles : Frs 1.6 w 50 D

For discharge nozzles : Frd (2w - Frs) 50 D

Top suction and top discharge pump nozzles are further limited by :

Frs and Frd = (Fx2 + Fz2)1/2 and the following;

For suction nozzles

a. Fxs 1.3 w 40 D

b. Fys (in compression) 1.2 w 50

D

c. Fys (in tension) 0.5 w 25 D

d. Fzs w 35 D

For discharge nozzles

a. Fxd (1.8 w Fxs) 40 D

b. Fyd (in compression) (2 w Fys) 50 D

c. Fyd (in tension) 0.5 w 25 D

d. Fzd (w Fzs) 35 D

End suction and top discharge pump nozzles are further limited by :

Frs = (Fzs2 + Fys2)1/2 and Frd = (Fxd2 + Fzd2)1/2 and the following;

For suction nozzles

a. Fxs 1.2 w 50 D

For discharge nozzles

a. Fxd (1.8w Fxs) 40 D


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b. Fys 0.6 w 35 D

c. Fzs w 40 D

b. Fyd (in compression) (2w Fys) 50 D

c. Fyd (in tension) 0.5 w 25 D

d. Fzd (w Fzs) 35 D

Limit tension and compression forces to 500 lb.

Where : F = force, lb.

Subscript r = resultant of forces

Subscript x = axis parallel to shaft

Subscript y = vertical 90o to shaft

Subscript z = horizontal 90o to shaft

w = weight of pump only, lb.

D = diameter, nominal diameter = I.P.S. = iron pipe size, in.

d = discharge or exhaust

s = suction or intake

Fr = resultant shear force in the plane of any specific flange face.

Sh = basic allowable stress for the material of construction at maximum operatingtemperature (see ANSI B31.3).

Each suction and discharge nozzle shall be designed to withstand the forcesdescribed for the specific configuration. Unit stresses in each nozzle shall be limited

to :

One-third of the allowable hot stresses Sh for pipe sizes 4 in.

One-half of the allowable hot stresses Sh for pipe sizes > 4 in.

as shown in ANSI B31.1 and ANSI B31.3.

The baseplate and pedestal support assembly on pumps having a discharge nozzle 4in. shall be adequate to limit the shaft displacement, when measured at the coupling,

to a maximum of 0.005 in. in any direction when subjected to the following loads.These loads represent the total effect of all external mechanical forces that may be

applied to a fully grouted pump base. They are to be applied to the pump throughthe suction and / or discharge nozzle.


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Mx = 3.0 w* ft-lb

My = 2.0 w* ft-lb

Mz = 1.5 w* ft-lb

where Mx = moment in y-z plane

My = moment in x-z plane

Mz = moment in x-y plane

w = weight of pump only

* Minimum w is 500 lb. in these computations.

For purposes of evaluating computed piping-imposed external moments and forces,they shall be transferred from both suction and discharge flanges to the intersection

of the X, Y and Z axes. An algebraic summation shall then be made for comparisonwith the moment limitation given above.

The vendor shall submit alternative criteria for pumps having a discharge flange 4 in.NPS. It is suggested that these criteria be developed as a result of tests.

design criteria for all pumps

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