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ShockView schematic

ShockView plots A, B, C

Input data for shock modeling

PulseView models relations

7 ocillographic plots

Necess. program input data

Equations& sources

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Input Data for Shock Modeling
Please collect the following information to use in the selection of pipeline shock, surge, & hammer prevention equipment.

Please first consider whether the addition of pressure vessels to your piping system, can be avoided completely.

A. Can the need for pump start up surge prevention be made unnecessary?

Please Quote                               

1.) To start a pump without a surge, start the pump slowly. If you specify a pressure that must not be exceeded Liquid Dynamics will quote for working out how slowly you must start your pumps, for you.

Please Quote                               

2.) Start as normal, but allow the flow to by-pass back to suction against a gradually increasing resistance of a slow closing valve in the bypass line. If you state the space available, and the pressure that must not be exceeded, - Liquid Dynamics will quote the by-pass system for you.


B.
Can the need for valve closure shock prevention be made unnecessary?

Please Quote                               

1.) To close a valve without a shock, close the valve more slowly, when you specify a pressure that must not be exceeded, Liquid Dynamics will quote for working out how slowly you must close your valve, for you.

Please Quote                               

2.) Stop the flow going through the fast closing valve in the normal way, but first open another valve in a smaller line from a "T" immediately ahead of the fast closing valve, this line will be piped back to a point nearer to point of volume supply. State the space available and the pressure that must not be exceeded.
Liquid Dynamics will quote for determining the back-pass system dimensions for you.

C. Can the need for pump shutdown back-flow hammer prevention be made unnecessary?
1.) To stop a pump, without a back-flow hammer, slow the pump down gradually; or de-clutch the pump from its driver & allow the pump to spin down, while the inertia of the mass flowing away from the pump pulls liquid through the pump.

Please Quote                               

2.) If you can not decouple the pump drive, then provide a "suck-by" circuit, allowing the void that is sucked out behind the liquid that continues to travel away from the pump, to be filled by sucking past the pump. Liquid Dynamics will quote for establishing the dimensions of the "suck-by" circuit, for you.

**Additionally, Include pressure wave speed (acoustic velocity) m/s when available.

When neither 1 nor 2 of A, B, C, above, "preventive methods" are possible, we can provide a list of companies who can provide vessels suitable for the duties established by a ShockView model of the data that you provide to Ldi, as below.

Both ASME vessel code and the EU Pressure Equipment Directive require your full disclosure of all use parameters.
INFORMATION REQ.
UNITS
LIQUID Examples.
Cust. Guestimates from past.
Pls. mark:-
U=From Process Log.
V=Physical tables
W=Guestimation
Liquid Density.
Specific Gravity
SG @ System Temp.
Grams per milliliter
Grams per Cubic cm.
Kg/Liter or g/cm3
Water
30% NaOH Solution
Ammonia NH3
1.00
1.30
@ -30 C 0.68
SG g/cm3
Liquid Viscosity
@ System Temp.
Centipoises, cP
Water
w/ absorbed CO2 30% NaOH Solution
Ammonia NH3
1.00
30.0
0.35

Viscosity

cP

Compressibility, reduction
in volume per unit change in pressure, @ system pressure & Temp.
parts of a Liter
per Bar L/Bar
Liters/Kg cm2
w/ absorbed air Water @ 10 Deg. C
Pentene & Pentane+HFacid Ammonia NH3

50e-6
@ + 40 C 19.6e-5
11.389E-4

Compressibility

L/Bar

A Dynamic (dt) equation must be resolved, accurate Time figure is essential
It has an exponential effect.
Pump run up time or valve closure time or pump run down Sec.
("Instantaneous" shall mean 0.01 Sec. 10ms)
1450 motor 6"x4" Centrif.
6" Air actuated butterfly
Diesel driven 24" x 20" Centrif.
Meter stop valve (depending on size)
2.0 Sec.
1.0 Sec
5.0 Sec.
0.05 to 0.300 Sec.

Time

Sec.

Bulk Modulus, Elasticity of pipe material
Pacalles
Pa
Steel
Concrete
Plastic PVC
2e+11
4.2e+10
2.89e+9

Elasticity

Pa.

Pipe Wall thickness mm
Millimeters (Dilation of pipe wall combined & liquid compressibility determines shock reduction & frequency) "effective softness"
 
Pipe Internal Diameter      Millimeters mm
mm
Force, Pressure at Pipe Inlet                Bar or Kg/cm2
Pipe Length        Meters (Feet x 0.305)
M
Pressure that Shock must not exceed.        Bar or Kg/cm2
Theoretical mass flow
Kilograms per second Kg/Sec.
US GPM x 3.8/60 x SG
Kg/Sec
Acceptable Materials of Construction
Metals                            Plastics
Synthetic Rubbers
Frequency of any current vibration Hertz, Hz.
Vapor pressure at suction temperature for item C2 above.

ShockView Verification

 

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