Liquid Dynamics International Ltd. - Piping System Analysis / Piping System Simulation

LDi – P28

Please collect the following information to use in the selection of pipeline shock, surge, and 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?

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.

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?

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.

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 shut down back-flow hammer prevention be made unnecessary?

1. To stop a pump, without a back-flow hammer, slow the pump down gradually; or declutch the pump from its driver and allow the pump to spin down, while the inertia of the mass flowing away from the pump pulls liquid through the pump.

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.

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.

Please mark: U = From Process Log, V = Physical tables, W = Guestimation

Information Required: Units: Liquid Examples: Customer
Guestimates:
1. SG – g/cm3

Liquid Density Grams per milliliter Water 1.00
Specific Gravity Grams per Cubic cm. 30% NaOH Solution 1.30
SG @ System Temperature Kg/Liter or g/cm3 Ammonia NH3 @ -30C 0.68

2. Viscosity – cP

Liquid Viscosity Centipoise, cP Water 1.00
@ System Temp. 30% NaOH Solution 30.0
(with absorbed CO2)
Ammonia NH3 0.35

3. Compressibility – L/Bar

Compressibility, reduction parts of a Liter Water @ 10 Deg. C 50e-6
In volume per unit change per Bar L/Bar (with absorbed air)
In pressure, @ system Liters/Kg cm2 Pentene & Pentane @+40C 19.6e-5 Pressure and temperature +HF acid
Ammonia NH3 11.389e-4

4. Time – Seconds

A Dynamic (dt) equation Pump run up time 1450 motor 6"x4" 2.0 secs.
must be resolved, accurate or valve closure time Centrifugal
Time figure is essential or pump run down Sec. 6" Air actuated 1.0 secs.
It has an exponential effect. ("Instantaneous" shall butterfly
mean 0.01 Sec, 10ms) Diesel driven 5.0 secs.
24”x20” Centrifugal
Meter stop valve .05 - .300 secs.
(depending on size)

5. Elasticity – Pa

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

Pipe Wall thickness in mm
(Dilation of pipe wall combined & liquid compressibility determines shock reduction & frequency) "effective softness"

Pipe Internal Diameter in mm

Pipe Length in Meters (Feet x 0.305)

Theoretical mass flow in Kilograms per second (Kg/Sec) US GPM x 3.8/60 x SG

Force, Pressure at Pipe Inlet in Bar or Kg/cm2
Pressure that Shock must not exceed in Bar or Kg/cm2

Acceptable Materials of Construction
Metals
Plastics
Synthetic Rubbers

Frequency of any current vibration Hertz, Hz.

Vapor pressure at suction temperature for item C2 above.