ITT BPHV manual Npsh

Page 47

NPSH

The minimum operating values that can be reached at the pump suction end are limited by the onset of cavitation.

Cavitation is the formation of vapor-filled cavities within liquids where the pressure is locally reduced to a critical value, or where the local pressure is equal to, or just below the vapor pressure of the liquid.

The vapor-filled cavities flow with the current and when they reach a higher pressure ares the vapor contained in the cavities condenses. The cavities collide, generating pressure waves that are transmitted to the walls. These, being subjected to stress cycles, gradually become de- formed and yield due to fatigue. This phenomenon, char- acterized by a metallic noise produced by the hammering on the pipe walls, is called incipient cavitation.

The damage caused by cavitation may be magnified by electrochemical corrosion and a local rise in temperature due to the plastic deformation of the walls. The materials that offer the highest resistance to heat and corrosion are alloy steels, especially austenitic steel. The conditions that trigger cavitation may be assessed by calculating the total net suction head, referred to in technical literature with the acronym NPSH (Net Positive Suction Head).

The NPSH represents the total energy (expressed in feet) of the liquid measured at suction under conditions of incipi- ent cavitation, excluding the vapor pressure (expressed in feet) that the liquid has at the pump inlet.

To find the static height (hz) at which to install the ma- chine under safe conditions, the following formula must be verified:

hp + hz ≥ (NPSHr + 2 feet) + hf + hpv

where:

hp

is the absolute pressure applied to the free liquid sur-

 

face in the suction tank, expressed in feet of liquid; hp

 

is the quotient between the barometric pressure and

 

the specific weight of the liquid.

hz

is the suction lift between the pump axis and the free

 

liquid surface in the suction tank, expressed in feet;

 

hz is negative when the liquid level is lower than the

 

pump axis.

hf

is the flow resistance in the suction line and its acces-

 

sories, such as: fittings, foot valve, gate valve, elbows,

 

etc.

hpv is the vapor pressure of the liquid at the operating temperature, expressed in feet of the liquid. hpv is the quotient between the Pv vapor pressure and the liquid‘s specific weight.

0.5is the safety factor.

The maximum possible suction head for installation de- pends on the value of the atmospheric pressure (i.e. the elevation above sea level at which the pump is installed) and the temperature of the liquid.

To help the user, with reference to water temperature (40ºF) and to the elevation above sea level, the following tables show the drop in hydraulic pressure head in relation to the elevation above sea level, and the suction loss in relation to temperature.

Water

68

104 140 176 194 230

248

Temperature (°C)

 

 

 

 

 

 

Suction

-.7

2.3

6.6

16.4 24.3 50.5

70.5

Loss (ft)

 

 

 

 

 

 

 

 

 

 

 

Elevation Above 1600 3300 4900 6500 8200 9800

Sea Level (ft)

Suction

1.8

3.6

5.4

7.2

9.0

10.8

Loss (ft)

 

 

 

 

 

 

To reduce it to a minimum, especially in cases of high suc- tion head (over 13 – 16 feet) or within the operating limits with high flow rates, we recommend using a suction line having a larger diameter than that of the pump’s suction port. It is always a good idea to position the pump as close as possible to the liquid to be pumped.

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Contents Goulds Pumps Goulds Pumps ContentsSSV Flow PHV Series constant pressure variable speed system Main ComponentsHV M 3 4 Part Numbering / Identification Codes PHV SeriesMUNICIPAL, COMMERCIAL, Industrial SpecificationsMarkets and Applications Markets ServedIrrigation and Agriculture Applications Further information is available in the Hydrovar manual ANSI/NSF 61 certified by CSA for potable drinking water SV33 and 46 MULTI-STAGE PumpsReference Standards Introduction Standard Optional Features VersionsHydrovar Versions Application Example MULTI-PUMP Cascade 60 Hz 3500 RPM LpA dB ±4 Operating Characteristics and LimitsOperation Description Noise Emission LevelsCalculating the Flow Rate Selecting a SETCustomer Supplied Fused Disconnect BOXHydrovar VFD Motor Install Power Supply3500 RPM, 60 Hz Motor DataMake the following calculation Performance with Varying Speed for Centrifugal PumpsSizing the Diaphragm Tank in Systems with Speed Variation Hydraulic Data Variable Speed Performance Curves1SV Variable Speed Curve Ssvb 304SS Model 1SVB 6 StageNpsh R Model 1SVB 9 StageModel 1SVB 15 Stage Model 2SVB 5 Stage 2SV Variable Speed Curve Ssvb 304SSModel 2SVB 8 Stage Model 2SVB 13 Stage Model 3SVB 7 Stage 3SV Variable Speed Curve Ssvb 304SSModel 3SVB 9 Stage Model 3SVB 13 Stage US GPM Feet Model 4SVB 2 StageModel 4SVB 4 Stage 4SV Variable Speed Curve Ssvb 304SSModel 4SVB 7 Stage Model 33SVB 1/1 Stage 33SV Variable Speed Curve SVB CI/316SSModel 33SVB 1 Stage Model 33SVB 2/1 Stage Model 33SVB 3/1 Stage Model 46SVB 1/1 Stage 46SV Variable Speed Curve SVB CI/316SSModel 46SVB 1 Stage 3SV 3500 RPM Technical Data Pump Hydraulics / Motor Sizing1SV 3500 RPM 2SV 3500 RPM33SV 3500 RPM 4SV 3500 RPM66SV 3500 RPM 46SV 3500 RPMMaximum Inlet Pressure Technical DataTefc PHV Packaged Hydrovar Series 1SVBPHV Packaged Hydrovar Series 2SVB PHV Packaged Hydrovar Series 3SVB PHV Packaged Hydrovar Series 4SVB PHV Packaged Hydrovar Series 33SVB PHV Packaged Hydrovar Series 46SVB Npsh Cubic ft/lb @ 39.2ºF @ 60ºF @ 68ºF Lb/cubic ft Psi Abs Technical Data Water Property ChartLength Volumetric CapacityVolume Pressure and HeadGoulds Pumps Page Engineered for life

BPHV specifications

ITT BPHV, short for ITT's Bacterial Purified Water and High Purity Valves, represents a breakthrough in the field of fluid control technology, particularly designed for applications requiring the highest standards of cleanliness and reliability. These valves are typically utilized in industries where the quality of fluid handling is crucial, such as pharmaceuticals, biotechnology, and food and beverage manufacturing.

One of the standout features of the ITT BPHV is its ability to handle both high purity and aggressive fluids without compromising system integrity or cleanliness. The design focus on valve components ensures that they are free from contaminants, which is essential for processes where even minute impurities can lead to significant quality issues.

The materials used in the construction of ITT BPHV valves are particularly noteworthy. They feature advanced polymers, stainless steel, and other corrosion-resistant materials that withstand the rigors of high-purity applications. These materials not only ensure durability and longevity but also meet stringent industry standards for safety and compliance.

Innovative technologies integrated into ITT BPHV valves enhance their performance. These include advanced actuation systems that allow for precise control and responsiveness, ensuring that the flow of fluids can be managed effectively, even in highly dynamic environments. Additionally, the valves are designed to facilitate easy maintenance, with features that allow for quick disassembly and cleaning without the need for specialized tools.

Another vital characteristic of ITT BPHV valves is their compact design, which maximizes space efficiency within installations. This is particularly beneficial in industries where real estate is at a premium and where large equipment can impede operational efficiency. The modularity of the valve design also means that it can be adapted easily to different system configurations.

Furthermore, ITT BPHV valves are engineered with safety in mind. They incorporate features such as fail-safe functionality and pressure regulation, providing operators with peace of mind during critical operations. The seamless integration of these valves into automated systems enhances productivity by enabling consistent and reliable fluid movement.

Overall, ITT BPHV stands as a pioneer in high purity fluid handling, offering cutting-edge technology and robust engineering to meet the demands of modern industries. With their focus on cleanliness, reliability, and operational efficiency, these valves are an essential component for any facility striving for excellence in fluid management.
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