Centrifugal pumps for chemical applications

Horizontal single-stage end-suction overhung impeller centrifugal pumps (for chemical applications includes ISO 2858, ISO 3069, ISO 3661, ASMEIANSI B73.1 designs)

ANSI, the American National Standards Institute, has a philosophy more similar to DIN than ISO in that it specifies materials and mechanical seal options. B73.1 is a standard for single stage centrifugal pumps, with back pull-out, intended for chemical and corrosive duties.  The Standard specifies bareshaft pump dimensions, also installation dimensions for complete packages with motor and baseplate. The Standard does not specify hydraulic duties. Mechanical seal arrangements, with various piping plans, are detailed to cover most applications. Depending upon materials and cooling arrangements pumpsmust be suitable for at least 260 deg. C.

IEC vs NEMA enclosure

NEMA Standards Enclosures for Electrical Equipment (1000Volts maximum) comparison to IEC 60529 Degrees of Protection provided by Enclosure IP Classification designation (cannot be used to convert IEC classification designations to NEMA type numbers)

NEMA Enclosure Type Number              IEC Enclosure Classification
                       1                                                                 IP 10
                       2                                                                 IP 11
                       3                                                                 IP 54
                       3R                                                              IP 14
                       3S                                                               IP 54
                       4 and 4X                                                    IP 56
                       5                                                                 IP 52
                       6 and 6P                                                    IP 67
                       12 and 12K                                                IP 52
                       13                                                               I P 54"

Hazardous Environment - Motors

Atmospheres can be classified as:

* Non-explosive atmosphere; the atmosphere does not contain explosive elements and all types of standard products can be used.
* Explosive atmosphere; the atmosphere does contain potentially explosive elements, either gas or dust.
Explosive atmosphere is referred to as 'Hazardous area' in IEC countries and 'HAZLOC' in North America

Equipment for explosive atmosphere is designed, installed, operated and maintained according to International standards and local regulations dedicated to this area.

Hazardous Area or Location is defined by 4 elements:
* Class
* Zone
* Group
* Temperature Class


Explosive atmosphere

The relevant parameters below characterize the potentially explosive atmosphere:

* Frequency with which potentially explosive atmosphere may exist
* Capability of gas or dust atmosphere to create an explosion

Explosive gas and dust is classified according to its likelihood to be ignited, according to its characteristics:

* Minimum ignition energy
* Minimum ignition temperature
* Auto-ignition temperature
* Layer ignition temperature"

Converting Pump Head to Pressure

Converting head in feet to pressure in psi
Pump curves in feet of head can be converted to pressure - psi - by the expression:

p = 0.434 h SG (1)

where
p = pressure (psi)
h = head (ft)
SG = specific gravity

Converting head in meter to pressure in bar
Pump curves in meter of head can be converted to pressure - bar - by the expression:

p = 0.0981 h SG (2)

where
h = head (m)
p = pressure (bar)

Converting head in meter to pressure in kg/cm2
Pump curves in meter of head can be converted to pressure - kg/cm2 - by the expression:

p = 0.1 h SG (2b)

where
h = head (m)
p = pressure (kg/cm2)

Converting Pressure to Head

Since pressure gauges often are calibrated in pressure - psi or bar, it may be necessary with a conversion to head - feet or meter, commonly used in pump curves.

Converting pressure in psi to head in feet

h = p 2.31 / SG (3)

where
h = head (ft)
p = pressure (psi)

Converting pressure in bar to head in meter

h = p 10.197 / SG (4)

where
h = head (m)
p = pressure (bar)

Converting pressure in kg/cm2 to head in meter

h = p 10 / SG (4b)

where
h = head (m)
p = pressure (kg/cm2)