Following is the list of documents that are typically required for final
dimensional and visual inspection and actions required based on these documents:
Data Sheets
Pump Train General Arrangement
Process & Instrument Diagram (P&ID)
Electrical and instrumentation wiring diagrams
Auxiliary Equipment GA, P&ID and BOM (seal reservoir, LOS (Lube oil system), Seal, Driver, Junction Boxes)
Packing List
Charlie Chong/ Fion Zhang
During visual inspection the following areas of concern should be addressed:
Piping assembly should be accessible for maintenance, disassembly, and gasket replacement.
Valve handles should have enough space for safe open-close action by an operator according to OSHA requirements to prevent hand jamming and injury.
All equipment should be mounted using secured methods without them being shaky or unsecured.
Workmanship of installation, welding and wiring should be without visible defects and within industry standards.
There should be no overhung equipment or piping extending beyond
perimeter of the baseplate except those shown on the approved General Arrangement. Usually only main terminal boxes of large motors are
allowed to overhang the baseplate.
Painting and paint thickness should be inspected and verified.
Quantity, condition, and packing for items shipped loose should be inspected and verified.
Charlie Chong/ Fion Zhang
Charlie Chong/ Fion Zhang
LOS (Lube oil system)
Charlie Chong/ Fion Zhang
LOS (Lube oil system)
http://www.cobey.com/news/API-614_Cobey_Celebrates_700th_Lube_Oil_Console/33.html
Charlie Chong/ Fion Zhang
Charlie Chong/ Fion Zhang
The Great Wall
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
The Great Wall
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
The Great Wall
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
NPSHA
NPSHA for those who hate that stuffy word
The dreaded term NPSHA means Net Positive Suction Head Available.
It`s a term that most people find difficult to relate to in part because they have no idea what value it should have. Before we discuss values and the exact definition of NPSHA, let`s get an intuitive understanding of NPSHA. NPSHA is a measure that corresponds to the level of pressure at the pump suction. The higher the pressure, the higher the NPSHA and the better the pump will
operate. Normally we measure pressure with a gauge that is calibrated in psig (pound per square inch gauge) or kPa in the metric system. This pressure scale is set at zero when there is no
pressure or the pressure is equal to atmospheric pressure. The atmospheric pressure at sea level as measured on an absolute scale such as psia (pounds per square inch absolute) is 14.7 psia. In the absolute scale, pressure starts at zero which is the lowest possible pressure and means that there is no molecules of matter in the environment that can create pressure such as in outer space. It then can have any value corresponding to a high pressure environment.
The term head in NPSHA has been well explained in the pump tutorial, the head component that we are most interested in here is the static head or the level of fluid above the pump suction.
Head is measured in feet in North America and in meters just about everywhere else. The value of NPSHA will vary between the lowest value of 0 feet, up to the value of the local atmospheric pressure head 34 feet plus the suction static head minus a small quantity which we will get to shortly. 34 feet is the value of atmospheric pressure at sea level expressed in terms of pressure head. If your tank has 10 feet of suction head, the NPSHA may be 34 + 10 = 44 feet which is ample. One should start to worry when the value of NPSHA falls below 20 feet.
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
34 feet of H2O
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
Most pumps can operate with a suction pressure that is below atmospheric pressure. A pressure that is below atmospheric pressure is referred to as a vacuum. That is why a value of 20 feet for NPSHA can be quite acceptable.
This is also how it is possible for a normal centrifugal pump to lift fluid from an elevation that is below the suction. For more information on low pressure at the pump suction see the pump tutorial.
Charlie Chong/ Fion Zhang
How can the value of NPSHA drop below 34 feet? This is possible if there is allot of friction or plugging which increases friction in the suction line. Sometimes these two occur together, when the level is low in the suction tank due to physical constraints or poor level control or other reasons, this decreases the overall NPSHA and a further decrease occurs due to friction.
How will you know if the NPSHA is adequate? The manufacturer tests the pump under various suction head conditions and provides a requirement or NPSHR for each flow condition on the characteristic curve of the pump. It is then a matter of checking this value against the NPSH available and making sure that the NPSHA is higher.
Why do you have to worry about atmospheric pressure, after all atmospheric pressure is everywhere, how could the operation of the pump be influenced by its value? Because atmospheric pressure depends on the elevation, the pressure varies significantly depending on the elevation above sea level. Atmospheric pressure gets added to the pressure provided by the static head and if you are at a high
elevation atmospheric pressure will be less and therefore the suction pressure will be less.
OK, so let's say that the suction tank is pressurized with a nitrogen blanket on top of the liquid surface at 100 psig for example, do you still have to account for the atmospheric presure?
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
OK, so let's say that the suction tank is pressurized with a nitrogen blanket on top of the liquid surface at 100 psig for example, do you still have to
account for the atmospheric presure?
Yes, you do. When you pressurize the tank you start pressurizing from some level, that level is the local atmospheric pressure. If your local atmospheric pressure is 10 psia and you add 100 psia of nitrogen pressure than your total on top of the liquid is 110 psia.
Always remember that:
NPSHa is independent of the pump, it is a hydraulic system variable, numerically
NPSHa = h
atm+ h
z– h
friction- h
vapor :■ Absolute pressure head hatm or habs
■ Hydraulic elevation head hz
■ Friction loss head hfriction
■ Vapor pressure head hvapor
http://www.history.com/topics/great-wall-of-china
Charlie Chong/ Fion Zhang
The NPSHr are pump characteristics which are unique to the pump model and varies with flows.
NPSHr, Net Positive Suction Head Required
All pumps have requirements to their performance, and no pump can perform well if you can't meet it's needs.
Below is part of the Cornell® 6NHTB-19 Pump Curve with a colored over-lay for this discussion.
Charlie Chong/ Fion Zhang
Charlie Chong/ Fion Zhang
What does the curve mean?
For this pump, running at 2100 RPM with its horsepower requirements met, you can pick a flow rate and easily find its NPSH REQUIRED.
■ 1500 GPM = 5.5 FT.
■ 2000 GPM = 8 FT.
■ 2500 GPM = 11 FT.
■ 3000 GPM = 17 FT.
Net Positive Suction Head Required is the required feet of head going into the back of the pump for it to function properly and achieve your desired flow rate.
For proper operation of the pump:
NPSHa > NPSHr
Charlie Chong/ Fion Zhang
Easy signs your pump's NPSHa>NPSHr is NOT met:
■ The pump is shaking
■ It sounds like you have rocks going through your pump
■ Gauges and Valves are falling off
■ The unit is vibrating
■ The tongue's jack is sunken into the ground from vibration
■ Your gauges are broken
■ Your suction cover shows physical damage of gouging and wash-out
■ Your impeller shows physical damage of gouging and wash-out CAUTION! Your Pump is Cavitating!
More about cavitation: http://www.pricepump.com/pumpschool/psles3.html
Charlie Chong/ Fion Zhang