question: What exactly is NSPH on a pump? I’m a hydraulic engineer and I still don’t get it.
comment: Net Positive Suction Head (NPSH) is the difference between the pump's Suction Head (how hard it sucks on the fluid) and the fluid's Vapor Head (the pressure where the fluid would rather evaporate than flow). It's usually for a specific fluid the pump is supposed to be used with.
passages: The fluid circuit, as well as containing the circulating pump, will also contain an expansion vessel, to accommodate changes in fluid pressure; a fill device, to ensure the system remains charged; controls to bypass and shut down the system when not required, and various other safety devices and ancillaries. Pipework runs should be kept as short as possible and should be sized for low velocities to keep frictional losses to a minimum, and hence reduce pump energy consumption. It is possible however to recover some of this energy in the form of heat given off by the motor if a glandless pump is used, where a water jacket surrounds the motor stator, thus water passing through the pump will pick up some of its heat.
   BULLET::::- Backup system and alarm for critical applications.
  
  Section::::Backup components.
  
  A secondary, typically battery-powered sump pump can operate if the first pump fails. A battery-powered secondary pump will have a separate battery and charger system to provide power if normal supply is interrupted. 
   In general, recent tubing developments have brought broad chemical compatibility to the peristaltic pump option that many chemical dosing applications can benefit over other current pump technologies.
  
  Section::::Key design parameters.:Occlusion.
   This style of protein skimmer has become very popular and is believed to be the most popular type of skimmer used with residential reef aquariums today. It has been particularly successful in smaller aquariums due to its usually compact size, ease of set up and use, and quiet operation. Since the pump is pushing a mixture of air and water, the power required to turn the rotor can be decreased and may result in a lower power requirement for that pump vs. the same pump with a different impeller when it is only pumping water.
  
  Section::::Design.:Counter-current flow systems.:Downdraft.
   "Normal saline" (NS) is the commonly used term for a solution of 0.9% w/v of NaCl, about 300 mOsm/L. Less commonly, this solution is referred to as "physiological saline" or "isotonic saline", neither of which is technically accurate. NS is used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed or are in danger of developing dehydration or hypovolemia. NS is typically the first fluid used when hypovolemia is severe enough to threaten the adequacy of blood circulation, and has long been believed to be the safest fluid to give quickly in large volumes. However, it is now known that rapid infusion of NS can cause metabolic acidosis.
   Metering pump
  
  A metering pump moves a precise volume of liquid in a specified time period providing an accurate volumetric flow rate. 
  
  Delivery of fluids in precise adjustable flow rates is sometimes called metering. The term "metering pump" is based on the application or use rather than the exact kind of pump used, although a couple types of pumps are far more suitable than most other types of pumps. 
   Although metering pumps can pump water, they are often used to pump chemicals, solutions, or other liquids. Many metering pumps are rated to be able to pump into a high discharge pressure. They are typically made to meter at flow rates which are practically constant (when averaged over time) within a wide range of discharge (outlet) pressure. Manufacturers provide each of their models of metering pumps with a maximum discharge pressure rating against which each model is guaranteed to be able to pump against. An engineer, designer, or user should ensure that the pressure and temperature ratings and wetted pump materials are compatible for the application and the type of liquid being pumped. 
   Experimentally, NPSH is often defined as the NPSH, the point at which the head output of the pump decreases by 3 % at a given flow due to reduced hydraulic performance. On multi-stage pumps this is limited to a 3 % drop in the first stage head.
  
  Section::::NPSH in a turbine.
   BULLET::::- Air vessels work in much the same way as water towers, but are pressurized. They typically have an air cushion above the fluid level in the vessel, which may be regulated or separated by a bladder. Sizes of air vessels may be up to hundreds of cubic meters on large pipelines. They come in many shapes, sizes and configurations. Such vessels often are called accumulators or expansion tanks.
   Section::::Important design characteristics.
   Other uses for submersible pumps include sewage treatment plants, seawater handling, fire fighting (since it is flame retardant cable), water well and deep well drilling, offshore drilling rigs, artificial lifts, mine dewatering, and irrigation systems.
  
  Pumps in electrical hazardous locations used for combustible liquids or for water that may be contaminated with combustible liquids must be designed not to ignite the liquid or vapors.
  
  Section::::Use in oil wells.
   Section::::Types.
  
  Section::::Types.:Cascaded electroosmotic pumps.
  
  High pressures or high flow rates are obtained by positioning several regular electroosmotic pumps in series or parallel respectively.
  
  Section::::Types.:Porous electroosmotic pump.
  
  Porous pumping is created by the use of sintered glass.
  
  Section::::Types.:Planar shallow electroosmotic pump.
  
  Planar shallow electroosmotic pumps are made of parallel shallow microchannels.
  
  Section::::Types.:Electroosmotic micropumps.
   A minimum of 600 mm (0.06 bar) and a recommended 1.5 metre (0.15 bar) head pressure “higher” than the NPSH pressure value required by the manufacturer is required to allow the pump to operate properly.
  
  Serious damage may occur if a large pump has been sited incorrectly with an incorrect NPSH value and this may result in a very expensive pump or installation repair.
  
  NPSH problems may be able to be solved by changing the NPSH or by re-siting the pump.
   Section::::References.
  
   US Patent #5358000.
  
  Section::::External links.
  
  BULLET::::- Control the flow with metering pumps. Accuracy is critical when using controlled-volume metering pumps.
  
  BULLET::::- Controlled-volume Metering Pump Hydraulic Institute Require high accurate, repeatable, and adjustable rate of flow.
   A standard APW extinguisher in the United States contains of water in a stainless steel tank. The water is discharged by means of a ½-inch hose, with a smooth-bore nozzle attached to the tip. They will initially produce a 40–50 foot stream of water, with a discharge time of about 50 seconds.
   Saline flush
  
  A saline flush is the method of clearing intravenous lines (IVs), Central Lines or Arterial Lines of any medicine or other perishable liquids to keep the lines (tubes) and entry area clean and sterile. Typically in flushing an intravenous cannula, a 5ml syringe of saline is emptied into the medication port of the cannula's connecting hub after insertion of the cannula. Blood left in the cannula or hub can lead to clots forming and blocking the cannula. Flushing is required before a drip is connected to ensure that the IV is still patent.
   After Stringliner was sold in 2014, an extended family member approached Black about an issue he was experiencing with chemical pumps in the oil and gas industry. Black recounted to DAWA Solutions Group, "He came to me and explained the number of problems he was having with chemical pumps in the field: ’I’m spending 60% of my time fixing malfunctioning pumps and blocked check valves, there’s got to be a better way,’ he told me." 
  
  Setting out to design a system that was low-maintenance with increased chemical metering accuracy, Black developed the FC500 fresh water and chemical injection system.
   Back-pressure occurs for example when air is blown through the straw and bubbles begin to erupt at the submerged end. If instead of air, natural gas had been forced into a potable water tank, the gas in turn could be carried to a kitchen faucet. This is an example of a direct cross-connection, with undesirable material being "pushed" into the system.
   The calculation of NPSH in a reaction turbine is different to the calculation of NPSH in a pump, because the point at which cavitation will first occur is in a different place. In a reaction turbine, cavitation will first occur at the outlet of the impeller, at the entrance of the draft tube. Denoting the entrance of the draft tube by "e", the NPSH is defined in the same way as for pumps:
  
  formula_9
   Feynman sprinkler
  
  A Feynman sprinkler, also referred to as a Feynman inverse sprinkler or as a reverse sprinkler, is a sprinkler-like device which is submerged in a tank and made to suck in the surrounding fluid. The question of how such a device would turn was the subject of an intense and remarkably long-lived debate.
   The pumped fluid will have to be protected from freezing in certain climates, and as such is normally treated with a glycol based anti-freeze. This also reduces the specific heat capacity of the fluid and increases the viscosity, increasing pump power consumption, further reducing the seasonal efficiency of the device. For example, a 20% glycol mixture will provide protection down to , but will increase system resistance by 15%.
   In addition to the standard ram functions, variable-bore pipe rams are frequently used as test rams in a modified blowout preventer device known as a stack test valve. Stack test valves are positioned at the bottom of a BOP stack and resist downward pressure (unlike BOPs, which resist upward pressures). By closing the test ram and a BOP ram around the drill string and pressurizing the annulus, the BOP is pressure-tested for proper function.
   Example 1: A tank with a liquid level 2 metres above the pump intake, plus the atmospheric pressure of 10 metres, minus a 2 metre friction loss into the pump (say for pipe & valve loss), minus the NPSH curve (say 2.5 metres) of the pre-designed pump (see the manufacturers curve) = an NPSH (available) of 7.5 metres. (not forgetting the flow duty). This equates to 3 times the NPSH required. This pump will operate well so long as all other parameters are correct.
   The premise behind these skimmers is that a venturi pump, or aspirator, can be used to introduce the bubbles into the water stream. The tank water is pumped through the venturi, in which fine bubbles are introduced, then enters the skimmer body. This method was popular due to its compact size and high efficiency but venturi designs are now more likely to be included in other skimmer designs rather than as a simple venturi design.
  
  Section::::Design.:Counter-current flow systems.
  
  Section::::Design.:Counter-current flow systems.:Aspirating: pin-wheel/adrian-wheel, needle-wheel, mesh-wheel.
   A plain tube can be used as a siphon. An external pump has to be applied to start the liquid flowing and "prime" the siphon (in home use this is often done by a person inhaling through the tube until enough of it has filled with liquid; note this may pose danger to the user, depending on the liquid that is being siphoned). This is sometimes done with any leak-free hose to siphon gasoline from a motor vehicle's gasoline tank to an external tank. (Siphoning gasoline by mouth often results in the accidental swallowing of gasoline, or aspirating it into the lungs, which can cause death or lung damage.) If the tube is flooded with liquid before part of the tube is raised over the intermediate high point and care is taken to keep the tube flooded while it is being raised, no pump is required. Devices sold as siphons often come with a "siphon pump" to start the siphon process.
  