Part 6 - Pumps: Centrifugal, Diaphragm, Progressive Cavity and Liquid Ring
Pumps are used for a variety of applications on remediation projects. For purposes of this discussion we will limit the pumps discussed to those that are installed above ground on a skid or in a remediation equipment enclosure. Some of the typical uses of these pumps include:
- Transfer of impacted water from one treatment or storage device to another
- Injection of water treatment additives(pH adjustment) into the water treatment tanks or into groundwater wells
- Dual phase extraction using high vacuum and flow pumps to extract impacted water, separate phase fluids(fuels and solvents) and air from a formation
A number of parameters need to be determined prior to selecting a pump for a specific purpose. Some of the typical parameters are as follows:
- Ambient temperature where pump will operate (freeze potential)
- Viscosity and corrosive properties of fluids to be pumped
- Treatment process of extracted fluids. Some pumps emulsify recovered fuels making them hard to separate in an oil\water separator
- Pressure required
- Flow required at a specific pressure
- Noise level allowed
- Pump runtime based on pressure and flow requirements
- Expected service life of pump components
- Maintenance required
- Cost of maintenance compared to other suitable pump types
- Power available to operate the pump
- Material composition and friction loss of piping to be connected to the pump
- Expected duration of the project
- Budget allowed for purchase
I always try to use quality equipment on the systems I build. When competing against companies that use cheap and poor quality equipment, it makes it hard to win a bid. I’ve had the good fortune to repair some of the systems built by others where I had lost the bid. Why did we get hired to fix it instead of the original builder? The original builder would not stand behind the equipment they built or the customer was so pissed at the poor quality they received they would not use them. Did that stop the customer from letting them bid and win the next bid? Nope! So needless to say if you are going to use "or equivalent" in bids and make sure you are getting an equivalent performance for the expected project duration. I prefer Goulds centrifugal pumps, Yamada diaphragm pumps, Moyno progressive cavity pumps, and Dekker liquid ring pumps.
Dual phase extraction is a very common remediation method that requires the liquid ring pumps and progressive cavity pumps to run continuously. The projects typically require 6 months to 3 years to complete depending on the size and concentration of the plume. Submersible pneumatic pumps coupled with a SVE system (also called vacuum enhanced pump and treat) has been the typical choice for these applications until the last decade where the liquid ring and rotary claw (see section 5) pumps have become more popular. Centrifugal pumps have trouble pulling against high vacuum in the knockout tanks and progressive cavity pumps require a lot of maintenance under continuous run applications while constantly soaked in fuel or solvents. Centrifugal pumps are typically used to transfer fluids from one tank or treatment device to another where pump run times are short.
Air outlet temperature is a concern for most dual phase extractions systems where air treatment will occur. Air after-coolers are used to cool the air prior to going through the carbon vessels or low temperature manifold piping typically used on these projects. Oil mist and moisture are also a concern on most DPE systems where catalytic oxidizers or media filters are used. Oil can foul catalyst materials costing thousands of dollars. Coalescing filters and\or secondary knockout tanks are used to remove oil prior to discharging to media (carbon) filters or catalytic oxidizers.
I do not use many diaphragm pumps in systems I build but some of the uses include: liquid additive metering\injection, shallow water recovery and movement of solids such as powdered additives. Some of the pros and cons of the pumps being discussed herein are presented below:
|Progressive Cavity Pump||
|Oil Sealed Liquid Ring Pump||
Remediation pumps probably get undersized more often than any other item found on remediation systems. It is important to get good equipment from the beginning as O&M budgets seem to get used up pretty quickly.
In Part 7 we will discuss air strippers.
- PILOT TEST EQUIPMENT SELECTION
- PERFORMING THE PILOT TEST
- FULL SCALE EQUIPMENT SELECTION
- BLOWERS: REGENERATIVE, POSITIVE DISPLACEMENT, ROTARY VANE, AND TURBO FANS
- COMPRESSORS: ROTARY SCREW, RECIPROCATING, ROTARY VANE, AND ROTARY CLAW
- PUMPS: CENTRIFUGAL, DIAPHRAGM, PROGRESSIVE CAVITY AND LIQUID RING
- AIR STRIPPERS: TRAY, TOWER, AND TANK
- OIL\WATER SEPARATORS: GRAVITY, COELESSING PLATE, DISSOLVED AIR FLOATATION
- COMPONENTS OF A SOIL VAPOR EXTRACTION SYSTEM
- COMPONENTS OF A DUAL PHASE EXTRACTION SYSTEM
- COMPONENTS OF AN AIR SPARGING SYSTEM
- CHEMICAL INJECTION, RISK BASED CORRECTION ACTION AND NATURAL ATTENUATION