Wanner Hydra-Cell Pro^® Pump Installation Guidelines

Nothing matches the minute before you hit start on a new skid. This article describes the piping and accessories that make start-up boring - in a good way.

 The following is the Wanner^® guidance for sealless positive-displacement pumps in industrial and metering service. The same rules apply to other PD designs.

What Are Positive Displacement Pumps?

They push a fixed volume per shaft turn. Inlet and discharge pressure do not change that volume the way they change a centrifugal. A centrifugal adds to inlet pressure and loses flow as discharge pressure rises.

Inlet Condition

A pressurized source — city water or a pressurized tank — makes “is there enough liquid?” easier to answer.

Pump Reservoirs

A supply tank needs enough volume for air to leave the liquid. That matters when the tank is filled often or when PRV bypass dumps back into it. Bring those returns in as far from the tank outlet as you can, and below low level so they do not splash. Oversized inlet pipe cuts velocity and the agitation that pulls air — and sometimes foam — into the pump.

Entrained Air Creates Problems

A PD pump displaces a fixed volume only if the liquid is not full of gas. Air or other gas makes the liquid compressible. Displacement then wanders.

Protecting the Pump System

If you filter to protect the pump or what sits downstream, filter on the way into the tank — not on the pump suction. A dirty strainer or bag cuts flow at a given pressure. A restriction on the inlet is how you get cavitation: bubbles collapse and the shock hits both centrifugal and PD pumps.

Inlet cavitation is common. A plugged filter or a tight fitting is the usual cause. Most current Wanner Hydra-Cell Pro^® frames shrug that off because of Kel-Cell. You still size the inlet as if they did not.

The other cause is short NPSH. Even a pump that can lift has a limit. NPSHa has to be at least NPSHr.

• Pt — atmospheric pressure
• Hz — vertical distance from liquid surface to pump centerline (negative if the liquid is below the centerline)
• Hf — friction loss in the suction line
• Ha — acceleration head at the pump suction
• Pvp — absolute vapor pressure of the liquid at pumping temperature

Use specific gravity and work in feet or meters absolute.

Acceleration head is the term that blows the “simple” look:

• L — actual suction-line length (ft), not equivalent length
• V — velocity in the suction line (ft/sec). V = GPM × (0.408 ÷ pipe ID²)
• N — crankshaft RPM
• C — constant for pump type
• K — compressibility: 1.4 for de-aerated or hot water; 1.5 for most liquids; 2.5 for highly compressible hydrocarbons
• G — 32.2 ft/sec²

The arithmetic gets ugly fast. That is why we use a spreadsheet.

Cut acceleration head and friction by keeping the inlet short (preferably ≤ 3 feet), using pipe larger than the pump inlet ID, and using as few fittings as you can. Target inlet velocity is 1–3 FPS (0.3–0.9 MPS).

Cover the tank so trash does not fall in. Put a vortex breaker at the outlet so the pump does not gulp air.

Bulkhead ID should match the suction line. Set the fitting off the tank floor so settled solids stay put.

One tank, more than one pump: give each pump its own tank outlet. Two pumps on one branch will fight for flow.

A joint that is not tight is another way air gets in. Hard to see unless the hose is clear. We had a low-rate metering pump that started fine and then lost volume. Clear tubing showed bubbles at a barbed elbow. A tighter hose clamp ended it.

Air collected in that simplex chamber and the chamber never filled. Suction leaks often do not drip. They just suck.

Helpful Accessories

Fewer fittings is better. A few extras earn their keep.

An inlet pulsation dampener cuts acceleration-head loss and calms a messy feed — a branch off a header, or one pump feeding another.

Pressure gauges. A compound gauge on the inlet is cheap confirmation of suction. If you filter, a differential gauge shows the drop. Reed switches can alarm a controller. Service the filter when NPSHa is closing on NPSHr, or when differential is 5 PSI above the clean reading.

Isolation valves keep liquid in the pipe when the pump comes out. Place them so you do not dump the line. Pipe the skid so the pump can come off without cutting steel.

A gauge ahead of a back-pressure or pressure-regulating valve is how you set that valve and how you see what the pump is actually doing.

Batch systems that start full of air: an automatic priming valve near the discharge lets the pump push that air out without walking it all the way downstream or standing there on a needle valve.

A layout that was thought through runs better and comes apart easier. That is part of every new application we quote.

Related Articles

• Components of a high-pressure pump skid
• Calculating horsepower required
• Sealless pressure regulating valves
• Troubleshooting Hydra-Cell Pro pumps
• How to repair a D10
• Pulsation dampeners