Nitric
Acid

Wilfley Heavy Duty Centrifugal Pumps Pump Nitric Acid

Wilfley’s chemical processing pumps have been setting the standards for concentrated nitric acid pumping since the 1930’s


Running Dry Is No Longer a Problem

Traditional sealing technologies (or even newer magnetic drive systems) used in nitric acid require constant thermal moderation of the primary seal or journal bearing surfaces in order to operate satisfactorily. Once the moderating liquid is lost or evacuated, the source of lubrication and ability to remove heat from these rubbing surfaces is also, and failure occurs – usually within minutes.

With Wilfley Sealing Technology, once the pump is operational the primary seal faces are separated and therefore do not require cooling via flushing. In fact, our governor-actuated static seals, such as the DryLock®, are designed to run dry (with separated faces) while the expeller manages all of the dynamic sealing requirements. By eliminating thermal stress induced by face tribology, the resultant failures of traditional sealing materials are also eliminated.


In It for the Long Haul

Commercial grade may suffice for certain automotive products and B2B markets, but nitric acid production requirements rely on equipment designed for continuous, mission critical operation. Moreover, operational demands often subject industrial equipment to rigors well outside a fully constrained design window.

Although the majority (75-90%) of pump ownership costs can be attributed to issues with seals and bearings, the basic design of the pump has a lot to do with its long term success. Wilfley’s philosophy is to produce heavy duty pumps that provide maximum productivity in the harshest of conditions like nitric acid. For instance, our robust ASME B73.1 A9 chemical process pumps are up to 60% heavier than Tier 1 competitors. And a similar trend exists on rotating elements: a common shaft robustness index follows an L3/D4 format and the A9 pump is on average 55% stiffer than others.

Frame
Size
Average Weight Shaft Stiffness Ratio
Standard
A9
% Heavier Standard
A9
% Stiffer
1 155 lbs
(70 kg)
50% 68 55%
2 325 lbs
(150 kg)
35% 62 45%
3 495 lbs
(225 kg)
60% 28 50%
4 1,005 lbs
(455 kg)
50% 17 70%

Wilfley’s philosophy is that downtime is unacceptable, so we continue to build robust pumps for continuous, tough and critical services.


Abuse Tolerant Seals

Pumping water in a controlled environment (such as a manufacturing test lab) is as easy as it gets. But pumping an acidic slurry non-stop, with variable and upset conditions with maximum uptime is another matter – but that is exactly where Wilfley shines.

A common scenario that can trigger a Lost Productivity Failure (LPF) in centrifugal pumps is loss of prime. This can occur in any industrial system, but more often in tanker/rail car off-loading applications. As a constant liquid supply is lost, the pumpage shifts to a two phase fluid (liquid and air) and flow drops to zero. Both conditions subject the rotating assembly of a centrifugal pump to abnormal loads and subsequently high vibration. The mechanical stress can be transmitted to brittle traditional seal faces with almost immediate consequences, even for double mechanical seal systems.

By contrast, Wilfley Sealing Technology separates the faces during operation, isolating detrimental mechanical vibration. Further, the allowable clearances are increased by over 270% when compared to mechanical seal requirements, allowing significantly more tolerance – all with fully isolated, full diameter shafting.


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Mark ScottNitric Acid | Pumps