Silicone plant solves hot acid pump problems

Because of dramatically changed manufacturing conditions, a large silicone production plant started losing control over its pumps, resulting in increased maintenance work and costs. Both seals and bearings in the main pump and its backup began failing regularly. A new pump installed with a condition-sensing system solved the problem.

The large plant, located in Waterford, N.Y., had been using two Goulds 3196 4X6-13 non-metallic pumps to handle a very corrosive solution that contained 42% hydrochloric acid at up to 200F.

Of the two pumps, one was always kept on reserve in case of a failure in the on-line pump. Unfortunately, the spare pump was often needed.

When the pumps were first installed, they were specified for a certain set of conditions. But, over time, due to manufacturing and market forces, those manufacturing conditions changed dramatically, making it harder to control processes with the original pumps.

According to Jerry Connolly, director of new business development at ITT Industries’ Goulds Pumps unit, “The system was moving the pump all over the curve and there was nothing the pump could do about it.”

The altered conditions at the plant were creating recurring problems with the pumps, including failed mechanical seals and ball bearings. Connolly noted, “The reason the seals were failing was that the customer was running the pump dry, as well as running the pump to the left of the minimum flow curve. This was because the customer wanted more pressure in the system than the pumps were hydraulically capable of performing.

“It was a very big maintenance problem in the plant, with the pump failing about every three to four months.”

With a spare always on hand, when the first pump failed, the customer turned to the spare while the first pump was fixed, repeating the process when the spare pump failed.

The non-metallic pump was replaced with a 60-hp Model 3298 Tefzel-lined mag-drive pump — a more current design. “We also put Pump-Smart on it,” said Connoly. The PumpSmart system can sense all of the conditions that are happening in the system, such as dry-running, low-flow, and cavitation. The PumpSmart system uses a standard centrifugal pump in conjunction with a controller and proprietary pump control software.

Instead of just letting the pump continuously run at a fixed high speed at that condition — which will cause a failure — PumpSmart alerts the customer that it is encountering that condition. It then slows the pump down to a safe speed to eliminate the possibility of damage.

In addition to eliminating the maintenance nightmare, the PumpSmart-equipped pump was able to accommodate the customer’s requirements of adding pressure in the system. This was done with PumpSmart safely overspeeding the pump at 2,100 rpm instead of the fixed 1,800-rpm speed of the earlier pumps.

By enabling the customer to stay with a 10-in. impeller diameter pump instead of moving up to a larger sized pump, PumpSmart allowed the customer to avoid an expensive re-piping of the system.

In addition, the system has enabled an existing, in-line control valve to be 100% open all the time. Although not taken out of the line, the control valve has effectively been taken out of the system.

The customer also connected a magnetic flow meter that was in the piping to PumpSmart. The system could still measure flow and do all of the calculations that it needed to with flow while using the customer-supplied flow measuring device.

The principal mechanical engineer at the Waterford facility stated, “The PumpSmart system has operated fully satisfactorily for over a six-month period, providing control to our process while maintaining a stable discharge pressure, despite ever-changing process conditions.”

Over six months of operation, there have been real, measurable maintenance savings to the customer. The Pump-Smart system pump has not failed once since installation, Connolly says. “That means that the customer has gone from a MTBF of about three months to over six months and counting.”