Established refineries and petrochemical plants have hundreds of process pumps, usually from myriad manufacturers, that may have been in operation for decades. Over the years, API 610 specifications, which govern their design, have evolved to improve both safety and reliability. Today, modern materials and design concepts from Sulzer can be used to improve the performance of existing pumps, as exemplified by a case in Mexico, where 35 process pumps were upgraded.
For time-served assets in refineries and petrochemical plants, extending service life can be a challenge and a replacement may appear to be the simplest option. However, in some cases, this may require extended lead times and changes in the existing pipework or pump foundations. A much quicker solution is to upgrade key components of the pump, bringing it in line with current specifications while simplifying the parts inventory at the same time.
Improvements for aging assets
For example, a refinery in Mexico, which was commissioned in 1976, processed several thousands of barrels per day. But since the refinery was built, API standards have moved on considerably, now in its 11th edition. Within the plant, process pumps are used for transporting propane, liquefied petroleum gas (LPG), sour water, and gasoline.
Maintenance engineers had identified several pumps that were manufactured to 6th edition standards and would benefit from improved reliability. For example, one of the significant factors affecting seal performance is pump vibration, and since the 8th edition, the API 610 specification for stiffness of the impeller shaft has increased, reducing vibration, and extending the mean time between failures (MTBF).
In addition, the design of the mechanical seals has also been enhanced, and, in this case, a double seal as per API 682 was implemented to further increase reliability and reduce fugitive emissions to comply with new environmental regulations. Thirty-five non-Sulzer OH2 process pumps had been identified for upgrade and Sulzer was selected to handle the issue.
Cost-effective retrofit solution
Sulzer engineers developed the OHX pump retrofit kit to offer the latest API specifications to any brand of OH2 pump while delivering overall performance improvements without replacing the casing or making any changes to the connecting pipework. Only the affected parts can be upgraded, which is more cost-effective than replacing the whole pump.
A new case cover with API 682 seal chamber meets latest API 610 standards, including the double mechanical seal. In addition, the bearings are upgraded to a longer life component, extending the expected service life from 25’000 hours to 50’000 hours. This improvement also includes upgraded oil guards, which offer much better oil sealing compared to the components of the 1970s.
The retrofit kit also introduces a cooling fan and an improved coupling and guard. The former helps to reduce bearing temperatures, extending their service life, while the latter meets the latest occupational safety and health administration (OSHA) requirements.
Isabel Najera, Project Manager for Sulzer, explained, “The objective of this retrofit solution was to optimize long-term performance and reliability without impacting the existing infrastructure. Pump upgrade projects such as the one for the refinery begin with essential information being gathered, including impeller diameter and volute measurements, which enable the case cover and other components to be manufactured without affecting the process pumps’ operation.”
Once all the parts are complete, they can be either installed on-site or at the local Sulzer service center, keeping downtime to an absolute minimum. In most cases, these process pumps are paired with a standby unit, enabling the application to continue while one is upgraded.
Following on from the retrofit program, the updated equipment at the refinery now has common parts with pumps on-site that have been installed more recently, allowing the spare parts inventory to be optimized.
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