Optimizing Hydrostatic Testing Procedures for Pump Casings
A detailed review of ASME and API pressure-testing requirements was conducted to assess two acceptable procedures: removing pump casing priming valves prior to testing or leaving these valves installed and fully open. The engineering team evaluated risks, compliance considerations, and potential waste associated with scrapping valves unnecessarily. The updated procedure, which includes leaving the pump casing priming valve in place and applying a pressure-rated plug at the outlet, was successfully implemented and validated across manufacturing applications involving water and seawater. Consequences of not revising the procedure included unnecessary component disposal, increased cost, and reduced verification of final assembly integrity.Â
Category: Blogs, Case Studies March 11, 2026
Intended Audience: Sector: Pump Manufacturers; Instruction Level: Intermediate; Category: Code complianceÂ
Objective: The primary objective of this case study is to demonstrate a compliant, efficient, and risk-informed approach to hydrostatic pressure testing of pump casings with mounted valves. The engineering team sought to clarify acceptable practices under ASME B31.1, ASME B31.3, API 610, and ISO 13709, and to determine whether existing procedures aligned with the intent of these standards. The goal was to eliminate unnecessary valve removal, ensure complete verification of final threaded connections, and improve overall manufacturing efficiency.
Description of System: The pumps evaluated in this case span a full range of horsepower levels and are used in both water and seawater service. For certain customers—particularly those requiring priming capability—priming valves were specified to be supplied and mounted directly onto the pump casing prior to shipment. Under the existing pressure-test practice, these valves remained installed during the hydrostatic test. Although the valves were rated for the intended service pressure, several units exhibited leakage through their internal seals during hydrostatic testing. Production teams interpreted this leakage as valve failure and routinely scrapped the valves, even though the purpose of the casing hydrostatic test—per ASME and API standards—is to verify the integrity of connections, not the internal sealing performance of a valve. In this configuration, the last pressure boundary being evaluated was the threaded connection between the priming valve inlet and the pump casing. This misalignment between testing objectives and testing outcomes resulted in unnecessary material waste, rework, and cost, and created inconsistencies in how auxiliary components were handled during pressure testing.Â
Description of Intervention: A structured technical review was performed, comparing two pressure-testing approaches against ASME B31.1, ASME B31.3, API 610, and ISO 13709. Two compliant options were validated: removing the valve and installing a blind plug, or leaving the valve in place, fully opening it, and plugging the outlet. Option 2 was selected based on its ability to verify complete assembly integrity and avoid unnecessary valve scrappage. Further review confirmed that mechanical seals should not be installed during pressure testing unless required by the customer, aligning with API 610 guidelines.
Summary of Results: Implementation of the revised procedure demonstrated several benefits. Manufacturing teams were able to retain and reuse valves, reducing material waste and cost. The inclusion of the final threaded connection in the hydrostatic test improved confidence in assembly integrity. No leakage or structural issues were identified during the transition to the updated method, confirming compliance with relevant codes. Additional clarification regarding seal installation requirements eliminated previous inconsistencies in testing practices.
Conclusion: The revised hydrostatic testing procedure met the objective of improving compliance and reducing waste while maintaining or enhancing verification of casing integrity. Key lessons include the importance of validating internal procedures against evolving standards and recognizing opportunities to reduce unnecessary component disposal. Future work may include expanding procedure clarification across other auxiliary components or validating pressure test practices for additional fluid types.
Source: This case study is summarized from analysis of internal engineering procedures and referenced standards including ASME B31.1, ASME B31.3, API 610, and ISO 13709.
Written by:
Carlos Cisneros, Manager of Engineering, Buffalo Pumps Inc., LinkedIn
Tom Watroba, Lead Product Engineer, Buffalo Pumps Inc., LinkedIn
Year of Publication: 2026
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