The core requirements for waterworks circulating water supply systems are straightforward: large flow capacity, continuous stable operation, and convenient maintenance. The SH-type single-stage double-suction split-case pump delivers mature performance across all three dimensions, making it a mainstream specification for municipal and industrial water treatment facilities. However, no pump type is universally applicable. Understanding where its advantages end is essential for sound decision-making.
Why Waterworks Favor SH-Type Split-Case Pumps
The SH-type is a horizontal centrifugal pump whose most distinctive structural feature is the horizontally split casing. This means maintenance access requires no disassembly of suction or discharge piping, no motor relocation—simply lift the upper half of the casing to reach the impeller, shaft seal, and other core components. For waterworks where continuous supply is mandatory, this design significantly reduces downtime for maintenance and lowers operational costs.
Hydraulically, the SH-type employs a double-suction impeller with water entering from both sides simultaneously. This configuration inherently balances axial thrust, minimizing bearing loads and maintaining low vibration levels during prolonged operation. It is well-suited to the 24/7 uninterrupted duty cycles typical of water treatment facilities. The flow range is broad, with specifications available from small-scale plants to large municipal distribution systems.
Typical Application Scenarios
In water treatment plants and raw water intake stations, SH-type pumps primarily serve the following clean water transfer duties:
Filter backwash water supply: Delivering high flow rates within short periods to meet the hydraulic intensity requirements for filter media cleaning
Plant circulating water: Continuous operation maintaining hydraulic circulation within the treatment process
Clear water reservoir transfer: Moving treated water from storage facilities to the distribution network
Raw water intake: Drawing water from the source and conveying it to the plant
The common characteristic of these applications is that the medium is ambient-temperature clean water with low suspended solids content—precisely within the standard service envelope of the SH-type pump.
Boundary Conditions for Selection
The standard SH-type configuration uses cast iron construction, which dictates that it is suitable only for clean water service. If the water exhibits significant corrosive characteristics—such as elevated chloride concentrations in certain surface water sources, seawater, or some industrial return flows—standard cast iron casings will corrode rapidly. In such cases, stainless steel wetted components (SS304, SS316, or duplex stainless steel) must be specified, which substantially affects procurement cost.
Additionally, the SH-type is a single-stage pump, which imposes a natural head limitation. It is generally appropriate for low-to-medium head applications. If the waterworks circulation system requires high discharge head due to topography or process constraints, a single SH-type pump cannot satisfy the requirement, and multi-stage pump solutions or special configurations such as series operation must be considered.
Distinguishing SH-Type from IS-Type Single-Stage Pumps
Many designers hesitate between the IS-type single-stage centrifugal pump and the SH-type split-case pump. The selection logic is clear:
The IS-type has a simpler structure and lower initial capital cost, making it suitable for small-to-medium flow applications with moderate operating intensity, such as auxiliary water supply at small plants or temporary intake points. The SH-type dominates where large flow capacity, long-term continuous operation, and high maintenance accessibility are priorities. In large-scale waterworks primary circulation systems, multiple SH-type pumps operating in parallel represent a mature industry configuration with proven stability and serviceability.
Conclusion
For conventional water treatment plant circulating water supply, filter backwash, and clear water transfer duties involving clean water, the SH-type single-stage double-suction split-case pump is a technically mature, cost-effective, and maintenance-friendly choice. Selection should confirm three key points: whether water corrosivity falls within cast iron tolerance, whether required head is within single-stage pump capability, and whether flow demand suits the hydraulic characteristics of the double-suction impeller. Where these conditions are satisfied, the SH-type is highly likely to be the appropriate solution.