SG 50-200 BL 7117-8 End Suction Centrifugal Pump

SG 50-200 BL 7117-8 End Suction Centrifugal Pump MB 360 DIN

The SG 50-200 BL 7117-8 is a heavy-duty, single-stage end-suction centrifugal pump complying with DIN EN 733 (formerly DIN 24255) for dimensions and hydraulics. The unit, suitable for continuous industrial and marine operations, is provided with an MB 360 bearing housing and the back-pull-out rotor concept that allows fast maintenance of the mechanical seal and the impeller without disconnecting the pump casing from the piping matrix. It provides the best fluid transfer efficiency for low viscosity, non-aggressive fluids, with a focus on NPSH margins and hydraulic stability at the Best Efficiency Point (BEP).

Model Details

• Model Number: SG 50-200
• Build/Variant Number: BL 7117-8
• Bearing Housing: MB 360
• Standard Compliance: DIN EN 733
• MPN: SG50200-BL71178-MB360

Key Features

1. Back-Pull-Out Architecture: Allows complete removal of the rotating assembly without dismantling the volute casing or disturbing the suction/discharge piping.
2. DIN EN 733 Standardization: Guarantees dimensional interchangeability with all conforming legacy and contemporary third-party pump installations.
3. Optimized Volute Geometry: Minimizes radial thrust on the impeller, extending the lifecycle of the MB 360 housing bearings and the mechanical seal.
4. High-Capacity Bearing Bracket (MB 360): Features robust cast-iron construction housing precision-machined heavy-duty bearings for high radial/axial load distribution.
5. Precision Cast Impeller: Dynamically balanced (ISO 1940 Class G6.3) closed impeller design providing high hydraulic efficiency and minimized vibration parameters.

Compatibility

• Electric Motors: Compatible with standard IEC frame standard motors (e.g., Frame sizes 132S through 160L depending on exact power requirements).
• Couplings: Requires a standard flexible spacer coupling to utilize the back-pull-out feature (e.g., Flender N-Eupex, Rexnord Omega).
• Mechanical Seals: Fits standard EN 12756 (DIN 24960) unbalance and balanced mechanical seals.

Part Number Cross-References

Direct hydraulic and dimensional equivalent to the following DIN EN 733 units:

• KSB Etanorm 050-200
• Allweiler NT 50-200
• Grundfos NKG 50-200
• Wilo CronoNorm-NL 50/200

Applications

• Marine & Offshore: Main engine jacket water cooling, ballast transfer, general service, and fire-fighting jockey systems.
• HVAC Systems: Chilled water circulation and cooling tower routing.
• Industrial Processing: Transfer of utility water, lightly contaminated liquids, and condensates in petrochemical and manufacturing plants.
• Water Treatment: Primary reverse osmosis feed and filtration transfer.

Marine Engineer Expert’s Guide

Pre-Commissioning Alignment: As a marine engineer, the most common failure point I see on end-suction centrifugal pumps of this size isn’t hydraulic—it’s mechanical, specifically driven by poor shaft alignment. Always perform a hot laser alignment after the pump reaches operating temperature. Do not rely solely on the factory alignment or a cold dial-indicator sweep. Misalignment on the MB 360 bearing housing will severely truncate the life of the inboard bearing and compromise the mechanical seal faces.

NPSH Margin Optimization: The SG 50-200 requires close attention to the suction head. At absolute maximum flow ranges (right side of the curve), the NPSHr (Required) spikes aggressively. Ensure your system’s NPSHa (Available) maintains at least a 1.0 meter margin over the NPSHr. In marine environments, where suction from ballast tanks or sea chests involves fluctuating static heads, installing a suction compound gauge is critical for diagnosing cavitation before impeller pitting occurs.

Seal Flush Line Checks: The BL 7117-8 variant requires uninterrupted seal flushing. Ensure the internal Plan 11 (or equivalent) flush line from the discharge volute to the seal chamber is unobstructed. If pumping liquids with heavy particulates, consider upgrading to a Plan 31 (with a cyclone separator) to protect the SiC/SiC seal faces from premature scoring.

Frequently Asked Questions (FAQs)

What does the “MB 360” designation mean on the SG 50-200 pump?

The MB 360 refers to the specific bearing housing assembly and bracket size. It dictates the shaft diameter at the seal and bearings, ensuring you procure the correct bearings, mechanical seal size, and spacer coupling for maintenance.

Is the SG 50-200 BL 7117-8 pump self-priming?

No, the SG 50-200 is a standard end-suction centrifugal pump and is non-self-priming. The volute casing and suction line must be fully flooded and vented prior to motor start-up to prevent dry-running the mechanical seal.

Can this DIN centrifugal pump handle salt water?

Yes, provided the proper metallurgy is selected. For seawater or brine applications, specify the marine configuration utilizing a Bronze or Duplex Stainless Steel impeller and a Bronze volute casing to prevent galvanic corrosion and chloride pitting.

What is the maximum operating speed for the SG 50-200?

This pump is designed to operate typically at 1450 RPM (4-pole motor at 50Hz) or 1750 RPM (4-pole motor at 60Hz). Running this 200mm impeller at 2950 RPM (2-pole) will drastically increase radial loads and requires strict verification against the manufacturer’s maximum allowable casing pressure and NPSHr limits.