How to calibrate and adjust the safety relief valve on SN pump?

The safety relief valve installed at the outlet of the SN Modular Triple Screw Pump is calibrated to prevent overpressure damage. The cracking pressure is typically set between 1.05 and 1.15 times the rated working pressure. During commissioning, slowly open the bypass valve while monitoring the gauge; when the pressure reaches the preset value, adjust the spring preload until the valve begins to lift slightly for relief. Never arbitrarily increase the setting during operation. If frequent relief occurs, inspect the suction side for cavitation or verify if fluid viscosity changes have reduced flow capacity.

What are the speed reduction rules for SN pump when handling high viscosity fluids?

When handling fluids with significantly increased viscosity, the operating speed of the SN Modular Triple Screw Pump must be reduced. High viscosity causes a sharp rise in frictional power loss and suction resistance; maintaining rated speed under these conditions can lead to cavitation, vapor binding, and motor overload. Speed reduction should follow Reynolds number guidelines or empirical formulas, typically reducing speed by 5% to 8% for every 100 mm²/s increase in viscosity. Variable frequency drives (VFD) should be configured with soft-start functions to prevent instantaneous torque shocks that could damage the screw bearings.

How to troubleshoot shaft seal leakage on SN pump?

The SN Modular Triple Screw Pump utilizes API 682 integrated mechanical seals. Routine inspections must focus on the cleanliness of the flushing scheme (Plan 53 or Plan 21). If minor leakage is detected, first verify that the flush fluid pressure exceeds the process medium pressure by 0.05 to 0.1 MPa. For packing glands, regularly adjust the gland follower bolts to the specified torque to prevent overheating from excessive tightness. Replace mechanical seal faces if wear exceeds 0.1 mm; always replace both rotating and stationary rings as a set. The bearing housing must be lubricated independently, never using the process medium for forced cooling or lubrication.

SN SERIES7 modelsHS: 8413.60.31

SN Modular Triple Screw Pump (SN Series)

Industrial Screw Pumps•SN

Flow Range: 1.2 ~ 600 m³/h
Pressure Range: 1.6 ~ 4 MPa
Motor Power: 1.5 ~ 250 kW
Model: SN-20 → SN-600
Customs HS Code: 8413.60.31

WhatsApp Quick Quote Email for Price & DrawingModel-by-Model Technical Specifications ↓

SN Modular Triple Screw Pump (SN Series)

Hydraulic Principle & Internal Construction

The SN series modular three-screw pump is engineered with interchangeable casing inserts and multiple mounting configurations (foot, flange, or submerged vertical). Capable of discharge pressures up to 4.0 MPa, the SN handles mineral oils, synthetic lubricants, and heavy fuel oils with whisper-quiet acoustics and high mechanical efficiency.

Model-by-Model Technical Specifications

Model	Inlet	Outlet	Flow (m³/h)	Pressure (MPa)	Speed (rpm)	Motor (kW)
SN-20	DN40	DN40	1.2	1.6	1450	1.5
SN-40	DN50	DN50	4	1.6	1450	4
SN-80	DN65	DN65	10	2.5	1450	11
SN-150	DN100	DN100	25	2.5	1450	22
SN-220	DN125	DN125	50	3.2	1450	45
SN-340	DN200	DN200	100	4	2900	110
SN-600	DN300	DN300	600	4	2900	250

Selection guidance: match your duty point to the closest model below, then confirm with our engineers. Values are rated operating points at the listed speed.

Need Complete Engineering Dimensions & Curves?

Download the official SN series 1-page technical datasheet covering all 7 model configurations.

Media Compatibility & Viscosity / Temperature Guide

Medium	Max Viscosity (cSt)	Application Note
Marine Main Engine Crankcase System Oil	1,500	API 676 Marine Duty
Gas Turbine Heavy Fuel Oil (HFO)	1,500	Burner Fuel Injection Feed
Turbine Oil / High-Pressure Hydraulic Fluid	680	Fine Filtration Duty
Light Cargo Oil / Marine Distillate Fuel	600	Barge & Tanker Transfer Bunkering

International Benchmark & Interchange Guide

International Benchmarks

IMO (Sweden) three-screw pumps (DIN 24297)
Bornemann / Leistritz three-screw pumps
API 676 compliant

Interchange Note

Modular triple screw pump. Direct equivalent to Allweiler SN, IMO D4/D6, and Settima G55/GR55 series for high-pressure oil lubrication and burner injection.

Materials & Shaft Seal Selection Guide

For the SN Modular Triple Screw Pump, we recommend using HT200-350 gray cast iron or QT400-18 ductile iron for wetted parts when transferring standard mineral oils, lubricating oils, and hydraulic fluids due to their excellent wear resistance and cost-effectiveness. For media containing trace corrosive components or requiring higher strength, 304 or 316L stainless steel is preferred. Regarding sealing systems, API 682 integrated mechanical seals are the primary choice; specifically, double mechanical face seals with external flushing fluids (such as clean oil or water) effectively isolate the atmosphere and dissipate heat. Packing seals are suitable for low-pressure, non-critical applications but require strict control of gland follower torque to prevent shaft sleeve wear.

Casing & Housing Materials: Ductile Iron (GGG40 / QT450)Forged Steel (A105)Cast Steel (WCB)
Rotor / Gear / Screw Elements: Quenched & Nitride-Hardened Alloy Steel Screws
Liner & Sleeve Materials: High-Tin Aluminum-Bronze Embedded Bushing
Shaft Sealing Options: API 682 Cartridge Mechanical Seal

Engineering FAQ

To prevent cavitation in the SN Modular Triple Screw Pump, ensure the suction pipe diameter matches or exceeds the inlet flange size to minimize flow velocity. Install at least 5 diameters of straight pipe upstream of the inlet to stabilize the flow field and avoid direct impact from elbows or valves. Crucially, maintain a Net Positive Suction Head Available (NPSHa) that exceeds the pump's NPSHr by a minimum safety margin of 0.5 meters, especially when handling high-viscosity fluids where vapor pressure considerations are critical.

📐 Engineering Selection Methodology

Correct pump selection starts from the fluid, not the pump. Confirm the medium name and actual viscosity at working temperature, the required flow and differential pressure or head, suction conditions (flooded or lift), and whether the fluid crystallizes, shears, contains particles or gas. Positive displacement pumps must always be protected by a relief valve or pressure bypass on the discharge line, and must never be started against a closed valve unless a bypass is fitted. For viscous duties, derate rotational speed to preserve volumetric efficiency; for crystallizing or high-freezing-point media, specify jacketed casings with steam or thermal-oil heating. Our engineers verify each enquiry against these rules before quoting.

🏭 Manufacturing & Quality Control

Castings are produced in our own foundry cluster with material certificates for each heat number. Gear profiles, screw threads and rotor lobes are hobbed, ground and wire-cut to tolerance, then assembled with matched bearing sets. Before dispatch every pump passes casing hydrostatic pressure testing, a run-in test at rated speed on an oil bench, and relief valve cracking-pressure verification; test records are archived against the pump serial number and can be supplied with the shipment.

📦 Export Packaging & Delivery

Pumps are preserved with anti-rust coating, flanges blanked, and packed in export-grade plywood cases with steel strapping for sea freight. Document packs include operating manual, performance test record, packing list and material certificates on request. Standard models ship from stock; engineered configurations typically require 15-35 days depending on casing material and seal options. Spare rotor sets, seal kits and relief valve assemblies can be quoted together with the base pump.

Typical Applications & Industry Use Cases

The media compatibility table above maps directly to real industry duties. In lubrication circuits, size the pump for continuous duty at 70-80% of rated flow to leave margin for viscosity drift as oil warms up. In chemical transfer, confirm the medium's specific gravity and whether it is shear-sensitive before fixing rotational speed. In food and sanitary service, schedule CIP cycles around the product changeover plan and verify elastomer compliance with the relevant food-contact regulation in your market. In hot oil and asphalt service, always pre-heat the casing to the medium temperature before start-up so internal clearances are at operating dimension - a cold start against solidified product is the single most common cause of gear pump failures reported from the field.

Commissioning & Maintenance Guidance

Before first start: verify rotation direction, fill the casing with medium, open the discharge bypass, and jog the motor to confirm free rotation. Check the relief valve setting against the system design pressure and lock the adjuster. During the first hour, record suction and discharge pressures, medium temperature, and motor current - deviations from the quotation duty point usually indicate suction restriction or an over-throttled discharge line. Routine maintenance intervals: inspect the shaft seal weekly during the first month, then monthly; check coupling alignment after any pipe work; drain and inspect the bearing housing annually. Keep a log of running hours so rotors, bearings and seals can be replaced on condition rather than after failure.

Troubleshooting Quick Reference

No delivery or loss of prime: check suction line for air ingress, verify foot valve and strainer are submerged and clean, and confirm the casing is primed for pumps without self-priming capability. Flow below nameplate: verify actual rotational speed against the data sheet, confirm medium viscosity is within the rated band, and inspect internal clearances for wear if the pump has long service hours. Abnormal noise or vibration: usually coupling misalignment, cavitation from excessive suction lift, or foreign matter in the pumping chamber. Seal leakage: confirm flush plan and seal face condition; never run a mechanical seal dry. Motor overload: check for over-viscous medium at start-up temperature and confirm the relief valve is not set above the motor's capability. For anything beyond these basics, send us the serial number and symptom - our engineers will respond with a diagnosis.

📋 Standards, Testing & Documentation

Gear pumps in this catalog are designed and acceptance-tested with reference to JB/T 6434 (external gear pumps), three-screw pumps to GB/T 10886, centrifugal chemical pumps to ISO 2858, and sealless or screw pumps to the relevant API 676 guidance, with mechanical seals supplied to API 682 configurations on request. Sanitary models are manufactured with surface finishes suitable for FDA / 3A style hygienic duties. Each shipment can include: performance test record against the quoted duty point, hydrostatic test certificate, material certificates for pressure-retaining parts, operating and maintenance manual, and a dimensional drawing with flange table. Tell us which standards your project specification cites and we will align the documentation pack accordingly.

🔧 Spare Parts & After-Sales Support

Every pump model page doubles as a spare-parts reference: rotor and gear sets, bearing and thrust assemblies, complete seal cartridges, relief valve kits and jacket gasket sets are manufactured in-house to the same drawings as the original build - so spares ordered years later still match. Recommended commissioning spares are one seal set and one gasket set per pump; for critical continuous-duty installations we recommend a full rotor set held on site. When ordering spares, quote the pump serial number and nameplate data so the correct material and clearance class is supplied. Technical support in English is available by email during China business hours, with video call diagnostics available for installation and commissioning issues.

ℹ️ Technical data on this page is sourced from the manufacturer's engineering database and applicable standards (JB/T 6434, GB/T 10886, ISO 2858, API 676). Final selection must be confirmed by our engineers against your actual duty conditions.

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