NTDL/NTD Series - NTDL, NTD drum pump systems

Measure internal clearances: rotor-to-bore max 0.2mm, rotor-flank max 0.4mm using precision calipers. Identify abnormal noise, vibration, loss of capacity, or reduction in discharge pressure as wear indicators. Perform tactile inspection for rotor eccentricity and stator bore erosion. Check for cavitation damage (surface pitting) on rotor and stator.

Inspect mechanical seal mating faces for pitting, scorching, or wear damage under magnification. Verify o-ring material elasticity (hardness test or visual crack assessment). Check for oil weeping or salt-water leakage at seal chamber. Replace seal assembly if any mating face damage detected or o-rings show hardening/cracking. Document seal replacement history.

Monitor suction pressure gauge (typical: <0.3 bar vacuum for clean suction). If pressure drops below gauge minimum, disassemble and clean inlet strainer screen (typically 100-150 microns for marine bilge/sludge). Inspect for scale, corrosion product accumulation, or foreign material (plastic, fibers, mineral deposits). Replace strainer mesh if perforation or structural damage visible. Perform on weekly schedule for active marine service.

Test pressure relief valve cracking pressure with hand pump or ship's test gauge (reference pump nameplate specification, typically 0.8-7.2 MPa depending on model). Verify valve does not chatter or oscillate. Check for corrosion, scale, or salt spray damage on valve body. Disassemble, clean, and reassess cracking pressure. Document baseline and current readings. If drift >10% or valve sticks, schedule overhaul.

Perform Shore A hardness test on accessible stator exterior wall (non-contact surface) to establish baseline elastomer condition. Extract small stator sample specimens during major overhaul and conduct tensile strength, elongation, and adhesion bond testing per ASTM methods. Compare results to original material specification. Monitor for surface crazing, swelling (chemical absorption), or discoloration (oxidation/heat). If hardness increases >10 Shore A units or tensile drops >20%, schedule stator replacement.