1. Field of application and purpose

This manual defines the single mandatory maintenance schedule for console and monobloc centrifugal pumps used on industrial enterprises in Ukraine. The document covers three critical operations: replacement of the mechanical seal, inspection of the impeller, and checking of operating characteristics (pressure, flow rate, vibration) in accordance with the requirements of DSTU ISO 9906 and EN 733.

The procedure is carried out during planned major or medium repair, as well as in case of detection of such signs of failure:

Leakage of the pumped medium through the stuffing box exceeding the normal limit (more than 5 drops per minute for a single mechanical seal).
Pressure drop of the pump by 10% and more from the nominal operating point.
Increase in vibration level on bearing supports above 4.5 mm/s (RMS) according to ISO 10816-3.
External noise, cavitation noise, or sudden increase in bearing housing temperature above 75 °C.

2. Safety Measures

DANGER! ELECTRICAL ENERGY AND HIGH PRESSURE.

Before starting any work, perform the Lockout/Tagout (LOTO) procedure: fully de-energize the pump motor at the distribution panel, install a padlock and a warning tag "Do not energize! People are working".

Ensure that the pressure in the suction and discharge piping is reduced to 0 bar, the shut-off valves are fully closed and locked. Allow the pump and working medium to cool down to a safe temperature below 40 °C.

Використовуйте засоби індивідуального захисту (ЗІЗ): захисні окуляри згідно з EN 166, маслобензостійкі рукавиці, захисне взуття з металевим носком (EN ISO 20345) та каску. У разі роботи з токсичними або агресивними середовищами обов'язково застосовуйте кислотостійкий фартух та респіратор відповідного класу захисту.

3. Required Tools and Materials

Tool / Material Name	Technical specification	Quantity
Torque wrench	Range 5–50 Nm and 20–200 Nm	1 pc.
Set of Hex and Socket Wrenches	M6 – M30 (metric system)	1 set
Hydraulic / mechanical remover	Double or triple lap, force up to 5 t	1 pc.
Alignment Laser System	Measurement accuracy up to 0.01 mm	1 set
Digital Vernier Caliper	0–150 mm, price per division 0.01 mm	1 pc.
Micrometer external	25–50 mm, price per division 0.01 mm	1 pc.
Flat feelers	0.05–1.00 mm	1 set
Non-contact thermometer (pyrometer)	Range -30 °C ... +500 °C	1 pc.
Vibrograph / Vibrohandle	Vibration velocity measurement (mm/s)	1 pc.
Sealant paste for seals	Silicone or soap solution (without petroleum products)	1 tube
Anaerobic Sealant / Threadlocker	Medium strength (for example, equivalent to Loctite 243)	1 bottle
Technical non-woven wipes	Industrial, solvent-resistant	1 pack

4. Check-list of the pre-inspection before disassembly

View Element	What to check	Acceptance / Rejection Criterion	Notes
Drive coupling	Condition of elastic elements (stars, bushings)	No cracks, breaks, wear of rubber over 15% of the original thickness.	Check the gap between the half couplings (usually 2-5 mm).
Axial play of the shaft	Shaft displacement along the axis using a dial indicator	Axial play shall not exceed 0.05–0.10 mm.	Bearing retention in the housing.
Radial runout of the shaft	Shaft runout under seal and bearing	Radial runout not more than 0.03 mm.	Measure with a dial indicator (type IC).
Condition of foundation bolts	Torque and presence of corrosion	Bolts are tightened to nominal torque, pump bracket play on the frame is absent.	Check with a key.
Drainage lines and bunding	Presence of leaks, missing valves, clogged impulse tubes	Pipes are clean, full flow, no signs of corrosion or leaks.	Sealing cleaning plan (Plan 11 / Plan 32).

5. Step-by-step procedure for repair and maintenance

Step 1: Disassembly of the pump unit and access to the seal

Дія: Виконайте повну ізоляцію електроживлення (LOTO), закрийте засувки на всмоктуванні та нагнітанні. Дренуйте залишки рідини з корпусу насоса через зливну пробку у спеціальну ємність.

Специфічні значення: Температура рідини перед зливом повинна бути нижчою за 40 °C.

Visual indicator: Complete cessation of liquid leakage from the drain fitting, pressure gauges on the line show 0 bar.

Typical error: Incomplete drainage of aggressive or hot medium leads to burns or chemical injury to personnel.
Action: Disconnect the electric motor from the pump, remove the protective coupling cover, loosen the bolts securing the half-couplings, and slide the half-coupling off the pump shaft (for constructions with spacer-type disassemblable couplings).

Specific values: The loosening torque of the coupling bolts depends on the strength class (for M10 bolts class 8.8 — the breaking torque is approximately 45-50 Nm).

Visual indicator: The gap between the half-coupling ends is sufficient for disassembly of the bearing unit or rotor.

Typical error: Applying impact tool directly on the pump shaft to remove the half coupling, causing shaft bending.
Action: Remove the cover seal / end face seal mounting bolts to the pump housing and carefully pull out the rotor assembly or release the seal unit.

Specific values: Loosen the cross-cross cover bolts evenly by half a turn to avoid misalignment and damage to ceramic/carbide rings.

Step 2: Replacement of the end seal

Action: Remove the old end seal from the shaft. Clean the shaft seat surface under the seal from scale, corrosion products and rubber residues using a lint-free cloth and a solvent.

Specific values: The surface roughness of the shaft's mounting surface shall be Ra <= 0.8 µm. Check the diameter of the shaft in the sealing area (tolerance h6) with a micrometer.

Visual indicator: The shaft surface is clean, with metallic luster without scratches and burrs along the axis.

Typical error: Using sandpaper with a coarse grit, which creates micro-grooves on the shaft and causes an inevitable leakage through the seal.
Action: Wet the inner surface of the rubber bellows or the inner ring of the new face seal with clean water or special silicone mounting paste (use of mineral oil-based lubricants is prohibited for ethylene propylene rubber EPDM).

Specific values: The movement of the node along the shaft should be performed by smooth hand force without using a hammer or a black metal punch.
Дія: Встановіть нерухому частину (стаціонарне кільце в сальнику) у гніздо кришки за допомогою пластикової монтажної оправки. Встановіть обертову частину ущільнення на вал і зафіксуйте її на заданій монтажній довжині (робоча довжина пружини $L_{work}$, зазначена в паспорті виробника ущільнення, наприклад, 32.5 мм ± 0.5 мм).

Visual indicator: Rings with a triangular cross-section (silicon carbide against tungsten carbide or carbon) are tightly fitted, without misalignment, working surfaces are ideally clean.

Typical error: Touching mirror surfaces with fingers; oily residues from hands cause local overheating and destruction of friction pairs during startup.

Step 3: Inspection and Defect Analysis of the Working Wheel

Дія: Зніміть робоче колесо з вала за допомогою знімача (після відкручування центральної стопорної гайки робочого колеса). Очистіть колесо від відкладень та корозії.

Specific values: The tightening torque of the central nut of the impeller for M16 thread is 85–95 Nm (fix with medium strength thread lock).
Дія: Перевірте стан лопатей робочого колеса на наявність кавітаційного зносу, абразивних вибоїн, тріщин та ерозійного стоншення.

Specific values: Allowable wear of the blade edges — not more than 25% of the initial thickness. Runout of the impeller face relative to the shaft axis — not more than 0.05 mm.

Visual indicator: Absence of deep cavitation pits deeper than 2 mm on the inlet edges and the back side of the disc.

Typical error: Operation of a wheel with imbalance exceeding class G6.3 according to ISO 1940; an unbalanced wheel destroys bearing supports within a few hours of operation.
Action: Measure the clearances in the labyrinth seals (sealing rings between the casing and the impeller).

Specific values: The radial clearance of the seal for standard pump execution should be 0.30–0.50 mm (depending on the impeller diameter according to the OEM instruction).

Visual indicator: Measurement with a bore gauge shows even clearance around the entire circumference without signs of wear.

Step 4: Pump Assembly and Shaft Alignment

Action: Assemble the pump unit in reverse order. Tighten the pump housing bolts and the stuffing box cover bolts with a torque wrench using even crosswise torque (for M12 studs — torque 40–45 Nm).

Visual indicator: Even gap between the body flange and the cover flange with paronite or spiral wound gasket (gasket thickness corresponds to the drawing, usually 1.5–2.0 mm).
Дія: Прокрутіть вал насоса вручну. Вал повинен обертатися вільно, без заїдань, ривків та сторонніх тертя.

Visual indicator: Smooth rotation by hand on the coupling.
Дія: Встановіть лазерну систему вирівнювання на напівмуфти насоса та електродвигуна. Виконайте вирівнювання (юстування) осей агрегату.

Specific values: Allowable radial misalignment — not more than 0.05 mm, angular misalignment — not more than 0.05 mm per 100 mm coupling diameter at a rotational speed of 2950 rpm (or 0.10 mm for 1450 rpm).

Typical error: Ignoring thermal expansion of the drive motor (if pumping hot fluid above 80 °C, a compensating tilt must be set in the cold state).

Step 5: Testing of operating characteristics (pressure, flow rate, vibration)

Action: Remove LOTO lockout, fully open the suction valve, close the supply valve by 90% (protection against motor starting current overload). Start the electric motor.

Visual indicator: Pressure increase on the pressure gauge, stable motor operating current below nominal value.
Action: Slowly open the suction valve until the pump reaches the operating point according to the technological procedure. Record the instruments' readings.

Специфічні значення: Виміряйте тиск на всмоктуванні ($P_1$) та на нагнітанні ($P_2$). Обчисліть повний напір $H$ за формулою: $H = ((P_2 - P_1) \cdot 10.2) / ho + (z_2 - z_1)$, де $ ho$ — густина рідини, кг/м³, $z$ — висота осей манометрів, м.
Дія: Виміряйте параметри вібрації вібрографом на передньому та задньому підшипникових щитах насоса у трьох взаємно перпендикулярних напрямках (горизонтальному, вертикальному, осьовому).

Specific values: RMS vibration velocity must comply with zone "A" or "B" according to ISO 10816-3 (for rigid foundations, motor class up to 15 kW: vibration < 2.3 mm/s; for powers above 15 kW: < 4.5 mm/s).
Дія: Контролюйте температуру підшипникових вузлів пірометром протягом перших 2 годин безперервної роботи.

Specific values: The maximum temperature of the rolling bearings shall not exceed 70 °C (or exceed the ambient temperature by more than 40 °C).

6. Check-list after repair and verification

Testing / Inspection	Expected result	Status (Passed / Not Passed)
Leak test through the seal	Dry or dripping not more than 1 drop per 3 minutes (for single-end face seal).	[ ] Pass / [ ] Fail
Vibration level (ISO 10816-3)	Vibration velocity RMS < 3.5 mm/s at the working point.	[ ] Pass / [ ] Fail
Temperature of the bearing unit	Stable temperature below 70 °C after 1 hour of operation.	[ ] Pass / [ ] Fail
Working pressure and pressure	Meets the pump's passport characteristics (±5%).	[ ] Pass / [ ] Fail
Electric current of the motor	Does not exceed the nominal current on the nameplate (cos(phi) within normal limits).	[ ] Pass / [ ] Fail

7. Troubleshooting Guide

Symptom	Likely cause	Corrective action
Significant leakage through the end seal immediately after start-up	Incorrect spring mounting length; contamination of friction surfaces; damage to the rubber ring during installation.	Stop the pump, perform LOTO, remove the seal, check the spring length and the condition of the friction pairs, replace the damaged rubber components.
The pump does not create pressure (the head is zero)	Ventilation of the pump housing; rotation of the impeller in the reverse direction (motor phase connection error); fully closed suction plug.	Stop the unit, perform a full filling of the pump and suction line with liquid through the air vent, check the direction of rotation of the motor (must match the arrow on the pump housing).
Increased vibration and characteristic noise (cavitation)	High suction line resistance; clogged suction filter; pump operation in the left or right limiting flow zone; low inlet pressure (NPSHa < NPSHr).	Purge the suction filter, fully open the suction valve, check the level in the suction tank, reduce the liquid temperature or raise the static level.
Rapid overheating of the bearing unit (> 80 °C)	Drawn-out or insufficient clearance in bearings; excess or lack of grease (for example, lithium-based according to NLGI 2); misalignment of the shaft due to poor coupling alignment.	Check the volume and type of grease (bearing filling 30-50%), perform re-laser alignment of the half couplings, check clearances.

8. Recommended Technical Maintenance Schedule

Maintenance Task	Execution frequency	Estimated duration	Qualification Level
Daily inspection (vibration, noise, leaks, temperature)	Daily (operator control)	15 minutes	Operator / Foreman Turner
Lubricant Control in Bearings and Replenishment	Every 1000 hours of operation	30 minutes	Plumber-Repairman (Level 2)
Laser Alignment Check of Coupling	Every 6 months	2 years	Reliability Engineer
Full rotor inspection, replacement of the end seal and bearings	Every 8000–12000 hours (or 1 time per year)	8–12 hours	Lead Mechanic / Repair Crew

9. Spare Parts Catalogue (UNITEC-D)

Description of the part	Typical specification	Category UNITEC
Cartridge type end seal	SiC/SiC/EPDM, shaft diameter 28–50 mm, PN 16 bar	Industrial Pump Seals
Rolling bearings (radial thrust / ball)	SKF / FAG series 63xx, 73xx (accuracy class P6)	Bearing units
Set of rotor seals (O-rings, gaskets)	EPDM / FKM (Viton), heat resistance up to +150 °C	Hydraulic Reconditioning
Drive coupling with elastic element	Spring clutch coupling or star (HRC / NM series)	Wet elements

For ordering original spare parts according to the manufacturer's catalog, visit our electronic catalog UNITEC-D.

10. Normative References and Standards

DSTU ISO 9906:2008 (ISO 9906:2012) — Dynamic Pumps. Hydraulic Testing of Working Characteristics. Accuracy Classes 1 and 2.
EN 733 — Centrifugal horizontal pumps with axial suction (nominal pressure 10 bar, with rating designation).
ISO 10816-3 — Vibration control for industrial machines with power over 15 kW.
ISO 1940-1 — Definition of residual imbalance of rigid rotors.