Description

CPJ series marine ejector

一. Overview:

The CPJ type jet pump features a coaxial suction inlet, discharge outlet, and nozzle, resulting in high efficiency. The working water pipe is J-shaped, with its flange perpendicular to the suction and discharge flanges, facilitating installation. With no moving parts, it boasts a long service life.

It is self-priming, enabling continuous and stable operation. Primarily used in ship drainage systems, it can also be applied in environmental protection, chemical, water conservancy, and building materials industries for pumping and discharging seawater and freshwater, mixed liquids, river dredging, and powder conveying.

二.Parameters and Models

model	flow m3/h	Working water pressure MPa	Working water consumption m3/h	Net suction height m	Discharge pressure MPa
CPJ40-50-65	10	1.2	15	5.0	0.25
CPJ50-80-80	30	0.8	30	3.0	0.12
CPJ80-100-100	70	0.7	56		0.10
CPJ100-100-125	50	0.6	115	2.5	0.22
CPJ100-125-125	100	1.0	110	3.0	0.20
CPJ100-150-150	120	1.0	120		0.20
CPJ125-150-150	130	0.9	320	5.0	0.30
CPJ125-150-200	100	0.7	150	7.0	0.12
CPJ125-200-200	130	1.0	250	5.0	0.30
CPJ150-200-200	300	1.25	400	4.0	0.25
CPJ150-200-250	300	1.15	470	5.0	0.25
CPJ200-200-250	170	0.25	600		0.10
CPJ200-250-300	600	1.2	340	4.0	0.10
CPJ250-250-300	250	0.30	1050		0.15
CPJ250-300-350	630	1.3	750	5.0	0.25
CPJ300-300-350	400	0.30	1750		0.15

How to choose a CPJ series marine jet pump?

When selecting CPJ series marine jet pumps (commonly steam/compressed air/powered water driven jetters/jet pump sets used for bilge/sewage/waste oil suction, priming, evacuation, etc.), you cannot only look at the “model diameter.” You must determine the nozzle/throat size, number of stages, and material based on your operating conditions. Following the steps below is a reliable approach.

1. First, confirm the “drive type” and application of the CPJ.

The meaning of the letters in CPJ may vary slightly between different manufacturers, but it is essential to clarify the following before selection:

Drive medium: Steam-driven / Air-driven / Water jet (powered water) driven?

Application: Liquid pumping (bilge/sewage/waste oil) or air pumping (vacuum priming/evacuation of tanks)?

The same series often includes two types: “liquid jet pump” and “vacuum ejector,” with different parameter systems.

2. Three essential operating parameters for pump selection (all are indispensable):

A. Pumping Capacity
Liquid pumping: m³/h (normal + maximum, continuous/intermittent recommended)
Air pumping: Nm³/h or kg/h (in air equivalent)

B. Suction Conditions/Vacuum
Suction height: Height difference between the liquid surface and the centerline of the jet pump
Target vacuum: kPa(abs)/mmHg (e.g., the required vacuum level for priming)
Suction pipe: Length, diameter, elbows, filter (resistance significantly reduces capacity)

C. Discharge Back Pressure
The highest back pressure before discharge to the overboard, sludge tank, collection tank, oil-water separator, etc.
Discharge pipeline losses (increase margin for two-phase flow)
For the same jet pump, the pumping capacity will significantly decrease under higher vacuum or higher back pressure conditions, so selection must be based on a combination of these three factors.

3. Driving Medium Conditions (Determines Compliance and Consumption)
Check the following separately for each driving method:

Steam Driven: Steam pressure (minimum usable pressure is critical), quality (dryness), temperature; whether condensate removal and drainage arrangements are permitted.
Air Driven: Air supply pressure, maximum available flow rate (Nm³/h), oil and water content, and dew point (affecting nozzle scaling/corrosion), noise limits.
Powered Water Driven: Powered water pressure and flow rate (from fire pumps/seawater pumps, etc.); whether mixed discharge of powered water and suction medium is permitted (acceptable in many systems, but not in some oily systems).

Require the manufacturer to provide: Driving medium consumption curves/tables (steam kg/h, air Nm³/h, powered water m³/h), otherwise energy consumption and supply verification cannot be performed.

4. Characteristics of the pumped medium → Determines material/wear resistance/anti-clogging
Seawater/corrosion: Bronze, duplex stainless steel (2205, etc.), or seawater-resistant stainless steel are more stable.
Sewage/bilge water containing sand: Nozzles/throat pipes are prone to wear; replaceable throat pipes and wear-resistant materials are preferred; if necessary, add a coarse filter at the inlet, but calculate the clogging pressure drop.
Waste oil/oily sewage: Pay attention to the sealing gasket material (FKM/PTFE, etc.) and anti-static grounding; if mixing with motive water is prohibited, do not choose a water jet type.
High temperature: Check the temperature resistance of materials and gaskets; for steam ejectors, also consider condensate corrosion and hydrophobicity.

5. Selection of structure and number of stages (especially for “vacuuming/priming”)
Single-stage ejector: Simple structure, but limited vacuum level; performance fluctuations are more pronounced with changes in back pressure.
Multi-stage ejector: Higher and more stable vacuum level, but consumes more driving medium and the system is more complex.

If the CPJ is used for “vacuum priming/evacuation,” it is often necessary to consider whether it is a two-stage/three-stage scheme.

6. Key Points for Piping Layout (Many “Can’t be drawn up” issues are due to piping problems)

The suction pipe should be as short and straight as possible, with a diameter not smaller than the interface diameter to avoid air pockets at high points.

When installing a filter/suction nozzle at the suction inlet, ensure sufficient flow area and consider clogging margin.

For two-phase flow on the discharge side, increase the pipe diameter and reduce sharp bends to avoid scouring and noise.

Steam type: Steam traps, condensate drains, and insulation must be considered to prevent water hammer.

Air type: Ensure proper noise reduction and exhaust guidance to avoid the influence of oil mist/odors.

7. Delivery Data Required from Manufacturers/Suppliers During Selection (Included in Technical Specifications)

Suction volume tables/curves corresponding to different vacuum levels + back pressures under your drive pressure.

Drive medium consumption (varying with operating conditions).

Allowable solid particle size/content, throat and nozzle material and whether they are replaceable.

External dimensions, interface standards, and weight.

Test reports and material certificates; if required by the project, provide relevant documents from classification societies such as CCS/ABS/DNV/LR.