DOP Submersible dredge pumps

GETTING STARTED

Excavator

Make sure you are ready to start your dredging job immediately by making some preparations. Below a few general tips & tricks to ensure a swift start of your DOP-dredging job.

HOW TO CONNECT TO YOUR EXCAVATOR

Flexible connection – fast & easy

The DOP submersible dredge pump can be connected to your excavator by means of a 2 or 3 legged chain spread. For this, hoisting lungs are provided on the top rim of the DOP’s sturdy casing, or on the hose guide should you have included it in your order.

This flexible mounting method can be used when your DOP pump is fitted out with the jet water assisted sand mining head or a leveler head. Do note to use a fixed mounting method for the cutter and auger unit (for explanations please see next paragraph).

Fixed connection – indispensable for cutter and auger unit

In some situations, the DOP pump needs a fixed connection to the excavator’s boom. This is when the DOP’s exchangeable suction heads exerts forces – such as the rotating force of the cutter unit and the cutting force of the auger head. These forces dictate the use of a fixed boom connection.

The DOP dredging pump can be fixed to the excavators boom by adding a top plate. This top plate, which can be supplied with your order as standard item, is bolted onto the upper rim of the DOP’s casing - acting as a large flange. This top plate is used as an adapter base plate. The owner has to arrange and weld excavator-specific counter coupling parts, or adaptors, to the base plate. Note that this has to be done locally upon arrival of the DOP dredging package.

When the fixed connection is used there are multiple dredging options : each of the 4 available suction heads can be used in this configuration. And you can be creative : add dredging depth to your project set-up by adding a pipe piece between the DOP dredge pump and the connector.

HOW TO POWER YOUR DOP PUMP

HYDRAULIC POWER – WHERE FROM?

Of course there are electrically and hydraulically powered DOP sub pumps. Concentrating on the hydraulically powered DOPs, the question is : how do you drive your pump? This can be done by a separate diesel-hydraulic power pack, or by the hydraulics of the excavator itself.

POWERED BY A DIESEL HYDRAULIC POWER PACK

When your excavator does not have sufficient hydraulics available, a separate power pack is the solution. The hydraulic oil flow and pressure to be supplied to a DOP dredging pump and, when required, the suction head can be found here. This type-specific oil flow can be varied to adjust the dredge pump or cutter head revolutions.

Damen power packs can be fitted out ready to feed both the DOP pump and the cutter unit or auger head separately. Do note that you will need a flow divider manifold if your existing power pack has not been designed for powering 2 devices. This flow divider manifold is to be fitted on the DOP’s hydraulic motor. Should this option be used, the advantage is that only one set of hoses needs to be used to connect. The speed of the cutter or auger unit will be linear to the DOP pump speed.

The minimum hydraulic pressure of the power pack must be ΔP = 250 bar over the pump drive plus the pressure drop in the flow divider manifold plus the total hydraulic hose resistance. Roughly use a hydraulic house resistance of ±0,15 bar per m for your calculations.

POWERED BY YOUR EXCAVATOR

When your excavator can handle the weight of your DOP, it is likely that the excavator’s hydraulic drive can supply sufficient power to drive it. You can check the required flow and pressure here.

Powering the DOP using your existing excavator is nice and practical – just divert some power using a Power Take Off (PTO). But do take some precautions - the load sensing feature of your PTO should not be used. Excavators normally work with such a load sensing unit. Yet, the DOP needs a constant flow to maintain constant revolutions. Therefore the internally installed load sensing unit in the excavator should be replaced by a constant flow control unit. The available hydraulic power remains the same. Modern excavators can be changed easily by changing the software settings, older types require physical replacement of the unit. The same works for a cutter unit.

Do make sure to turn the load sense feature off before you start dredging otherwise the DOP pump will stop pumping and your discharge system is clogged – all due to an unstable feedback control loop in your hydraulic system.

Should you have a cutter unit which need hydraulic power as well, this can be delivered by the excavator or through a separate power pack.

PREPARE YOUR HYDRAULICS

QUICK COUPLINGS

The hydraulically driven DOP pumps are fitted out with SNAPTITE quick couplings. Each connection, being Pressure (P), Return (R) and Leak (L) has its specific location and size. The location of connection is identified on the block with an engraved P, R or L. The correct size of the connection differs per function and dredge pump or cutter head size. They can be checked here at the top right hand side.

Prepare the hydraulics connections before arrival of your DOP package. To speed up your start-up process we include the DOPs SNAPTITE counter couplings to be mounted on your power pack, excavator or hoses.

HYDRAULIC HOSES

Between the hydraulic power pack – whether it is a separate one or if you are using your excavator – you will need flexible hydraulic hoses to bridge the distance to the DOP – or cutter head. This connection usually is made by hydraulic hoses with quick couplings on both ends; as a standard we have sets of hoses of 20m length in stock.

There are a few tips & tricks : connect the hoses to the boom of the excavator to ensure they follow the unit’s movement. Damage to the package of hoses due to movement of the crane boom will be minimized when you allow for sufficient over-length for bends and mount the hoses using straps, thus avoiding sharp edges of quay walls etc. It would be even better to install hydraulic piping along the boom to connect the hoses to.

For guiding the hoses from DOP to boom a “hose guide” is available. It is even possible to mount this hose guide “higher up”, that is with a 3-legged chain spread between DOP upper rim and hose guide, ensuring maximum support of the hydraulic hoses( and the jet water hose if applicable).

Moreover, always flush and fill every single hydraulic hose with oil before connecting it to the system and make sure to work as clean as possible. Furthermore make sure to connect the hoses correctly to the hydraulic power supply and the DOP, choosing the correct connection and tightening them firmly. The SNAPTITE couplings have to be checked if that are clean, if the seal is in good condition, and if they are connected firmly to open the oil flow. This may require a well-aimed blow with a hammer.

PREPARE YOUR EXCAVATOR’S HYDRAULIC SYSTEM

When your excavator can handle the weight of your DOP, it is likely that the excavator’s hydraulic drive can supply sufficient power to drive it. You can check the required flow and pressure here.

Powering the DOP using your existing excavator is nice and practical – just divert some power using a Power Take Off (PTO). But do take some precautions - the load sensing feature of your PTO should not be used. Excavators normally work with such a load sensing unit. Yet, the DOP needs a constant flow to maintain constant revolutions. Therefore the internally installed load sensing unit in the excavator should be replaced by a constant flow control unit. The available hydraulic power remains the same. Modern excavators can be changed easily by changing the software settings, older types require physical replacement of the unit. The same works for a cutter unit.

Do make sure to turn the load sense feature it off before you start dredging otherwise the DOP pump will stop pumping and your discharge system is clogged – all due to an unstable feedback control loop in your hydraulic system.

Should you have a cutter unit which need hydraulic power as well, this can be delivered by the excavator or through a separate power pack.

PREPARE YOUR DREDGING DISCHARGE

DISCHARGE PIPING

Once the DOP dredge pump is up and running, it will deliver a continuous flow of sediment. To transport the sediment to the desired location, piping is to be connected to the submersed pump discharge flange. As for the diameter of the connection and the discharge flange dimensions: they can be found here.

The first bit of piping is flexible to accommodate for the DOPs movements. For this a number of rubber hoses are used, fitted out with floats. Do note that dredging deeper dictates the use of less floats on the discharge line to prevent excessive buoyancy of the deeply submerged hose.

To create a more important discharge distance, HDPE piping is connected to these flexible rubber hoses. The HDPE pipes are available in containerised lengths fitted out with connection flanges for practical mounting. The piping can be used on land or afloat when floats are added.

During project set-up a few things should be kept in mind : the discharge line should remain “open”, therefore without kinks etc. To ensure this, allow the discharge line to follow the movement of the excavator’s boom by connecting the flexible hoses with, for instance, straps to keep the unit manageable. Keep in mind that bends in the hose will result in a lower production. In case of shallow water dredging, you may want to add a 45° bend at the DOPs discharge flange to prevent the kink.

Moreover Sniffer Valves are practical additions. It is when you start up the pumping process, all air in discharge hoses and pipe lines should be able to leave the system quickly. And should the discharge pipe cover different geodetical heights, a sniffer valve – or deaerator - is to be mounted at each high point of the discharge line to prevent vacuum peaks.

HOW TO STORE THE DISCHARGED MIXTURE

The discharge piping ends at the location where the dredged sediment can be stored. Beside storing the sediment, the transport water can flow back here into the environment such as a river, a lake, a harbour etc. The settlement field needs a raised dyke around its circumference, and a surface corresponding with the type of soil, the dredge pumps output and the overall volume of the dredging project. Should you need assistance in this lay-out, we can arrange for a consultant to assist you.

Beside the open settling field, GeoTubes can be used to store dredged materials. These GeoTubes are containers made in special textile allowing water to seep out, whilst sand and silt remain inside. The GeoTubes come in different sizes and shapes, and can be used to build break waters or strengthen shores. Another practical use is trapping contaminated materials inside to dispose of in a safe way. The clean transport water will return to surface waters.

PREPARE YOUR JET WATER ASSISTENCE

WHEN TO ARRANGE JET WATER SUPPLY

Both the sand mining head and the leveler head need a constant supply of jet water during the dredging activities to boost the production. This pressurised water – allow for about 8 bar pressure at the jet nozzles – is to be delivered by a jet water pump through hoses to the suction head. Do take pipe line losses of the pressure into account.

A leveler head is provided with a lot of smaller nozzles which are actually hollow bolts. Sometimes not all nozzles are necessary for your particular dredging job. In this case the nozzles can easily be blinded off by using standard bolts.

The cutter unit and auger head do not need jet water assistance.

HOW TO ARRANGE JET WATER SUPPLY

Some suction heads need a constant supply of jet water during the dredging activities. This pressurised water – allow for about 8 bar pressure at the jet nozzles – is delivered by a jet water pump, usually as a jet pack. This is a separate containerised unit consisting of a diesel drive with jet water pump, which can be shipped with your DOP to your jobsite.

The jet pack is fitted out with sound attenuating casing and hoisting lugs and is a self-sufficient unit which is to be located on your jobsite at the water edge. The capacity of the jet pack depends of your DOP pump size as it flows the dredging capacity. Make sure to meet both the pressure and the capacity requirements, also should you use an existing local jet pack. For more details on the required pressure and capacity in bars and m3/h –which differ per DOP type - please check here.

Do note that the suction height of the jet pack is limited. This is the vertical distance between the water level and the suction inlet of the pack. Make sure to minimize this suction height to less than 2 m.

HOW TO ARRANGE JET WATER TRANSPORT BY HOSES

To deliver the pressurised water from the jet pack to the suction heads, flexible hoses are required. These flanged hoses connect on one side to the jet water pump discharge, and the other to the jet piping on the DOP pump.

Make sure the hoses follow the excavators boom, using the same methods as the discharge hose avoiding kinks etc. The jet water discharge hoses are available in 10m and 20m lengths complete with flanged connections.

On the suction side of the jet water pump you will need suction piping. Do make sure you can prime the jet water pump (fill it with water before starting up). Moreover, do make sure the suction piping only draws in water; the bottom material such as sand or silt should not be included.

Do take pressure losses of the length of the jet water hoses into account in your calculations.

HYDRAULIC DRIVE REQUIREMENTS
JET WATER REQUIREMENTS