Custom HDPE (high density polyethylene) Tank Making for all Purposes

High density Polyethylene (HDPE) tank systems overcome the persistent corrosion problems of stainless steel and mechanical failure of flexible bags.

HDPE, next to being versatile and durable, will ensure an almost condensation free environment for fuel and will provide water clean and free of any undesired taste for the galley. We have been involved in replacement tanks for boats previously fitted with mechanically unreliable flexible bags or stainless and aluminium tanks with electrolysis problems.

HDPE tanks are built in 8-12 mm thick HDPE sheets and are pressure tested to 0.2 bar equivalent to a fill point 2 metres above the tank. Higher pressures can be achieved and should be specified when placing an order. Standard specifications include baffles placed approximately every 300 mm which protrude through the top of the tank and are then welded. This is to prevent the top of the tank from “pumping” when under pressure.

The inspection hatches should be bolted on with fully encapsulated stainless steel bolts and gaskets should be made of resistant polymers like neoprene. The usual practice is to supply tanks with welded female thread sockets of gas pipe thread [*]. Different sockets, Metric, Special and Oversize, can be supplied to customers to fit their own fittings if need be. Different sockets, metric, special and oversize, can be supplied to customers to fit their own fittings if need be.

The tanks all have some sort of internal baffling to design specifications for two main reasons: firstly, to introduce rigidity to the tank, and secondly, to limit movement of contents. The baffles should have generous bores each in order to allow access from the inspection hatch to the adjacent compartments to facilitate cleaning and inspection.

Tanks built from rigid HDPE lend themselves to one-off production because there are no expensive mould tools to build. HDPE cannot be curved excessively for one-off applications, but multifaceted shapes normally solve most of the design problems.

HDPE tanks are ideal solutions for the custom and production boat builder for storing diesel fuel and fresh, grey and waste water. marineSOLUTIONS will be pleased to help with any design problems.

Production Examples in HDP

• Tanks for fresh water, diesel fuel, grey water and waste water.
• Collectors with strainer and pump for shower water and the sink drain.
• Shower trays
• Watertight liners for chain lockers.
• Watertight liners for cockpit lockers, lazaretts etc.
• Raw water strainers for main engines, generators and similar.
• Ice boxes, freezers and fridges.
• Mosquito nets for portholes.
• Almost any engineering product of your imagination.

Some Design Guidelines

1. Make sure the tank can be installed into the space it is designed for, i.e. will it go through the locker door/companion way? Make sure the tank can be easily removed.
2. Do not make the tank a too tight fit. The material, like all welded materials, distorts slightly during manufacture.
3. Make sure the inlet, outlet and vent pipes can be pushed onto the spigots without kinking and that jubilee clips can be tightened and later inspected.
4. Avoid curved tanks and wide shallow tanks placed athwartships.
5. Give careful consideration to fastening tanks down.
6. Fix tank down with one or more of the following methods. They are all acceptable but are listed in order of preference.
I. Box in with 12 mm marine ply.
II. Set into position with self rise foam.
III. Strap down using strong webbing and fastening buckles or stainless steel straps.

Following information is required when seeking a quotation:
1. Maximum outside dimensions of tank including templates of any relevant angles, shaped ends etc. If sending drawings then please mark right angled faces, if any, on irregular shaped tanks.
2. Positions and outside diameters of all inlet, outlet and vent spigots for water tanks, external diameters of copper or nylon tube for diesel tanks.
3. Indicate the maximum hydraulic head the tank is likely to sustain, i.e. distance from the bottom of the tank to the deck filler.

Dr. Yusuf Civelekoglu, CMI
Images: marineSOLUTIONS archive