Bulk & Fluid Storage

Scope and product flow

Dry bulk reaches the rig as powder blown up a hose from the supply vessel. It goes into the main bulk tanks, then moves by compressed air to surge tanks above the cement unit or the mud mixing hoppers. Liquids such as fuel, drill water, potable water, base oil and brine are pumped aboard into hull tanks or portable tanks. Mud pits, mixing hoppers and the cement unit sit in other Categories, see mud mixing and storage and cementing units.

Choosing between the sub-Categories

• Bulk storage tanks hold the rig's main supply of barite, bentonite and cement, as fixed tanks or skid-mounted portable tanks.
• Storage and surge tanks are the smaller buffer vessels that feed the cement unit or mixers, plus liquid and portable tanks for base oil, brine and chemicals.
• Fluid transfer hoses carry each product from the supply vessel to its loading station and are the most consumable item in the group.

Codes and rules across the group

• Pressure vessels built in the US usually follow ASME Section VIII Division 1, carry the ASME certification mark with the U designator and may be registered with the National Board. Repairs and alterations then follow the National Board Inspection Code (NBIC) and need an R-stamp holder.
• European vessels may carry CE marking under the Pressure Equipment Directive 2014/68/EU.
• On a classed unit, the class society approves pressure vessels in the rig's systems and surveys them on its own schedule.
• A tank in a frame that is lifted offshore is also an offshore container or portable offshore unit. DNV-ST-E271 (DNV 2.7-1) and DNV-ST-E273 (DNV 2.7-3) cover the frame, pad eyes and lifting set.
• A portable tank for dangerous goods also needs approval under chapter 6.7 of the IMDG Code, with its own periodic tests.

Integration questions

• Dry bulk moves only with dry air. Check your compressor and air dryer can deliver the tank's discharge pressure at a low enough dew point, since moisture cakes cement and barite.
• Match fill, vent and discharge line bores and routes, and size the dust collector or vent for the fill rate.
• Wire load cells and level gauges into your control or bulk monitoring system.
• Check that loading station couplings match the hose ends used by your supply vessels.
• For portable tanks, check deck space, sea fastening points and that your crane can lift the full tank.

Where equipment in this group wears

• Internal corrosion under caked powder, worst in tank cones and near aeration inlets
• Erosion at outlets and elbows, because barite and cement are abrasive in dense-phase flow
• Seized or leaking discharge valves, and blocked vents or dust collector filters
• Lapsed relief valve certificates, which stop a tank from going back into service
• Cracked pad eyes and frame welds on portable tanks, found by magnetic particle inspection
• Hose covers and linings that age in storage as well as in use

What matters when sourcing used

A pressure vessel without a data plate, manufacturer's data report and hydrostatic test record is hard to return to service. Ask for thickness readings and internal inspection reports, because damp powder caked on a wall holds moisture against the steel. Fixed tanks are rarely worth removing from a hull. Portable tanks and hoses change hands far more often. Naventr can arrange an independent inspection on request and pass on questions about the code file to the Seller.