Tank Pit Design

Design Consideration:

• Design piping around the tank inside the dike basically as sleeper piping.
• Arrange utility piping in the middle and process piping on both sides corresponding to which side the tank needs to connect to.
• Piping inside a dike that is not related to the tank should not go through the inside dike. Design that piping so that it does not penetrate the dike as much as possible except the pump suction pipe. A pipe sleeve or wrap can be used to penetrate the dike. In the concrete wall, you can use the Link Seal to close the wall.

• Make sure there is no air pocket part in the pump suction pipe.
• The pump suction pipe penetrating the dike should be flexible so that the heavy load by thermal expansion does not influence the pump nozzle. Normally the dike penetration will be considered as a fixed point in the stress calculation.
• Install the isolation valve directly on the tank nozzle. Install the emergency shutdown valve as near as possible to the tank. Sometimes, TRV is installed to protect the line from pressure build-up due to solar heat, an additional nozzle can be added to the tank.

• Stress calculation usually checks the following:
  • The load caused by the settlement of new tanks
  • The load caused by settlement due to the filling and emptying of the tank. Normally clients should have this information.
  • Load caused by tank bulging. As per API 650, a tank with a diameter of more than 36 meters should consider external load in the shell opening.

• If a large(heavy) valve is attached directly to the tank nozzle, check if the nozzle should be reinforced. Examine the following reinforcing method by discussing it with the machinery manager.
  • Method to attach reinforcement pad
  • Method to attach support to the tank shell
  • Method to attach support to the tank foundation
• If the block valve for the safety valve is a gate valve, install it to a straight pipe so that if any disc problem occurs because of corrosion it can be maintained in open form.
• Piping installed in the dike should be supported by a U-bolt or a hold-down clamp that is able to hold so that the piping does not float up by buoyancy in case of rain or contents leakage.

• For locations predicted for possible tank settlement, select between the following plans and reflect it in the design.
  • Installation of L type or type horizontal loop
  • Install Flexible Tube
  • Install Expansion Joint
  • Install Adjustable Type Support (first support from tank nozzle)