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Function and Description

PROTEGO® SI/DP in-tank valves are used as additional internal shut-off valve for double-walled containers, e.g., for storing liquefied gases, cryogenic gases, or other low temperature products or chemicals.

The external connection piece of the housing is usually fitted with a gate valve that is provided by the customer and aids the normal operating procedure. During normal operation, the valves are kept in the open position. It is only closed in case of emergency or for necessary repairs to the gate valve.

The key feature of these valves is the shut-off element inside the container.

The internal safety valve consists of three housing parts (1) with lateral connecting nozzle (2) for installation of pipeline; a valve cone (3) with sealing (4); and a pneumatic actuator (5). The lapped valve seat (10) and the seal guarantee the desired tightness. Bushings (8) guide the split valve spindle (6), which is equipped with double universal joint (7). Two compensators (9) are provided to accommodate the change in length due to temperature variations.

The in-tank valve is operated/opened by a pneumatic actuator. The required closing force is provided by sufficiently dimensioned compression springs installed in the actuator. The controls must be designed in a way so that in the event of a malfunction, i.e., if the control substance (compressed air for the actuator and/or electrical power for the 3-way solenoid valve) fail, the internal safety valve automatically seals tightly.

By attaching an additional element, the in-tank valve can also be opened or closed manually. This attachment must be removed for the valve to operate automatically.

The PROTEGO® SI/DP is available in various nominal sizes. Optionally, the internal safety valve can be equipped with an internal nozzle to connect to a suction and filling pipe or a swing pipe system.


DN a b
150 / 6"300 / 11.81350 / 13.78
200 / 8"400 / 15.75400 / 15.75
250 / 10"500 / 19.68450 / 17.72
300 / 12"600 / 23.62500 / 19.68
Dimensions in mm / inches


HousingStainless Steel
Valve discStainless Steel
Valve spindleStainless Steel
Spindle sealingPTFE

Data Necessary for Specification

Stored medium
Tank height/Tank diameter (m or ft)
Jacket space L1
Tank material
Connection diameter of drain pipe, DN (mm or inch)

Selection and Design

Together with the customer our engineers design and specify the valve for each specific application. The relevant plant specifications are taken into account when defining the required nominal sizes and connection types. Also the operating temperature and resulting special operating conditions may require special materials. The mounting flange material must be compatible with the tank material. If there are special requirements for the valve or operating parameters please contact us: If necessary we will arrange for special designs.

Flange connection type

EN 1092-1; Form B1
ASME B16.5 CL 150 R.F.
Other types upon request

In-tank valve PROTEGO® SI/DP for a full containment tank System as per API 625.