HAM-LET® H-900 Relief Valves

The Ham-Let® H-900 Series is a relief valve for low pressure service.

The valve is normally closed.

It will open when the system pressure reaches the set level. It will re-close when the system pressure fall below the set level.

Setting and Resealing Pressure

  • Upstream set pressure is the first indicator of flow process. Every pressure relief after the first indication is repeatable within a deviation of 5% at room temperature.
  • Blocked upstream set pressure is the first indicator of a stopped flow process and is always lower than the set pressure.
  • Calculation of set pressure valve design demands back pressure consideration as the system back pressure increases the set pressure. To balance the system the back pressure must be multiplied by 0.8 and the result shall be subtracted from the required set pressure.


  • The H-900 relief valve designs have been tested for Proof and Burst.
  • Every valve is factory tested for proper set and resealing performance.


  • H-900 relief valves gradually open when pressure increases.
  • As such, they are not certified to ASME due to not having capacity rating at a given pressure rise (accumulation)

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