Number of Safety Valves on a Steam Boiler

[Keef]

I am looking for a definitive answer to how many safety valves are require on a saturated steam shell boiler. I am aware of two standards that mention the required quantity - BS2790:1992 (which states only 1) and BS6759: Part 1:1984 (which says that boilers with an evaporation rate of more than 3700kg/h must befitted with 2 safety valves or 1 double seated valve). I am aware of the UK boiler manufacturers only using one safety valve on all sizes of boilers and I have made attempts at obtaining clarification as to which standard is in force - to which I have received ambiguous answers!

 

[TTT]

Australian Standards would require 2 pressure safety valves, one must be spring-loaded type

 

[GeraldV]

Hi -

BS 6759 is more inline with BS 1113 (water tube boilers), you must stick to your manufacturing code that you are using, unless it refers you to BS 6759 for the rules.

Over and above the code you must also be aware of your countries statutory requirements.

Regards,

Gerald

 

[shipvibration]

1. each boiler requires atleast 1 safety v/v but if heating surface exceeds 500sq.ft then another v/v is required.
also if the boiler is electric powered with power input >500kw, then more than 1 v/v is reqd.
when more than 1 v/v of differing size is fitted then the relieving capacity of the small v/v is to be not less than 50% of the larger v/v.
minimum relieving capacity of safety v/v is max.steaming rate of the boiler.
UK conditions state >100sq.m heating surface area of a boiler require 2 safety v/vs. (hope i am correct on this)
hope this info helps.