HYDRO TESTING OF VALVE AS PER API 598
API 598 states that the hydro test pressure maximum is determined using yield strength.
- For body shall test pressure shall be 1.5 times the pressure rating .
- Where as for Disc seat Hydro test will be 1.1 times of the pressure rating.
In Oil & Gas sector valves need to be tested as per API 598 standard only to be suitable for the stringent requirement in refinery sector.
Testing valves at different
pressure rating as per API 598 is as follows:-
|
Rating |
Design pressure as per rating |
Shell test pressure |
Seat Test Pressure |
|
PN10 |
10 bar |
15 bar |
11 bar |
|
PN16 |
16 bar |
24 bar |
17.6 bar |
|
#150 |
21 bar |
32 bar |
23 bar |
|
#300 |
52 bar |
78 bar |
57.2 bar |
|
#600 |
104 bar |
156 bar |
114.4 bar |
|
#900 |
150 bar |
22 5 bar |
165 bar |
- Shall test pressure on
Body
- Seat test pressure on Disc
As per the above table is was
understood that as the rating increase design pressure also increase hence the
shall test pressure and it is to be noted that soft seat will not sustain and
will break away in the high pressure and are successful till pressure rating of
#150 class only. As at #300 pressure rating i.e 52 bar design pressure
were the shall testing is required to be done at 78 bar which is itself a
very high pressure, soft seating even PTFE will break up so , it was found that
vendors to pass the valve, do shall testing at 1.1 times (i.e. 58 bar) on shall
test in place of 1.5 times (78 bar). Which is a very wrong practice and
could lead to catastrophic accident in refineries and petrochemicals as due to
sudden surge or break up valve disc seat will break up as soft seat is not
designed to sustain and perform at such a high pressure , they are suitable
only for normal pressure and medium like water mostly.
We are attaching the API 598 Table 2 & 3 illustrating the shall test and seat test pressure mark ups on the design pressure for your kind pursual and reference .
We hope our above given justification will fulfill your requirement and will able you to take a right decision in betterment of project.
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