15-1000
(1.03-68.9)
40 0,6 0,017
20 0,3 0,0085
1500
(103.4)
60 0,9 0,026
30 0,45
0,013
2000
(137.9)
80 1,2 0,034
40 0,6 0,017
2500 (172.4)
100
1,5
0,043
50
0,75
0,021
3000 (206.8)
100
1,5
0,043
60
0,9
0,026
4000
(275.8)
100 1,5 0,043
80 1,2 0,034
5000
(344.8)
100 1,5 0,043
100 1,5 0,043
6000
(413.7)
100 1,5 0,043
100 1,5 0,043
Sapag Safety Valves Series 8400/8500/8490/8590
Installation and Maintenance Instructions
Emerson reserves the right to change the contents without notice
page 8
Seat Leakage Tests
Ambiguous terms such as “bubble tight”, “drop tight”, “zero leakage” and “commercial tightness” are
sometimes used to describe seat tightness. These terms, however, lack uniform definition and true practical
meaning.
• Test Procedure
API Standard 527 provides a standard for “commercial” tightness and has been adopted by industry and
users in order to clarify testing methods and tightness criteria. This standard applies to flanged inlet nozzle
type pressure relief valves.
• Test Apparatus
A typical test arrangement for determining seat tightness for pressure relief valves per API Standard 527 is
shown in Figure 4. Leakage is measured using a 5/16 in. OD tube with 0.035 in. wall. The tube end is cut
square and smooth, is parallel to and 1/2 inch below the surface of the water. A snap-on type test clamp
shown in Figure 5 is available .
• Procedure
With the valve mounted vertically, the leakage rate in bubbles per minute shall be determined with pressure at the
pressure relief valve inlet raised up to and held at 90 percent of the set pressure (or cold differential test pressure -
CDTP) immediately after popping. This applies except for valves set at 50 psig or below, in which case the pressure
shall be held at 5 psig below the set pressure immediately after popping. The test pressure shall be applied for a
minimum of one minute for valves of inlet sizes through 2”; two minutes for sizes 21/2”, 3” and 4”; five minutes for
sizes 6” and 8”. Air (or nitrogen) at approximately ambient temperature shall be used as the pressure medium.
• Tightness Standard
a. Metal-to-Metal Seated Valves. The leakage rate in bubbles per minute shall be observed for at least one minute
and shall not exceed the values indicated in table 6 below.
b. Soft Seated Valves. For soft seated valves there shall be no leakage for one minute (zero bubbles for one minute).
Table 6 - Maximum seat leakage rate - Metal seated pressure relief valves
Set
Effective Orifice Sizes 0.307 In
2
and Smaller
Effective Orifice Sizes Larger than 0.307 In
2
Pressure
Max. Bubbles
Approximate Leakage Rate
Max. Bubbles
Approximate Leakage Rate
PSIG
per Minute
Per 24 Hours
per Minute
Per 24 Hours
(BarG)
Standard
Standard
Standard
Standard
Cubic Feet
Cubic Meters
Cubic Feet
Cubic Meters
• Sapag Seat Tightness Standard-Liquid Service Valves (Style 8500/8590)
Sapag liquid service pressure relief valves are checked for seat tightness by a quantitative seat
leakage test.
All of the test fluid passing through an assembled valve is collected and measured per the
following test procedure:
1. The inlet pressure is adjusted to a test pressure which is 90% of the Cold Differential Test
Pressure.
Valves set below 50 psig are tested at 5 psig below the cold differential test pressure.
2. The test pressure is maintained for a period of not less than ten minutes.
• Allowable Leak Rate
The maximum allowable leakage rate should not exceed 10 cubic centimeters per hour per inch of
diameter of nominal valve inlet size. For nominal valve sizes of 1 inch or less, the leakage rate shall
not exceed 10 cubic centimeters per hour. For soft seated valves there shall be no leakage for one
minute.
• Soft Seated Valves
For exceptional seat tightness, Sapag offers an O-ring soft seat design. Refer to Figure 13 on page
15.
The Sapag soft seat design will provide a valve that has no visible leakage at a test pressure of 90
percent of the set pressure or cold differential test pressure. Soft seated valves are tested using
the same test procedure used for metal-to-metal seated valves.
Figure 4 - Typical test arrangement
Figure 5 - Seat leak apparatus for 150
& 300 lb. outlets 1 inch through 10
inch sices
Note: the cover plate should be
fitted with a suitabble device to
releive body pressure in case of
accidental popping of valve
Note: the tube must
be bent so that reservoir runs
parallel to face of coverplate
Tube 5/16” O.D. x 0.0035” Wall
7.92 mm O.D. x .88 mm Wall
Cover plate
Air receiver
