US 7,031,851 B2 · Method of determining valve leakage based on upstream and downstream temperature measurements

Abstract

Disclosed is a method for measuring leakage flow rate of a valve wherein fluid flows through the valve in a single-phase flow of a gas or steam. The underlying principle upon which the leakage flow rate may be determined is that the heat loss across a length of bare pipe located downstream of the valve causes a decrease in the temperature of the leakage flow. Also disclosed is a method for measuring the leakage flow rate when the fluid passing through the valve transitions from a liquid-phase flow into a two-phase flow of liquid and steam. In two-phase flow, the underlying principle upon which the leakage flow rate may be determined is that any leakage of the valve will cause an increase in the pressure on the downstream side of the valve because of frictional resistance to flow in the downstream piping which corresponds to an increase in temperature thereof.

Claims13

Dependent claims

A method for detecting leakage across a valve having an inlet and an outlet and being fluidly connected to a second pipe section of length (L) having first and second ends, the first end being connected to the outlet, wherein fluid is in single-phase flow at the inlet, the method comprising the steps of:

measuring a temperature (T2-1) of a surface of the second pipe section at the first end;
measuring a temperature (T2-L) of the surface of the second pipe section at the second end thereof;
and
comparing T2-L to T2-1;
wherein substantially different values for T2-L and T2-1 indicates an absence of leakage across the valve.

2 more elements

A method for measuring a leakage flow rate of a valve having an inlet and an outlet wherein fluid is in single-phase flow at the inlet and at the outlet, the method comprising the steps of:

moving the fluid through a second pipe section of length (L) having a first end and a second end, the second pipe section being fluidly connected to the outlet at the first end;
measuring a temperature (T2-1) of a surface of the second pipe section at the first end;
measuring a temperature (T2-L) of the surface of the second pipe section at the second end;
measuring a temperature (T2-x) of the surface of the second pipe section at a predetermined distance (x) downstream of the first end;
measuring an ambient temperature (Tamb) of air surrounding the second pipe section;
and
calculating the leakage flow rate Wleak of the valve according to the formula
W
leak
=
⁢
[
.60
+
.387
[
g
⁡
(
(
T
2
-
1
-
T
2
-
L
)
2
)
⁢
D
out
3
(
T
amb
)
⁢
v
⁢
⁢
α
[
1
+
[
.559
v
α
]
9
16
]
16
9
]
1
6
]
2
⁢
κ
CpD
out
+
⁢
ɛ
⁢
⁢
σ
⁡
[
T
2
-
x
4
-
T
amb
4
]
⁢
D
out
⁢
L
⁢
⁢
π
wherein Dout=outer diameter of the second pipe section, ν=kinematic viscosity of air at Tamb, α=thermal conductivity of air at Tamb, Cp=specific heat of air at Tamb, ε=emissivity of the surface of the first pipe section, σ=Stefan-Boltzmann constant, and g=gravitational constant.

91 more elements

A method for measuring the leakage flow rate of a valve in a piping system, the valve having an inlet and an outlet wherein fluid passing through the valve transitions from liquid-phase flow at the inlet to two-phase flow at the outlet, the method comprising the steps of:

providing a vessel downstream of the outlet;
providing a first and a second pipe section, the first pipe section being fluidly connected to the inlet, the second pipe section fluidly connecting the outlet to the vessel;
moving the fluid from the first pipe section, through the valve, through the second pipe section and into the vessel;
measuring a temperature (T1) of a surface of the first pipe section;
measuring a temperature (T2) of a surface of the second pipe section;
measuring a pressure (P2) of the fluid within the vessel;
determining a saturation pressure (P2s) of the fluid within the vessel by correlation to temperature T2;
determining a density (ρ2-0) of the fluid within the vessel by correlation to the saturation pressure P2s;
determining frictional losses (Kp2) for the second pipe section;
and
calculating a leakage flow rate Wleak according to the formula
W
leak
=
ρ
2
-
0
⁡
(
D
i
⁢
⁢
n
2
)
2
⁢
π
⁢
2
⁢
(
P
2
⁢
⁢
s
-
P
2
)
ρ
2
-
0
⁡
[
K
p2
]
wherein Din=inner diameter of the pipe.

50 more elements

Dependencies are inferred from the claim text.

Method of determining valve leakage based on upstream and downstream temperature measurements

Life of this patent

Method of determining valve leakage based on upstream and downstream temperature measurements

Life of this patent

Abstract

Claims13