RU2100790C1 - Process testing leak-proofness of articles - Google Patents

Abstract

FIELD: test of connections of pipe-lines operating under conditions of passage of high-temperature gas. SUBSTANCE: proposed process consists in feed of gas and helium high-pressure mixture into article heated to temperature at which article functions, in continuous evacuation of mixture from closed space with the aid of two pumps - pump of leak detector and mechanical pump and in determination of leak by formula. Technical result of invention lies in simplification of technological circuit of testing bed thanks to absence of leak detector in main line of additional mechanical pump continuously evacuating intensive gas liberation. Leak of connection is defined more exactly by formula with allowance for productivity of pumps. EFFECT: enhanced authenticity of process.

Description

 The invention relates to the field of testing products for leaks, and in particular to methods for testing the tightness of pipe connections working with a duct of high-temperature gas.

где Q_эт величина гелиевого потока, выходящего из диффузионной течи (л. мкм.рт.ст./с);
С процентное содержание гелиево-воздушной смеси (см. ОСТ 92-1527-89, с. 83-86).A known method of monitoring the tightness of assemblies of pipe joints, according to which the joints of these compounds are isolated from the environment using covers, forming a closed volume. A high pressure air-helium mixture is supplied to the assembly. If the compounds are leaking, helium penetrates into the confined space, and its concentration is fixed using the probe of the leak detector PTI (see OST-92-1527-89, p. 22-32). The process proceeds in statics and requires a helium content in the air of at least 10%
There is also a known method of tightness control, according to which the sealed cavity around the assembly of the pipe connection is evacuated using a mechanical vacuum pump and a vacuum pump included in the IPT. The helium-air mixture is pressurized to the piping assembly. The leakage of the connection of the pipelines is determined by IPI taking into account the effect of diffuse leaks α _y , α _floor according to the following formula:

where Q _{et the} magnitude of the helium flux emerging from the diffusion leak (l. µm.rt.st / s);
With the percentage of the helium-air mixture (see OST 92-1527-89, p. 83-86).

Evacuation of a closed cavity around the assembly of the connection of the pipelines is carried out in two stages. The mechanical vacuum pump works for the time during which the vacuum is created (10 ^-2 ), after which it is turned off, and this line is closed. Further evacuation of the closed cavity is carried out using a PTI pump.

When testing the nodes of the leak in the dynamic mode, when a high-temperature medium (700-800 ^o C) high pressure passes through the node, intense gas evolution from the structural elements of the node into a closed cavity occurs. To ensure the operation of IPT in such conditions, it is necessary to continuously evacuate a closed cavity using an additional mechanical pump (i.e., do not turn it off, as is done in the prototype). However, in this case, it is necessary to take into account the entrainment of helium, which penetrated through the connection into the closed cavity, along the line in which the mechanical pump is installed. This problem can be solved by installing an additional PTI on this line, but this will complicate the process of leak testing and require additional material investments.

 The objective of the invention is to provide a method for testing nodes for leaks in dynamic mode with a flow through the product of a high-temperature gas medium with the introduction of at least 2% helium into it and measuring helium leaks from the joint into a closed cavity only along the PTI line with a continuously running additional mechanical pump.

где V₁ производительность насоса ПТИ (л/с)
V₂ производительность вспомогательного механического насоса (л/с)
Q_эт величина потока индикаторного газа, выходящего из гелиевой течи (л. мкм.рт.ст./с);
α_c величина отклонения стрелки измерительного прибора от потока гелия, прошедшего через микронеплотность стыка (В);
α_эт- величина отклонения стрелки прибора от гелиевой течи (В);
с процентное содержание гелия в рабочем газе, прошедшем через сборку (% ).This problem is solved by supplying a gas-helium mixture to the product, heated to the temperature at which the product operates; evacuation of a closed cavity is carried out continuously during the test by a mechanical pump and a PTI pump along parallel lines, and the leakage of the product is determined by the formula:

where V _{1 the} productivity of the pump PTI (l / s)
V ₂ performance auxiliary mechanical pump (l / s)
Q _{et the} value of the flow of the indicator gas emerging from the helium leak (l. Μm.rt.st / s);
α _c is the deviation of the needle of the measuring device from the helium flow passing through the micro-tightness of the joint (B);
α _et - the deviation of the arrow of the device from the helium leak (B);
with the percentage of helium in the working gas passing through the assembly (%).

 An example implementation of the method.

It is necessary to check the tightness of the flange connection of the line at a gas-gel mixture pressure of ≈150 kG / cm ² and temperatures of ≈750 ^o C with a sensitivity of at least 1 • 10 ^-3 l.mkm.hg / s.

Before work, a patch camera is installed around the flange joint. A PTI device and a mechanical vacuum pump are connected in parallel to this chamber. At the inlet of the flange connection serves gas at a pressure of P ≈150 kG / cm ² and a temperature of T ≈750 ^o C, which is released into the environment. Helium ≈2% of the gas flow rate is introduced into the same gas line. After 6-7 minutes of heating the flange connection, with continuously operating vacuum pumps with a capacity of 1 l / s PTI and a capacity of 3 l / s of a mechanical pump, they begin to control the tightness of the flange connection.

Upon reaching a vacuum in the overhead chamber ≈8 • 10 ^-2 mm Hg a working helium leak detector is connected to it, which is checked for a helium leak on a measuring device. In our example, α _et ≃ 1.5B.
Then, leakage is measured by the presence of helium that has penetrated into the overhead chamber, and from it to the line where the PTI is installed, while helium is not measured in the line with an additional mechanical pump. In our case, the PTI device displays α _c 40 V.

Based on the obtained measurement data, the leakage of the flange connection is determined with the following data:
V ₁ PTI pump capacity 1 l / s
V ₂ productivity of the mechanical vacuum pump 3 l / s
Q _et 5 • 10 ^-5 l.m.km.Hg / s;
α _et 1.5 V; with 2%

Claims (1)

A method of monitoring the tightness of products by supplying a high-pressure gas-helium mixture to them, evacuating a closed cavity around the product by means of an auxiliary vacuum pump and a pump included in the leak detector, monitoring the gas-helium leak penetrating from the product into a vacuum cavity connected to the leak detector, characterized in that the gas-helium mixture fed into the product heated to the temperature at which the product operates, evacuation of the closed cavity is carried out continuously during the test by two of us wasps, and the leakage of the product is determined by the formula

where V _{1 the} performance of the mechanical pump of the leak detector, l / s;
V ₂ productivity of the auxiliary vacuum pump, l / s;
Q _e value _t tracer gas stream exiting the helium leak l • mm Hg / s;
α _c is the deviation of the arrow of the measuring device from the helium flow passing through the micro-tightness of the joint, V;
α _et - the deviation of the arrow of the measuring device from the helium leak, V;
C the helium content in the working gas passing through the assembly,