LPDC casting water pressure leakage test, pressure parameters, holding time, and leakage cause investigation

LPDC casting water pressure leakage test, pressure parameters, holding time, and leakage cause investigation
Hydraulic pressure testing is the final sealing verification of shell, valve, and water-cooled chamber castings. Many castings pass X-ray inspection and leak during pressure testing; Leakage is not necessarily caused by pores, but by intergranular looseness, cold insulation, microcracks, and machining damage.
1、 Compression pressure, holding time, and medium quantification standards
Conventional hydrostatic test pressure: 1.5 times the rated working pressure of the casting; The minimum holding pressure for shell types is 3-5 minutes; High pressure valves maintain pressure for 5-10 minutes.
Pressure medium: clean water, add rust inhibitor to prevent rusting inside the cavity; The water temperature should be controlled between 20-40 ℃, as low-temperature water can easily cause pressure readings to drift.
Requirements before compression: The inner cavity of the casting should be cleaned thoroughly, and the aluminum shavings and release agent residue should be blown clean; The sealing gasket for the plug is made of water-resistant rubber, and the tightening torque is standardized.
Judgment criteria: no pressure drop during the holding period, no water seepage, water droplets, or sweating on the outer surface; Slight sweating is often caused by slight looseness, and it will slowly leak later on.
Xinfeng Machinery provides customers with matching pressure fixtures and plug solutions, distinguishing between dry pressure and wet pressure testing standards.
2、 Classification and location investigation of leakage defects
Point leakage: isolated pores, single point looseness, mostly from melting hydrogen content and local gas holding;
Linear leakage: cold insulation, micro hot cracks, intergranular looseness, distributed along the fusion line and at the junction of ribs;
Facial sweating: Large areas scattered and loose, poor sequential solidification, insufficient pressure retention;
Leakage after machining: Internal loose channels are opened through machining and cutting, and X-rays may not be visible before machining.
Pressure sequence: First, pre charge and exhaust the air with low pressure, then slowly increase the pressure. It is forbidden to suddenly increase the pressure and impact the expansion of microcracks.
3、 Differences in overseas customer suppression testing control
Southeast Asian customers have a short pressure holding time, and slight sweating allows for infiltration and repair. Once the re pressing is approved, the product will be released.
North American car water-cooled shell, automatic recording of pressure data, archiving of pressure curves, direct rejection of any pressure drop, and does not accept infiltration remediation even if sweating.
European customers distinguish between type testing and online sampling. Type testing involves holding pressure for a long period of time to verify long-term sealing.
The shell of Middle Eastern construction machinery has high working pressure, with a compression ratio increased to 1.75 times, extended holding time, and zero tolerance for slight sweating.
4、 Pressure leakage failure chain
Filling and holding, insufficient degassing → subcutaneous pores → pressure point leakage;
Gate shrinkage failure → looseness of hot joints → surface sweating and leakage;
Structural stress concentration → micro thermal cracking → linear leakage;
Machining cutting too deep → opening up internal loose channels → leakage only after machining.
5、 Long tail traffic layout ideas
Low pressure casting water pressure test, pressure leakage test, shell sealing test, aimed at quality engineers and quality inspectors.
keywords LPDC casting hydrostatic test、pressure housing leak test low pressure casting；
Problem class: Hydro test pressure 1.5 times working pressure aluminum casting;
Comparison class: Air lean test vs water hydro test for aluminum housing.
Suitable for quality control of sealed pressure parts special page.
6、 Common misconceptions in the industry
Misconception 1: If there is no leakage during pressure suppression, it is completely qualified. Some micro looseness will not leak during short-term pressure maintenance, but gradually leak after long-term pressure cycling.
Misconception 2: Intense pressure testing is faster, and impact pressure can spread small cracks, causing misjudgment and scrapping.
Misconception 3: All leaks can be repaired by infiltration, while crack leaks cannot be cured by infiltration, and they may recur after pressure fluctuations.
FAQ
Q: What is the standard pressure multiple for hydrostatic testing?
A: Rated working pressure 1.5 times.
Q: How long does a regular shell hold pressure for?
A：3–5min。
Q: Why do we need to exhaust air before suppression?
A: Air can be compressed, causing inaccurate pressure readings.
Q: What are the common defects of point leakage?
A: Isolated pores or single point looseness.
Q: What are the common causes of linear leakage?
A: Cold insulation and slight thermal cracking.
Q: North American shell compression requirements?
A: Archive the pressure curve, reject directly for pressure drop and sweating.
Q: What are the reasons for newly added leakage after machining?
A: Cut and open up internal loose channels.
Q: Pressure medium water temperature?
A: 20-40 ℃, reduce pressure drift.