When encountering issues with a tensile testing machine, it's important to start by inspecting the physical appearance of the device. Check for any oil leaks from the hydraulic pipes, such as leaks at the joints, cracks, or sand holes. Also, examine the oil valves, including the delivery valve and return valve, as well as the oil cylinder, for signs of leakage.
(1) If the return valve handle is tightened but oil continues to flow through the drain pipe, this suggests that the return valve is not sealing properly. The issue may be due to a poor seal between the valve needle and the valve body.
Solution: Loosen the nut on the valve needle slightly, then push the needle handle inward. Use one wrench to hold the nut sleeve while another hand turns the needle handle inwards. Afterward, turn the nut sleeve back out a bit and tighten it again. This usually resolves the issue. If the problem persists, the valve needle and nut sleeve may be mismatched, and replacing the nut sleeve could help.
(2) If the delivery valve handle is fully opened, yet there is still a large amount of oil overflowing from the overflow pipe and the load cannot increase, several potential causes exist:
1. The damping gap between the damper rod (valve needle) and the valve body is too small, leading to insufficient pressure compensation in the rear chamber of the piston. As the piston moves backward, the oil pumped from the pump flows directly back into the tank through the overflow valve.
Solution: Replace the damper rod or rework the flat surface of the rod to increase the damping gap.
2. Contaminants like solid particles may be present on the piston and piston sleeve surfaces. These can cause abrasive wear, resulting in the piston sticking or moving unevenly, which keeps the overflow port open.
Solution: Remove the fixed wire behind the delivery valve, take out the piston and sleeve, and polish them using an abrasive rod and sandpaper.
(3) If the working cylinder’s drain pipe is leaking a significant amount of oil and the test machine cannot be loaded, consider the following reasons:
1. The oil viscosity is too low.
Solution: Replace the lubricant with a higher viscosity oil.
2. The clearance between the cylinder and piston is too large.
Solution: Repair or replace the piston if necessary.
(4) If no issues are found with the oil supply, return, or working piston valves, check whether the oil pump is producing sufficient high-pressure oil.
Testing method: Close the return valve and open the supply valve. If no oil flows from the overflow pipe, the issue likely lies with the oil pump. Disassemble and inspect the pump. Common problems include:
1. A failed or broken return spring, causing inadequate suction or discharge from the piston.
Solution: Replace the spring.
2. Faulty steel balls in the inlet and outlet valves, often caused by impurities blocking the one-way valve seat.
Solution: Remove the front nut, extract the valve seat, and clean it. If worn, use a special tool to attach a new steel ball and grind it until it fits properly. Severe damage may require replacing the entire seat.
3. Poor sealing at the high-pressure oil pipe joint. If the gasket fails, oil will leak, preventing proper pressure buildup.
Solution: Replace the aluminum washer at the connection point.
4. Excessive clearance between the plunger and sleeve, or a loose sleeve, causing oil to collect in the oil collector and increasing internal back pressure, preventing the plunger from resetting during suction.
Solution: Clean the pump, replace the plunger, or tighten the sleeve nut.
(5) Insufficient oil in the tank can also cause problems. When applying a certain load, you might hear a "plop" sound from the overflow pipe, indicating low oil levels and air bubbles. If the load stops rising and no oil flows from the overflow pipe, it's time to top up the oil.
Solution: Add oil to the tank until the level reaches halfway up the sight glass.
(6) A clogged oil filter mesh inside the fuel tank can restrict oil flow, reducing the pump's output.
Solution: Cover the oil spill valve with a hose, run the pump to expel oil, drain the remaining oil, remove the filter mesh, and clean it in gasoline or diesel. Wipe the tank’s bottom and reinstall the filter.
(7) A loose drive belt can cause slippage, preventing the pump from operating properly under load.
Solution: Adjust the belt tension by loosening the motor bolts, tightening the tension bolt, and then securing the bolts again. If the belt is worn or damaged, replace it entirely.
(8) If the oil collector is not properly pressed against the pump body, it can lead to improper operation under load.
Solution: Tighten the fixing nut at the end of the oil collector. If the issue remains, remove the collector and replace the "O" ring between the collector and the pump body.
Yuhai piezo materials include : hard piezo material, soft piezo material and lead free piezo material
Soft piezo material exhibits: larger piezoelectric constants, higher permittivity, larger dielectric constants, higher dielectric losses, larger electromechanical coupling factors, low mechanical quality factors, a lower coercive field, poor linearity, and is easier to depolarize. The ideal application of soft piezo materials is sensing needs. Yuhai soft pizeo materials are PZT-5, PZT-5H, PSnN-5 and PLiS-51.
Hard piezo material exhibits: smaller piezoelectric constants, lower permittivity, smaller dielectric constants, lower dielectric losses, smaller electromechanical coupling factors, high mechanical quality factors, a higher coercive field, better linearity, and is harder to depolarize. The ideal application of hard piezo materials is high power transducer needs. Yuhai hard pizeo materials are PZT-4, PZT-8, PCrN-4 and PBaS-4.
Yuhai company developped lead free piezo material BaTiO3 and apply for the Chinese Patent in 2011, to meet the needs of environmental protection in today's society.
Piezoelectric ceramic material
Properties and Classification
General description of material properties
Material Code
Properties
Application
Soft PZT ceramic
PZT-51
Characteristics:
larger piezoelectric constants, higher permittivity, larger dielectric
constants, higher dielectric losses, larger electromechanical coupling
factors, low mechanical quality factors, a lower coercive field, poor
linearity, and is easier to depolarize.
low-power ultrasonic transducers
PZT-52
low-frequency sound transducers
PZT-53
applications with high g coefficient, for example,
PZT-5H
microphones,vibration pickups with preamplifier
PLiS-51
low-frequency vibration measurements
PMgN-51
Hydrophones, transducers in medical diagnostics
PSnN-5
Actuators
Hard PZT ceramic
PZT-41
Characteristics: smaller
piezoelectric constants, lower permittivity, smaller dielectric
constants, lower dielectric losses, smaller electromechanical coupling
factors, high mechanical quality factors, a higher coercive field,
better linearity, and is harder to depolarize.
PZT-42
High-power acoustic applications
PZT-43
Hydroacoustics, sonar technology
PZT-82
piezomotor
PCrN-4
PBaS-4
Lead free piezo ceramic
BaTiO3
Characteristics: Low density, low curie temperature, lead free.
Ultrasonic transducers suitable for low-temperature underwater, for example ultrasonic transducer in fishfinder
Piezoelectric Material,Piezo Ceramic Element,Piezo Electric Cylinder ,Piezo Sphere
Zibo Yuhai Electronic Ceramic Co., Ltd. , https://www.yhpiezo.com