Shijiazhuang Zhengrong Pump Co., Ltd. is a professional manufacturer and exporter of slurry pump. It, established in 1998, has three production base, of which the ZR series production base covers about 60000㎡ with modern factory and office buildings.
ZR is equipped with mobile sand mixer, automatic reproduction line of resin sand, mobile type sand mixer and eight medium frequency electric furnaces. The maximum weight of the workpiece is 20 tons and the annual production is 5000 tons. As for the conventional pieces, our company has a large number of product inventory, so the delivery date is usually within 10 days.
                                   Shakeout Machine                                                                     Electric Furnace
Physical and chemical lab
Our company has professional chemical laboratory, physical laboratory and measuring room to conduct the product component analysis, metallographic analysis, hardness test and ultrasonic testing. The furnace material elements testing adopts the most advanced material inspection equipment—Original Germany direct reading spectrometer to ensure the material ratio meeting requirement. And ZR controls strictly every process to guarantee that all products satisfy the production need. 
ZR owns a large scale mould base with various models and a majority of advanced aluminum mold to produce a variety of industrial pump castings. At the same time, ZR also equips the most advanced EPC casing line to meet the special requirement for casting, OEM and processing with supplied drawings.
                                   Mould Base                                                                                    Mould
ZR has 3 heat treatment furnaces with a capacity of 60 cubic meters and the largest furnace is of 5100L*4600W*1560H (mm).
Equipped with large machine processing workshop, our factory owns 20 machine tools like CNC vertical lathe, horizontal lathe, drilling machine, milling machine and digital display floor-type boring machine and the total processing capability is 300 tons per month. The maximum processing diameter is 6300mm and the maximum loading of the machine tools is 30 tons.
                Machine Processing Workshop                                                                    Machine Tool
Established with large pump test station whose accuracy meets the international standard, ZR is able to complete the research and development of new products and materials independently to provide the best products and materials applying to various conditions.
                     Assembling Workshop                                                                     Pump Test Station

1. Material improvement
The basic components of AO5/GLH-1 used in slurry pump domestic and abroad are as follows:

Material  Cr  Ni  Mo  Cu 
A05/GLH-1  2.3-2.8  24-26  0.4-0.6  0.6-1.0  1.5 

Problems: The thick-walled waste components in the mineral separation field of other manufacturers were conducted cross-section observation. It shows that the cross-sections present obvious layer and the middle layer was of coarse particles and slightly loose. Besides, the transmitting slurry is of smaller particles having little impact force.

Improvements: our company has adjusted the materials as follows:

Material  Cr  Ni  Mo  Cu 
A05  2.8-3.0  26-27  0.7-1.0  0.6-1.0  1.5 

Validation: The hardness is improved from HRC56-60 to HRC60-64, and the service life increases by over 30%.
2. The improvement of casting technology compared with Warman Pump (take the front guard plate for example)
The original problems: at the root to the entrance of the front guard plate occurs shrinkage porosity, which is a small hole formed at the solidification zone of the castings not being filled with liquid metal. The front guard plate scrappage caused by wear out on the shrinkage porosity accounts for 85% of the total cover board scrappage.
Improvement time: 2012
Reasons: The confluence of the two sides is thick, located in hot spot where lacks of feeding.
1. The riser support is enlarged from φ100 to φ130 to enlarge the feeding channel for prolonging the riser solidification duration.
2. At the confluence of the two sides paves chrome ore sand to accelerate the cooling rate of the hot spot.
3. The number of riser has increased to 4 from 2, covered with insulation cotton, to delay the cooling time of the riser.
Effect verification: The shrinkage porosity degree reduced greatly and the service life increases by over 1 times. 
3. The improvement of machine processing compared to Warman 
Improved parts: guard plate, sleeve and the 15 degrees V-shaped interface.
The original foreign size and tolerance: guard plate: Φ1300 0 -0.20; sleeve: Φ1300 +0.42 +0.22
The improved size and tolerance: guard plate: Φ1300 0 -0.05; sleeve: Φ1300 +0.22 +0.12
Improvement time: 2012
1. The production bases of Warman are scattered and there were not CNC lathes in some poor areas to effectively control the accuracy. So they have to increase the fit clearance to ensure the interchangeability. But ZR owns CNC lathe to ensure the size accuracy.
2. In processing the guard plate and sleeve, the finishing stage is further refined into rough and fine finishing sections. When being fine finishing section, the machined piece is under low temperature and pressure, so the size tolerance caused by thermal expansion and contraction is controlled within 0.02mm.
3. The speed is controlled within 10r/min during the fine finishing section and the ovality of the sleeve is controlled within 0.02mm which is superior to the original ovality of 0.08mm.
Effect verification: after the improvement of the size tolerance of the 15° V-shaped interface, the parts scrappage caused by the erosion damage of the interface has not occur. 
4. Impeller improvements
1. The shrinkage porosity and air holes are obvious on the root of the riser( the supplementary part attached to the top or side of the castings to avoid the defects) and the confluence of the blade and the cover plate, with a depth of 15-30mm.
2. During the production and use of the impeller, the crack rate reaches 50%. A complete set of pump was damaged due to the crack of the impeller when operating in 2012.
Improvement time: 2013
Cause analysis
1. The cover plate and the main blade are thicker leading to a higher hot spot on the intersection which in turn need a large feeding of iron liquid. But due to a limited feeding rate on the insulation riser of 20%-25%, coupled with that the iron liquid comes from below when teeming, the iron liquid temperature no the riser is low and the feeding effect is affected.
2. The compaction no the root of the riser is not enough to prohibit the iron liquid from immerging, so the defects occur caused by the reactant air.
3. The humidity on the production field is 50%-70%, which make the sand mould/ mould core absorb moisture leading to a large gas generation for the resin sand. The gas escapes when teeming, then the air porosity occurs.
4. The internal stress in the process of casting and cooling is not fully released leading to the crack of the impeller.
1. By connecting the runner with riser, the temperature on the riser is increased to improve the supplement shrink efficiency.
2. The compaction of the sand near the riser seat is improved and the paint is conducted mainly around the riser seat with alcohol-based zircon power.



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