Technical Documents Issued by GM > PRODUCT INTRODUCTION

Chengdu Zhiyuan Machine Science & Technology Co,. Ltd.   

Xu Zhi     Hou Liangping


China is a country of poor in oil and rich in coal. As the improvement of people’s life and the development of society, the international situation becomes more complicated. China needs to be stronger and more united and reaches the world fist class. Coal resource is crucial in the world, so the development of coal chemical industry is very important. To some point, it shows a country’s advance or not! So, we only need advanced process technology, but also advanced equipments which is the basic guarantee for long term steady production. Among them, High pressure self-energized flange ZY-LOC replacing traditional flange is very important, we can say ZY-loc made an epoch-making progress.

二.ZY-LOC Structure Principle

1. ZY-LOC Structure

A set of ZY-loc is made up of 2 clamps, 2 hubs, 1 seal ring and 4 sets of Bolts and nuts ( see Picture A).

                                    Picture 1    ZY-loc Structure

2. Sealing principles of ZY-loc and traditional

Let’s simplify traditional flange into flat welding flange. Please see the structure and stress analysis (see picture 2).

                                      Picture 2   Analyize Tranditional flange

 Metallic gasket’s rigidity is softer than flange.That bolt tightening force makes the seal ring plastic deformation and the micro gap on the seal surface will be filled, it seals in this way. That belongs to soft-sealing. But face to face sealing is perpendicular to the centre line of pipes and connecting bolts are parallel to the centre line of the pipes.  That will cause two problems.

A. Working with pressure, pipe inner pressure will make the sealing face not fit closely with each other and it will reduce its sealing capacity. This will enlarge the bolts preload force and it also enlarge the flange blending force, so the structure size is much bigger. Even so, it can’t avoid major defect that the sealing pressure in operation is lower than pre-tightness.

B. The connecting bolting is parallel to pipeline, so pipeline load (like stretching or compressing, pressure change, blending, torque, shock, etc) increases in operation. And the bolting will first bear the load, it will also decrease the pre-tightness and impact the sealing capacity.

This is why traditional pipeline can’t avoid the problem of leaking in high temperature and high pressure circumstances.

ZY-loc, R&D by Chengdu Zhiyuan Machine Science and Technology Co,. Ltd., thoroughly changed the sealing way of traditional flange and improved the entirety quality of pipelines.




Picture 3  ZY-LOC’s structure and sealing principle


ZY-loc structure and sealing principle (see picture 3). High pressure self-energized flange relay on elastic deformation of seal ring’s lip (T-arm) to seal and it is hard-sealing. The seal ring is “T” structure, its rib and lip functions respectively. The rib bears the force and the lip responsible for sealing. The rib, HUB, clamp and pipe become an integral entirety. The lip and hub become an elastic seal by twice external force (the first force is from bolting and the second from pipe internal pressure “P”). And the clamp become the main stressed part (ZY-loc is different from traditional flange whose stressed part is bolts). This kind of structure can make the T seal ring bear the force 360°. It shows in Picture 3.  

a) α<β,the T-ring’s lip and HUB become closer and closer under the pressure of external force and be self-energized and pressure-energized.

b) When bolts tightened, “h” is near to 0, and from the initial seal and the internal pipe pressure rises and falls continuously. T-ring will expand or contract, the lip varies flexibly and forms the self-energized seal.

c) T-ring, under the protection of HUB, bearing the force 360°, is not disturbed by outside force. It is like a mechanic spring, which can be used repeatedly without beyond its yield limitбs.(see picture D)

d)T-ring’s material can be harder  and stronger than HUB. The change of the T-arm physical dimension depends on its sealing, which belongs to hard sealing.

e) F, F1, F2 functions directly, without the force arm H from traditional flange, so there is no torque M, which shrinks the size greatly.

Picture 4 spring theory---T-ring under twice mechanical force

f) Lip conical face is compressed or expanded at last, which is controlled strictly within the range of elastic deformation. Lip and HUB’s conical face form a interference fit and form a contacting pressure, that is initial seal pressure y0(MPa).

In pipelines, when inner pressure increases, seal lip expands outside because of inner pressure and makes the seal pressure rise up, and enhances the seal capacity, self-energized efficiencyη=△y/p

Within the regular seal lip’ conical angleη=91%~98%

 So the real seal pressure in operation: y=y0+ηp   y≥y0

y=y0+ηp   y≥y0

So, higher operation pressure and y is higher. Self-energized Zy-loc’s operation pressure P is proportional to seal pressure y. Traditional flange can’t equate with ZY-loc in sealing.

After thermodynamic calculation of thermo expansion and stretching by inner pressure of pipelines, if the some pipe bears the tensile stress σt, traditional flange’s sealing pressure will be roughly (y0t), otherwise if the compressive stress is σp, the pressure seems to be (y0t), but the two flange curve corner decrease (at the same time flange pressure distribution changed), and it decreased bolting pre-tightness force. It causes bolting easy to be disassembled and y0 decreased. At last, it is y<y0. But the two situation will not occur to ZY-loc.

  g) Clamp, designed to surround HUB 360°and divided from the centre, can even the load from seal ring and HUBs. There is an arc-shaped groove, which can reduce clamp rigidity and make clamp even the force to HUB’s conical surface. The four sets bolting are vertical to pipeline. There is no installation direction requirement for clamp.

h) The strength and stiffness of self-energized ZY-loc

Compared to traditional welding neck flange, our ZY-loc sealing principle changed, and its rational force structure make ZY-loc be light.

The seal ring’s rib can not only precisely localize ZY-loc to make sure sealing lip not bear excessive pressure, but also transfer the pressure and  bending load from one HUB to the other. As to the severe pipe load, the rib loop area is much larger than pipe’s. So, when ZY-loc material and pipe material is the same, its strength will be much higher than pipeline.

As to pipe torsion load, ZY-loc can bear much larger torque load than pipe itself. In one destruction test, the connection pipe has appeared crack, but ZY-loc was still very well.

As to pipe torque load, after several test, it proves that under the harsh torque condition, there is no looseness or damage. In one on site engineering test, ZY-loc was welded to a φ63*φ49 pipe. And there is a 1000mm big deflection, there is no leakage and parallel to pipeline. Because of the structure, the 4 sets bolts is Perpendicular to the pipe, there is less temperature affect to bolts. For example, the medium in the pipe is 360℃, but there is only 160℃ on bolts. Because the medium’s temperature transfer from HUB to clamp then to bolts, the temperature decreases gradually.

As for pressure load, under the general condition of pipeline, ZY-loc will not overload. To sum up, self-energized ZY-loc is reliable. 

i)                    Less space and light weight

As it has only four connecting bolts, compare with the traditional welding neck flange, The appearance size and weight are greatly reduced for Ly-loc.(see picture attached)

Based on the same nominal parameter, here is the comparison table of Zy-loc and traditional flange









High-pressure self-tight flange

















High-pressure self-tight flange















ANSI is the standard of American National Standards Institute, JB/ZQ4465-2006 is China national standard. As we see from the picture, Zy-loc’s outer diameter is smaller and shorter in length, also the clamp has no requirement for installation position, so it can be easier for installation. All these feature provide good condition for the whole piping designment

j) Saving investment and operating cost

It is proved in practice that in the disassembly of a traditional flange of the time, we can complete 3-8  Zy-loc disassembly. It save a lot of time and working load.

Once the product is put into use, we don’t have to do tighten the bolts regularly and reduce maintenance cost.

As the deformation of the sealing lip is controlled in the elastic range, so the sealing ring can be reused, so does the clamp and the hub. In this case, the spare parts storage will be greatly reduced.

k) Easy connecting with other parts

We have some auxiliary products which can be connected with zy-loc, such as three-way tube, elbow, valve, orifice plate, blind hub for pressure testing, switching for the blind, etc.

Others, such as the valve, pump, compressor..... Even the pressure vessel, we need to weld our hub in the joint and it can be safely connected into the system.

Even for a variety of reasons, such as the hub which is welded in the outlet pipe joint , it bore out of roundness as the heat treatment after welding. If the error is not big, we can also link into the system with our flange. Because sealing lip is essentially a thin conical shell, which has considerably geometric flexibility. It has compensation ability for the hub cone shape error. It can form secure interface sealing in the effection of inner pressing expansion. Of course, these sealing rings should have special design.

Please see the table below (Zhiyuan’s regular materials for ZY-loc).




A105, 16MnD, A350-LF2, A182-316316L etc.


A105A182-F304304 etc.

Seal ring

35CrMoA, 4140, A564-630, A638-660 etc.

Bolts and Nuts

35CrMoA, 304, 316 etc.

三、ZY-loc comparing with similar products aboard

1. As we all know all standards in the world refer to US ASME when we first set. China’s GB150 is no exception. Considering there is a big gap in China’s mechanic material’s metallographic structure, P, S content, synthesized mechanical properties, and corrosion resistance, we are sound on goose when we formulate GB150, so security coefficient is high, allowable stress is low and big corrosion allowance. ZY-loc is designed based on GB150, but the most important part is imported from US and west Europe. So it is safer than similar products aboard.

2. Products aboard allow 10-15% plastic deformation (They think it is safe and reliable), while ZY-loc’s design are 100% elastic deformation. ZY-loc is safer and ZY-loc’s compensation ability for deformation is higher.

3. There are only US Grayloc, UK Vector, Italy G-loc and China ZY-loc four kinds of similar products. Though basic principle is the same but the sealing angle, width, and protector against scouring are different. They can’t be exchange with each other.

4. Zy-loc delivery time is shorter. Usually it is 2 months, because clamps which cost longest time before have had moods and clamps, precision forgings, are in high quality and nice in surface. However, foreign products need 6 months or even longer.

5. Zhiyuan can solve all kinds of manufacture and engineering problems on site, ie. Erodos coal-direct-to-oil project, Sichuan Tianhua BDO project, Xinjiang Meike BDO project are the best on site example.

6. Zy-loc price is only 1/3 of foreign products.

四、Zy-loc’s application

1. Zy-loc are used in China Shenhua first 1000 thousand ton/year coal-direct-to- oil plant, size from DN15 to DN600, pressure P=28MPa, T=470℃, material from carbon steel to stainless steel(304, 316L, 347H, high temperature alloy steel A638). ZY-loc have been well-used since 2008. For the project, they imported clamp connector of Grayloc, Vector and G-loc from abroad. But on site, different size, different parts and different brands are mixed together. And clamp parts losing, installation error problems came out. That delayed the project operation time. “Chengdu Zhiyuan” , like a good rain after a long drought, helped in time. We know the difference of the 3 brands and their structure. So we design and manufacture different ZY-loc which can match them. We meet Shenhua’s project need. Moreover, hydrogenation reactor is made by India. Its HUB (DN450 F321) was deformed for not properly thermal treatment, so the seal ring can’t be installed. They invited foreign experts in high price, but didn’t solve the problem. At that moment, it is “Chengdu Zhiyuan” again who  helped. We used China’s design principle, and made non-standard seal ring by compensation method. At last, we solved the problem and it has been well-used till now.

  Dalian Jinzhong chose our Zy-loc and used in 2010 FMOT plant exported to Belarus, Zy-loc are well performed without any quality problems.

2. Sichuan Jiangyuan Machine Co,. Ltd. bought all the clamp connector (Zy-loc) used in Shanxi Chemical Engneering Group 60 thousand ton/year and 100 thousand ton/year1.4-BDO project, P=35MPa, medium (hydrogen, BDO etc) flammable and easy to explosive.

3. “Xinjiang Meike” 100 thousand ton/year 1.4-BDO project was used US Grayloc, but different kinds of problems came out when installation and working. Meike arranged 4 experts to “Chengdu Zhiyuan” consulting and inspecting. And our engineers also went on site to direct their working. At last, they think that “Chengdu Zhiyuan” is the real company who can R&D, manufacture, and solve problems on site. And they said they will use ZY-loc to replace Grayloc gradually in future. The initial ZY-loc has been sent to Xinjiang.

4. When Shanxi BDO Chemical Engineering Company invited bid for 100 thousand ton/year 1.4-BDO project, the designing institute required that only foreign clamp connectors can be used, otherwise the engineering quality can’t be secured. So the company had to import and they chose Grayloc at last. But the delivery time was delayed. They need dozens of clamp connectors immediately and asked for 25 days to finish it. “Chengdu Zhiyuan” worked overtime for this and met their demand in the end.  

5. “Sichuan Tianhua” 60 thousand ton/year 1.4-BDO project has been used for one year. Among the clamp connectors, big size and complex structure ones are ZY-loc. Being used till now, there is no leakage and no problem. Vice versa, there are problems for Grayloc installation. And the owners are buying from “Chengdu Zhiyuan” again and again.

6. ZY-loc have been used in Hubei Huaqiang Group’s synthesis ammonia equipment and Urea equipment, Sichuan Honghe Group’s synthesis ammonia and Caustic soda projects, Tangshan Steel Group’s roiling mill etc. They all worked very well and there is none rejected goods control record.

五. The work that “Chengdu Zhiyuan” is doing

1. We are planning to set up a bigger and better Zy-loc factory in Guanghan (near Chengdu), Sichuan. It planned to be finished this year.

2. ZY-loc clamp now have moods from DN25 to DN250, we will gradually make more, till DN500. The precision forgings are nice both in quality and surface. It is better than foreign similar products. It can meet the demand of different fields.

3. We are cooperating with Sichuan Jingkong Valve Co, Ltd. We have signed Technical Cooperation Agreement. That Zy-loc connect with valve fills a valve blank in China.

4. We are negotiating with “Sulzer Pump” for ZY-loc connecting with their pump. Sulzer is our honest client and we are both Shenhua Group’s supplier.

5. Sinopec East China Designing Institute’s experts advise that Zy-loc should stand on highlight of system engineering. It can be used in electricity, gas, instrumentation fields. That will help the whole system to be much safer and steadier. We are looking for excellent suppliers in these fields.

6. Although ZY-loc have been mature now, we are still R&D in 3 sides.

a. size≥DN600

b. Zy-loc connecting with special petroleum and petrochemical equipments

c.T≤ -100℃ and T≥600℃, we are looking for materials that can meet this temperature.

d. Doing simulation test of high erosion and scouring

e. Doing strength limit test


Chengdu Zhiyuan Machine Science Technology Co,. Ltd. established in March, 2002. We have many engineers with rich experience and they use to work in R&D institutes and China owned big enterprises for many years. We R&D for nearly 10 years and we have experienced innumerable trials and hardships without government’s support or sponsor. All the scientific research funds is from the profit of our engineering EPC. Now ZY-loc has been used in country’s high-end equipment, like world class harsh working condition----coal-direct-to-petroleum project, SEI petroleum refining, hydrogen projects, and synthesis ammonia, urea, steel roiling projects, and high temperature pipelines, export to USA, Switzerland, Turkmenistan, Oman, Belarus, etc. Thousands of ZY-loc have been used, but there is no rejected record. We have earned the honor from customers! We filled the blank in this field in China. In fact, we have analyzed foreign technical, and we keep the positive attributes of flash, while removing the negatives. We researched and designed our own ZY-loc. But we meet the problem that in the market people always think foreign products are better than “Made in China”, in the end foreigners earned much money from Chinese.

     Society is changing and transforming. There is a big market for ZY-loc. If we only relay on ourselves, it is not enough. We need more and more excellent experts, cooperators in different fields to support and help us! Let’s work together for China’s better future!

© 2014 Chengdu Zhiyuan Machine Science & Technology Co., Ltd. / TEL:028-85266505 85266063 85266506 / FAX:028-85266506-8009 /
ADD:D1-1301, Fund International Plaza, No. 6, Hangkong Road, Chengdu, Sichuan