7D Single Spring Mechanical Seal
The 7D single spring mechanical seal is built for heat and speed. With an O-ring pusher design rated to +200C and 18 m/s, it runs where standard single spring seals fade - hot water, thermal media, and high-speed two-pole motor pumps. Shaft sizes 10 mm to 100 mm, pressure to 0.8 MPa. Contact us for quotation!
The 7D trades the higher pressure rating of pusher seals like the Z2 for a wider temperature and speed window. That makes it the right single spring mechanical seal for moderate-pressure pumps that get hot or spin fast - not for high-pressure duty, where a balanced or multi-spring seal is the better choice.
The 7D single spring mechanical seal is built for heat and speed. With an O-ring pusher design rated to +200°C and 18 m/s, it runs where standard single spring seals fade - hot water, thermal media, and high-speed two-pole motor pumps. Shaft sizes 10 mm to 100 mm, pressure to 0.8 MPa. Buy the 7D single spring mechanical seal direct from the Qixing factory in China at OEM and wholesale pricing.
The 7D trades the higher pressure rating of pusher seals like the Z2 for a wider temperature and speed window. That makes it the right single spring mechanical seal for moderate-pressure pumps that get hot or spin fast - not for high-pressure duty, where a balanced or multi-spring seal is the better choice.
When the 7D Is the Right Choice
Three conditions point to the 7D over a standard single spring seal:
- High media temperature. At +200°C with FKM O-rings, the 7D handles hot water, hot oil, thermal fluid and hot condensate that would harden or extrude the elastomer in a standard seal rated to +150°C.
- High shaft speed. The 18 m/s rating covers fast two-pole motor pumps and boosters. On a 50 mm shaft that is roughly 6800 rpm of surface speed headroom - well above standard single spring limits.
- Moderate pressure. Below 0.8 MPa the 7D is efficient and long-lived. Above it, step up to a balanced O-ring or multi-spring seal; the 7D is not a high-pressure design and should not be specified as one.
Why the O-ring Pusher Design Suits Heat
The 7D uses an O-ring as the secondary seal that slides axially along the shaft (a pusher design) rather than a fixed rubber bellows. Two things follow. First, the O-ring can be FKM, which holds chemical and thermal stability to +200°C where NBR and EPDM cannot. Second, the pusher action lets the seal face track wear and thermal growth at high temperature without losing contact - the reason the 7D keeps sealing through the thermal cycling that opens up bellows seals. SiC/SiC or SiC/Carbon faces dissipate the frictional heat generated at 18 m/s, keeping the running interface within tolerance.
Specifications
| Parameter | Value | Parameter | Value |
| Shaft diameter | 10 mm to 100 mm | Stationary face | SiC / TC / Carbon |
| Temperature | -30°C to +200°C | Rotary face | SiC / Carbon / TC |
| Pressure | ≤ 0.8 MPa | Secondary seal | FKM / EPDM / NBR (O-ring) |
| Shaft speed | ≤ 18 m/s | Spring & metal | SS304 / SS316 |
| Construction | Single spring, O-ring pusher, bi-directional | Rotation | Both directions |
Dimensions Chart
All dimensions in millimetres. Shaft diameter d is measured at the seal cavity. The 7D covers 10 mm to 100 mm across 33 standard sizes.
| Model | d | D7 | D6 | D3 | L3 | L4 |
| 7D-10 | 10 | 21.00 | 17.0 | 19.00 | 15.00 | 7.00 |
| 7D-12 | 12 | 23.00 | 19.0 | 21.00 | 18.00 | 7.00 |
| 7D-14 | 14 | 25.00 | 21.0 | 23.00 | 22.00 | 7.00 |
| 7D-16 | 16 | 27.00 | 23.0 | 26.00 | 23.00 | 7.00 |
| 7D-18 | 18 | 33.00 | 27.0 | 29.00 | 24.00 | 10.00 |
| 7D-20 | 20 | 35.00 | 29.0 | 31.00 | 25.00 | 10.00 |
| 7D-22 | 22 | 37.00 | 31.0 | 33.00 | 25.00 | 10.00 |
| 7D-24 | 24 | 39.00 | 33.0 | 35.00 | 27.00 | 10.00 |
| 7D-25 | 25 | 40.00 | 34.0 | 36.00 | 27.00 | 10.00 |
| 7D-28 | 28 | 43.00 | 37.0 | 40.00 | 29.00 | 10.00 |
| 7D-30 | 30 | 45.00 | 39.0 | 43.00 | 30.00 | 10.00 |
| 7D-32 | 32 | 48.00 | 42.0 | 46.00 | 30.00 | 10.00 |
| 7D-33 | 33 | 48.00 | 42.0 | 46.00 | 39.00 | 10.00 |
| 7D-35 | 35 | 50.00 | 44.0 | 49.00 | 39.00 | 10.00 |
| 7D-38 | 38 | 56.00 | 49.0 | 53.00 | 42.00 | 13.00 |
| 7D-40 | 40 | 58.00 | 51.0 | 56.00 | 42.00 | 13.00 |
| 7D-43 | 43 | 61.00 | 54.0 | 59.00 | 47.00 | 13.00 |
| 7D-45 | 45 | 63.00 | 56.0 | 61.00 | 47.00 | 13.00 |
| 7D-48 | 48 | 66.00 | 59.0 | 64.00 | 47.00 | 13.00 |
| 7D-50 | 50 | 70.00 | 62.0 | 66.00 | 46.00 | 14.00 |
| 7D-53 | 53 | 73.00 | 65.0 | 69.00 | 56.00 | 14.00 |
| 7D-55 | 55 | 75.00 | 67.0 | 71.00 | 56.00 | 14.00 |
| 7D-58 | 58 | 78.00 | 70.0 | 76.00 | 56.00 | 14.00 |
| 7D-60 | 60 | 80.00 | 72.0 | 78.00 | 56.00 | 14.00 |
| 7D-63 | 63 | 83.00 | 75.0 | 81.00 | 56.00 | 14.00 |
| 7D-65 | 65 | 85.00 | 77.0 | 84.00 | 66.00 | 14.00 |
| 7D-68 | 68 | 90.00 | 81.0 | 88.00 | 64.00 | 16.00 |
| 7D-70 | 70 | 92.00 | 83.0 | 89.60 | 64.00 | 16.00 |
| 7D-75 | 75 | 97.00 | 88.0 | 98.00 | 64.00 | 16.00 |
| 7D-80 | 80 | 105.00 | 95.0 | 100.00 | 72.00 | 18.00 |
| 7D-85 | 85 | 110.00 | 100.0 | 107.50 | 72.00 | 18.00 |
| 7D-90 | 90 | 115.00 | 105.0 | 111.00 | 72.00 | 18.00 |
| 7D-95 | 95 | 120.00 | 110.0 | 119.00 | 72.00 | 18.00 |
| 7D-100 | 100 | 125.00 | 115.0 | 123.80 | 72.00 | 18.00 |
Applications
- Hot water circulation - boiler circuits, heating systems, hot service water
- Thermal oil and heat-transfer fluid pumps (FKM O-ring)
- High-speed booster and two-pole motor pumps
- Condensate and hot-well pumps in steam plant
- Light chemical transfer at elevated temperature and moderate pressure
- OEM pump platforms specifying a high-temperature single spring mechanical seal
Manufacturing
Faces lapped to ≤ 0.0009 mm flatness and verified optically. FKM O-rings qualified for the +200°C service range. Each 7D single spring mechanical seal is dimension-checked and spring-load tested before packing; Certificate of Conformity and material certificate ship with the order on request.
Quotation
Send the shaft size, media temperature and shaft speed for a same-day quotation. Stock sizes ship 3-7 days; OEM custom orders 15-25 days. Buy the 7D single spring mechanical seal direct from the Qixing factory in China at OEM and wholesale pricing.
Hot Tags: China 7D Single Spring Mechanical Seal Manufacturer, Supplier, Factory
Related Category
- Single Spring Mechanical Seals
- Multi Spring Mechanical Seals
- Cartridge Mechanical Seals
- Chemical Pump Mechanical Seals
- Rubber Bellow Mechanical Seals
- Sanitary Pump Mechanical Seals
- Grundfos Replacement Mechanical Seals
- Flygt Replacement Mechanical Seals
- Alfa Laval Replacement Mechanical Seals
- Mechanical Seal Components
Send Inquiry
Contact Info
-
Address
Unit 102, Building 7, Huiding Chuangzhi Park, No. 277 Shengyuan Road, Fenghua District, Ningbo City, Zhejiang Province, China
-
Tel
-
Request a quotation from Qixing for mechanical seal purchase, OEM customization, bulk orders, factory price and professional sealing solutions.
