FAQs of PPR Stainless Steel Insert

1. What is the difference between PPR stainless steel inserts and Brass inserts?

Plumberstar PPR stainless steel inserts (304/316 material) and brass inserts differ most in valve compatibility, application scenarios, and supporting services.
In terms of valve matching, Stainless steel inserts are made to the same standard as Plumberstar PPR valves. Size tolerance is ±0.1mm, ensuring a perfect fit for the connection. The material won’t react chemically with valve seals. It’s ideal for industrial-grade high-pressure and corrosion-resistant valves.
Brass inserts are different. They easily cause electrochemical corrosion when paired with stainless steel valves. They’re only suitable for low-pressure civil use. Plus, lead leaching issues restrict their application.
In terms of application scenarios, Stainless steel inserts are well-suited for harsh, high-demand environments. In industrial pipelines, coastal municipal water supply systems, the food and medical sectors, and HVAC systems. Service life is 10–15 years, delivering great long-term cost performance.
Brass inserts are only recommended for ordinary civil low-pressure cold water systems. The service life is only 5–8 years, and regular replacement is necessary.
Other differences: Stainless steel inserts support non-standard customization and OEM services. They also come with full foreign trade support, including door-to-door logistics and customs clearance documents. You can combine them with valves to cut costs.
Brass inserts have weak customization capabilities. Foreign trade certifications are incomplete, and after-sales protection is limited.

2. PPR stainless steel insert stamping process is divided into which steps?

From OneMonroe

Plumberstar Stamping Forming Process

Multi-Station Continuous Stamping Technology

Plumberstar manufactures a multi-station continuous stamping process for stainless steel inserts, comprising five core forming stages. Each stage is strictly controlled to ensure dimensional accuracy, structural strength, and long-term reliability.

1. Raw Material Cutting

Stainless steel coils with a thickness range of 1.2–3.0 mm are used, selected according to the insert size
(e.g., DN15: 1.2 mm, DN110: 3.0 mm).
Cutting dimensional tolerance: ≤ ±0.1 mm
Cutting speed: 30–50 pcs/min
Burr control: optimized cutting parameters to prevent edge burrs on the coil material
This step ensures uniform material preparation and stable downstream forming.

2. Preforming (Cylindrical Blank Forming)

The cut stainless steel sheets are pressed into a cylindrical primary blank using precision molds.
Pressing pressure:
8 MPa for small-size inserts
15 MPa for large-size inserts
Forming temperature: room temperature
Roundness tolerance of the blank: ≤ 0.05 mm
This guarantees consistent geometry and avoids deformation in subsequent steps.

3. Sawtooth (Serration) Forming

Serrations are pressed onto the outer wall of the cylindrical blank using a progressive stamping die.
Serration height: 0.3–0.5 mm
Tooth pitch: 1.0–1.5 mm (larger sizes use larger pitch)
Forming method: 2–3 serrations per station
This multi-step forming method avoids metal fatigue that could occur with single-step stamping, ensuring strong mechanical bonding during PPR hot-melt fusion.

4. Double-End Flaring

Both ends of the cylindrical insert are flared to improve pull-out resistance and sealing stability.
Flare diameter: 1.0–2.0 mm larger than the main body diameter
Flaring pressure: 5–10 MPa
Flaring angle: 15°–30°
Strict control ensures no cracking or wrinkling at the flared sections.

5. Shaping, Trimming & Initial Airtightness Test

Final shaping and trimming are performed using calibration dies.
Outer diameter & length tolerance: ±0.1 mm
Burr height after trimming: ≤ 0.02 mm
After trimming, each insert undergoes an initial airtightness test:
Test pressure: 0.5 MPa
Holding time: 10 seconds
Acceptance criteria: no leakage

3. What is the thread machining process for threaded PPR stainless steel inserts? 

Threaded Insert Manufacturing – Rolling Thread Process

Plumberstar threaded inserts use a rolling thread process, instead of traditional cutting. This method preserves the integrity of the metal fibers and prevents strength loss due to fiber breakage, resulting in enhanced thread strength and improved sealing performance.

1. Thread Pre-Forming

After the insert body is stamped, a pre-rolling die is used to form the thread blank.
Thread angle: 60°, compliant with both metric and American standards
Pre-rolling pressure: 10–12 MPa
This step prepares a uniform thread profile and ensures stable conditions for final rolling.

2. Precision Thread Rolling

Final thread forming is completed on a high-precision thread rolling machine (ISO accuracy grade 4H).
Rolling speed: 15–20 rpm
Thread accuracy:
6g for metric threads
2A for American threads
Thread pitch tolerance: ≤ ±0.02 mm
Lead error: ≤ ±0.01 mm
The rolling process produces dense, smooth threads with high dimensional consistency and strong load resistance.

3. Thread Inspection & Valve Matching Test

From each production batch, 20 samples are inspected using Go / No-Go gauges in accordance with GB/T 197.
Go and No-Go gauges must screw in smoothly
The No-Go gauge insertion depth must not exceed 2 threads
At the same time, the threaded insert is tested with a Plumberstar valve of the same size to verify real installation performance:
Manual screwing without jamming
Airtightness test after assembly: 0.8 MPa, holding 10 seconds, no leakage
This dual inspection ensures full compatibility between the insert and the valve thread in actual use.

4. How to control the roundness error of the insert in the production process?

Roundness Control by Mold Accuracy and Process Inspection

Plumberstar controls roundness through a double guarantee: precise molds and regular process checks.

1. Mold Accuracy Control

Stamping dies are made from Cr12MoV tool steel, with a hardness of HRC 58–62.
The roundness tolerance of the die inner hole is ≤ 0.03 mm
The die is recalibrated after every 10,000 inserts produced
This prevents roundness deviation caused by long-term mold wear.

2. In-Process Inspection

During production, roundness is checked regularly.
Every 500 inserts, 10 samples are measured
Testing equipment accuracy: 0.001 mm
Insert body roundness: ≤ 0.05 mm
Flared ends roundness: ≤ 0.08 mm
This ensures stable shape control throughout the whole production process.

3. Out-of-Tolerance Handling

If abnormal roundness is found, for example, a batch reaching 0.1 mm, production is stopped immediately.
The mold is adjusted or repaired, such as by replacing the guide sleeve or correcting the mold bore
All out-of-tolerance products are scrapped and not allowed to enter the next process
This prevents defective parts from flowing into assembly or delivery.

5. Can you provide a sample support for the PPR stainless steel Insert?

Sample Support Service

1. Sample Options
We can provide 1–5 standard samples in different sizes, such as DN25 or DN32 inserts in 304 stainless steel.

2. Sample Cost

Standard samples: Free for first-time customers
Shipping: Express cost paid by the customer (collect or prepaid)
Custom samples: For non-standard designs, a sample fee of RMB 500–1,000 applies
The full sample fee is refundable after a bulk order is placed

3. Delivery & Documents

Shipping by DHL or FedEx
Delivery time: 3–7 working days
Sample shipments can include material certificates and test reports, making it easy for customers to evaluate quality

6.  Can you provide a “valve +PPR stainless steel insert” package solution?

One-Stop Integrated Solution from Plumberstar

1. Coordinated Product Selection
Based on the customer’s piping system, we recommend the right valves (such as PPR ball valves or globe valves) together with matching inserts in the correct material, size, and surface finish.
This ensures full compatibility and avoids fitting problems caused by incorrect self-selection.

2. Integrated Packaging for Easy Installation
Valves and inserts are packed as complete installation sets.
For example, one valve is packed with two matching inserts, and each connection position is clearly labeled, such as “Inlet valve + DN25 insert”.
This helps customers identify parts quickly and install them correctly on site.

3. Cost Optimization
Customers who purchase valves and inserts together receive a 10%–15% combination discount.
Shipping costs are calculated based on combined weight, which is 20%–30% lower than ordering the items separately.

7. What is the core competitive advantage of the PPR stainless steel inserts?

As a professional valve manufacturer, Plumberstar produces inserts and PPR valves under the same unified production standards. This includes ball valves, globe valves, and balancing valves.

From the start, all key parameters are fully aligned.
The material composition uses 304 / 316 stainless steel, which complies with GB 4806.9 and FDA food-contact standards.
Dimensional tolerances strictly follow GB/T 18742.3 and ISO 15874.
Pressure ratings are matched to S3.2 / S4 / S5 pipeline systems.

Because the standards are synchronized, the insert and valve fit perfectly by design.
For example, the DN25 insert thread and flare size are precisely matched to the inlet and outlet of the DN25 PPR valve. Customers can assemble the parts directly, without modification or adjustment. This avoids common problems such as installation jamming, misalignment, or leakage caused by size differences found in universal inserts.

8. How flexible is the factory with design changes of the PPR stainless steel Insert?

For design changes to PPR stainless steel inserts, Plumberstar has built a clear and efficient response system. Changes are handled based on size and complexity, allowing adjustments to be completed with minimal delay.

Minor changes
For small adjustments, such as changes in thread type or surface finish, no new mold is required.
The technical team can complete parameter updates within 24 hours, and the production line can switch over and restart within 48 hours.

Medium-level changes
For changes like slight size adjustments or anti-slip thread structure optimization, modular tooling is used.
This greatly reduces mold modification time. The full adjustment cycle takes 3–5 days, much faster than the industry average of 7–10 days.

Major changes
For larger changes, such as new structural designs, the R&D team participates directly in the process.
Design proposals are provided within 72 hours, and mold making with the first samples can be completed in 10–15 days, keeping pace with customer project schedules.

9. Can mixed container loading of the PPR stainless steel Insert be supported?

Flexible LCL Shipping Support

We offer strong flexibility for LCL shipments.
PPR stainless steel inserts with the same specifications can be packed together. They can also be shipped together with other Plumberstar products, such as PPR ball valves, stainless steel filters, and water separator fittings.

Customers can freely mix different models and materials in one shipment, based on their real order needs. There is no need to ship inserts in separate full cartons. This helps reduce logistics costs, especially for small or trial orders.

Protective Packaging for Safe Transportation

To reduce the risk of damage and product mixing during LCL transport, Plumberstar uses a layered protection packaging system.

Each PPR stainless steel insert is packed in an individual PE bag. This protects the threads from scratches and prevents surface corrosion.
Products with different specifications or categories are packed into separate cartons with clear identification. Foam padding is added inside the cartons to absorb impact and reduce vibration.