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Technical Parameters of Lug Type Valves
| Parameter | Typical Specification |
|---|---|
| Design | Fully lugged body with threaded bolt holes, concentric or double offset |
| Body material | CF8, CF8M, CF3M (A351); ductile iron with stainless disc on request |
| Disc material | 304, 316L, duplex, PTFE-coated disc |
| Stem material | 304, 316, 17-4PH, 2205 duplex |
| Seat material | EPDM, NBR, FKM, silicone, PTFE, RPTFE, metal |
| Size range | DN40 to DN600 (1.5 inch to 24 inch) |
| Flange drilling | PN10, PN16, ASME Class 150, JIS 10K; dual drilling available |
| Thread of lugs | UNC / UNF for ASME flanges, metric (M) for EN / JIS flanges |
| Pressure rating, both flanges | Typically 10 to 16 bar for concentric designs; higher for double offset |
| Pressure rating, dead end | Reduced, typically to about half of the full rating, depending on size and design |
| Working temperature | -10 °C to +120 °C EPDM; -20 °C to +180 °C PTFE; higher for metal seat |
| Operation | Lever, gear, pneumatic, electric, with ISO 5211 pad |
Dead-end service rating
Dead-end service means the valve is used with a flange only on one side, so that the valve alone holds back the line pressure when the other side is open. Because the lugs and bolts carry the load, the pressure rating is reduced. Every lug valve we supply comes with its dead-end pressure rating, listed by size, and we advise using a blind flange on the open side for safety.
Please note whether your application needs dead-end service when you ask for a quotation, because a specially reinforced body or full-length bolting may be needed.
Lug Valve Range and Installation Accessories
Lug valves are chosen mostly for flexibility during installation and maintenance. To support that, we supply them with the studs, nuts, gaskets and blind flanges that make a complete joint, and with actuators and accessories that turn them into automated valves.
| Product | Size Range | Typical Use |
|---|---|---|
| Lug butterfly valve, lever operated | DN40 to DN200 | Water, HVAC, general fluids |
| Lug butterfly valve, gear operated | DN200 to DN600 | Large lines and isolation |
| Lug butterfly valve, pneumatic actuated | DN40 to DN600 | Process automation |
| Lug butterfly valve, electric actuated | DN40 to DN600 | Remote control and building services |
| Double offset lug butterfly valve | DN50 to DN600 | Steam, hot water, higher pressure |
| Lug check valve and spacers | DN40 to DN300 | Backflow prevention and spacing |
| Blind flanges, studs, nuts and gaskets | DN40 to DN600 | Dead-end and joint completion |
| Position switches, solenoids and positioners | Matched to valve | Automation accessories |
Why contractors choose lug valves
- Easier maintenance: one section of pipe can be taken apart while the other remains in service, if a blind flange is fitted.
- Dead-end capability: useful at the end of a line, on tank connections and at future extension points.
- Stable installation: the valve is bolted individually to each flange, which reduces movement.
- Wide compatibility: dual drilling covers several flange standards with one valve.
If your pipeline does not require dead-end service or one-side removal, a wafer valve may be more economical, and we will tell you honestly which suits the job better.
Buyer tip: state in the inquiry whether a valve will be used for dead-end service, because it affects body design, bolt length and price. For a mixed order, mark each valve line as either through-line or dead-end, so we can propose the right design for each position and avoid paying extra where it is not needed.
Standards for Lug Type Butterfly Valves
Lug valves follow the same family of standards as wafer valves, with added requirements for lug threads and dead-end rating. Below are the references we use when producing and testing lug type valves.
| Area | Standard Reference |
|---|---|
| Butterfly valve design | API 609 (Category A lug type), EN 593, MSS SP-67, MSS SP-68 for high-pressure types |
| Face-to-face length | EN 558 Series 20, ISO 5752, API 609 |
| Compatible flanges | ASME B16.5 Class 150, EN 1092-1 PN10 / PN16, JIS B2220 10K, DIN 2501 |
| Lug thread | ASME B1.1 (UNC), ISO 261 / ISO 262 (metric) |
| Actuator mounting | ISO 5211 |
| Pressure and temperature ratings | ASME B16.34 (where applicable), EN 12516, manufacturer ratings for rubber seats |
| Material | ASTM A351 CF8 / CF8M / CF3M |
| Testing | API 598, EN 12266-1, ISO 5208 |
Specify lug thread type. A lug valve for ASME flanges uses inch threads such as 5/8-11 UNC, while one for EN flanges uses metric threads such as M16. Mixing them damages the threads and gives a weak joint, so please state the flange standard and bolt size in the inquiry.
If a customer requires API 609 compliance, please say so in advance. Some models are built and tested to the full requirements of that standard, while others follow EN 593 only.
Reference note: MSS SP-67 and API 609 address butterfly valves in different ways, particularly on body strength and testing. Many projects ask for API 609 Category A lug type valves in Class 150, and we can prepare the documents that support that request before production begins. Please tell us early whether your specification refers to these standards, so that our design and test plan match it from the first drawing.
Certificates and Approvals for Lug Valves
Lug valves frequently go into isolation duties, such as shutting off equipment for maintenance, where safety is critical. Documentation therefore needs to show not only material quality, but also pressure performance and, where relevant, dead-end rating.
- Material certificate: EN 10204 3.1 for body, disc and stem, with heat numbers.
- Pressure test report: shell test and seat test in both directions, per API 598 or EN 12266-1.
- Dead-end rating declaration: stating the pressure rating for dead-end service per size.
- Lug thread inspection report: thread gauge results for sampled valves.
- Seat compliance documents: FDA, EU or WRAS and NSF 61 statements for suitable seats.
- CE and PED: available for qualifying models.
- Fire safe test reports: available for selected double offset designs.
- Quality management: ISO 9001 style system with batch records.
Be precise about dead-end ratings. Marketing claims of "full pressure dead-end service" appear on some low-cost valves without backing test data. We state the actual tested rating and give recommendations for safe installation, which protects your installers and your customers.
Sample certificate packs are available before order placement.
Audit tip: keep the dead-end rating table with the valve data sheets for each project. Maintenance teams often forget the reduced rating, and having it in the project file prevents unsafe practices later, such as removing a downstream flange with the line still pressurised. We can print the rating on a nameplate or label on request, so it stays with the valve, even after the project documents are archived.
Traceability for Lugged Bodies and Fasteners
The lugs carry the bolt load, so their quality matters as much as the valve body itself. A lug valve also uses many bolts, which may be supplied by the contractor, and the grade of the bolts affects the joint. Our traceability records cover the body, the lug threads, the disc, the stem and the seat.
- Body casting: heat number and grade are stamped on each body, with foundry records for chemistry and heat treatment.
- Lug thread control: tapping programmes are labelled by thread type, with gauge checks at the start and during the run.
- Disc and stem: bars and castings are received with certificates and verified by PMI.
- Seat moulding: compound batch, cure date and hardness are recorded.
- Assembly and test: serial numbers link the body, disc, seat and test results.
- Bolting recommendation: studs and nuts supplied with the valve are marked with grade and lot, with certificates on request.
| Item | Record | Purpose |
|---|---|---|
| Body | Heat number and certificate | Proof of material and strength |
| Lug threads | Thread type, gauge result | Secure bolting and no cross-threading |
| Disc and stem | PMI and lot number | Corrosion and torque capacity |
| Seat | Compound batch and hardness | Sealing and compatibility |
| Bolting | Grade mark and lot | Joint integrity |
A mix-up of inch and metric threads is a frequent field error, so we mark the thread type on the body or the carton, and record it in the packing list.
Thread mix-up prevention: inch and metric lug threads look similar and are among the most common sources of site errors. We mark each carton, and each body where possible, with the thread type, and the studs we supply match that marking, so installers can check before beginning assembly and avoid damaging the lugs.
Testing Capability for Lug Valves
Lug valves are tested for pressure integrity and sealing, as other butterfly valves are, but we add checks on the lug threads and, when specified, a dead-end test with one side blanked.
| Test | Method | Frequency |
|---|---|---|
| Shell test | Hydrostatic at 1.5 times rated pressure | 100% of valves |
| Seat test, both directions | Hydrostatic at 1.1 times rated pressure | 100% of valves |
| Low-pressure air test | Compressed air under water | 100% of resilient-seated valves |
| Lug thread inspection | Thread gauges for UNC or metric lugs | First article and sampling |
| Dead-end test | Valve fitted to one flange with the other side open, pressurised to the stated rating | Type test, on request for production lots |
| Operating torque | Torque tester at stem or actuator pad | Sampling, 100% for actuated valves |
| Dimension check | Face-to-face, flange drilling, stem square | First article and sampling |
| PMI | XRF analyser for body, disc and stem | Incoming and sampling |
| Cycle test | Repeated open and close operation | Type test or on request |
Dead-end testing is not routine on all valves, because it requires special fixtures. It is normally done as a type test on a sample from each design and size group, and the result is documented in a report. If your project needs a dead-end test on each valve, we can add it, with a small extra charge.
You are welcome to attend any test, or ask for a video of the setup and pressure gauge.
Why a type test is useful: a dead-end type test shows that a design can hold the stated pressure with one flange open, including the bolts, lugs and seat retention. It is done once for each design family and size group, and the report remains valid as long as the design and materials stay unchanged.
Frequently Asked Questions about Lug Type Valves
Q: What is dead-end service?
It is a duty where the valve alone holds back the pressure because the downstream flange has been removed or is not installed. Lug valves can do this with reduced pressure rating, while wafer valves cannot.
Q: Is the dead-end rating the same as the full rating?
No. It is normally lower, often about half, because the bolting and lugs carry the load. Our data sheet lists the actual dead-end rating by size.
Q: What bolts should I use with a lug valve?
Use two sets of shorter bolts or studs, one for each flange, with proper thread engagement. Bolt length depends on flange thickness and lug depth, and we can supply the correct length with the valve.
Q: Can I use a lug valve in place of a wafer valve?
Yes, in most cases. A lug valve fits between the same flanges, and costs a little more. It adds flexibility for maintenance and end-of-line use.
Q: Are lug valves suitable for chemical media?
With a 316L or duplex disc and a PTFE or RPTFE seat, yes for many chemicals. Check compatibility of the whole wetted path, including the stem sealing and any coating.
Q: Do lug valves need extra gaskets?
With resilient seats, the seat face acts as the gasket. For PTFE or metal-seated valves, add flange gaskets as recommended.
Q: What flange standard is the lug thread based on?
For ASME Class 150 flanges, the lugs are threaded in UNC sizes, and for PN10, PN16 or JIS flanges, in metric sizes. Dual-drilled valves use a mix, and are marked accordingly.
MOQ and Pricing for Lug Valves
Lug valves cost a little more than equivalent wafer valves because of the additional machining and tapping. We keep minimum quantities modest so that contractors can order for single projects.
| Item | Typical Terms |
|---|---|
| Sample order | 1 to 3 pieces per model |
| Standard MOQ | 20 to 50 pieces per size, mixed sizes accepted |
| Actuated valves | Small quantities accepted; actuator brand and voltage to be specified |
| Double offset valves | Project quantities, from 1 piece in larger sizes |
| Pricing basis | EXW, FOB Ningbo, CFR or CIF in USD |
| Quote validity | 30 days, adjusted for stainless steel price changes |
| Payment | 30% T/T deposit, 70% before shipment; L/C at sight for approved accounts |
Price comparison guide
As a rough guide, a lug body costs about 10 to 25% more than a wafer body in the same size and material, because of the lugs and threading. In return, you get dead-end capability and one-side removal. For double offset designs, the price is higher again, reflecting more complex machining and metal or PTFE seats.
- Size and material: main cost drivers, as with other valves.
- Seat type: PTFE and metal seats raise the price.
- Operator and accessories: actuators, positioners and switches are quoted separately.
- Dead-end test: unit testing adds a small charge.
If you only need isolation with flanges on both sides, ask us for a wafer alternative to compare cost and risk.
Ordering advice: if some positions in your system might become end-of-line in the future, such as extension points on a header, choose lug valves for those positions at the start. The small additional cost can save a shutdown and valve replacement later, when a new branch is added to the system.
Lead Time, Customisation, Packaging and Trade Terms
Lead time and stock
Standard lug butterfly valves in popular sizes can ship in 20 to 30 days. Actuated assemblies, double offset designs and large sizes usually need 35 to 55 days. If you need part of an order earlier, we can split the shipment.
Customisation
We can customise lug thread type, flange drilling, disc material, seat material, stem material, operator, handle colour, coating and marking. For retrofit projects, we can copy the dimensions of an existing valve and match drilling and face-to-face length.
Packaging
- Valve with the disc slightly open to avoid seat compression
- Protective covers on both faces to protect the seat and lug threads
- Individual cartons for small sizes, wooden cases or pallets for larger valves
- Studs and nuts packed separately and labelled with thread type and size
- Neutral or customer-branded packing on request
Shipping and trade terms
| Term | Details |
|---|---|
| Incoterms | EXW, FOB Ningbo, CFR, CIF, DAP |
| Port | Ningbo-Zhoushan; Shanghai as an alternative |
| Transport | Sea freight, air freight for urgent items, express courier for samples |
| Documents | Invoice, packing list, bill of lading, origin certificate, material and test certificates |
We can ship lug valves together with blind flanges, gaskets and studs in one consolidated order, so the complete installation kit arrives together.
Installation advice: tighten the bolts in a cross pattern, check that the disc can open freely before final tightening, and use a blind flange on any open end. We include a short installation note with our valves on request, to help contractors avoid common mistakes that cause leaks or damage the seat.
