Search Tenders

Filters

Reset All

Tender Status

All India TendersNew TendersLive TendersArchive Tenders

T18 Ref No

All States

All Cities

All Agencies

Tender ID

Due Date

Tender Value

Tender Source (GeM, Cppp & Others)

Tender Type

114Latest Flap valve Tenders List

Name: Tender18 Infotech Private Limited
Address: B-913/914, Sivanta One The Business Park,Opp. Bank of Baroda, Pritam Nagar, Paldi ,, Ahmedabad, 380007, IN
Telephone: 7069661818
Price range: 00

Latest Flap valve Tenders in India – Verified Leads & Real-Time Insights by Tender18

Finding the right Flap valve tenders in India’s competitive e-procurement ecosystem requires more than just access—it demands accurate data, real-time monitoring, and expert analysis.

At Tender18 Infotech Private Limited, we bring deep industry experience in government procurement to help businesses identify, evaluate, and win Flap valve tenders efficiently. With a centralized platform aggregating 1100+ live tenders, we provide a single, trusted source for opportunities from central, state, and PSU departments.

Real-Time Flap valve Tender Intelligence & Monitoring

Our advanced dashboard delivers actionable insights and structured tender data, enabling you to make faster and smarter bidding decisions.

We categorize Flap valve tenders into:

Supply Tenders – BOQs and specifications sourced from GeM and PSUs
Service Tenders – NITs and scope of work from CPPP and state portals
EPC Projects – Large-scale infrastructure tenders with financial and design data

✔ This structured approach ensures complete transparency and deeper bid analysis before submission.

Comprehensive Sources of Flap valve Tenders

Tender18 acts as a centralized gateway by aggregating tenders from trusted and official sources:

Central Government Portals – CPPP, NIC, and Government e-Marketplace (GeM)
Railways & Transport – IREPS and Metro Rail projects
Power & Energy PSUs – NTPC, ONGC, NHPC, PowerGrid
Defense & Strategic Sectors – MES and DRDO tenders
State e-Procurement Portals – Gujarat, Maharashtra, Tamil Nadu, UP, and more

✔ Every listing is verified and regularly updated to maintain data accuracy and trust.

Step-by-Step Guide to Participate in Flap valve Tenders

1. Eligibility & Prequalification

Before bidding, ensure compliance with:

Financial turnover requirements (30–50% of tender value)
Past experience (2–3 similar projects)
Valid solvency certificate

2. Mandatory Documentation Checklist

Prepare the following to avoid disqualification:

Digital Signature Certificate (Class 3 DSC)
GST, PAN, MSME/Udyam registration
EMD (Earnest Money Deposit) or exemption proof
Technical bid with execution methodology

3. BOQ Analysis & Financial Bidding

The BOQ (Bill of Quantities) is the most critical component:

Analyze item-wise pricing
Ensure competitive yet sustainable quotes
Avoid underbidding risks (L1 pressure)

✔ Expert analysis can significantly improve your bid success ratio.

Why Tender18 is a Trusted Platform for Flap valve Tenders

✔ Proven Expertise in Government Procurement

We combine industry knowledge with practical bidding experience.

✔ Verified & Reliable Data

All Flap valve tenders are sourced from official portals and cross-checked for accuracy.

✔ Advanced Filtering Tools

Filter tenders by value, EMD, location, and category for precise targeting.

✔ Corrigendum & Update Tracking

Get instant alerts on deadline changes and specification updates.

✔ Historical Data Insights

Analyze past tender results to understand pricing trends and competition.

✔ End-to-End Bidding Support

From discovery to submission, including GeM onboarding and strategy.

Growth of Flap valve Sector in 2026

With the Government of India focusing on digital procurement and infrastructure expansion, the Flap valve sector has seen significant growth in e-tendering opportunities.

The rise of GeM-based procurement models like:

L1 Purchase
Direct Procurement
MSME-friendly policies

…has made it easier for startups and SMEs to participate and win contracts

Frequently Asked Questions (SEO Optimized)

How can I get daily Flap valve tender alerts?

You can register on Tender18 and select your preferred category. You will receive daily email alerts with all new Flap valve tenders.

Is EMD mandatory for all Flap valve tenders?

No, MSME and Udyam-registered businesses may get exemptions. Always check the NIT for specific conditions.

What is the difference between a Flap valve work tender and supply tender?

A supply tender involves delivering goods, while a work tender includes execution, labor, and project completion.

Can I access private Flap valve tenders on Tender18?

Yes, we also track major private sector and EPC tenders along with government opportunities.

Get Expert Support for Flap valve Tenders

Tender18 is more than a listing platform—we are your strategic partner in winning tenders.

Our services include:

Tender discovery & analysis
Documentation support
Bid strategy & submission
GeM registration & OEM onboarding

📞 Call / WhatsApp: +91 7069661818
🌐 Website: www.tender18.com

T18 Ref No : 17084155

Location : pedagantyada , andhra pradesh

NEW TENDER

corrigendum tender for overhauling of sea water valves intermediate valves and flap valves as per annexure on orv samudra ratnakar

Agency / Dept :

hindustan shipyard limited HSL

Due Date :

Sep 04, 2026 (1 day left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17071644

Location : kupwara , jammu & kashmir

Source : GEM Tenders

NEW TENDER

tender for 235 65 r17 tyre tubeless with valve ceat , 215 75 r15 tyre tubeless with valve ceat , 235 75 r15 tyre tubeless with valve ceat , 900 x 16 tyre with tube and flap ceat , 1000 x 20 tyre with tube and flap ceat, tyres, 236 65 r17 tyre tubeless with valve ceat, 215 75 r15 tyre tubeless with valve ceat, 235 75 r15 tyre tubeless with valve ceat, 900 x 16 tyre with tube and flap ceat, 1000 x 20 tyre with tube and flap ceat

Agency / Dept :

border security force BSF

Due Date :

Sep 05, 2026 (2 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17075948

Location : doda , jammu & kashmir

Source : GEM Tenders

NEW TENDER

tender for trailer control valve tata , cabin lifting pump stln , clutch booster stln , fan belt stln , clutch cyl tata , dual brake valve stln , hub bearing rear stln , sunvisor tata , head light assy mg , mud flap tata , repair kit injector assy marksman , rod spring assy stln, fan belt, trailer control valve tata, cabin lifting pump stln, clutch booster stln, fan belt stln, clutch cyl tata, dual brake valve stln, hub bearing rear stln, sunvisor tata, head light assy mg, mud flap tata, repair kit injector assy marksman, rod spring assy stln

Agency / Dept :

indian army

Due Date :

Sep 12, 2026 (9 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 16812218

Location : palghar , maharashtra

Source : GEM Tenders

LIVE TENDER

Agency / Dept :

directorate of purchase and stores DPS

Due Date :

Sep 08, 2026 (5 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 16937195

Location : visakhapatnam , andhra pradesh

Source : GEM Tenders

LIVE TENDER

tender for ee6045d-5435015 , ee6045d-5437623 , ee6045d-5774000 , ee6045d-5917800 , ee6045d-6542810 , ee6045d- 6542997 , ee6045d-6544769 , ee6106b-5430595 , ee6106b-5430646 , ee6106b-5430612 , ee6106b-5430668 , ee6106b-5430805 , ee6106b-5430834 , ee6106b-5435181 , ee6106b-5437598 , ee6106b-5490522 , ee6106b-5774002 , ee6106b-6540153 , ee6106b-6540349 , ee6106b-6541218 , ee6106b-6541708 , ee6106b-6549104 , ee6106b-70701001 , ee6106b-iv6574014 , ee6106b-m6543036 , ej4939d- 54110000 , ev4045v-5917013 , ev4045v-5959902 , ev4045v-25-2000-002 , ee6045d-5957600 , ee6106b- 5511200 , ee6106b-iv6549102 , ee6106b-iv6552314 , ee6106b-iv6552318 , ee6106b-iv6552320 , ee6106b- iv6552324 , ee6106b-iv6552325 , ee6106b-xb4ba21 , ej4939d-023200210 , ej4939d-023280060 , ej4939d- 032300100 , ej4939d-101100010 , ej4939d-34532203 , ev4045v-25-2020 , ev4045v-25-2021 , ev4045v-25-6017 , ev4045v-25-8001 , ev4045v-25-8021 , ev4045v-25-8025 , ev4045v-3rt2024-1al20 , ev4045v-6543002, 26vevc002, discharge valve separator, vaccum gauge, water valve evac 90 shock, pipe coupling 58-48.100 epdm for pipes 48-52, discharge valve, water valve, rubber bend, shut off valve, nozzle, level switch, non return valve complete, o-ring, conical rubber, pressure switch, mechanical seal for 5 5-qsh 101-f and 7.5-hk 80-1, vacuum gauge glycol filled, solenoid valve r1-2 in 2-way 230v, bearing 6206.z.nr pump 5 5-qsh 101-f vem kper, spare parts set for discharge pump, actuator 3-2, 1-8 220 ac, level switch ssp-3k, 3 way pn valve 1 1-4, spares part kit for ejector, fd valve, o ring, mini check valve - ss vacuum toilet - vts-stp p17a, coil z530a-24ac, t connection, membrane, 2 way pn valve 1, o-ring p2-437 50sh 2 s lid nbr well lub, l-connector 1-4 mx6mm black - red, o-ring seal p2-242 2-3 screen nbr s, cap seal 2 nbr, brush assembly 2 t, pushbutton, end plate suct. chamber, flap valve compl., vpc-v controller, l-coupllng, backwash valve fw004 second stage oil flushing valve bl001, first stage oil discharge valve sl002, pressure relief valve sv001 activation at 6 bars, pressure gauge, air pressure regulator, second stage oil level detection device, 12a tp ac3 duty power contractor 230 v ac aux supply, discharge valve - ss vacuum toilet - vts stp p17a

Agency / Dept :

indian navy

Due Date :

Sep 14, 2026 (11 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17050290

Location : bathinda , punjab

Source : GEM Tenders

LIVE TENDER

tender for rev selector shaft , brg tapered roller taper roller brg , mud flap , reed valve , cable assy control , elbow hose , unloader valve , anti freezer unit , solenoid , slave cylinder , drive assy , slave cyl clutch , hose , cab lift handle 78 odx11 bg thk 1 mtr , wheel nut spanner , rpm meter , parts kit hose assy non metalic , spring brake shoe retaining , tube metallic , ball bearing , air compressor repair kit , dc valve , water filter , door operating handle mech left , lock plate for grooved nut , brush carrier assy , door lock rear gate , hose demister line to swc bracket , speedometer cable , oil seal ring, lv7/stln f-3309911 rev selector shaft, lv7/stln 3110-72-0000230 brg tapered roller/taper roller brg, lv7/stln x3000650 mud flap, lv7/stln p-1008739 reed valve, lv7/stln 2590-024062 cable assy control, lv7/stln f1910160 elbow hose, lv7/stln f-7411300 unloader valve, lv7/stln f-4130200 anti freezer unit, lv7/stln p3702620 solenoid, lv7/stln x-7413400 slave cylinder, lv7/stln 6105-72-0487249 drive assy, lv7/stln f-3921800 slave cyl clutch, lv7/stln 4720-72-0000155 hose, lv7/stln 5120-423406/x-1915315 cab lift handle 7/8 odx11 bg thk 1 mtr, lv7/stln x-4700500 wheel nut spanner, lv7/stln f-7423700 rpm meter, lv7/stln 4720-016164 parts kit hose assy non metalic, lv7/stln p4300136 spring brake shoe retaining, lv7/stln 4710-042037 tube metallic, lv7/stln 3110-72-0491960 ball bearing, lv7/stln 2530-018123/p-1007451 air compressor repair kit, lv7/stln 4820-72-0484053 dc valve, lv7/stln x-4007000 water filter, lv7/stln b0n00677 door operating handle mech left, lv7/stln 5310-72-0064126 lock plate for grooved nut, lv7/stln p-3705939 brush carrier assy, lv7/stln 5340-72-0473320 door lock rear gate, lv7/stln x-1918050 3/8 hose demister line to swc bracket, lv7/stln 2520-72-0473321 speedometer cable, lv7/stln 5330-72-0268123 oil seal ring

Agency / Dept :

indian army

Due Date :

Sep 10, 2026 (7 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17034858

Location : visakhapatnam , andhra pradesh

Source : GEM Tenders

LIVE TENDER

tender for custom bid for services - hiring of services for repair and refurbishment of 08 water tight sluice valve , manufacturing of 30nos wheel and flap handles for wtsv valves onboard ship

Agency / Dept :

indian navy

Due Date :

Sep 21, 2026 (18 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17032730

Location : songadh , gujarat

Source : GEM Tenders

LIVE TENDER

tender for et-6342: ceramic lined mpo , et-6342: ceramic lined multi discharge valve (mdv) with flap & shaft

Agency / Dept :

gujarat state electricity corporation limited GSECL

Due Date :

Sep 21, 2026 (18 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 17034261

Location : nighasan , uttar pradesh

Source : GEM Tenders

LIVE TENDER

tender for m. s. fabricated pneumatic pan discharge valve (puri make) size– 600mm, 1. m. s. body. 2. flap seat o

Agency / Dept :

uttar pradesh cooperative sugar factories federation ltd UPCSFFL

Due Date :

Sep 10, 2026 (7 days left)

Tender Value :

Refer Document

View Documents

T18 Ref No : 16875201

Location : salem , tamil nadu

Source : GEM Tenders

LIVE TENDER

tender for 651010405507 bearing block for coil car cbl model , 651110405505 bearing case for ii nd inter , 651110405509 guide bush as u roll rack zm1 2 , 651110405510 adaptor spacer -as u roll for rack- zm-1 , 651110405511 non collar wheel-coil car without key , 651110405512 non collar wheel-coil car with key zm-1 , 651110405513 collar wheel - coil car without key zm-1 , 651110405514 collar wheel - coil car with key zm-1 , 651110405515 arm connecting bracket-1st inter ds , 651110450504 universal joint , 651120405516 flap dis-butterfly valve chamsan filter , 651130405517 shaft,keys for filter belt drive - sgl , 651170405506 cup for 1 st inter roll connection , 651170405518 3 roll wiper end bearing cap , 651170405521 support arm 1st inter zm-3 , 651170405522 gripper bar , 651170405523 fixed top gripper bar , 651170405524 fixed bottom gripper bar, bearing, 651010405507 bearing block for coil car cbl model, 651110405505 bearing case for ii nd inter, 651110405509 guide bush as u roll rack zm1 2, 651110405510 adaptor spacer -as u roll for rack-zm-1, 651110405511 non collar wheel-coil car without key, 651110405512 non collar wheel-coil car with key zm-1, 651110405513 collar wheel - coil car without key zm-1, 651110405514 collar wheel - coil car with key zm-1, 651110405515 arm connecting bracket-1st inter ds, 651110450504 universal joint, 651120405516 flap dis-butterfly valve chamsan filter, 651130405517 shaft,keys for filter belt drive - sgl, 651170405506 cup for 1 st inter roll connection, 651170405518 3 roll wiper end bearing cap, 651170405521 support arm 1st inter zm-3, 651170405522 gripper bar, 651170405523 fixed top gripper bar, 651170405524 fixed bottom gripper bar

Agency / Dept :

steel authority of india limited SAIL

Due Date :

Sep 10, 2026 (7 days left)

Tender Value :

Refer Document

View Documents

About Government Tenders for Flap Valve

Every year, central and state government departments release thousands of high-value contracts specifically dedicated to Flap Valve. Whether it involves bulk material supply, executing specialized operational services, or end-to-end turnkey project execution, the demand for capable vendors in the Flap Valve sector is massive.

At Tender18, we help businesses cut through the noise and exclusively target the exact work categories they specialize in. Instead of browsing through generic procurement sites, our platform isolates high-potential opportunities that match your specific industry capabilities.

Work Dynamics in the Flap Valve Sector

Government requirements for this specific vertical generally fall into distinct procurement patterns:

Product & Material Supply: Tenders focused strictly on sourcing, testing, and delivering high-quality items that meet the exact technical specifications of the buyer.
Service Level Agreements (SLAs): Long-term hiring of expert agencies for routine maintenance, manpower deployment, or continuous operational management.
Execution & Turnkey Projects: Comprehensive contracts where the bidder is responsible for everything from raw material procurement to final site installation and testing.

By focusing purely on your core strength in Flap Valve, you can build a highly profitable and stable pipeline of government clients.

Flap Valve Tender Information Service

Stop wasting time filtering through irrelevant notices. Our Flap Valve Tender Information Service is engineered for precision. We track exact product codes, service names, and specialized work terms across all government portals nationwide. When a buyer publishes a requirement that matches your specific business profile, our system alerts you instantly.

Deep Technical Insights & Documentation For Flap Valve Tenders

Bidding for specific works requires studying strict technical parameters. We provide immediate access to the core documents you need to evaluate the project:

Detailed Specifications & Drawings: Download the exact engineering guidelines, material testing standards, and quality benchmarks demanded by the buyer for Flap Valve.
Financial BOQ Spreadsheets: Access the official blank pricing formats where you need to input your unit rates, tax configurations, and total bid value.
Real-Time Technical Amendments: If the buying department changes the product specifications, alters the service scope, or shifts the delivery timeline, we instantly update the parent file so you are never caught off-guard.

Tender Bidding Service in Flap Valve

Winning a contract for Flap Valve depends entirely on how perfectly your technical capabilities match the buyerâs demands. Even if you have the best product or service, a poorly formatted document or a missing compliance certificate will lead to instant technical rejection. Tender18âs Tender Bidding Service eliminates this risk by taking complete ownership of your digital submission.

Flawless Compliance & Portal Execution For Flap Valve Tenders

Under this service, Tender18 assigns a Dedicated Experienced Technical Person to your profile. This expert handles the heavy lifting of the entire bidding cycle:

Capability Mapping: We thoroughly cross-check your past completion certificates, ISO standard proofs, and financial turnover against the strict eligibility criteria required for Flap Valve bids.
Secure System Integration: Our technical desk seamlessly links your Class III Digital Signature Certificate (DSC) with the required e-procurement servers to securely encrypt your technical and financial envelopes.
Error-Free Financial Uploads: We audit your quoted BOQ pricing sheets for any formula or formatting errors before the final upload, ensuring your bid is successfully locked before the portal's closing hours.

Flap Valve GeM Consultant & Registration Service

Government buyers are aggressively using the Government e-Marketplace (GeM) for the direct procurement of Flap Valve. If your business profile is not accurately mapped on this portal, you remain practically invisible to these purchasing officers. Recognized as a trusted and expert GeM consultant, Tender18 offers specialized support to build, optimize, and maintain a highly visible vendor account for your business.

With an industry-leading support success ratio of over 95%, we handle the complex marketplace compliance so you can focus entirely on executing your orders

Expert Profile Management & Catalogue

Our dedicated consultants ensure your GeM presence is structurally perfect:

Precise Catalogue Listing: We upload and categorize your specific offerings under the exact search terms and parameters used by government buyers looking for Flap Valve, ensuring maximum search visibility.
OEM Dashboard & Assessment: For original manufacturers and creators, we guide you through the mandatory Quality Council of India (QCI) vendor assessments to successfully unlock your official OEM panel.
Profile Compliance & Caution Money: We manage your statutory documentation, brand approvals, and caution money limits to keep your account immune from technical suspensions.

Strategic Live Bid Participation

Beyond setup, we actively drive your market participation. Our team expertly handles the digital paperwork and rate configurations for GeM Custom Bids and Reverse Auctions (RA) related to Flap Valve, maximizing your chances of securing L1 status.

Frequently Asked Questions (FAQs) for Flap Valve Tenders

How do I find government contracts exclusively matching my work in Flap Valve?

The easiest way is through the Tender18 platform. Instead of searching department by department, our system uses advanced keyword matching to gather all live supply, service, and execution tenders related directly to your core business in one place.

Do I need specific testing or quality certificates to apply for these contracts?

It heavily depends on the nature of the work. For supply contracts, buyers often ask for ISO certifications, BIS marks, or specific lab testing reports. For service contracts, they may ask for labor licenses or past performance certificates (work orders).

What is a BOQ and why is it important for my bid?

The Bill of Quantities (BOQ) is the official financial Excel sheet where you enter your competitive prices. Any mistake in this file—like adding extra rows, changing formulas, or saving it in the wrong format—will cause the portal server to reject your entire bid.

Are samples required to be submitted physically before the digital bid opens?

For many product-based Flap Valve tenders, buying departments do ask bidders to submit physical samples to their office before the digital technical evaluation date. This requirement is always clearly mentioned in the official NIT document.

How does the Dedicated Tender Expert from Tender18 help me?

Our assigned expert manages your total portal compliance. They extract the hidden rules from long tender PDFs, create a precise document checklist for your team, map your digital signature, and securely upload your technical and financial files onto the government servers.

What is the role of a Digital Signature Certificate (DSC)?

A Class III DSC is a secure USB device that contains your digital identity. You cannot upload a bid without it. It is used to securely encrypt and lock your sensitive price data and technical documents so no one can view them before the official opening date.

As an MSME, can I get financial benefits when bidding for Flap Valve?

Yes, the government strongly supports MSMEs. By uploading a valid Udyam Registration Certificate in the technical envelope, small businesses are frequently exempted from paying the initial Tender Document Fee and the Earnest Money Deposit (EMD).

Why should I list my services or products on GeM for this category?

GeM is now the primary digital marketplace for all government agencies. If you are properly cataloged for Flap Valve, officers can view your profile and generate direct purchase orders or invite you to participate in exclusive Custom Bids.

What makes Tender18 a reliable GeM support partner?

As a highly trusted and expert GeM consultant, Tender18 holds a proven support success ratio of over 95%. From flawless profile creation and complex catalogue mapping to OEM panel approvals and live Reverse Auction (RA) support, we handle it all seamlessly.

10.

What does "L1" mean in these government contracts?

"L1" stands for "Lowest Bidder 1". In government procurement, after all technical envelopes are approved, the financial sheets (BOQs) are opened. The bidder who has quoted the lowest compliant price for Flap Valve is declared L1 and is generally awarded the contract

Search Tenders

Filters

114Latest Flap valve Tenders List

Latest Flap valve Tenders in India – Verified Leads & Real-Time Insights by Tender18

Real-Time Flap valve Tender Intelligence & Monitoring

Comprehensive Sources of Flap valve Tenders

Step-by-Step Guide to Participate in Flap valve Tenders

1. Eligibility & Prequalification

2. Mandatory Documentation Checklist

3. BOQ Analysis & Financial Bidding

Why Tender18 is a Trusted Platform for Flap valve Tenders

✔ Proven Expertise in Government Procurement

✔ Verified & Reliable Data

✔ Advanced Filtering Tools

✔ Corrigendum & Update Tracking

✔ Historical Data Insights

✔ End-to-End Bidding Support

Growth of Flap valve Sector in 2026

Frequently Asked Questions (SEO Optimized)

How can I get daily Flap valve tender alerts?

Is EMD mandatory for all Flap valve tenders?

What is the difference between a Flap valve work tender and supply tender?

Can I access private Flap valve tenders on Tender18?

Get Expert Support for Flap valve Tenders

Unlock Full Tender Access

Unlock Full Tender Access

Unlock Full Tender Access

About Government Tenders for Flap Valve

Work Dynamics in the Flap Valve Sector

Flap Valve Tender Information Service

Deep Technical Insights & Documentation For Flap Valve Tenders

Tender Bidding Service in Flap Valve

Flawless Compliance & Portal Execution For Flap Valve Tenders

Flap Valve GeM Consultant & Registration Service

Expert Profile Management & Catalogue

Strategic Live Bid Participation

Frequently Asked Questions (FAQs) for Flap Valve Tenders

How do I find government contracts exclusively matching my work in Flap Valve?

Do I need specific testing or quality certificates to apply for these contracts?

What is a BOQ and why is it important for my bid?

Are samples required to be submitted physically before the digital bid opens?

How does the Dedicated Tender Expert from Tender18 help me?

What is the role of a Digital Signature Certificate (DSC)?

As an MSME, can I get financial benefits when bidding for Flap Valve?

Why should I list my services or products on GeM for this category?

What makes Tender18 a reliable GeM support partner?

What does "L1" mean in these government contracts?

GeM Registration & Consultant Services By State

GeM Registration & Consultant Services By City

Tender Bidding Service & Consultancy By Authorities

Explore Government Tenders and GeM Portal Blogs