Leo Engineering
A ship's company fallen in on the deck of an Indian Navy landing ship at a commissioning ceremony.

FAQ

Questions about Indian defence and marine engineering

Short answers to the questions most often asked about defence vendor registration, naval quality assurance, indigenisation, naval power equipment and ship repair in India. Each links to a full guide with its sources.

Questions
110
Topics
9
Full answers
In the guides
Sources
On every guide

01

Selling to Indian defence

Is there one central portal to register as an Indian Navy vendor?

No. The Navy's "Information for Vendors" pages route firms to separate procurement units and quality assurance establishments, and naval dockyards such as Visakhapatnam publish their own registration guidelines. Tenders themselves are published on the Defence e-Procurement portal, GeM and the Central Public Procurement Portal, which are bidding platforms rather than a single vendor registry.

Read the guide: How to register as a vendor with the Indian Navy

What does Naval Dockyard Visakhapatnam ask a new vendor to submit?

Its published guidelines ask for company, ownership, financial and compliance details with supporting documents. Applicants are assessed and then registered in categories matching their core competencies. The guidelines do not publish a fee or a validity period, so confirm both, and the current document checklist, directly with the dockyard before applying.

Read the guide: How to register as a vendor with the Indian Navy

What is DGQA?

DGQA, the Directorate General of Quality Assurance, is the Ministry of Defence organisation that assures the quality of defence stores bought for the Services. Its technical directorates, such as DQA(N) and DQA(WP) for naval items, approve Quality Assurance Plans, inspect goods, run factory acceptance trials and accept stores. It also registers and assesses supplier firms.

Read the guide: DGQA and DGAQA vendor registration explained

What is DGAQA?

DGAQA, the Directorate General of Aeronautical Quality Assurance, works under the Department of Defence Production. It is the authority for quality assurance and final acceptance of military aircraft, aero engines, airborne systems, avionics and allied ground systems, overseeing design, development, production, repair and overhaul work at defence PSUs and private firms, and registers firms.

Read the guide: DGQA and DGAQA vendor registration explained

How do I register as a vendor with Mazagon Dock Shipbuilders?

Mazagon Dock runs an online vendor registration portal on mazagondock.in, alongside a separate e-procurement system. The company also runs regular vendor development programmes for MSMEs, SC/ST entrepreneurs and women-owned enterprises, and publishes guidance on TReDS invoice onboarding for MSME vendors. Confirm the current document checklist through the portal itself before applying.

Read the guide: Vendor registration with defence shipyards and DPSUs

How do I register with Garden Reach Shipbuilders (GRSE)?

GRSE, a Kolkata-based defence shipbuilder, publishes an online vendor registration route and a Notice for Vendor Registration on grse.in, governed by its own Policy on Vendor Development. It also guides MSME vendors onto the TReDS invoice discounting portal. Contact GRSE's vendor cell for the categories and items it is currently buying.

Read the guide: Vendor registration with defence shipyards and DPSUs

What documents does a new defence vendor usually need first?

The common core is PAN, a GST registration certificate, company incorporation documents, an MSME declaration or Udyam certificate, recent financial statements and past purchase orders. MIDHANI, for instance, asks for three years of financial statements and orders executed with major PSUs. Many buyers then visit the factory to assess capability and quality systems.

Read the guide: What documents does a defence buyer ask a new supplier for?

Is defence vendor registration free?

It depends on the buyer. Udyam registration is free and the government warns that no fee is payable to anyone for it. Some defence PSUs charge an assessment fee: BEML asks qualified vendors for a non-refundable Rs 10,000 demand draft towards assessment and processing. Check each buyer's current terms before paying any intermediary.

Read the guide: What documents does a defence buyer ask a new supplier for?

02

Quality assurance and type approval

What is JSS 55555 used for?

It is the Indian armed forces' specification of environmental test methods for electrical and electronic equipment. Design authorities and inspecting authorities use it to decide which tests, such as vibration, damp heat, salt corrosion or shock, an item must pass before it is accepted, and how each test is to be run so results are comparable across laboratories.

Read the guide: What is JSS 55555, the environmental test specification?

Who approves JSS 55555 and keeps it current?

The Directorate of Standardisation, Ministry of Defence, approves the specification. It is applied in practice through the Directorate General of Quality Assurance and its service-specific directorates, including DQA(N) for naval equipment, which reference it in quality assurance plans and type approval schedules.

Read the guide: What is JSS 55555, the environmental test specification?

What does NSS Grade I mean on a specification?

It means the item affects the ship's combat efficiency and must survive an underwater shock event and continue to operate afterwards. It is the more severe of the two Indian Naval Shock Standard grades, used together with the UK's BR 3021 shock manual, and test levels within the grade still depend on the equipment's mass and its position on the ship.

Read the guide: What are NSS shock grades and how is naval equipment shock tested?

What is the difference between NSS Grade I and Grade II?

NSS Grade I applies where equipment failure affects the ship's fighting capability, and the item must keep working after shock. NSS Grade II applies where it does not, and the requirement is mainly that the item stays fixed and does not become a hazard. Grade I is more severe, and the applicable grade is fixed by the equipment's own specification.

Read the guide: What are NSS shock grades and how is naval equipment shock tested?

What frequency range is used for naval vibration testing?

Naval shipboard equipment is commonly vibration tested over 5 to 33 Hz, the range EED-Q-071 cites in line with JSS 55555, at constant displacement swept across the range and then held at fixed frequencies for endurance. Minor war vessels can call for a wider band, such as 7 to 300 Hz, so the applicable range still depends on the item's own specification.

Read the guide: What do vibration, bump and inclination tests check on shipboard equipment?

What is the difference between a bump test and a shock test?

A bump test applies many moderate mechanical shocks in succession, such as 1,000 bumps at 40g, to reproduce handling, transport and routine rough service. A shock test applies a small number of much larger pulses, such as an NSS Grade I shock, to reproduce a single severe event like an underwater explosion near the ship.

Read the guide: What do vibration, bump and inclination tests check on shipboard equipment?

What is the difference between steady-state and cyclic damp heat testing?

Steady-state damp heat holds temperature and humidity constant, commonly around 40 degrees Celsius and above 93 percent relative humidity for 16 hours, to test moisture absorption. Cyclic damp heat swings the temperature between ambient and a higher point at high humidity, causing condensation to form as the specimen cools, which tests a different failure mode.

Read the guide: What do damp heat, mould growth and salt fog tests simulate?

How long does a mould growth test take?

A typical mould growth test runs about 28 days at warm, humid conditions, for example 30 degrees Celsius and above 90 percent relative humidity in one published qualification schedule, and can be extended to 84 days where the result at 28 days is inconclusive. Specimens are inoculated with specified fungi rather than left to pick up mould naturally.

Read the guide: What do damp heat, mould growth and salt fog tests simulate?

What does a DQA(N) type approval certificate contain?

It names the equipment and its part number, states the specification and quality assurance plan the item was qualified against, and is issued by DQA(N) once qualification testing and factory acceptance trials are complete. It is tied to a specific design, so it references the approved drawings that design was made to.

Read the guide: What is a DQA(N) type approval certificate, and what does it contain?

What is a quality assurance plan (QAP)?

A QAP lists every inspection and test stage an item goes through: raw material checks, in-process inspections, special processes, type and routine tests and final acceptance, with the acceptance criteria and who witnesses each stage. For naval stores, DQA(N) approves the quality assurance plan and the drawings it references before manufacture proceeds.

Read the guide: What are a QAP, a FAT and an ATP in defence supply?

What is a factory acceptance test (FAT)?

A FAT is acceptance testing carried out at the supplier's own premises, usually before an item is dispatched or installed, often witnessed by the buyer or inspecting authority. It typically covers a completeness check, verification against the contract, a functional proof and a final inspection, and for naval stores it is conducted by DQA(N) against the approved quality assurance plan.

Read the guide: What are a QAP, a FAT and an ATP in defence supply?

What does NABL accreditation actually mean?

NABL, a constituent board of the Quality Council of India, accredits testing laboratories against ISO/IEC 17025, confirming their technical competence and the reliability of their results. Accreditation is scoped to specific tests and standards, so it does not mean a laboratory is approved to test everything; the scope needs checking against the specific test required.

Read the guide: How is defence equipment type testing organised through accredited laboratories?

03

Indigenisation and Make in India

Is SRIJAN a single registration portal for all defence vendors?

No. SRIJAN publishes items that DPSUs and Service Headquarters want indigenised; it is not a vendor registration system. Registering as a supplier still happens separately with each buyer, for example through a DPSU's own vendor registration page or a naval dockyard's guidelines. SRIJAN tells industry what is wanted; registration is a different, buyer-specific step a vendor completes on its own initiative.

Read the guide: What is the SRIJAN portal and how do vendors use it?

How many items have been offered on SRIJAN?

More than 33,000 items had been offered on SRIJAN by June 2026, according to the Ministry of Defence. The Ministry has also reported more than 15,700 items indigenised through the wider effort, with an estimated import substitution value of about Rs 9,000 crore over the preceding five years. The count grows as DPSUs and Service Headquarters list new items, so treat any figure as dated to its reporting month.

Read the guide: What is the SRIJAN portal and how do vendors use it?

How many Positive Indigenisation Lists are there as of September 2026?

As of September 2026 there are five Department of Military Affairs lists, covering 509 items for the Services, and six Department of Defence Production lists for DPSUs. The first five DDP lists covered 5,012 items and the sixth, notified on 18 August 2026, added 405 more. Expect the count to keep rising as further lists are notified.

Read the guide: What is a Positive Indigenisation List, and what is in the sixth list?

What should a vendor do if the sixth list names an item it can make?

Check the item's detail on the SRIJAN portal, where the sixth list's line replaceable units, sub-systems, spares, components and raw materials are published. The relevant DPSU or the Indian Coast Guard then runs its own Make procedure or in-house development route, publishing an Expression of Interest or RFP on its own website. A listing alone is not an order; it is an invitation to develop and qualify the item.

Read the guide: What is a Positive Indigenisation List, and what is in the sixth list?

What is the difference between iDEX, DISC and ADITI?

iDEX is the overall framework; DISC and ADITI are challenge formats run under it. DISC and Open Challenge grants run up to Rs 1.5 crore. ADITI is reserved for critical and strategic technologies and pays up to Rs 25 crore. In DISC and ADITI the problem statement is set by a Service, the Coast Guard, a DPSU or another nodal agency; in an Open Challenge, the innovator sets it.

Read the guide: How do iDEX, DISC and ADITI fund defence startups and MSMEs?

How is an iDEX grant actually paid to a winner?

Under the SPARK grant agreement, iDEX pays in six milestones: 10 percent at milestone 0, 20 percent at each of milestones 1 to 4, and a final 10 percent at milestone 5. Each release depends on meeting that milestone's deliverables, so cash flow planning has to assume staged payment rather than a lump sum at signing.

Read the guide: How do iDEX, DISC and ADITI fund defence startups and MSMEs?

How much can a single project receive from the Technology Development Fund?

TDF covers up to 90 percent of a project's cost, and since June 2022 the fund's per-project ceiling has been Rs 50 crore, raised from the previous Rs 10 crore limit. The exact amount sanctioned for any specific project depends on DRDO's evaluation of the proposal and its cost estimate, not a fixed entitlement.

Read the guide: What is the Technology Development Fund, and who can apply?

Can a startup apply to TDF alone, without an industry partner?

Yes. TDF is aimed at Indian MSMEs and startups, which may additionally partner with other industry or academic institutions in a consortium, but a partnership is not mandatory. Read the current scheme guidelines on DRDO's TDF site for the applicant registration conditions that apply at the time of application.

Read the guide: What is the Technology Development Fund, and who can apply?

What is the main difference between Make-I and Make-II?

Make-I involves government funding for part of prototype development; Make-II does not. Under Make-II the vendor develops and funds the prototype itself, typically to substitute an import or offer an innovative solution, and the return is the prospect of an order once the prototype is accepted rather than a development grant along the way.

Read the guide: What is the Make-II procedure, and how does it differ from Make-I?

Does Make-II guarantee an order once the prototype works?

Not automatically, but the terms are moving that way. The draft DAP 2026 proposes five years of assured orders for Make and iDEX projects once accepted, and DPM 2025 already provides for assured orders running up to five years and beyond for items developed under indigenisation. Exact quantities and terms are still fixed case by case in the resulting contract.

Read the guide: What is the Make-II procedure, and how does it differ from Make-I?

Why can't handheld XRF measure carbon content in a steel sample?

Carbon is a very light element, and the X-ray fluorescence it produces has very low energy, which air and the sample itself absorb before it reaches a handheld detector. That means standard XRF cannot quantify carbon, even though carbon content decides a steel's grade and weldability. Spark optical emission spectroscopy, or combustion analysis, is used instead wherever carbon matters.

Read the guide: How is an obsolete spare reverse engineered and qualified?

Should a reverse engineering job use XRF or spark OES?

It depends on the alloy and whether the sample can be marked. XRF is non-destructive, portable and fast, and reliable for heavier elements such as chromium, nickel and molybdenum, so it suits stainless and nickel alloys. Spark OES leaves a small burn mark but measures carbon, sulphur and phosphorus directly, so it is the usual choice for carbon and low-alloy steels.

Read the guide: How is an obsolete spare reverse engineered and qualified?

Where does an indigenisation project for a naval spare actually start?

Most start with a listing: the Navy, a shipyard or a DPSU publishes the item on the SRIJAN portal, or it appears on a Positive Indigenisation List with an indicative timeline for indigenisation. A vendor responds to the Expression of Interest or RFP that the listing organisation publishes on its own website, not to SRIJAN directly, and begins development from there.

Read the guide: How does a naval spare go from sample to an approved indigenised item?

Who inspects and approves an indigenised naval spare?

For electrical, electronics and weapon equipment and naval stores, DQA(N) is the naval directorate responsible; for marine engineering and hull machinery, DQA(WP) covers the same ground. Both approve the drawings and quality assurance plan for the item, then run inspection and factory acceptance trials against that approved plan before the spare is accepted, whichever directorate the purchase order names.

Read the guide: How does a naval spare go from sample to an approved indigenised item?

04

Procurement and tendering

Is DAP 2020 still in force?

Yes. As of 23 September 2026, the Defence Acquisition Procedure 2020 remains the governing procedure for capital acquisitions. A draft DAP 2026 was released on 10 February 2026 for comment, but no final notification replacing DAP 2020 has been found. Recheck mod.gov.in and PIB before assuming the draft applies to a live tender.

Read the guide: DAP 2020 procurement categories explained, and the DAP 2026 draft

What is the Buy (Indian-IDDM) category?

Buy (Indian-IDDM) means buying from an Indian vendor equipment that is Indigenously Designed, Developed and Manufactured. It is the most preferred category in defence capital acquisition. DAP 2020 requires at least 50 percent indigenous content in it; the draft DAP 2026 proposes raising that to 60 percent, with a single-vendor route for mature technology.

Read the guide: DAP 2020 procurement categories explained, and the DAP 2026 draft

When did DPM 2025 take effect?

The Ministry of Defence released DPM 2025 on 23 October 2025, and it became effective for RFPs issued on or after 1 November 2025. It replaced DPM 2009 as the manual governing revenue procurement, worth roughly Rs 1 lakh crore a year, for the three Services and other Ministry of Defence establishments.

Read the guide: What changed in the Defence Procurement Manual 2025 (DPM 2025)

Which tenders follow DPM 2025 and which follow DPM 2009?

RFPs issued on or after 1 November 2025 follow DPM 2025. Cases where the RFP was issued up to 31 October 2025 continue under DPM 2009 as amended. If an older RFP is retracted and reissued on or after 1 November 2025, the reissued RFP follows DPM 2025. Check the RFP date on the tender itself.

Read the guide: What changed in the Defence Procurement Manual 2025 (DPM 2025)

What is GeM and is it mandatory for defence buyers?

GeM, the Government e-Marketplace, is the online marketplace for government purchases of goods and services. Rule 149 of the General Financial Rules makes it mandatory for procuring entities to buy goods and services available on GeM. The Ministry of Defence has been among the largest buyers on GeM by order value.

Read the guide: How GeM works for defence suppliers

Is GeM seller registration free? Do I still pay caution money?

GeM announced in 2025 that new sellers no longer need to deposit caution money, and that existing sellers can withdraw their deposits through the seller dashboard. Before registering, read GeM's seller terms for any other charges or checks, such as OEM vendor assessment, that apply to a specific product category.

Read the guide: How GeM works for defence suppliers

Where are Indian defence tenders published?

Most Ministry of Defence tenders appear on the Defence e-Procurement portal (defproc.gov.in), on GeM for goods and services listed there, and on the Central Public Procurement Portal (eprocure.gov.in). Defence PSUs and shipyards also run their own e-procurement portals, such as HAL's and Bharat Electronics' SRM portal. Watch all the portals a target buyer actually uses.

Read the guide: Where Indian defence tenders are published, and how to bid

How do I register on the Defence e-Procurement portal (defproc.gov.in)?

defproc.gov.in runs on NIC's government e-procurement system. Bidders enrol online through the portal's bidder enrolment process and must hold a Class III digital signature certificate, with signing and encryption, to bid. Register the certificate against a bidder profile well before a first bid deadline, and check the portal's help desk page for any current enrolment steps.

Read the guide: Where Indian defence tenders are published, and how to bid

What is EMD or bid security in government tenders?

Earnest money deposit, or bid security, is money a bidder deposits to show a serious bid; it is forfeited if the bidder withdraws or fails to sign after winning. Under Rule 170 of the General Financial Rules it ordinarily ranges from 2 to 5 percent of the estimated value. Registered MSEs are exempt under the MSE policy.

Read the guide: EMD and performance bank guarantee rules in defence tenders

Are MSMEs exempt from EMD in defence tenders?

Yes. Micro and small enterprises registered on Udyam are exempt from earnest money deposit under the Public Procurement Policy for MSEs, in tenders by central ministries, departments and CPSUs. The exemption does not cover performance bank guarantees or security deposits, and it does not apply to works contracts.

Read the guide: EMD and performance bank guarantee rules in defence tenders

What benefits do MSMEs get in defence procurement?

Under the Public Procurement Policy for MSEs, central ministries and CPSUs, including the Ministry of Defence and defence PSUs, must source at least 25 percent of annual procurement from micro and small enterprises. MSEs get free tender sets, exemption from earnest money deposit, possible relaxation of prior turnover and experience, and an L1 plus 15 percent price-matching right.

Read the guide: MSME benefits in Indian public procurement, and what is excluded

Does the MSME procurement policy apply to works contracts like CPWD jobs?

No. The Public Procurement Policy for MSEs covers goods and services only; works contracts are outside its purview, with definitions in the General Financial Rules. MSE benefits such as EMD exemption do not apply automatically to works tenders. Read each notice inviting tender, which states any concession the buyer chooses to give.

Read the guide: MSME benefits in Indian public procurement, and what is excluded

What is L1 in a government tender?

L1 is the lowest priced bid among bidders who are technically qualified; L2 is the next lowest, and so on. Contracts normally go to L1, subject to rules such as Make in India purchase preference and MSE price matching, which can let a qualifying bidder supply part of the order by matching the L1 price.

Read the guide: How L1 evaluation and reverse auctions work in government tenders

How does a GeM reverse auction work?

A reverse auction only opens to bidders who have already cleared technical qualification, the same threshold logic as an offline tender. Above the value threshold the General Financial Rules set for GeM, price is then decided through a live, descending-price event rather than a single sealed bid, and the lowest bidder at close wins.

Read the guide: How L1 evaluation and reverse auctions work in government tenders

Is Udyam registration free?

Yes. Udyam registration is free of cost, paperless and based on self-declaration, and the Ministry of MSME states that no fee is to be paid to anyone and that no other website or app is official. Agents charging for Udyam registration are offering a service the government provides free.

Read the guide: How Udyam registration helps a defence supplier

Do I need Udyam registration to get MSME tender benefits?

Yes. Since 1 July 2020 the benefits of the Public Procurement Policy go to micro and small enterprises registered under Udyam. The older Udyog Aadhaar Memorandum remained valid for this purpose only until 31 March 2022. Enterprises registered with other Ministry of MSME bodies were required to register on Udyam as well.

Read the guide: How Udyam registration helps a defence supplier

05

Naval electrical power

What is the difference between a battery charging rectifier and a battery charger?

In ship and industrial practice the two terms describe the same equipment: a rectifier that converts AC to DC to charge and maintain a battery bank. Standby duty chargers are usually specified as float cum boost units, so one rectifier both floats the battery continuously and switches to a higher boost voltage to recharge it after a discharge, rather than needing two separate machines.

Read the guide: What Does a Battery Charging Rectifier Do on a Ship?

Can a battery charging rectifier run the DC load with the battery disconnected?

Yes, most rectifiers are sized to carry the connected DC load on their own, which is why voltage regulation and ripple specification matter even without a battery attached. A well regulated unit holds output within about plus or minus 0.5 to 1 percent from no load to full load, because the load sees the rectifier directly whenever the battery is isolated for maintenance.

Read the guide: What Does a Battery Charging Rectifier Do on a Ship?

How is float voltage worked out from electrolyte specific gravity?

A rule of thumb gives open circuit voltage as electrolyte specific gravity plus 0.845, with float voltage about 0.12 V above that figure. A flooded cell at specific gravity 1.215 works out to roughly 2.18 V float, and a valve regulated cell at specific gravity 1.300 works out to roughly 2.265 V. The battery maker's own figure always takes priority over the estimate.

Read the guide: Float vs Boost vs Equalising Charge, Explained

What is a float cum boost battery charger?

A float cum boost charger is a single rectifier that supplies the connected DC load continuously while keeping the battery on float, then switches to a higher boost voltage, automatically or manually, to recharge the battery after it has been discharged. It replaces the older arrangement of separate float and boost chargers on one battery bank.

Read the guide: Float vs Boost vs Equalising Charge, Explained

What does a phase fail alarm on a battery charger mean?

It means the three phase AC input has lost one phase or a phase has fallen outside acceptable limits. A rectifier bridge cannot deliver rated output on the remaining two phases without overheating or producing heavy DC ripple, so most chargers inhibit or derate automatically. Check input fuses, the supply breaker and phase sequence at the incoming terminals first.

Read the guide: What Do Battery Charger Alarms Mean?

Why does reverse polarity protection matter on a battery charger?

Connecting a battery backwards puts it in series opposition with the charger's own output, which can blow fuses, destroy rectifier devices and damage the battery in the process. Chargers check polarity before closing the battery contactor and alarm or block the connection if it is wrong, which is why the alarm exists rather than relying only on correct wiring at installation.

Read the guide: What Do Battery Charger Alarms Mean?

How is the DC bus voltage for a battery charger determined?

It is the number of cells in the bank multiplied by the float voltage per cell, typically 2.25 to 2.27 V per cell for flooded lead acid at 25 degrees Celsius. A 55-cell bank works out to roughly 124 V. Valve regulated chemistry and other cell counts shift the figure, and the battery maker's stated float voltage always takes priority over an estimate.

Read the guide: How to Size a Battery Charger for a Ship's Battery Bank

What charging current should a battery charger be rated for?

It follows the battery maker's maximum recharge current, commonly specified as a fraction of rated capacity such as one fifth of the ampere hour figure at the eight hour rate. A 100 Ah cell, for example, should not be recharged above about 20 A. The charger's current limiting is set at or below that figure once the connected DC load is accounted for.

Read the guide: How to Size a Battery Charger for a Ship's Battery Bank

Is a rotary frequency converter more efficient than a static one?

It depends heavily on size and load. One manufacturer comparison gives rotary converters about 60 to 65 percent efficiency on the smallest units, rising to 85 to 92 percent on large ones, against static converters quoted at roughly 60 to 92 percent across sizes. Efficiency should always be compared at the load the converter will actually run, not at its nameplate rating.

Read the guide: Rotary vs Static Frequency Converter: What Is the Difference?

Why do some navies prefer rotary frequency converters for sensitive loads?

The motor-generator shaft electrically separates the ship's own supply from the 400 Hz output, so voltage dips, transients and general distortion on the input do not reach the load. The rotating mass also rides through brief interruptions, and the generator produces a clean sine wave regardless of input quality, which matters for radar, weapon and navigation equipment that is sensitive to power disturbances.

Read the guide: Rotary vs Static Frequency Converter: What Is the Difference?

What equipment on a warship runs on 400 Hz?

400 Hz supplies commonly feed naval radar, weapon, communication and navigation equipment, along with aircraft operating from or embarked on the ship. It sits alongside the ship's main 50 or 60 Hz supply rather than replacing it, and is produced locally by static or rotary frequency converters rather than generated directly at 400 Hz.

Read the guide: Why Do Navies Use 400 Hz Power?

Why does a 400 Hz supply leave less noise on a DC signal after rectification?

Ripple frequency on a rectified supply rises with the AC input frequency, so 400 Hz produces ripple at a much higher frequency than 50 or 60 Hz does. A filter of a given size removes higher frequency ripple more completely, which is why radio and combat systems equipment on naval ships is often powered at 400 Hz specifically to reduce noise on the DC side.

Read the guide: Why Do Navies Use 400 Hz Power?

Do all Indian Navy ships run at 440 V, 60 Hz?

No. The Navy's own motor and starter specification, EED-Q-071, requires equipment to be suitable for 380 V 50 Hz, 415 V 50 Hz or 440 V 60 Hz depending on the individual ship's main supply, and its own default table of AC supply characteristics is built around 415 V, 50 Hz rather than 440 V, 60 Hz.

Read the guide: Does Indian Naval Power Run at 50 Hz or 60 Hz?

What is EED-Q-071?

EED-Q-071 is the Indian Navy's Specifications of Motors and Starters for Naval Ships, issued by the Directorate of Electrical Engineering at Integrated Headquarters, Ministry of Defence (Navy). Revision 4 is dated May 2014. It covers supply voltage and frequency, environmental conditions, shock and vibration, enclosure protection, efficiency and the type and routine tests motors and starters have to pass.

Read the guide: Does Indian Naval Power Run at 50 Hz or 60 Hz?

What does a motor-generator set actually convert?

It converts electrical power from one form to another: between frequencies, such as 50 or 60 Hz to 400 Hz, between AC and DC, or between voltages. The motor draws power in one form from the supply and the generator, mechanically coupled to it, delivers power in the other form to the load, with no direct electrical connection between the two sides.

Read the guide: What Is a Motor-Generator Set?

How does a motor-generator set isolate a load from a noisy power supply?

The load connects to the generator, not directly to the incoming supply, so spikes and variations in dirty input power do not pass straight through. The set's own mechanical inertia also filters out transients in the input, letting equipment fed from the generator ride through brief blackouts and switching disturbances that would otherwise reach it.

Read the guide: What Is a Motor-Generator Set?

06

Marine engineering and ship repair

What is shaft alignment on a ship?

Shaft alignment is the static condition of a ship's propulsion shaft line at its bearings, calculated and set with the system at rest. It aims to keep every bearing, including the stern tube bearing and the engine or gearbox bearings, within an acceptable load across loaded, ballast and hot running conditions, not just as built in dry dock.

Read the guide: Marine shaft alignment explained

What is the sag and gap method of shaft alignment?

Sag and gap is a pre-assembly check made with the shaft flanges uncoupled. The vertical offset (sag) and the angular opening (gap) between the mating flanges are measured and compared with the alignment calculation. It is most reliable in dry dock; afloat, hull deflection changes the readings and has to be allowed for.

Read the guide: Marine shaft alignment explained

What is a tailshaft survey?

A tailshaft survey is the classification survey of a ship's propeller shaft, its bearings and its seals. Under IACS UR Z21 the full version draws the shaft, examines shaft, seals and bearings, removes the propeller, crack-tests the forward taper and keyway, checks bearing clearances, and records weardown after reassembly.

Read the guide: Propeller shaft survey intervals under IACS UR Z21

How often is a propeller shaft survey required?

For oil-lubricated or closed-loop fresh-water-lubricated shafts, IACS UR Z21 sets a survey every 5 years by Method 1, 2 or 3, depending on the propeller connection and on prerequisites being met. Keyless propellers can go up to 15 years between full Method 1 or 2 withdrawals, with Method 3 surveys allowed between them.

Read the guide: Propeller shaft survey intervals under IACS UR Z21

What is a stern tube on a ship?

The stern tube is the tube through the hull at the stern that carries the propeller shaft from inside the ship to the propeller. It houses the stern bearings that carry the shaft and propeller weight, is filled with oil, grease or water as lubricant, and has seals at each end to keep the water out.

Read the guide: Stern tube seals and bearings: types and wear

What is the difference between a lip seal and a face seal?

Lip seals use several elastomer rings, usually fluoroelastomer, running on a chrome-steel liner, pressurised from header tanks, and are the common choice for oil-lubricated stern tubes. Face seals seal axially between a rotating and a stationary face and are often used instead where the bearing is water-lubricated.

Read the guide: Stern tube seals and bearings: types and wear

How often does a ship need dry docking?

Under the IMO Harmonized System of Survey and Certification, a cargo ship's outside bottom must be inspected at least twice in every five-year period, with one inspection linked to the renewal survey. These are normally done in dry dock, though the flag Administration may accept an in-water inspection for one of them.

Read the guide: Dry docking intervals and extended dry docking (IRS)

What is the Extended Dry-Docking (EDD) scheme?

The Extended Dry-Docking scheme, based on IACS Recommendation 133, lets an eligible ship replace two dry dockings with consecutive in-water surveys and stretch the docking interval from 5 to 7.5 years. It needs class and flag approval, applies only to ships up to 10 years old, and excludes several ship types.

Read the guide: Dry docking intervals and extended dry docking (IRS)

What is ultrasonic thickness measurement (UTM) on a ship?

Ultrasonic thickness measurement is a non-destructive test that measures remaining plate thickness from one side using a calibrated ultrasonic probe. Surveyors compare readings with the original scantling and the classification society's allowable diminution to decide whether plating, frames or stiffeners need renewal. Gauging firms must be approved by class.

Read the guide: Hull plate renewal and thickness gauging basics

Who is allowed to carry out hull thickness gauging?

Thickness gauging used in a classification survey report has to be carried out by a firm approved by the ship's classification society. An unapproved reading, however accurate, cannot be accepted as the basis for a survey decision on renewal.

Read the guide: Hull plate renewal and thickness gauging basics

What is a sea chest on a ship?

A sea chest is a rectangular or cylindrical recess in the hull below the waterline from which seawater cooling and service pumps draw water. It is covered by a removable grating and often fitted with baffle plates to smooth flow at speed or in a seaway. Sea valves and strainers sit between the chest and the pumps.

Read the guide: Sea chest maintenance

How is a sea chest cleaned and inspected in dry dock?

In dry dock the gratings are removed and the sea chest is cleaned of barnacles, silt and marine growth, inspected for corrosion and cracks, and recoated. Grating fastenings, gaskets and bolts are checked for watertight integrity, anodes inside the chest are renewed, and the connected sea valves are overhauled and pressure-tested.

Read the guide: Sea chest maintenance

What is the difference between sacrificial anodes and ICCP on a ship?

Sacrificial anodes of zinc, aluminium or magnesium alloy corrode in place of the hull steel and need no power, but they are consumed, add drag and cannot be adjusted. Impressed current cathodic protection (ICCP) uses a DC supply, inert anodes such as platinised titanium and reference electrodes to control protection automatically, suiting large hulls.

Read the guide: Cathodic protection on ships: anodes vs ICCP

How often should hull anodes be replaced?

Hull anodes are sized to last the planned interval between dockings, so they are inspected at every docking and renewed when substantially consumed. One widely cited marine reference treats about five years as a typical replacement life. Unusually fast wastage points to stray current, a paint breakdown or a bonding fault.

Read the guide: Cathodic protection on ships: anodes vs ICCP

What is Sa 2½ surface preparation?

Sa 2½ is the ISO 8501-1 grade for very thorough abrasive blast cleaning. Mill scale, rust, old paint and foreign matter are removed so that any remaining traces show only as slight stains or shades on a uniform metallic surface. It is the usual minimum for immersed ship hull coatings and most high-performance epoxy systems.

Read the guide: Hull coating systems during dry dock

What is the difference between Sa 2½ and Sa 3 blast cleaning?

Sa 3 is blast cleaning to white metal: all mill scale, rust and foreign matter are removed, leaving a uniform metallic colour. Sa 2½ is one step lower, allowing faint shadows or slight discoloration. Sa 3 costs more time and abrasive and is specified for demanding linings; Sa 2½ is the common hull and tank specification.

Read the guide: Hull coating systems during dry dock

What is an ASD (azimuth stern drive) tug?

An ASD tug has two steerable propulsion units under the stern that each rotate through 360 degrees, so thrust can be pointed in any direction without a rudder. This makes the tug highly responsive and powerful for harbour towing and escort work. The drives are usually Z-drives powered by diesel engines.

Read the guide: Hydraulic system overhaul on tugs

What is a Z-drive thruster?

A Z-drive is an azimuthing thruster whose power path forms a Z: a horizontal input shaft from the engine, a vertical shaft down through the steering column, and a horizontal output shaft to the propeller, linked by bevel gears. The lower unit rotates to steer, so no rudder is needed.

Read the guide: Hydraulic system overhaul on tugs

What ship repair and dry docking facilities does Visakhapatnam have?

Visakhapatnam's main docking facilities are the Naval Dockyard, which has three dry docks, and Hindustan Shipyard Limited, which has a dry dock, wet basin and repair dolphin used for ship and submarine repair and refits, plus a separate covered building dock for new construction up to about 80,000 DWT.

Read the guide: Ship repair and dry dock facilities in India by port

How big is Cochin Shipyard's dry dock?

Cochin Shipyard commissioned a new 310-metre-long dry dock in January 2024, able to take vessels up to about 300 metres, such as Suezmax tankers, container ships and Capesize bulk carriers. The yard lists ship repair capability up to about 125,000 DWT and has refitted the aircraft carriers INS Viraat and INS Vikramaditya.

Read the guide: Ship repair and dry dock facilities in India by port

07

Defence fabrication and interconnection

What does the E number mean in an IS 2062 steel grade?

The E number in an IS 2062 grade states the steel's minimum yield strength in megapascals, so E250 has a minimum yield strength of about 250 MPa and E350 about 350 MPa. The grade also carries a letter suffix, A, BR, B0 or C, that sets whether and how the steel is impact tested, which matters as much as the yield strength for low-temperature or shock-loaded service.

Read the guide: Which welding and structural steel standards apply to defence fabrication?

What is the difference between IS 2062 grades BR, B0 and C?

Grade A needs no impact test. Grade BR carries an optional impact test at room temperature. Grade B0 requires a mandatory impact test at 0 degrees C. Grade C requires a mandatory impact test at minus 20 degrees C and must be killed steel, deoxidised during casting. The suffix is chosen against the expected service temperature and any shock loading, independent of the E number.

Read the guide: Which welding and structural steel standards apply to defence fabrication?

What is the difference between continuity and insulation resistance testing on a cable harness?

Continuity testing confirms that every intended connection exists at low resistance, catching an open circuit or a missed crimp. Insulation resistance testing measures leakage current at a set DC voltage between conductors that should be isolated, catching gradual insulation degradation rather than a broken connection. Both are run on the same harness because they check opposite failure modes: missing connection versus unwanted leakage.

Read the guide: What do continuity, insulation resistance and hipot tests check on a cable harness?

What hipot test voltage does IPC/WHMA-A-620 set for a cable harness?

Where the customer drawing or specification does not set its own value, IPC/WHMA-A-620's default hipot, or dielectric withstanding voltage, test is 1000 V DC for a Class 2 assembly with a 0.1 second dwell, and 1500 V DC for a Class 3 assembly with a 1 second dwell. Wire and connector voltage ratings are checked first, since testing above a component's rating can damage sound insulation.

Read the guide: What do continuity, insulation resistance and hipot tests check on a cable harness?

08

Building operation and maintenance

Are all fire extinguisher types pressure tested every five years?

No. IS 2190:2010 Annex E sets hydraulic pressure testing at three years for water, foam and stored-pressure dry powder extinguishers, and at five years only for carbon dioxide types. Several websites quote a flat five years for everything, which understates the water, foam and powder interval by two years and can leave a cylinder overdue for test.

Read the guide: How often should fire extinguishers be refilled and pressure tested?

How often does a fire extinguisher need refilling in India?

Under IS 2190:2010 Annex D, stored-pressure water and foam extinguishers are refilled every two years, BC and ABC dry powder every three years, and nine-litre gas-cartridge water and foam types every five years. Halve every interval in a corrosive atmosphere, and refill immediately after any discharge, partial or full.

Read the guide: How often should fire extinguishers be refilled and pressure tested?

How often should a standby DG set be run on load?

At least once a month, for at least thirty minutes, at no less than one-third of the set's nameplate rating, using the building load or a load bank if the building load is not available. This keeps parts lubricated, prevents electrical contacts from oxidising and uses fuel before it degrades in the tank, and it is the single check most often skipped.

Read the guide: What is the right maintenance schedule for a standby DG set?

What is wet stacking in a diesel generator?

Wet stacking is unburned fuel and soot accumulating in the exhaust system of a diesel generator run for long periods at light or no load, because the cylinders never reach combustion temperature. It shows as oily black smoke and residue at the exhaust stack, and the remedy is to minimise unloaded running and exercise the set at meaningful load, not to treat it as a fault.

Read the guide: What is the right maintenance schedule for a standby DG set?

How often is an 11 kV substation transformer inspected under IS 10028?

IS 10028 (Part 3) sets a layered schedule: hourly load and temperature readings in an attended substation, daily breather checks, monthly oil level checks, quarterly bushing checks, half yearly gasket and cable box checks, yearly dielectric, earth resistance and relay tests, and a full inspection roughly every five years. Transformers of 1000 kVA and above carry extra checks at most of these intervals.

Read the guide: What is the maintenance schedule for an 11 kV substation transformer?

What extra checks apply to transformers of 1000 kVA and above?

IS 10028 (Part 3) adds winding and oil temperature to the hourly round, the relief diaphragm to the daily round, oil dielectric strength and water content plus cooler and tap changer checks quarterly, and oil acidity and sludge testing yearly. The five-yearly overall inspection extends to lifting the core for internal examination on transformers up to 3000 kVA.

Read the guide: What is the maintenance schedule for an 11 kV substation transformer?

What does a non-comprehensive building O&M contract include?

A non-comprehensive contract covers scheduled preventive maintenance, inspection rounds, lubrication, adjustments and breakdown labour within the fixed contract value, while spare parts are billed separately as they are needed. It suits an owner who wants a predictable base maintenance cost and can approve and pay for parts quickly enough that a breakdown is not held up waiting on a purchase order.

Read the guide: What is included in a building E&M operation and maintenance contract?

What does a comprehensive building O&M contract include?

A comprehensive contract folds spare parts and most repair costs into the same fixed annual value as the maintenance work, so the contractor carries the risk of an expensive, unplanned failure instead of the client. It costs more than a non-comprehensive contract, and the exclusions list, consumables, misuse damage and end-of-life assemblies, decides how much protection the higher price actually buys.

Read the guide: What is included in a building E&M operation and maintenance contract?

09

The Indian defence industry

Does making a component for a defence system automatically require an industrial licence?

No. DPIIT's Press Note 2 (2019) clarified that manufacturing parts or accessories in the defence sector needs no industrial or arms licence unless the specific part is named in Press Note 1's Annexure I or II. Most components and sub-assemblies fall outside the licensed list; only the specifically named systems and items require a licence before production starts.

Read the guide: When does a defence manufacturer need an industrial licence?

How long does a defence industrial licence last?

An Industries (Development and Regulation) Act licence is valid for 15 years, extendable by 3 more years, giving 18 years in total within which commercial production must begin. Arms Act licences have no fixed validity period, but the licensed facility has to be established within 7 years, extendable by a further 3. Both clocks start running from the date the licence is granted.

Read the guide: When does a defence manufacturer need an industrial licence?

What is the maximum FDI allowed in Indian defence manufacturing without government approval?

Up to 74 percent is permitted through the automatic route under Press Note 4 (2020 Series), meaning no prior government approval is needed for investment up to that level. Beyond 74 percent, up to 100 percent is possible, but only through the government route and only where the investment is likely to bring access to modern technology, a case-by-case decision rather than an automatic entitlement.

Read the guide: How much foreign investment is allowed in Indian defence manufacturing?

Does every defence FDI proposal get a security review, even under the automatic route?

Yes. Press Note 4 (2020 Series) makes clear that foreign investment in defence, whichever route it uses, remains subject to a national security review. The automatic route removes the need for prior government approval of the investment itself; it does not remove the separate national security screening that defence sector investment carries.

Read the guide: How much foreign investment is allowed in Indian defence manufacturing?

What is SCOMET, and why does it matter for defence exports?

SCOMET is India's list of Special Chemicals, Organisms, Materials, Equipment and Technologies whose export is controlled. Category 6 is the Munitions List, covering military items, and the Department of Defence Production issues the export authorisation for anything in it. Other SCOMET categories are handled by the Directorate General of Foreign Trade and other authorities, so identifying the right category is the first step, not the last.

Read the guide: How does a company get authorisation to export defence items from India?

Who actually issues the licence to export a defence item?

For munitions list items, the Department of Defence Production issues the export authorisation, notified by the Directorate General of Foreign Trade as the licensing authority for SCOMET Category 6. Applications are filed on DDP's own online portal and authorisations are digitally signed and issued under its standard operating procedure, rather than through the general SCOMET process used for other categories.

Read the guide: How does a company get authorisation to export defence items from India?

Which cities are inside the Uttar Pradesh Defence Industrial Corridor?

Six nodes: Aligarh, Agra, Jhansi, Kanpur, Chitrakoot and Lucknow, with the Uttar Pradesh Expressways Industrial Development Authority as the nodal agency coordinating investment and infrastructure across them. A company setting up inside one of these nodes deals with UPEIDA directly for the corridor-specific incentives, separately from any national defence procurement or licensing process.

Read the guide: What are India's defence industrial corridors, in Uttar Pradesh and Tamil Nadu?

Is there a Defence Industrial Corridor in Telangana or Andhra Pradesh?

No. India's two nationally notified Defence Industrial Corridors run through Uttar Pradesh and Tamil Nadu only. Telangana and Andhra Pradesh instead host established defence organisations directly, such as DPSUs, a naval dockyard and a naval quality assurance establishment, and run their own separate state-level aerospace and defence industrial policies.

Read the guide: What does the defence and aerospace ecosystem in Hyderabad and Visakhapatnam look like?

What defence organisations are based in Hyderabad?

Hyderabad hosts Bharat Dynamics Limited, a DPSU making missiles, and MIDHANI, which makes special alloys for aerospace and defence use, along with CQAE(N), the Chief Quality Assurance Establishment (Naval), a DQA(N) field unit in the DGQA Complex at Manovikas Nagar, Secunderabad. Together they give a local supplier both DPSU buyers and a naval quality assurance authority in one city.

Read the guide: What does the defence and aerospace ecosystem in Hyderabad and Visakhapatnam look like?

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