Paket Umroh Plus Turki,

Jenis-jenis Valve dan Fungsinya

Jenis-jenis valve dan fungsinya :
1. Gate Valve
Gate Valve adalah valve yang paling sering dipakai pada sistem perpipaan. Fungsinya untuk dapat membuka dan menutup aliran (on-off), tetapi tidak bisa untuk mengatur besar kecil aliran (throttling). Kelebihan Gate Valve, minimnya halangan/ resistan saat valve ini telah dibuka penuh, sehingga aliran bisa
maksimal. Gate Valve telah mengontrol aliran melalui badan valve yang berbentuk pipa, dengan sebuah lempengan atau baji vertikal  yang bisa bergeser naik turun saat handel valve diputar. Valve ini telah didesain untuk dapat mengatur posisi terbuka penuh, atau tertutup penuh. Jika valve ini dalam keadaan setengah terbuka, maka akan dapat menyebabkan pengikisan pada badan valve, dan turbulensi aliran zat bisa dapat menyebabkan getaran pada baji valve sehingga dapat menghasilkan suara gemeretak.

2. Globe Valve
Globe Valve biasanya akan digunakan pada situasi dimana pengaturan besar kecil aliran (throttling) sangat diperlukan. Dengan mudah memutar handel valve, besarnya aliran zat yang telah melewati valve bisa diatur. Dudukan valve yang sejajar dengan aliran, telah membuat globe valve efisien ketika dapat mengatur besar kecilnya aliran dengan minimum erosi piringan dan dudukan. Namun demikian tahanan didalam valve cukup besar. Desain globe valve yang sedemikian rupa, telah memaksa adanya perubahan arah aliran zat didalam valve, sehingga tekanan menurun drastis dan dapat menyebabkan turbulensi di dalam valve itu sendiri. Dengan demikian, Globe Valve tidak disarankan diinstal pada sistem yang menghindari penurunan tekanan, dan sistem yang menghindari tahanan pada aliran.

3. Angle Valve  
Sama seperti globe valve, angle valve juga akan digunakan pada situasi dimana pengaturan besar kecil aliran telah diperlukan (throttling). Namun angle valve telah di buat dengan sudut 90°, hal ini untuk dapat mengurangi pemakaian elbow 90° dan fitting tambahan.
4. Check Valve
Check Valve telah memiliki perbedaan yang sangat signifikan dari Gate Valve dan Globe Valve. Valve ini telah di disain untuk dapat mencegah aliran balik. Ada beberapa jenis check valve, tapi ada 2 jenis yang paling umum yaitu Swing Check dan Lift Check. Swing Check Valve biasanya telah dipasangkan dengan Gate Valve, sedangkan Lift Check Valve oleh beberapa pabrikan digunakan untuk dapat menggantikan fungsi Ball Valve sebagai Ball Check Valve. Check Valve tidak menggunakan handel untuk dapat mengatur aliran, tapi dengan menggunakan gravitasi dan tekanan dari aliran fluida itu sendiri. Karena fungsinya yang juga dapat mencegah aliran balik (backflow). Check Valve juga sering digunakan sebagai pengaman dari sebuah equipment dalam sistem perpipaan.
5. Ball Valve
Ball Valve adalah alternatif murah dari jenis valve-valve yang lain. Ball valve dengan menggunakan bola logam yang tengahnya ada lubang tembus, diapit oleh dudukan valve untuk dapat mengontrol aliran. Sering dipakai pada proses hydrocarbon, ball valve mampu untuk dapat mengatur besar kecil aliran gas dan uap terutama untuk tekanan rendah. Valve ini juga dapat dengan cepat ditutup dan cukup kedap untuk menahan fluida/ zat cair. Ball valve tidak menggunakan handwheel, tetapi dengan menggunakan ankle untuk dapat membuka atau menutup valve dengan sudut 90°.
6. Butterfly Valve
Butterfly Valve telah memiliki bentuk yang sangat unik jika dibandingkan dengan valve-valve yang lain. Butterfly dengan menggunakan plat bundar atau wafer yang dioperasikan dengan ankel untuk posisi membuka penuh atau menutup penuh dengan sudut 90°. Wafer ini tetap berada ditengah aliran, dan dihubungkan ke ankel melalui shaft. Saat valve dalam keadaan tertutup, wafer tersebut tegak lurus dengan arah aliran, sehingga aliran terbendung, dan saat valve terbuka wafer sejajar/ segaris dengan aliran, sehingga zat dapat mengalir melalui valve. Butterfly valve telah memiliki turbulensi dan penurunan tekanan (pressure drop) yang minimal. Valve ini sangat bagus untuk pengoperasian on-off ataupun throttling, dan bagus untuk dapat mengontrol aliran zat cair atau gas dalam jumlah yang besar. Namun demikian valve ini biasanya tidak memiliki kekedapan yang bagus, dan harus digunakan pada situasi/ sistem yang memiliki tekanan rendah (low-pressure).

7. Relief Valve
Relief valve telah memiliki fungsi yang sangat berbeda dari valve-valve yang lain. Valve ini telah didisain khusus untuk dapat melepas tekanan berlebih yang ada di equipment dan sistem perpipaan. Untuk dapat mencegah kerusakan pada equipment, dan lebih penting lagi cedera pada pekerja, relief valve dapat melepas kenaikan tekanan sebelum menjadi lebih ekstrim. Relief valve menggunakan pegas baja, yang secara otomatis akan terbuka jika tekanan mencapai level yang tidak aman. Level tekanan pada valve ini bisa diatur, sehingga bisa ditentukan pada level tekanan berapa valve ini akan terbuka. Ketika tekanan kembali normal, relief valve secara otomatis akan tertutup kembali.

Editor : Dian Sukmawati

United’s first-class and business fliers get Rhapsody, its high-minded in-flight magazine, seen here at its office in Brooklyn. Credit Sam Hodgson for The New York Times

Last summer at a writers’ workshop in Oregon, the novelists Anthony Doerr, Karen Russell and Elissa Schappell were chatting over cocktails when they realized they had all published work in the same magazine. It wasn’t one of the usual literary outlets, like Tin House, The Paris Review or The New Yorker. It was Rhapsody, an in-flight magazine for United Airlines.

It seemed like a weird coincidence. Then again, considering Rhapsody’s growing roster of A-list fiction writers, maybe not. Since its first issue hit plane cabins a year and a half ago, Rhapsody has published original works by literary stars like Joyce Carol Oates, Rick Moody, Amy Bloom, Emma Straub and Mr. Doerr, who won the Pulitzer Prize for fiction two weeks ago.

As airlines try to distinguish their high-end service with luxuries like private sleeping chambers, showers, butler service and meals from five-star chefs, United Airlines is offering a loftier, more cerebral amenity to its first-class and business-class passengers: elegant prose by prominent novelists. There are no airport maps or disheartening lists of in-flight meal and entertainment options in Rhapsody. Instead, the magazine has published ruminative first-person travel accounts, cultural dispatches and probing essays about flight by more than 30 literary fiction writers.


Sean Manning, executive editor of Rhapsody, which publishes works by the likes of Joyce Carol Oates, Amy Bloom and Anthony Doerr, who won a Pulitzer Prize. Credit Sam Hodgson for The New York Times


An airline might seem like an odd literary patron. But as publishers and writers look for new ways to reach readers in a shaky retail climate, many have formed corporate alliances with transit companies, including American Airlines, JetBlue and Amtrak, that provide a captive audience.

Mark Krolick, United Airlines’ managing director of marketing and product development, said the quality of the writing in Rhapsody brings a patina of sophistication to its first-class service, along with other opulent touches like mood lighting, soft music and a branded scent.

“The high-end leisure or business-class traveler has higher expectations, even in the entertainment we provide,” he said.


Some of Rhapsody’s contributing writers say they were lured by the promise of free airfare and luxury accommodations provided by United, as well as exposure to an elite audience of some two million first-class and business-class travelers.

“It’s not your normal Park Slope Community Bookstore types who read Rhapsody,” Mr. Moody, author of the 1994 novel “The Ice Storm,” who wrote an introspective, philosophical piece about traveling to the Aran Islands of Ireland for Rhapsody, said in an email. “I’m not sure I myself am in that Rhapsody demographic, but I would like them to buy my books one day.”

In addition to offering travel perks, the magazine pays well and gives writers freedom, within reason, to choose their subject matter and write with style. Certain genres of flight stories are off limits, naturally: no plane crashes or woeful tales of lost luggage or rude flight attendants, and nothing too risqué.

“We’re not going to have someone write about joining the mile-high club,” said Jordan Heller, the editor in chief of Rhapsody. “Despite those restrictions, we’ve managed to come up with a lot of high-minded literary content.”

Guiding writers toward the right idea occasionally requires some gentle prodding. When Rhapsody’s executive editor asked Ms. Russell to contribute an essay about a memorable flight experience, she first pitched a story about the time she was chaperoning a group of teenagers on a trip to Europe, and their delayed plane sat at the airport in New York for several hours while other passengers got progressively drunker.

“He pointed out that disaster flights are not what people want to read about when they’re in transit, and very diplomatically suggested that maybe people want to read something that casts air travel in a more positive light,” said Ms. Russell, whose novel “Swamplandia!” was a finalist for the 2012 Pulitzer Prize.

She turned in a nostalgia-tinged essay about her first flight on a trip to Disney World when she was 6. “The Magic Kingdom was an anticlimax,” she wrote. “What ride could compare to that first flight?”

Ms. Oates also wrote about her first flight, in a tiny yellow propeller plane piloted by her father. The novelist Joyce Maynard told of the constant disappointment of never seeing her books in airport bookstores and the thrill of finally spotting a fellow plane passenger reading her novel “Labor Day.” Emily St. John Mandel, who was a finalist for the National Book Award in fiction last year, wrote about agonizing over which books to bring on a long flight.

“There’s nobody that’s looked down their noses at us as an in-flight magazine,” said Sean Manning, the magazine’s executive editor. “As big as these people are in the literary world, there’s still this untapped audience for them of luxury travelers.”

United is one of a handful of companies showcasing work by literary writers as a way to elevate their brands and engage customers. Chipotle has printed original work from writers like Toni Morrison, Jeffrey Eugenides and Barbara Kingsolver on its disposable cups and paper bags. The eyeglass company Warby Parker hosts parties for authors and sells books from 14 independent publishers in its stores.

JetBlue offers around 40 e-books from HarperCollins and Penguin Random House on its free wireless network, allowing passengers to read free samples and buy and download books. JetBlue will start offering 11 digital titles from Simon & Schuster soon. Amtrak recently forged an alliance with Penguin Random House to provide free digital samples from 28 popular titles, which passengers can buy and download over Amtrak’s admittedly spotty wireless service.

Amtrak is becoming an incubator for literary talent in its own right. Last year, it started a residency program, offering writers a free long-distance train trip and complimentary food. More than 16,000 writers applied and 24 made the cut.

Like Amtrak, Rhapsody has found that writers are eager to get onboard. On a rainy spring afternoon, Rhapsody’s editorial staff sat around a conference table discussing the June issue, which will feature an essay by the novelist Hannah Pittard and an unpublished short story by the late Elmore Leonard.

“Do you have that photo of Elmore Leonard? Can I see it?” Mr. Heller, the editor in chief, asked Rhapsody’s design director, Christos Hannides. Mr. Hannides slid it across the table and noted that they also had a photograph of cowboy spurs. “It’s very simple; it won’t take away from the literature,” he said.

Rhapsody’s office, an open space with exposed pipes and a vaulted brick ceiling, sits in Dumbo at the epicenter of literary Brooklyn, in the same converted tea warehouse as the literary journal N+1 and the digital publisher Atavist. Two of the magazine’s seven staff members hold graduate degrees in creative writing. Mr. Manning, the executive editor, has published a memoir and edited five literary anthologies.

Mr. Manning said Rhapsody was conceived from the start as a place for literary novelists to write with voice and style, and nobody had been put off that their work would live in plane cabins and airport lounges.

Still, some contributors say they wish the magazine were more widely circulated.

“I would love it if I could read it,” said Ms. Schappell, a Brooklyn-based novelist who wrote a feature story for Rhapsody’s inaugural issue. “But I never fly first class.”

Rhapsody, a Lofty Literary Journal, Perused at 39,000 Feet

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